Proper full report

Aerospace Application – Valveless Pulsejet Engine 1 | P a g e
ABSTRACT/SUMMARY
In the past, the idea of pulse jet engine was utilized as a propulsive system to power
certain military weapons involved in the war. Due to the high demand for fuel, this
system was very costly to operate and are now replaced by modern turbine engines.
Engineers have come to the point that these engines can only be used for light
applications which do not demand high running time such as UAVs. There are basically
two types of pulsejet engines which are the valve and the valveless designs.
To successfully design the valveless pulse jet engine, the manufacturer needs to
consider some parameters that relate the intake, combustion chamber and tailpipe.
These parameters include the shape dimensions and material as they highly affect the
engine efficiency. The design of the intake is what determines the amount of air allowed
to flow toward the combustion chamber. The overall length and the volume of fluid
flowing through the pipe determine the amount of thrust generated by the engine. This
means the intake pipe should be wide enough to allow enough flow of air to the
combustion chamber. The combustion chamber should be designed to ensure a proper
mixture of the incoming air with the fuel. The tail pipe should be designed to allow
enough expansion for the gas to provide the required power. It should be long enough
to ensure the generation of strong pressure waves which will keep the engine running.
Apart from the above methods mentioned, another way to improve the engine efficiency
is by making use of dual ignition system and fitting an augmentor ahead of the engine.
Pulsejet engine operates at extremely high temperatures which can reach up to 1000
degree Celsius. To ensure the safety of the operator and its surroundings, there must
be a mechanism which prevents the hot exhaust gases from flowing towards the fuel
tank through the fuel supplying pipe.

Contents
ABSTRACT/SUMMARY................................................................................................................1
NOMENCLATURE........................................................................................................................6
INTRODUCTION..........................................................................................................................7
AIMS AND OBJECTIVES...............................................................................................................8
GANTT CHART............................................................................................................................8
Initial Gantt chart...................................................................................................................8
Final Gantt chart ....................................................................................................................9
THEORY....................................................................................................................................10
Kadenacy effect....................................................................................................................10
Acoustic resonance..............................................................................................................11
Working Cycles.....................................................................................................................12
Lenoir Cycle......................................................................................................................12
Humphrey Cycle...............................................................................................................13
OPERATION..............................................................................................................................14
Self-sustaining......................................................................................................................15
PARAMETRIC STUDY ................................................................................................................17
Analysis of existing pulsejet engines....................................................................................17
Lockwood hiller valveless pulsejet engine:......................................................................17
Chinese Valveless pulsejet engine:..................................................................................17
Valved “Red Head” pulsejet engine:................................................................................18
Material choice for the valveless pulsejet engine design................................................20
Fuel choice .......................................................................................................................21
Nozzle parametric study ..................................................................................................22
CALCULATIONS.........................................................................................................................23
ENGINEERING DRAWING .........................................................................................................24
CONSTRUCTION OF THE ENGINE .............................................................................................26
Combustion Chamber ..........................................................................................................27
Combustion chamber cone ..................................................................................................31
Tailpipe.................................................................................................................................34
Intake pipe ...........................................................................................................................35
Nozzle...................................................................................................................................39
Spark plug attachment.........................................................................................................44
Pulsejet Engine Stand...........................................................................................................46
TESTING AND TROUBLESHOOTING..........................................................................................51

SAFETY PRECAUTIONS..........................................................................................................51
TESTING PROCEDURES.........................................................................................................51
Fuel Line Connection........................................................................................................51
Ignition System.................................................................................................................52
Engine starting .................................................................................................................52
Engine stopping................................................................................................................52
TESTING RESULTS AND IMPROVEMENTS ........................................................................52
CHALLENGES FACED.................................................................................................................63
RECOMMENDATIONS...............................................................................................................65
APPLICATIONS..........................................................................................................................66
X-Jet......................................................................................................................................66
Dubai Civil Defence..............................................................................................................66
FUTURE IMPROVEMENTS AND DEVELOPMENTS ....................................................................68
Pulse Detonation Engine......................................................................................................69
CONCLUSION............................................................................................................................70
REFERENCES.............................................................................................................................71
ACKNOWLEDGEMENT..............................................................................................................72
APPENDIX .................................................................................................................................73
Appendix A : Interim Report ................................................................................................73
Appendix B : Proposal ..........................................................................................................79
Appendix C : Project Ethical Evaluation Form......................................................................87
Appendix D : Matlab Code...................................................................................................90
Appendix E : Online Pulsejet Calculator...............................................................................92
List of Figures
Figure 1- Gantt chart at the start of project ..............................................................................8
Figure 2- Updated Gantt chart...................................................................................................9
Figure 3 Compression wave at the beginning of the combustion cycle (J. Reynolds, 2010)...10
Figure 4 Reflection of Rarefaction Wave (J. Reynolds, 2010)..................................................10
Figure 5 Reflection of Compression Wave and restart of the combustion process (J.
Reynolds, 2010)........................................................................................................................11
Figure 6 Lenoir Cycle (IJATES 2015) .........................................................................................12
Figure 7 Humphrey cycle (IJATES 2015)...................................................................................13
Figure 8 Self-Sustaining Process ..............................................................................................16
Figure 9- Shows the Lockwood hiller engine ...........................................................................17
Figure 10 Chinese pulsejet engines .........................................................................................17
Figure 11- Shows the "Red Head" Valved pulsejet engine......................................................18

Figure 12- 2D AutoCAD drawing of Thermojet........................................................................24
Figure 13 Side View – 3D..........................................................................................................25
Figure 14 Top View – 3D..........................................................................................................25
Figure 15 Back View – 3D........................................................................................................25
Figure 16 SS 316 Sheet.............................................................................................................27
Figure 17 TIG Welding..............................................................................................................28
Figure 18 TIG Welding..............................................................................................................29
Figure 19 TIG Welding Machine...............................................................................................29
Figure 20 Cutting the Combustion Chamber Cover.................................................................30
Figure 21- Using compass to make arc ....................................................................................32
Figure 22- Shows how shape of part removed from sheet .....................................................32
Figure 23- Bending the sheet on round bar.............................................................................33
Figure 24- Cutting the sheet ....................................................................................................33
Figure 25- Welding of cone with combustion chamber ..........................................................34
Figure 26- Pipe cutting for exhaust..........................................................................................35
Figure 27- Cutting the intake pipe ...........................................................................................36
Figure 28- Shaping the edge of intake pipe .............................................................................36
Figure 29- Appearance of intake that attaches with cone ......................................................37
Figure 30- Making hole for intake............................................................................................37
Figure 31- Drilling a hole for intake .........................................................................................37
Figure 32- Welding of intakes..................................................................................................38
Figure 33- Before grinding .......................................................................................................38
Figure 34- After grinding ..........................................................................................................38
Figure 35- Compass for making arc for nozzle.........................................................................40
Figure 36- Cutting sheet...........................................................................................................41
Figure 37- Bending of sheet.....................................................................................................41
Figure 38- Welding of nozzle with the exhaust .......................................................................42
Figure 39- Polishing of Cone ....................................................................................................43
Figure 40- Polishing of combustion chamber ..........................................................................44
Figure 44- Cutting of Mild steel ...............................................................................................46
Figure 45- Shows the arrangement of steel.............................................................................46
Figure 46- Arrangement of steel..............................................................................................47
Figure 47- General look of stand..............................................................................................48
Figure 48- Attached piece........................................................................................................49
Figure 49- Drilled holes in steel plate ......................................................................................50
Figure 50 Testing with twin intakes.........................................................................................53
Figure 51 Testing with new spark plug ....................................................................................54
Figure 52 Combustion Chamber Cone Increased to 10cm. .....................................................55
Figure 53 Dual spark plug.........................................................................................................56
Figure 54 Relocation of intake tubes .......................................................................................57
Figure 55 Testing with the new intakes...................................................................................58
Figure 56 Testing with single intake ........................................................................................59
Figure 57 Testing with very high compressed air....................................................................60
Figure 58 New Engine Design...................................................................................................62
Figure 59 Operating engine .....................................................................................................62
Figure 60 X-Jet application for pulsejet ...................................................................................66

Figure 61 Dubai jetpacks for Civil Defence, Gulf Elite 2016.....................................................67
Figure 62 Carbonated Intake (IJATES 2015).............................................................................68
Figure 63 Simulation of Thrust Augmenter (AARDVARK 2015) ...............................................68
Figure 64 Rutan Long-EZ (Wikipedia 2016)..............................................................................69
Figure 65 Motorbike powered by Pulsejet Engine (Power Blog 2015)....................................69
Figure 66- 2D AutoCAD drawing of Thermojet design ............................................................73
Figure 67- Welding of Burner...................................................................................................75
List of Tables
Table 1- Comparison of Pulsejet models .................................................................................19
Table 2- Properties of materials...............................................................................................20
Table 3- Properties of fuels......................................................................................................21
Table 4- Nozzle Statistical Analysis ..........................................................................................22

