1. An Investigation into the Design & Operation of Pulse Jet Engines
Oliver Zaccaria [K1117763] Supervisor: Dr Adam Baker School of Aerospace & Aircraft Engineering
Introduction:
Pulse Jet Engines are one of the most basic types of internal combustion engines that rely on very few sources to operate.
These devices are commonly enjoyed by hobbyists because of their feasibility, simple manufacturing complexity and wide
range of parts and materials. Conventional designs consist of few or no moving components. Generally there are three
variants of system design; Valved, Valve-less and Chinese.
References:
Figure 1 – http://www.jetaerospace.org/Pulsejet/
Figure 2 – http://www.home.no/andreas.sunnhordvik/English/mechanical/valveless_e.htm
Figure 3 – http://www.cottrillcyclodyne.com/Focused_Wave/Photos/fwe_glowing_small.jpg
Figure 4 – http://upload.wikimedia.org/wikipedia/commons/thumb/2/2c/Puls1Motor_en.gif/350px-Puls1Motor_en.gif
Figure 5 – http://home.sandiego.edu/~ksievert-07/pic4.jpg
Figure 6 – http://farm2.staticflickr.com/1327/4602625785_acdc3e7012.jpg
Figure 7 & 8 – http://sobchak.wordpress.com/2008/11/25/american-helicopter-co-xh-26-jet-jeep/
Figure 1 - Valved System Figure 2 - Valve-less Design Figure 3 - Chinese System
Project Approach:
Before manufacturing could commence it was
paramount to perfect the attributes of the
design phase. Initially, in-depth background
research was conducted into Pulse Jet Engines
to identify requirements and issues. A Valved
Pulse Jet was selected because of the simple
construction, low cost, greater efficiency and
available accredited theoretical formulas.
Additionally, a Pulse Jet Sizing Calculator was
designed through the application of analytical
calculations. Once the System sizing was
complete, the CAD was produced on
SolidWorks. The manufacturing stage consisted
machining a customised combustion chamber,
convergent nozzle and tailpipe. Furthermore
this Pulse jet had a modular valve mechanism
that allows alternative valves to be
interchangeable.
Operation:
Although system set ups vary between designs, the operation for each system is the same. The
geometry of design of a system affects the systems operability. Any type of safe flammable gas can
be used to fuel the system. Common gases that are used include; Propane, Diesel and Gasoline.
First compressed air is forced through the inlet of a given system which is instantly mixed with fuel
and then ignited within the combustion chamber. Once the highly combustible mixture is ignited,
the gases begin to expand then rapidly heat up and the pressure suddenly increases. Under the
properties of physics; when a gas is under pressure it immediately escapes through the nearest
exhaust outlet. After the flow has left the combustion chamber it then flows through the taper
(also referred to as ‘The Cone’) which increases the speed of the flow, increases the pressure and
decreases the temperature. It then proceeds down the tail pipe and escapes into the atmosphere.
American Helicopter XH-26 – Jet Jeep
Prime User - United States Army.
Powerplants: XPJ49-AH-3 Pulse Jets x 2
Tactical Single Seat Helicopter.
Propelled by two jets; one per rotor blade.
Could be easily assembled with basic tools
within 20 minutes.
Future Work:
The next stage of the project will be to test the
internal combustion engine. Experimentation
entails; determining operability, efficiency, noise
and frequency. Experimentation will be
performed in the Kingston University Rocket Lab
Facility using the Rocket Test Chamber, providing a
safe testing environment.
Figure 4 - Operation of a Valved Pulse Jet
Shortcomings:
Pulse Jets can be
problematic with ignition
and difficult to maintain
constant smooth operation.
Extremely inefficient as they
consume fuel quickly.
Low thrust outputs.
Very loud.
Impractical as an additional
engine is required in order
to become airborne.
Testing
Manufacturing
Phase
Computer
Aided Design
(CAD)
Conceptual
Drawings
Initial Sizing
System
Selection
Historic Applications:
Iconically used to power the V1 Flying Bomb
(Doodlebug, Buzz bomb)
Prime User – Luftwaffe
Powerplant: Argus As 109
Designed by Georg Madelung & Paul Schmidt
Proposed to German Ministry of Defence
Was used by Nazi Germany to bomb Britain
during WWII.
Project Aims:
To conduct background research on
different areas of Pulse Jets.
To design a Pulse Jet Engine system
capable of producing 30N of thrust
and revise any current shortcomings.
1. The system must be safe
and portable.
2. To carry out the project
within the set time frame.
3. To not exceed the project
budget.
4. Capable of being tested at
Kingston University
To manufacture the Final Pulse Jet
Design
To test and record relevant data of
the final prototype.
Figure 5 – V1 Flying Bomb Figure 6 – Argus As 109 Figure 7 – XH-26 Figure 8 – Jet Jeep Assembly
Figure 9 – Process Chart of the Project
Figure 10 – CAD Design of Valved Pulse Jet (SolidWorks) Figure 11 – Final Pulse Jet Product