NOMENCLATURE
A Mean Engine Area
D Exhaust Pipe Diameter
L Exhaust Pipe Length
D Intake Pipe Diameter
l Intake Pipe Length
Vcc Volume of Combustion Chamber
LPG Liquefied Petroleum Gas
𝜌 𝑎𝑖𝑟 Density of Air
𝜌 𝐿𝑃𝐺 Density of LPG
𝜌 𝑚𝑖𝑥𝑡𝑢𝑟𝑒 Density of Mixture
𝛾 Constant
𝑅 Universal Gas Constant
𝑇 Temperature

INTRODUCTION
Jet propulsion devices are commonly used to power machines. Pulsejet engines are
one of these propulsion method used to power or drive other systems to provide thrust.
Pulsejet engines use a pulse generating working principle in their operation to provide
the required power. According to the mechanism through which they operate, there
are two different types of pulsejet engines: the valved pulsejet engines and the
valveless pulsejet engines. The latter is the design type used and implemented in this
project.
Valveless pulsejet engines are basically the simplest type of jet propulsion devices in
design and in operation. Valveless pulsejet engines are known to operate with no
mechanical parts. There is no moving part in the design of a valveless pulsejet engine
as there is no need of actuation to initiate the mechanism during operation. The design
configuration of the engine is the main factor responsible for controlling the flow from
the intake to the exhaust. Actually, valveless pulsejet engines use the simplest thrust
generation method that consist of the mixture of propellant and air. The introduction of
air into the engine is done through an intake. A twin intake designconfiguration is used
in this project. The propellant used in this project is a propane gas. The presence of
fuel (propane) and air is not the only condition for combustion to occur. Added to the
presence of air and propane, heat is also one of the condition required for the
combustion to start and maintain the process. There is a need to design a combustion
chamber that can initiate and sustain the process of combustion. This means the
combustion chamber should be able to heat the air and propane at adequate
temperature for the engine to run. The combustion chamber design should not only
take into account the process ignition. In order for the process to be sustained and
maintained, the design of the combustion chamber should ensure a proper mixture
(stoichiometric mixture) of the air and the fuel. There is expansion of the gas emitted
as the result of the combustion that needs to be discharged to atmosphere through
the exhaust.
This present report will talk in detail about the presentation and operation of a
valveless pulsejet engine. A description of the different part will be covered from
manufacturing process to prototype realization.

AIMS AND OBJECTIVES
The objectives of this project are:
I. Design a self-starting valveless pulsejet engine using a computer aided design
software.
II. Analyze twin intake valveless pulsejet engine.
III. Manufacture, control and improve the intake, the combustion chamber of a
valveless pulsejet engine for better efficiency.
IV. Safely control a valveless pulsejet engine.
V. Improve and test the valveless pulsejet prototype.
GANTT CHART
Initial Gantt chart
Figure 1- Gantt chart at the start of project

Final Gantt chart
Figure 2- Updated Gantt chart
The groups were formed and the decision to manufacture a valve-less pulsejet was
decided. The complete manufacturing was done in Sharjah industrial area. From the
start of this project, all activities were done according to plan till the manufacturing of
stand. Once the prototype was ready to be tested it was advised to test it in the Civil
Defence Station. But the permission was denied since no official document was
provided by the university to make this project legit. After a series of requests to
provide the document, the permission to test was granted in the university campus
which took three weeks.

THEORY
The theories behind the operation of a pulsejet engine is described by the kadenacy
effect and the acoustical resonance.
Kadenacy effect
The kadenacy effect is about the pressure waves created during the motion of the
gases due to inertia. The kadenacy effect is actually the results of oscillating
pressures.
Figure 3 Compression wave at the beginning of the combustion cycle (J. Reynolds, 2010)
The internal pressure is increased in the engine as the gas is compresses. There is a
compression wave that build up inside the engine due the rapid rise in pressure that
follows the first explosion. The compression wave reaches the intakes first and then
continue to travel toward the exhaust. As it reaches the intakes, there is a rarefaction
wave that is created, reversing the flow.
Figure 4 Reflection of Rarefaction Wave (J. Reynolds, 2010)
There is pressure drop during the rarefaction wave as the gas reaches the end of the
exhaust. This rarefaction wave that occurs due to the decrease in density is reflected
in the opposite direction from the exhaust also. The gas is still flowing even if the
pressure drops below the ambient pressure. The engine is now in its breathing cycle.

Due to inertia, there are still some remaining parts of the gas that flow toward the
exhaust.
Figure 5 Reflection of Compression Wave and restart of the combustion process (J.
Reynolds, 2010)
The pressure drop is below the atmospheric pressure, causing the flow to fully reverse
in the opposite direction. The reverse of flow is forced by the atmospheric pressure
being higher than the exhaust pressure. The rarefaction wave at the exhaust is
reflected as weak compressive wave. This compression wave is sufficiently slowed
enough to initiate the process of combustion using the remaining hot gas for the cycle
to restart. (Digitalcommons.calpoly.edu, 2010)
Acoustic resonance
The theory of acoustic resonance to explain the working principle of the valveless
pulsejet engine is similar to the kadenacy effect as it also concerns the pressure
wave’s movements within the combustion chamber. In the pipes, there is a
deflagration in addition to the pressure waves that follow the combustion.
The motion of the gas is restricted in the combustion chamber than in any other part
of the valveless pulsejet engine. The combustion chamber is the part of the engine
with the highest resistance to motion or change of speed with time. It is therefore the
region of lowest impedance. In the chamber, there are pressure waves that strike the
engine ducts and tubes. (Pulse-jets.com, 2005)
The part of lowest impedance within the engine are areas located at the exit of the
intakes and exhaust. Due to the effect of exchange between the internal and external
pressure (outside pressure), these ports are parts of the engine that experience the
highest disturbance. They offer the lowest resistance to the change between the
maximum and minimum speeds and therefore are parts of lowest impedance.

The resulting pressure waves that strike the ducts and tubes and reflect back meet
at a certain frequency to form a standing wave.
Working Cycles
The operation of pulsejet engines involves the combination of two cycles that are:
 The Lenoir cycle
 The Humphrey cycle.
Lenoir Cycle
Figure 6 Lenoir Cycle (IJATES 2015)
The Lenoir cycle starts with an air/fuel intake at point “a” and operates in the
following thermodynamic process:
A-b: isochoric combustion (heat addition at constant volume)
B-c: isentropic expansion (adiabatic expansion)
c-a: heat rejection at constant pressure (isobaric)
There is heat absorption in the isochoric heating. The expansion during the
isentropic process is done without interaction of heat. Work is rejected during the

isentropic expansion process. There is also work consumption during isobaric
cooling where waste is rejected. (Liquisearch.com, 2015)
Humphrey Cycle
Figure 7 Humphrey cycle (IJATES 2015)
The Humphrey cycle is same as the Lenoir cycle. The only difference is about the
starting of the process where there is compression before combustion in the process
from “a” to “b”.
A-b: isentropic compression
B-c: isochoric combustion (heat addition at constant volume)
C-d: isentropic expansion (adiabatic expansion)
d-a: heat rejection at constant pressure (isobaric)
(Anon, 2015)

OPERATION
Pulsejet engine is just a jet engine which can produce thrust in pulses as the
combustion occurs in pulses. The main difference between pulsejet engines and
normal gas turbine engine is that there are no moving parts at all. The valveless
pulsejet engine is just a hollow pipe which has one combustion chamber, intake pipe
and the exhaust pipe. There are basically two types of pulsejet engines one is valved
pulsejet engine and the other one is valveless pulsejet engine. In the valved pulsejet
engine there is one mechanical valve present which is mostly made of aluminum. The
function of this valve is to prevent the exhaust gases from flowing back towards the
intake and prevent the disturbance of the fresh air which is coming from the intake.
This valve is made in such a way that it allows the exhaust gases to flow through only
the tail pipe. The disadvantage of this valved pulsejet engine is that it cannot be run
for a very long time as the aluminum valve just burns out and gets destroyed. Due to
this reason the aluminum valve has to be replaced after some specific time of running.
The second type is the valveless pulsejet engine in which there is no mechanical part
at all. Since there is no valve present the engine can be run for almost unlimited time
until the fuel supply runs out. The valveless pulsejet engine operation is based on its
own geometry to control the flow of exhaust out of the engine. In valveless engine the
exhaust gases go out from the exhaust as well as from the intake. This also means
that 60% of the thrust is provided by the exhaust and the remaining 40% of the thrust
is provided by the intake. Due to this reason both the intake and the exhaust should
be facing in the same direction to contribute in thrust.
To operate a pulsejet engine either it is valved or valveless engine, there are few things
which are needed or without the proper equipment and setup it will be impossible to
be able to operate it.
 One of the important instrument is the igniter. In pulsejet engines there are various
ways to ignite the fuel but the proper selection of the ignition method solely
depends on the choice of fuel. If for example the fuel used is liquid fuel then one of
the ways to ignite is the use of glow plug and apart from the glow plug the other
way is heating one side of the combustion chamber with a flame torch. If a gas is
fuel as a fuel source then a spark plug is sufficient to ignite the fuel gas.

 Fuel pipelines are also very important and without the fuel pipelines the fuel
cannot flow from the cylinder to the engine. These fuel pipelines can be of different
type and there is an adapter connection which connects one pipe with another.
The pipe which comes from the cylinder is basically made of rubber and this pipe
is then connected with an adapter connector which connects it with the mild steel
fuel pipe which goes inside intake. The reason for the usage of this mild steel fuel
pipe is because since this pipe goes inside intake where the temperature is very
high this mild steel pipe will not melt.
 Non-return valve is a type of check valve which prevents the gases from flowing
backwards. This is very important for safety reasons as there might be a chance
that the fire in the combustion chamber might get inside intake pipe and hence into
cylinder and explode it.
 Ignition system is used to power the spark plug. This system is used only for
some time as after the engine starts self-sustaining the gases are hot enough to
ignite the fresh mixture of air and fuel. Ignition system consists of one ON and
OFF switch which is connected to the Lithium battery and there are two cables
which come from the ignition system. One cable is always red in color and that’s
the positive cable which is connected to the spark plug and the second cable is
black in color as it’s the negative cable and it can be connected anywhere around
the stand.
Self-sustaining
All pulsejet engines need fuel, spark and external air supply to start but once it starts
it doesn’t need anything except the fuel, in other words it self-sustains. The principle
of operation of pulsejet engine is that when the fuel flows inside the combustion
chamber and mixes with air which comes from the external compressor, the mixture
ignites with the help of a spark plug. When the mixture ignites the exhaust gases go
towards exhaust as well as intake and this exit of gases from the combustion chamber
creates a vacuum inside the combustion chamber. The result of vacuum formation is
that it will suck air back in from the exhaust and intake. Fresh air will be sucked in from
the intake and the hot exhaust gases come back to combustion chamber as a result
of vacuum formation. When the fresh air mixes with a fuel and the hot exhaust gases
come in contact with this mixture in the combustion chamber the ignition take place.

This taking place of ignition due to the vacuum formation is called as self-sustaining.
When the engine starts self-sustaining the ignition system can be disconnected and
the external air is not needed anymore.
Figure 8 Self-Sustaining Process

PARAMETRIC STUDY
Analysis of existing pulsejet engines
Lockwood hiller valveless pulsejet engine:
This pulsejet engine is the valveless engine which means it does not have reed valve
to stop the exhaust gas from going back towards the intake. The shape of this engine
is a U shape which means the air from external compressor goes inside the intake
which takes it to the combustion chamber where the fuel is supplied and single spark
plug is used to ignite the air to fuel mixture. The exhaust gas from the combustion
chamber goes to the exhaust and intake. The idea of facing exhaust and intake in the
same direction ensures that the air which comes out of intake is also used to provide
thrust. In this type of pulsejet engine about 70% of the thrust is provided by the exhaust
(tailpipe) and the remaining 30% is provided by intake. The picture below shows the
shape of Lockwood hiller pulsejet engine:
Figure 9- Shows the Lockwood hiller engine
Chinese Valveless pulsejet engine:
Figure 10 Chinese pulsejet engines
This pulsejet valveless engine is straight shaped unlike the Lockwood engine. This

engine has one intake pipe which is approximately half the diameter of the tailpipe and
this intake pipe accommodates the fuel to bring it to combustion chamber. Since it is
single intake design, there needs to be an external supply of compressed air if the
liquid fuel is to be used. Use of propane gas as fuel eliminated the use of external
compressed air just like the Thermojet (our design). The mixture of air and fuel is
ignited by using a NGK CM-6 spark plug. An adjustable fuel valve is used in this engine
which can be used to regulate fuel flow if the fuel used is liquid.
Valved “Red Head” pulsejet engine:
As the name suggests, this is a valved pulsejet engine which means there is a reed
valve present to prevent the exhaust gas from flowing back into the intake which would
disturb the flow of intake air which is driven due to the vacuum created inside the
engine. This engine consists if the “Red Head” which is the starting part of the engine.
It is attached to the combustion chamber with the help of the locking ring. This “Red
Head” knob is used to bring the air and fuel to the combustion chamber; it also
accommodated the reed valve. Only Gasoline can be used in this design of pulsejet
engine and hence it needs an external air supplier to start the engine easily. The spark
plug is mounted on top of the combustion chamber and it is powered using the ignition
system.
Figure 11- Shows the "Red Head" Valved pulsejet engine

Table 1- Comparison of Pulsejet models
Lockwood hiller
valveless engine
Chinese
valveless
pulsejet engine
Valved “Red
Head” pulsejet
engine
Valveless
“Thermojet”
engine.
Single intake Single intake Single intake Twin-intake
Needs external air
compressor to
start the engine.
Needs external air
compressor to
start the engine.
Needs external air
compressor to
start the engine.
Do not need
external air
compressor.
Stainless steel Mild steel Stainless steel Stainless steel
Single-spark plug Single-spark plug Single-spark plug Can use single-
spark plug or dual-
spark plug to
increase efficiency.
Hard to start Hard to start Hard to start Super easy to start
due to twin-intake.
No valve- More
duration
No valve- More
duration
Reed valve used-
Less duration
No valve- More
duration
Less thrust Less thrust Less thrust Higher thrust as
twin-intakes
provide thrust as
well.
The comparison table compares the Thermojet with three different types of pulsejet
engines and it shows that Thermojet is more efficient and improved version of pulsejet
engine. It has a twin-intake design which is something new in the production of
valveless pulsejet engines and this twin-intake ensures sufficient air enters the
combustion chamber for better efficiency which in turn eliminates the use of external
air compressor as well. There is no valve in Thermojet so it can be operated for longer
time as no moving part to burn out or destroy. Thermojet also do not need replacement
of valve which reduces the cost. It is even much easier to start the Thermojet as it has

twin-intake and the use of propane gas fuel will make it possible due to its higher
burning ratios.
Material choice for the valveless pulsejet engine design
Table 2- Properties of materials
As it can be seen in the above table, the materials with the highest melting point are
titanium, Stainless Steel and Mild steel. Since titanium is very costly and not easily
accessible, this material is not going to be used. The mild steel and the stainless steel
are left.
The mild steel has a density similar to the stainless steel. Examining both materials,
they have almost the same density and cost, but the stainless steel is easier to work
on, and exists in a wide variety. Stainless steel is also more durable and stronger than
mild steel
Stainless steel therefore appears to be the material of choice for the design of the
valveless pulsejet engine. Added to the low cost of the material, it is easily accessible.

Fuel choice
Table 3- Properties of fuels
The flash point (FP) of a fuel is the temperature at which the fuel may sustain
continuous combustion. A low FP is required.
The Auto-Ignition Temperature (AIT) is the lowest temperature at which it will
spontaneously ignite without ignition. In the case of AIT, the higher the temperature
the safer the fuel source.
A low FP and high AIT is ideal for application and therefore propane is the fuel of
choice for the design.
Kerosene fuels are also a good alternative but they do cause problems during cold
starting and need to be vaporized before injection, requiring the use of a heat
exchanger coil. Engines. The disadvantage with using liquid fuels is the need for a fuel
pump to provide the correct fuel pressure. This adds complexity to the project.
The problem with fuel pressure can be overcome if a gaseous fuel such as propane
or butane is used. It is decided to use propane as a fuel due to its high energy density
(50 MJ/kg). It also eliminates the use of a fuel pump system and therefore participate
in the overall project cost reduction.

Nozzle parametric study
Table 4- Nozzle Statistical Analysis

CALCULATIONS
Dimensional Analysis
Engine Area
𝑇ℎ𝑟𝑢𝑠𝑡 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑑 = 12 𝑙𝑏
𝑇ℎ𝑢𝑟𝑠𝑡 = 2.2 × 𝐴𝑟𝑒𝑎
𝐸𝑛𝑔𝑖𝑛𝑒 𝐴𝑟𝑒𝑎 = 5.4 𝑖𝑛𝑐ℎ2
Exhaust Diameter
𝐴 =
𝜋𝐷2
4
= 𝐷 = √
4𝐴
𝜋
𝐷 = √
4 × 5.4
𝜋
𝐷 = 2.6 𝑖𝑛𝑐ℎ𝑒𝑠 𝑜𝑟 6.6 𝑐𝑚
Exhaust Length
𝐿 = 12 𝐷 (From Statistical Analysis)
𝐿 = 12 × 2.6 = 31.2 𝑖𝑛𝑐ℎ𝑒𝑠
Intake Diameter
𝑑 = 2.6 ×
80
100
= 2.08 𝑖𝑛𝑐ℎ𝑒𝑠 𝑜𝑟 5.2 𝑐𝑚
𝐸𝑎𝑐ℎ 𝐼𝑛𝑡𝑎𝑘𝑒 =
5.2
2
= 2.64 𝑐𝑚
Intake Length
𝑙
𝐿
= 0.16
𝑙 = 312 ×
16
100
= 5 𝑖𝑛𝑐ℎ𝑒𝑠 𝑜𝑟 12.7 𝑐𝑚
Volume of Combustion Chamber
𝑇ℎ𝑟𝑢𝑠𝑡 = 4453.98 𝑉𝑐𝑐 + 1.448
4453.98 𝑉𝑐𝑐= 4.552
𝑉𝑐𝑐 =
4.552
4453.98
= 1.022 × 10−3
𝑚−3

Operational Analysis
A stoichiometric mixture of air to fuel is 15:1 . Since the fuel used if LPG it has a
ratio of 15.5.
𝜌 𝑎𝑖𝑟 = 1.2
𝑘𝑔
𝑚3
𝜌𝐿𝑃𝐺 = 1.898
𝐾𝑔
𝑚3
𝜌 𝑚𝑖𝑥𝑡𝑢𝑟𝑒 = 1.898 + (
1
15.5
) × 1.2 = 1.975 𝑘𝑔/𝑚3
Frequency
Temperature is assumed as 1000K for a normal pulsejet.
𝑓 =
√ 𝛾𝑅𝑇
4𝐿
𝑓 =
√1.4 × 287 × 𝑠
4 × 0.97
𝑓 = 163 ℎ𝑧
ENGINEERING DRAWING
The engineering drawing of the valveless pulsejet engine was made using AutoCAD
Computed Aided Design Software.
Figure 12- 2D AutoCAD drawing of Thermojet

Figure 13 Side View – 3D
Figure 14 Top View – 3D
Figure 15 Back View – 3D

CONSTRUCTION OF THE ENGINE
This phase of the project comes only after designing of the valveless pulsejet engine
and calculations. Before commencing the actual construction of the engine there are
certain parameters which should be considered in order to maintain the general
requirements of the pulsejet engine. One of the important parameters is the selection
of material because the temperature inside the pulsejet engine can reach 1000 oC
easily due to the continuous combustion inside the combustion chamber. If the
material is not carefully selected then there will be chances that the structure of the
pulsejet engine might melt while it’s operating. There are mainly three types of
materials which can be used for the construction of pulsejets and they are mentioned
below:
 Inconel
 Stainless Steel
 Mild Steel
After all the analysis and research, it was concluded that stainless steel was the best
material to be used in pulsejet engines and there are multiple reasons which can
support this choice. One reason is that the Inconel is extremely expensive as
compared to the other two materials, after that comes the stainless steel and the least
expensive material is mild steel. Inconel has the highest temperature resistance as
compared to other two materials and mild steel has the least temperature resistance.
Stainless steel is much easier to work on and fabricate and it is hardest to shape and
fabricate the Inconel. The appearance matters a lot in all project work and the
appearance of stainless steel is much more attractive as it is usually treated with a
mirror finish. All the reasons mentioned above concludes that Stainless steel was the
best choice of material for manufacturing of valveless pulsejet engine. Below is the
table which outlines a brief comparison of the three materials:
After the selection of material the next step is to search for places which can provide
this material in the desired dimensions. There were basically two options before the
purchasing of the material, one option was to use sheets for the complete construction
and the other option was to use pipes of different dimensions which can be welded
together. For using sheets, the process was to cut the sheets depending on the part
dimensions and then rolling it either with the help of roller machine or mallet

hammering. This takes a much longer time and the expense increases drastically and
because of that the decision was made to use stainless steel 316 pipes of desired
dimension and weld them together. There are many different types of welding, the one
which was used in this engine manufacturing was TIG (Tungsten Inert Gas) welding.
The reason for this selection was because the TIG welding is leak free and also the
threads in this welding don’t come off due to extreme temperature.
Combustion Chamber
The designing of the combustion chamber was
the most challenging part as it is that part of the
engine where combustion of the air to fuel mixture
takes place and hence the designer must make
sure there is no turbulence inside the combustion
chamber and the exhaust gases go from
combustion chamber to exhaust and intake
without any blockage. According to the
calculations, the dimensions of the combustion
chamber were 11 centimeter diameter and 13
centimeter length. One simple procedure that
could’ve made the manufacturing of combustion
chamber much easier was to use pipe of accurate
dimensions which are mentioned above and just
weld other parts of the engine with it. However, this was not the case as the biggest
pipe available in the market was only of 10 centimeter diameter and the minimum
length which was available to the buyer was of 6 meters. This option was not
considered as the length required was only 13 centimeters which is far less than 600
centimeters so there would be a huge waste of material and money. To counteract
this problem, a Stainless steel 316 sheet of 1.2 millimeter thickness was bought which
was then used to roll into a combustion chamber of the desired dimensions.
To use sheet for making the combustion chamber, the first step was to cut the sheet
into accurate measurements which would make a combustion chamber if rolled. To
make sure sheet is cut with proper dimensions, value of length of the combustion
chamber and the circumference of the combustion chamber were used. As mentioned
Figure 16 SS 316 Sheet

earlier, the length of the combustion chamber was calculated as 13 centimeters and
the circumference was calculated as 34.5 centimeters. The rectangle was cut from the
sheet with the one side of 13 centimeters and the other side of 34.5 centimeters. This
rectangle was then bent using the mallet to form into a circular shape and hence into
a combustion chamber. The reason for forming the combustion chamber circle
manually and not using the roller machine to simply roll is because the roller machine
cannot roll sheets which are less than 2 meters in length.
After the combustion chamber circular shape was made with the help of mallet
hammering, the sides were welded together to make it into permanent circular
combustion chamber shape. The welding was done throughout the length of the
combustion chamber which was 13 centimeters. The type of welding used in this
process was not an ordinary welding instead TIG welding was used. TIG stands for
Tungsten Inert Gas welding and the inert gas used is Argon. The reason for the use
of this welding is because TIG welding threads can withstand extremely high
temperatures which can range up to 1200 oC. Another reason is that this welding is
leak free which means the threads won’t come off at high temperature exposure and
also it is very precise which makes it the most ideal choice of weld for our engine.
Figure 17 TIG Welding

Figure 18 TIG Welding
Figure 19 TIG Welding Machine
The next stage in the combustion chamber manufacturing is the construction of that
bottom plate which houses the spark plug for the combustion chamber. It was decided
that the plate should be slightly bend by approximately 1 degree as it makes the
reflection of the pressure waves more easier. Same sheet that was used for the

combustion chamber was also used to manufacture the bottom plate. The diamater of
the combustion chamber was 11 centimeter which means the diamater of the plate
required from the sheet will also be 11 centimeter. A compass was used to make a
marks for the circular plate on the sheet and then a circular blade cutting machine was
used to cut off that circular part from the sheet. Once this circular plate was cut off
from the sheet it was further filed using the circular filer machine to make the edges
smoother and make sure its perfect round. Once the proper circular shaped plate was
made ready it was kept on the object that was having a smooth concave cross-section
and mallet was used to hammer it and bend the plate by 1 degree. After that this plate
was attached to the combustion chamber using the TIG welding.
Figure 20 Cutting the Combustion Chamber Cover
After the welding, all the edges of the combustion chamber were filed using the circular
filing machine to make the surface smooth and even out all the edges. The next part
was to make a hole in the bottom plate because it will house the spark plug. The spark
plug should attach with the plate exactly in the centre point and to make it easier a nail
was used to mark the spot which needs to be drilled in order to fit the spark plug. To
drill a hole in the centre of the plate a drill bit of 11 millimetres was used and a reason
for this is that the diameter of the spark plug thread is 12 millimetres so this drill bit
was perfect to make sure the spark plug tightly fits in.

Combustion chamber cone
A combustion chamber cone is that part which joins the combustion chamber with the
exhaust pipe. Same sheet which was used to make the combustion chamber and back
cover of combustion chamber was also used to make a cone. There are no laws or
calculations which helps one define the dimensions of this cone and for this reason
the dimensions of the cone were chosen by doing a complete parametric study of other
pulsejet engine designs. The inlet diameter of the cone will be same as the diameter
of the combustion chamber as it gets attached to the combustion chamber, whereas
the outlet of the cone will be same as the diameter of the exhaust pipe as that outlet
part of the cone gets attached to the exhaust pipe. The straight length of cone which
is basically a gap between the inlet and outlet of a cone is decided as 5.5 centimeters.
Before cutting the sheet a compass was used to make marks on the sheet which
represents the area which needs to be cut. First a semi-circle was made with the
compass on the sheet and then another semi-circle was made ahead of that previous
one with a gap of same 5.5 centimeters. Both the semi-circles were joined at the edges
and this semi-circle represents the area of the sheet which needs to be cut in order to
make a cone.

Figure 21- Using compass to make arc
Figure 22- Shows how shape of part removed from sheet
A circular blade cutting machine was used to cut the sheet on the lines of the semi-
circle and the piece was then hammered with the mallet to form it into a cone shape.
To make a proper cone shape, it is important to keep this stainless steel sheet on a
circular object and then hammer it so that it takes that circular shape and eventually
form into a cone. To make this possible, a round metal bar of random diameter was
welded to the side of the metal working stable station and then this round bar was
used in a way to support the metal sheet while it gets deformed by the mallet. As it

gets deformed, since it is placed on a round metal bar it will eventually take shape of
this round metal bar and in this way a proper circular cone was manufactured.
After manufacturing a cone, the outlet diameter and inlet diameter were rechecked
and they were exactly the same as the diameter of combustion chamber and exhaust
pipe. The next part of the construction was to weld this cone to the combustion
chamber. TIG welding was used in overall welding of this Thermojet valveless pulsejet
engine and the welding was done carefully to make sure that there are no leaks in the
weld and not any spot is left unwelded.
Figure 23- Cutting the sheet
Figure 24- Bending the sheet on round bar

Figure 25- Welding of cone with combustion chamber
Tailpipe
This is one of the most critical part of the pulsejet engine. The operation of pulsejet
engines is such when the fuel and air mixture is ignited by the spark plug, the exhaust
gases flow into the tailpipe which creates a vacuum inside the combustion chamber.
This formation of vacuum sucks air back in from the tail pipe and the intake and when
this air is mixed with the fuel it is ignited again due to the hot gases which came back
from the tailpipe. For this reason, if the tailpipe is not properly calculated and
manufactured then the engine will have a lot of problems in order to self-sustain.
According to the calculations the required tailpipe diameter was 6.3 centimeter and
the length of the tail pipe should be around 80 centimeter. The tailpipe was purchased
from one company named Hidayth and it was 100 centimeters long. Since the required
length was only 80 cm the tail pipe was cut using a circular blade cutting machine. The
procedure of cutting the tailpipe is very simple as the tailpipe should be placed on that
cutting machine under the blade and then the power should be turned on. Once the
power is on and the circular cutting blade is rotating at a very high RPM, carefully push
the handle down slowly until the blade passes through the whole cross sectional area
of the pipe and cuts it smoothly.

Figure 26- Pipe cutting for exhaust
Intake pipe
These intake pipes are also very crucial part of our pulsejet engine as they control the
amount of air that goes in from the surrounding. This is very important because if the
correct proportion of the air to fuel mixture is not achieved then it will be extremely
difficult to start the engine and in most cases it will simply not start. According to the
Thermojet valveless pulsejet engine design, it has two intake pipes which are attached
to the cone which joins the combustion chamber with the tail pipe. These two intake
pipes were welded completely opposite to each other and the length and diameter of
these intake pipes were determined by doing appropriate calculations. According to
the calculations, the diameter of the intake pipe should be about 5.28 centimeters and
since there are two of these intake pipes the diameter of each intake pipe should be
around 2.64 centimeters.
The calculations regarding the intake pipes were all done but the best option available
to group was to use an intake pipe of size 2.5 centimeters each. This is because of
the availability of the pipes. All pipes come in standard sizes only and there was no
pipe available which had the inner diameter of 2.64 centimeters. Another problem
which the group faced was that the 2.5 centimeter outer diameter pipe was still big
enough to fit onto the combustion chamber cone. The diameter of combustion
chamber is only 11 centimeters and it cannot accommodate materials that exceed this
thickness altogether. The exhaust pipe diameter is 6.6 centimeters and the both

intakes diameter of 5 centimeters will make it 11.6 centimeters all together. This is why
it was not possible to make pulsejet engine with bigger intake pipes. The finalized
pipes had an outer diameter of 1.6 centimeters each which means the inner diameter
will be only 1.3 centimeters each consider 0.3 centimeters of pipe thickness.
To make the intake pipes a long 1.6 centimeter outer diameter intake pipe was
purchased from stainless steel suppliers. This intake pipe was about 20 centimeters
long and to transform it into two pipes it was cut from the middle using the circular
blade cutting machine. After cutting, each pipe was 10 centimeters long and this length
was further reduced to 8 centimeters each as according to calculations the length
should not be more than 10% of the length of exhaust pipe.
Figure 27- Cutting the intake pipe
To make it perfectly fit on the combustion chamber cone, the intake pipes were cut
from one corner with angle which was the same angle as the angle of the combustion
chamber cone. Once one corner of the intake pipes was cut with the same angle, it
was placed on the cone to test if it rests on the cone surface evenly. It was noticed
that the surface was slightly uneven where the part was cut with the same angle as
the burner cone angle. Due to this very reason it was not perfectly placed on the cone.
To counteract this problem, that surface was filed using a round filer machine and the
results were positive as it was properly resting on the burner cone.
Figure 28- Shaping the edge of intake pipe

Figure 29- Appearance of intake that attaches with cone
After cutting the intake pipes with an angle, the next part was to make a hole on the
cone where the intake pipe was to be placed to allow air moving inside the combustion
chamber and out. To make sure the holes are made at the right spot and of the correct
size, the cone was covered with a tape and then the marks were drawn of the intake
pipe dimension by placing the intake pipe once again on the burner cone. After that
since the group knew that the hole shouldn’t exceed this mark, a drill machine was
used to drill a hole inside that mark and then the intake pipe was supposed to be
placed on the cone and welded. The group realized that the drilled hole is not big
enough to allow air move in and out without causing turbulence, apart from that by
drilling a hole of certain size will contribute towards decreasing the area available for
air to move in and out. It was decided that a circular blade cutting machine should be
used to make a rectangular cut that will increase the hole area and hence make the
flow of air much easier. After making a rectangular cut, the intake pipes were placed
again on the cut part and it was found that the cuts were exceeded and is exposed
even if the intakes are placed on the cut. TIG welding was used to weld the exceeded
cuts and seal them completely to prevent air leaking out from exceeded cut. After the
TIG weld of exceeded cut, the intake pipes were placed on the holes and the sides
were welded properly and this is how intake pipes were manufactured.
Figure 30- Making
hole for intake
Figure 31- Drilling a
hole for intake

Once the welds were allowed to cool it was noticed that due to the excessive welds
applied around the intake pipes, the appearance of the part was spoiled. The group
had to find a way to erode this excessive welding threads and make them smooth to
improve the appearance. To overcome this issue, the group used round stone filers
which are used in the same way as the drill bits. These round stone filers were fixed
to the pneumatic drill and then the excessive part of weld was filed to make and smooth
and improve the appearance.
The pictures above shows how the welded part looked like before grinding the
excessive welds and how it turned out to be after using stone grinding with pneumatic
drills. This part of the construction was carried out in university workshop. All the
members of the group participated equally in to make the surface look smooth and
better. The tools used for this process include the pneumatic drill, carbon and ceramic
stones which will help grinding the excessive weld. The technique used for this
grinding was to first tightly fix the pulsejet engine on the workshop bench and then use
Figure 32- Welding of intakes
Figure 33- Before grinding Figure 34- After grinding

pneumatic drill with the grinding stone to rub the excessive part. The grinding was
carefully done to make sure the stone don’t grind it too much and make a hole and
also applying force while grinding was avoided to ensure the stones don’t get damaged
or deformed.
Nozzle
This part of the engine was also very important as it helps in correctly managing the
pressure different between the engine and the atmosphere. The air that goes to the
exhaust will have very high velocity which also means that the pressure will be less
than the atmospheric pressure. This pressure difference will allow the air from the
atmosphere to get inside the engine which is not something that is required for the
working pulsejet engine. The addition of nozzle to the valveless pulsejet engine
prevents this from happening. This is because as the nozzle is convergent the area
increases which increases the pressure and reduces the velocity of the exhaust gases.
This increase of pressure at the nozzle means the pressure in the nozzle is more than
the pressure of the atmosphere so the gases will go from high pressure to low pressure
thus the thrust will be higher.
Since there were no direct calculations regarding the nozzle of the valveless pulsejet
engine, the dimensions of the nozzle were selected based on the statistical analysis
of few valved or valveless models that have nozzle in their design. According to the
statistical analysis done by the group the dimensions of the nozzle were as follows:
The inlet diameter: 6.3 centimeters
The outlet diameter: 10 centimeters
The length of the nozzle: 15 centimeters
The dimensions above were used for the construction of the nozzle for valveless
pulsejet engine. The inlet diameter is the diameter of the part of nozzle which is
attached to the end of tailpipe and this would also mean the diameter of the tailpipe
and the nozzle were exactly same as 6.3 centimeters. The outlet diameter represents
the diameter of the part from where the air leaves the nozzle and goes to the
atmosphere and this outlet diameter is 10 centimeters as it is mentioned above. The
length of the nozzle represents the distance of the straight line from the inlet of the

nozzle to the outlet of the nozzle and as it is mentioned above the length of the nozzle
was 15 centimeters. As the nozzle has greater outlet diameter than the intake diameter
it would also mean that there would be some positive angle or elevation angle of the
nozzle and that angle is approximately 13.8 degrees.
For the construction of the nozzle the same sheet was again used which was also
used for the construction of combustion chamber and the construction of cone which
connects the combustion chamber to the tailpipe. The same technique of combustion
chamber cone was also used for the manufacturing of the nozzle. Initially a large
compass was used to make marks on the sheet which would help determine the area
which needs to be cut from the sheet and the marks were made based on the
dimensions of the nozzle. First a small arc was made of the length calculated by finding
the circumference of the inlet of the nozzle and the calculated circumference was
about 19.8 centimeters. After that, a second arc was drawn about 15 centimeters
ahead of the first one as the nozzle should have a length of 15 centimeters. This
second arc was bigger than the first arc as the outlet diameter of the nozzle was 10
centimeters. The calculated circumference of the outlet diameter was about 62.8
centimeters and this was how the length of the second arc was determined. Once both
the arcs were made with the help of compass the two arcs were joined together at
both the ends just with the marker. The purpose of joining the two ends is simple as
the group would easily follow the line which needs to be cut from the sheet in order to
make a nozzle.
Figure 35- Compass for making arc
for nozzle

The sheet was cut using the same circular blade cutting machine and the cutting was
done on the lines which were previously drawn by the group. After cutting the sheet,
the piece which was going to be used for making nozzle was placed on a circular bar
which was previously welded to the steel table for making the combustion chamber
cone. Once the sheet was placed on a round bar in exactly the middle, force was
applied by hand to bend it as much as possible. After bending it slight, rubber mallet
was used to deform it even further in order to fabricate it into a circular shape. There
was a technique which was used while hammering the sheet to bend it using the
rubber mallet. After hammering a certain point for some time, the position of the
stainless steel piece must be changed and a new point of the sheet should be
hammered and vice versa. The action of hammering should be such that after
hammering a certain spot for a specific time the sheet should be rotated in order to
ensure it forms a proper smooth circle from all directions. It took about 2 and a half
hour to completely fabricate it into the nozzle shape and then the next part was the
welding of the corners to join the sheet and form it into a circular nozzle shape.
Figure 36- Cutting sheet
Figure 37- Bending of sheet

The welding of the nozzle was done also using TIG welding as this was the best
welding available considering our project application. The welding was applied
throughout the length of the nozzle to ensure each and every single point of the nozzle
end is sealed properly and there are no leaks. It was noticed by the group that the inlet
diameter surface and the outlet diameter surface of the nozzle were not smooth as a
circular blade cutting machine was used to cut this stainless steel piece from the
stainless steel sheet. To overcome this problem, both the surfaces were filed slightly
by using the same circular blade cutting machine but this time instead of the blade a
round filer was used which will not cut the surface but only file it and hence the surfaces
turned out to be smoother.
The nozzle was all ready and set to be joined to the tailpipe of the valveless pulsejet
engine. For joining the nozzle to the exhaust pipe, the inlet of the nozzle which had
the smaller diameter was placed on the end of the exhaust pipe. TIG welding was
applied on the joints to permanently weld the two parts together. Welding was applied
slowly all around the joints to make sure all the areas are welded and there are no
leaks.
Figure 38- Welding of nozzle with the exhaust
Once the welding was allowed to cool the engine was taken for the polishing to give
good stainless steel appearance. Initially all parts of the engine were filed using the
round filers, the purpose of fling the whole engine was to eliminate the marks and

stains which were present on the body of all parts as they were subjected to mallet
hammering and TIG welding. The technique used for filing was to slowly move the filer
in circular motion as it is rotated by the machine and apply these steps to all the areas
which needs good finishing. This filer rubbed off the stains and black spots due to
welding and also gave the engine a stainless steel type of finishing. To further improve
the appearance of the engine body it was subjected to polishing machine which had
polishing rollers rotating at certain rpm. The technique used was to hold the area which
needs good polishing next to the polishing brushes and as the brushes rotates it cleans
off the surface and gives it a good finish. Further, a clay type of material was used to
give brushes a good finishing capability. Before using the brushes of polishing
machine, this clay was subjected to rotating brushes and as brushes rotate they are
coated with this material which enables the brushes to give stainless steel materials a
good and clean finish.
Figure 39- Polishing of Cone

Figure 40- Polishing of combustion chamber
After the nozzle construction was completed along with the polishing, the group
noticed that there was some excessive area present which was basically the edge of
the tail pipe. The reason for the presence of that excessive area was because the
stainless steel thickness used for the construction of tailpipe was not the same as the
stainless steel used for the construction of nozzle. The thickness of material for the
tailpipe was about 1.5 millimeters but since the sheet was used for the construction of
nozzle the thickness of nozzle material was 1.2 millimeters. This difference in the
thickness created an excessive edge on the inside of the nozzle which might create
some turbulence and can be the reason if the engine fails to operate. To counteract
this issue, a round filer was used to file off that excessive edge and to make it smoother
to prevent the formation of turbulence.
Spark plug attachment
As previously mentioned above, to attach the spark plug at the bottom section of the
combustion chamber a hole was made in the middle of the bottom of the engine using
a drill bit of 11 millimeters. There were numerous options available to configure the
spark plug attachment but the idea chosen was really simple. To make a hole of
appropriate diameter and then use the speak plug thread screw to make a thread in
the hole which will enable us to screw the spark plug as the threads are same and
then tight it using a spanner. The tightening of the spark plug should be done carefully
as if it’s exceeded then the spark plug will just slip and it will not tightly fix until a new
thread is made.

The technique used while making a spark plug thread was to use a thread screw of
size M14 x 1.25 and then fixing this screw tightly in the rotating screw handle. This
screw was placed on the 11 millimeters hole and the handle was rotated continuously
until the threads are made. The important point to make sure it’s properly done is that
one should apply force simultaneously as the handle is being rotated to make a spark
plug thread. Once the thread was made, to see if the spark plug will smoothly fit into
the threads and get tight it was tested and the results were positive.

Pulsejet Engine Stand
This was the last phase of construction and constructing it was very important as
without the stand it’s impossible to test the engine. The valveless pulsejet engine
which the group is working on is supposed to produce about 12 Lb.’s of thrust and this
is why it is mandatory to construct a stand which can hold it tightly. The design of the
stand which the group decided on consisted
of the mild steel material. The reason for this
selection of material is that this material is
very light and also it can bear and resist heat
which might be radiated from the pulsejet
engine while it is operating. The design of
the stand is very simple and it doesn’t
require so much man power for the
construction of this stand.
The design decided by the group should have two big A’s which are connected to each
other by a single rod. There will be two clamps which are supposed to be attached to
the top of two A’s and it is these clamps which will hold
the engine in its place tightly as the clamps should be
able to be screwed. The more tightly it is screwed the
more tightly it will hold the engine. The construction of
the stand was started by taking one long squared mild
steel rod which was hollow from inside and cutting it to
certain lengths which will form in a shape. The
dimensions of the stand will depend on the height
which the group wants. After some discussions the height was decided to be around
50 centimeters above the ground. The length of the stand which also means the gap
between one clamp and the other will also depend on the length of the engine as one
clamp is meant for holding the combustion chamber while the other clamp will hold the
exhaust pipe of the engine. To make this height possible a mild steel rod was cut using
the circular blade cutting machine into two rods of 60 centimeters each and then for
the second A the same step was repeated and four rods of length of 60 centimeters
each were obtained. After that the group decided the angle of the A should be higher
Figure 41- Cutting of Mild steel
Figure 42- Shows the
arrangement of steel

as the pulsejet engine will vibrate vigorously so the stand needs to be as stable as
possible. Another rod was cut using the same circular blade cutting machine and two
rods of length 44 centimeters each were obtained. When the rods were placed
together the shape looked like the one shown in the picture below:
Figure 43- Arrangement of steel
This A shape which is shown above in the picture was then welded together using a
normal weld. The welds were applied on the top of two sticks which will permanently
join them together and then the center stick which is of length 44 centimeters is joined
with the two side sticks with the normal weld. After two similar A’s were obtained then
they were joined together using with the single log rod which will completely hold them
together. After the welds the two A’s were attached to each other so the next step was
to apply clamps on the top of two A’s.
The clamps were purchased from ordinary hardware shop and one clamp had a bigger
diameter as it was supposed to house the combustion chamber. The second clamp
was for housing the exhaust pipe and it has a much smaller diameter than the first
clamp. The bigger clamp was first welded to the top of one of the A’s and the reason
for this welding was to make it attached properly and permanently to the A. Both the
clamps were made of mild steel and the reason for using the mild steel clamps is
because they are not supposed to meld when they are exposed to extremely high
temperatures specially the bigger clamp which will be used to hold the combustion
chamber.

Figure 44- General look of stand
The picture above shows the general shape of the pulsejet engine stand with one of
the clamp already attached and the clamp attached was the combustion chamber
clamp. Once the joining of combustion chamber clamp was completed the next stage
of stand construction consisted of the welding of the exhaust clamp. The group noticed
one major mistake which was about to be occurred while the construction of the clamp.
Group realized that the diameter of the combustion chamber is 11 centimeters
whereas the outer diameter of exhaust pipe was around 6.6 centimeters. The height
of both the A’s is exactly same and if the two clamps are attached on both the A’s, the
height of both the clamps will be same as well. This is a big mistake as the diameter
of the two engine parts vary so it was suggested by the group that the clamp for
exhaust pipe should be a little higher in order to make sure the engine is linearly
straight. The counteract this problem a small piece of the mild steel was taken and
attached to the top of other A where the clamp for exhaust pipe was supposed to be
attached. The welded was done between that small piece and the top of the A to make
it permanently attached. The picture below shows how the part looked like after
attachment of the small mild steel piece for the purpose of increasing the height.

Figure 45- Attached piece
Once the clamps were complete the next part was to attach the wheel or bearings
which would make the stand move due to the thrust when the valveless pulsejet engine
is operating. There was a big confusion in the group whether the wheels or large
bearing should be used for the purpose of moving the stand. It was discussed that if
the wheels are used there would be some little friction present inside which would
make it move less easily but if the bearing are used the friction would be minimum so
the stand would move more easily when the engine is operating. Another point which
was raised in the group was that if wheels are used the grip between the wheels and
the floor would be much more as there is rubber or sponge present on all wheels but
it was decided that it does not matter if there is rubber present or not the main aim is
the least friction and hence bearings were used. Four bearing were purchased and
two of them will attach under each A and apart from bearings four screws of 10
millimeters size and nuts were also purchased to attach the bearings.
The next problem faced was how to figure out the attachment of the bearing under the
stand. The technique used for the attachment of bearing was that to make a small
minute cut on the bottom and outer side of the mild steel rod. The cut was made using
the small circular blade cutting machine and the cut was made on all four side sticks.
After making a cut the spot was hammered using the mallet to make it straight. The

next part was to take small mild steel plates and drill a hole of 11 millimeters in all of
the small mild steel plates. As each side stick will accommodate two of such plates in
total there were eight of them which were drilled and welded to the bottom section of
all four side sticks of both A’s. The next part was very simple as it required just the
placement of bearings in between those plates and passage of screws through the
plates and bearings all together and then tightening of those screws with the nuts that
were purchased earlier along with the screws and bearings.
.
Figure 46- Drilled holes in steel plate

TESTING AND TROUBLESHOOTING
SAFETY PRECAUTIONS
All of these testing required the adoption of safety measures as they were a need to
comply with safety rules. The safety precautions included:
 The use of safety equipment to avoid hazards while testing. The safety
precautions included:
1. The use of safety clothes to protect the operators from being exposed to the
fire or the high running temperature of the engine.
2. The use of gloves to avoid direct contact with the engine.
3. The use of eye protection to protect the eyes from fire.
4. Ear protection to cancel the emitted noise.
 The establishment of a safety distance between the engine and its surroundings
(cars, flammable objects).
 The fuel transmission line being out of the line of the exhaust to avoid hazard
related to uncontrolled ignition.
TESTING PROCEDURES
Fuel Line Connection
 The LPG connection from the cylinder to the engine was made with safety and
performance of the engine in mind.
 Initially, the gas tank is fixed with a variable pressure regulator which can release
pressure up to 2 bar. This regulator was important because, in order to achieve
optimum fuel to air ratio the pressure of the gas should be adjustable and might
need high pressure to start the engine.
 From the regulator, a rubber hose of five meters is connected to a non-return valve.
The rubber hose was made long because, the gas tank should be placed away
from engine in order to avoid fire hazard. The non-return valve, ensures the flaming
gas from retuning back to the gas tank causing a fire accident.
 The non-return valve is mounted on a T – connector. Since there are two intakes,
the T- connector evenly divides the gas into two fuel lines. The fuel pipes are bent
in L-shape and made of Stainless Steel material.
 To fix the fuel arrangement to the engine a clamp was used. This simple effective
method was chosen in order to experiment with the correct position of the fuel pipe

to the intake. This placement is very important because a small change in airflow
could affect the performance of the engine in a tremendous way.
 All the connections made, were reinforced with bolts and hose clamps as an added
protection.
Ignition System
 The ignition system of the engine consists of a power box containing the battery
source and switch. The ignition system has a fail-safe system in which, a cover is
placed on the switch.
 First the cover should be opened, in order to turn on the ignition system. It has two
wires black and red. The red coloured wire is positive and must be connected
directly to the spark plug.
 The black coloured wire is negative and it should be connected to the stand. Once
the switched is turned on, the spark plug starts to produce sparks.
Engine starting
 The ignition system should be turned on. Using an air blower or compressor, air
should be started to blow into the intake, simultaneously gradually increasing the
gas.
 Many pops and booms will be heard. In order for the engine to start the air blower
should be moved in different angles to get the exact pressure required. Once the
engines start makes roaring noise, increase the level of fuel and try to remove the
external air.
Engine stopping
 To stop the engine, put the ignition off.
 Turn off the gas.
 Wait for at least 10 minutes before getting in contact with the engine as it is still hot
within this period.
 Disconnect the testing equipment.
TESTING RESULTS AND IMPROVEMENTS
The design of a valveless pulsejet engine required a lot of testing. Each one of these
testing provided relevant information about the parameters to take into account for the
upcoming testing. A series of testing has therefore been made during the project. A

single testing has many test phases. The details about theses testing are developed
below rather than the different phases of every single part of the tests.
TEST 1
Figure 47 Testing with twin intakes
Testing location: University parking area
The engine was prepared for testing as planned after applying all the required safety
measures. Unfortunately, the engine faced some problems as it failed to start. The air
and fuel might not be getting mixed in the combustion chamber as there were no sign
of heat effect.
Result: the testing was unsuccessful.
Possible reasons of failure
The spark plug could not ignite the LPG gas because it might have been damaged.
The intake pipe might not be reaching the point at which it could effectively send
sufficient air into the combustion chamber in the direction of the spark plug.
Improvements
Since the intake pipe might not provide the required amount of air to burn the LPG
gas because of its small size, one of the intake ports can be freed to provide more
space for air to get into the combustion chamber.
The fuel pipe can be made straight for the next testing as it was not effectively
ignited. Making the fuel pipe straight would add the pipe length in the horizontal
axis, allowing the fuel pipe to get closer to the spark plug.

As there was a doubt about the spark plug condition, the next testing can be
experimented with a new spark plug.
TEST 2
Figure 48 Testing with new spark plug
Testing Location: University parking area.
The engine was prepared for testing according to the preliminary safety requirements.
There was no fire taking place in the combustion chamber. A piece of tissue was
externally ignited and sent into the combustion chamber through the exhaust. This
action gave a single louder detonation every time successive testing were conducted.
The detonation caused the tissue to get propelled out of the engine through the nozzle
at high speed after the “boom” every time the testing was conducted. The change of
spark plug did not have any effect on the operation as the testing almost gave the
same result as the precedent testing. Therefore, the issue is not about the spark plug.
Result: the testing was unsuccessful. However, a single “boom “occurred.
There might not be sufficient air to ensure proper combustion inside the combustion
chamber. This might be due to the rich mixture produced by a very little amount of air
available for a high amount of fuel. The proper mixture of fuel and air in the combustion
chamber should take place in order for the engine to operate and provide the required
thrust.

Improvements
Modify the converging cone of the combustion chamber.
Addition of an external compressed air.
The cancellation of a fuel transmitted pipe line to avoid the rich mixture.
The intake could be subjected to modification).
Usage of a lift blower.
TEST 3
After a series of testing as the engine did not work, the converging cone of the
combustion chamber to the exhaust pipe chamber has been increased from 5cm to
10 cm.
The 2D AutoCAD drawing of the modification made to the intakes is as follow:
Figure 49 Combustion Chamber Cone Increased to 10cm.
After applying all the necessary precautions, the engine was completely prepared for
testing according to the plan. A fuel pipe line was cancelled as conducted in the
precedent testing. The available spark plugs were individually tested for the best
selection. The most efficient spark plug was chosen for usage. The result was much
better as the engine made 3 to 5 “booms” at different interval of time.
Result: the testing was unsuccessful. However, a series of “booms “occurred.

The amount of compressed air might be very small. The air exiting from the exhaust
was manually checked and found to be not enough as only very less air could be felt
on hand. The engine might therefore need more compressed air.
Improvements
Increase the supply of compressed air.
Use a twin spark plug mechanism to drive the engine. A parallel connection could
be made for the ignition system to drive both spark plug.
The possibility of using fire crackers to force the combustion.
The predicted parallel connection which was though to function was not possible.
The ignition system and the spark plug couldn’t work at the same time.
The air being sent has only 21% of oxygen. With only 21% of oxygen available for
combustion in the small amount of air being sent, no burning could take.
TEST 4
After observing all the required safety measures, the engine was prepared for testing
as planned. The testing was conducting using a single fuel pipe.
Figure 50 Dual spark plug

Result: the testing did not take place.
Improvements
 As the testing did not take place, further researches could be made toward the
intake of the engine. Increasing the intake will allow lore air to be available for
combustion.
 The location of the intakes could be modified to get them closer to the spark
plug as the air might be getting disturbed during suction. The intake could be
placed at the top.
TEST 5
After the 4th testing, it was obvious that the engine could not be tested using a twin
spark plug. The actions taken was to change another variable. The relocation of the
intakes was undertaken for the 5th testing.
The 2D engineering drawing of the modification is as follow:
Figure 51 Relocation of intake tubes
precautions. Before carrying out the 5th testing, some amendments have been made
to the valveless pulsejet engine based on the following researches:
The ratio of the intake diameter to the exhaust diameter should be same as existing
design. This was a design error that needs to be corrected. From statistical
analysis,
d
D
= 80~85%

Now the exhaust diameter is increased to reach 2.5 cm (1 inch) to supply enough air.
The intakes location of the engine was shifted to the top of the combustion chamber
to effectively make the air available for combustion.
Figure 52 Testing with the new intakes
Results: the testing was unsuccessful but there were some improvements during the
test. The engine made some signs of working evidence. The series of “booms
“occurred more often than before. A loud “boom” sounded after the 1st trial and then 3
more successive bangs were produced. Also, the engine partially operates without the
addition of fire crackers during some phases of the testing for about a minute, then
stopped. The pulsejet worked a little better than that the previous tests. The
combustion chamber became very hot and the colour showed some burning evidence.
The flames that were produced were bigger and lasted for more time compared to that
in the previous tests.
The proper mixture of air and fuel is not reached.
The LPG gas efficiency might affect the engine operation.
Improvements: the engine run for a short amount of time. In order the the engine to
run continuously during operations, further actions were planned to be applied.
The addition of more compressed air.
Testing with single intake
Give more testing time as it was found through researched that the continuous
combustion occurs only at a certain burning temperature.

The consideration of the possibility of a vertical testing.
TEST 6
Figure 53 Testing with single intake
The engine was prepared for testing according to the preliminary safety requirements.
A single intake was used for the testing to check the progress.
Also, air was later applied through both intakes. A compressed air was used to supply
air through one of the intake and a leaf blower was used to supply air through the other
intake.
Results: the testing was same as the precedent. The addition of an external
compressed air did not make any difference as the air supplied by the compressed air
is very small.
The engine might need very high compressed air to operate.
The combustion chamber might be bigger. This is may be preventing the engine
from producing continuous thrust.
Improvements: Use a very big compressed air for the next testing.

TEST 7
Testing location: Dubai fire station
The testing location was changed to fire station. The reasons for testing at the fire
station was because of a need of more compressed air. As the engine was not
continuously producing thrust, it was thought to be caused by the less amount of air
made available to the engine.
precautions. As the engine was not continuously producing thrust, the problem was
thought to be about the fuel. This time testing location was changed to a place where
high compressed air is available.
Figure 54 Testing with very high compressed air
Result: The testing was done with high compressed air but the engine reacted as in
5th and 6th testing. This means the problem is not about the amount of air but about
the design.
Possible reason of failure: the problem is not about the air but the design
Improvements: Make a new design by:
Either modifying the combustion chamber design and make it smaller
Or change the exhaust pipe and make it smaller

The 1st option is the most feasible option as it has many advantages. It is easy to
realize and has less time consumption.
TEST 8
After applying all the necessary precautions, the engine was completely prepared for
testing according to the plan. This time the volume of the combustion chamber has
been reduced for testing as suggested by the project supervisor. The plan was agreed
by the group members for establishment.
Result: the engine did not start. It made the same signs as the first three testing.
Possible reasons of failure:
The problem might be about the air/LPG mixture ratio.
LPG might be far less efficient that propane gas.
Improvements: to make the engine continuously run:
Change the design to a single intake design. As the problem is not a matter of air,
one of the intake can be eliminated to avoid the gas from exiting from the other end
when air and fuel are being sent through one of the end.
Change the LPG to propane gas in case the new design does not work.
TEST 9
After the 8th testing, it has been concluded that the engine failure to start was not
relating the spark plug, the ignition, the supplied compressed air and the intake. The
solution was to make a new design of a valveless pulsejet engine.
The AutoCAD drawing of the new engine design is as follow:

Figure 55 New Engine Design
precautions.
As the engine is now designed with a single intake. This is to avoid the escape of gas
through the other intake when one of the intake is being supplied. LPG and air are
now sent through a single intake.
Result: the testing was successful.
Figure 56 Operating engine
It took less time than the previous time for the engine to start. After the ignition was
engaged, the LPG and air were sent. It just required 30 seconds for the engine to
sustain and continuously run. The lift blower that was supplying the air was no longer

required as the engine started to run. The ignition system was then put off and the
engine was effectively working as expected. The engine was then left running for 15
minutes and then operated without stopping. The engine operating temperature was
estimated to be 1000℃.
The engine was then stopped as the testing was shown to be successful.
Frequency for New Design
𝑓𝑚𝑎𝑥 = 190𝐻𝑧, calculated from online calculator (pulsejet calculator, appendix
section E)
𝑓 =
√ 𝛾𝑅𝑇
4𝐿
𝑓2
=
𝛾𝑅𝑇
16𝐿2
𝑇 =
16𝑓2
𝐿2
𝛾𝑅
𝑇 =
16 ∗ 1902
∗ 0.732
1.4 ∗ 287
= 766 𝐾 = 493 𝑑𝑒𝑔𝑟𝑒𝑒 𝑐𝑒𝑙𝑠𝑖𝑢𝑠
CHALLENGES FACED
The theories and calculations required during the designing phase of the project
could not be found easily. The reason is, pulsejets are mainly utilized by hobbyists.
This is a competitive field in which most of the hobbyists hide the calculations
designs as a secret.
The materials required for manufacturing the pulsejet was not available in small
required lengths. Since stainless steel was sold in six meter pipes, it was hard to
locate a possible seller.
The bolt required for the spark plug, to attach to the combustion chamber could not
be found at any retail shops.
The fuel pipes with a diameter of 0.7 cm was not available in most of shops. After
checking in almost 30 shops, it was found in a pipe company.
Lack of knowledge and experience in machinery, limited the opportunity to work
on the manufacturing process in order to finish the project swiftly. This was a
problem because the workshop was had many big projects, which made them
delay.

One of the main challenges faced were during the trouble-shooting phase. During
testing, the reason for non-operation of engine could not be determined because
of many variables and a single problem could not be pointed.
Since the engine did not start, loads of time was wasted in determining the problem
and make the appropriate changes.
Twin spark plug was employed to make sure the gases combust, but both the spark
plugs did not work simultaneously with one source even though it was wired in
parallel.
An official letter was required from the university to the civil defense station in order
to test in their vicinity. This not approved by the university that delayed the testing
phase by two weeks.
Since approval for testing was not given for civil defense station, it had to be done
in university every time. This did not give the flexibility to test whenever possible.
Commuting from university to workshops and hardware shops were a major issue
during the final stages of the project due to lack of transportation.
The initial fuel chosen to be used in this project was propane, but due to the high
cost, LPG (which contains 70% of propane) was used.
High pressure compressor was required to start the engine, even though the
university was equipped with one, it could be utilized because of lack of extension
cables for the compressed air.
While testing the engine with high pressure compressor from the civil defense
station, it was held by hand facing the intake. The engine started ad moved for two
seconds and flamed out. This is because when the engine suddenly moves,
compressed air is still supplied to the previous position of the engine. Therefore,
no supply in air makes the engine hard to self-sustain.

RECOMMENDATIONS
The use of flare that is leaving the end of the exhaust pipe facing outward can
make a significant difference between working and non-working engine.
The size of the combustion chamber cone should be equal or more than the length
of combustion chamber in order for the flow to be non-turbulent.
Intake pipe diameter should always between 60% - 80% of the exhaust pipe
diameter.
Varying pressure of air is required to start an engine, in order to determine the right
amount of air to fuel ratio in a practical way.
The engine combustion chamber, is over flooded if high amount of gas is supplied
in the start. Thus, to start the engine minimum throttle should be given and can be
gradually increased.
The smaller the fuel pipe is, the more convenient it is for the fuel to mix with outside
air. This mixture can equal to one part of fuel, for five parts of air.
The fuel pipe should be placed in the middle of the intake tube. This enables the
fuel to mix with enough air from the atmosphere.
Fire crackers can be used as a substitute for spark plug because at times the spark
plug does not perform efficiently under certain conditions.
The material used in this engine was SS 316 which is of very high quality. This
material when welded with TIG welding would give a good result.
The exhaust pipe should be along the direction of wind, this is because when
external air enters through the exhaust it could cause turbulence and eventually
flame out the engine.
It is always recommended to flush the engine with air after a test, to make sure any
residual gas has been removed from the engine.

APPLICATIONS
The weight, performance and reliability of pulsejet engines are limitations for their
applications. However, they are advanced researches being done toward the
development of pulsejet engines that have the advantages of turbojet engines for
applications. Pulsejet engines could be used for Unmanned Aerial Vehicles (UAVs) and
Remotely Piloted Vehicles (RPVs).
X-Jet
An example of valveless pulsejet engine developed for UAV application is the X-Jet.
Figure 57 X-Jet application for pulsejet
The X-Jet engine is one of the most advanced application of pulsejet. It is a valveless
pulsejet engine that almost has performances similar to a turbojet engine (Anon,
2003). Added to these advantages, it also combines the advantages of a basic
valveless pulsejet engine that are: no moving parts, low cost, low maintenance and
high durability.
The X-Jet engine is one of the most efficient application of pulsejet engines.
Dubai Civil Defence
Dubai firefighters have employed around 20 jetpacks. This was ordered from Martin
Aircraft Company which is a leading company in manufacturing drones. In this
prototype, pulsejet is used as one of the thrust vector.

They are also researches being conducted toward the development of Pulse
Detonation Engines (PDEs) using pulsejet engines for application in supersonic
flight.
Pulsejets engines can be used in universities for the study of powerful engines at
both undergraduate and postgraduate levels
Figure 58 Dubai jetpacks for Civil Defence,
Gulf Elite 2016

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