This document provides information about 3D printing technology and the design of a turbojet engine. It begins with introductions to 3D printing, describing how 3D printers work by building objects layer by layer from a digital file. It then discusses the author's project, which involves using 3D modeling software to design and develop a prototype turbojet engine. The rest of the document details the components and design of a turbojet engine, including the fan, compressor, combustor, turbine and nozzle. It also discusses parameters and the Brayton cycle that models the thermodynamics of a gas turbine. The author aims to use 3D printing to produce a prototype turbojet engine.

1. Industry oriented mini project on
3d printing technology and design
of turbojet engine
BY LALITH TUSHAR MITRA.S
17311A0349
SNIST, MECHANICAL DEPARTMENT
GUIDE: KOSURI SUBRAMANIAM SIR

2. Introduction
What is 3D Printing?
 3D printing or additive manufacturing is a process of making three
dimensional solid objects from a digital file.
 The creation of a 3D printed object is achieved using additive processes.
In an additive process an object is created by laying down successive
layers of material until the object is created. Each of these layers can be
seen as a thinly sliced cross-section of the object.
 3D printing is the opposite of subtractive manufacturing which is cutting
out / hollowing out a piece of metal or plastic with for instance a milling
machine.
 3D printing enables you to produce complex shapes using less material
than traditional manufacturing methods.
 In the 1980s, 3D printing techniques were considered suitable only to
produce functional or aesthetic prototypes, and a more appropriate term
for it at the time was rapid prototyping. As of 2019, the precision,
repeatability, and material range of 3D printing have increased to the
point that some 3D printing processes are considered viable as an
industrial-production technology, whereby the term additive
manufacturing can be used synonymously with 3D printing.
 Additive manufacturing (AM) or additive layer manufacturing (ALM) is the
industrial production name for 3D printing, a computer-controlled process
that creates three dimensional objects by depositing materials, usually in
layers.

3. How Do 3D Printer's work?
3d printing is a part of additive manufacturing family and uses similar
methods and traditions to a typical inkjet printer albeit in 3D. It takes a
combination of top-of-the-line software, powder like materials and precision
tools to create a three-dimensional object starting from the scratch.

4. How does 3D printing work?
It all starts with a 3D model. You can opt to create one from the ground up or
download it from a 3D library.
3D Software:
The first step of any 3D printing process is 3D modeling. To maximize
precision (and because 3D printers can’t magically guess what you want to
print), all objects must be designed in a 3D modeling software. Some designs
are too intricate and detailed for traditional manufacturing methods. That’s
where this CAD software comes in. Modeling allows printers to customize
their product down to the tiniest detail. The 3D modeling software’s ability to
allow for precision designs is why 3D printing is being hailed as a true game
changer in many industries. This modeling software is especially important to
an industry, like dentistry, where labs are using three-dimensional software to
design teeth aligners that precisely fit to the individual. It’s also vital to the
space industry, where they use the software to design some of the most
intricate parts of a Rocketship.
Slicing the Model:
Once a model is created, it’s time to “slice” it. Since 3D printers cannot
conceptualize the concept of three dimensions, like humans, engineers need to
slice the model into layers for the printer to create the final product. Slicing
software takes scans of each layer of a model and will tell the printer how to
move in order to recreate that layer. Slicers also tell 3D printers where to
“fill” a model. This fill gives a 3D printed object internal lattices and columns
that help shape and strengthen the object. Once the model is sliced, it’s sent
off to the 3D printer for the actual printing process.

5. The 3D Printing Process
When the modeling and slicing of a 3D object is completed, it’s time for the
3D printer to finally take over. The printer acts generally the same as a
traditional inkjet printer in the direct 3D printing process, where a nozzle
moves back-and-forth while dispensing a wax or plastic-like polymer layer-
by-layer, waiting for that layer to dry, then adding the next level. It
essentially adds hundreds or thousands of 2D prints on top of one another to
make a three-dimensional object. There are a variety of different materials
that a printer uses in order to recreate an object to the best of its abilities.
Here are some examples:
Acrylonitrile butadiene styrene (ABS): Plastic material that is easy to shape
and tough to break. The same material that LEGOs are made from.
Carbon Fiber Filaments: Carbon fiber is used to create objects that need to
be strong, but also extremely lightweight.
Conductive Filaments: These printable materials are still in the
experimental stage and can be used for printing the electrical circuits
without the need for the wires. This is a useful material for wearable
material.
Flexible Filaments: Flexible filaments produce prints that are bendable, yet
tough. These materials can be used to print anything from wrist watches to
phone covers.
Metal Filament: Metal filaments are made of finely ground metals and a
polymer glue. They can come in steel, brass, bronze and copper in order to
get the true look and feel of a metal object.

6. The 3D Printing Process
The 3D printing process takes anywhere from a few hours for simple prints,
like a box or a ball, to weeks for much larger detailed projects, like a full-
sized home.
There are also different types of 3D printing depending on the size, detail and
scope of a project. Each different type of printer will vary slightly on how an
object gets printed. Fused Deposition Modeling (FDM) is probably the most
widely-used form of 3D printing. It’s incredibly useful for manufacturing
prototypes and models with plastic. Stereolithography (SLA) Technology is a
fast-prototyping printing type that is best suited for printing in intricate
detail. The printer uses an ultraviolet laser to craft the objects within hours.
Digital Light Processing (DLP) is one of the oldest forms of 3D printing. DLP
uses lamps to produce prints at higher speeds than SLA printing because the
layers dry in seconds.

7. 3D Printing Examples
3D printing has permeated almost every single sector and has offered some
innovative solutions challenges all over the world. Here are a few cool
examples of how 3D printing is changing the future:
3D Printed Houses
Nonprofits and cities all over the world are turning to 3D printing to solve the
global homeless crisis. New Story, a nonprofit dedicated to creating better
living conditions, is printing homes right now. Using a 33-foot-long printer,
New Story can churn out a 500 square-foot home, complete with walls,
windows and two bedrooms in just 24 hours. So far, New Story has created
mini 3D-printed home neighborhoods in Mexico, Haiti, El Salvador and
Bolivia, with more than 2,000 homes being 100% printed.
3D Printed Organs and Prosthetic Limbs
In the near future, we’ll see 3D printers create working organs for those
waiting for transplants. Instead of the traditional organ donation process,
doctors and engineers are teaming up to develop the next wave of medical
technology that can create hearts, kidneys and livers from scratch. In this
process, organs are first 3D modeled using the exact specifications of the
recipient’s body, then a combination of living cells and polymer gel (better
known as bioink) are printed off layer-by-layer to create a living human
organ. This breakthrough technology could change the medical industry as
we know it and reduce the drastically-high number of patients on the organ
donation waitlist in the US.

8. What are the prerequisite questions do
you have to ask yourself before getting
into any 3D printing operation
 What Do You Want to Print?
 What Size Objects Do You Want to Print?
 What Materials Do You Want to Print With?
 How High of a Resolution Do You Need?
 Do You Want to Print in Multiple Colors?
 What Surface Should You Build On?
 Do You Need a Closed Frame if so what type of frame do you need?
 How Do You Want to Connect to the Printer?
 What Software Do You Need?
 So, Which 3D Printer Should I Buy?

9. TYPES OF PRINTERS THT CAN BE
USED FOR A 3D PRINTING
OPERATION
Choosing the right 3d printer is also an art, because the type of 3d printer you
choose decides the print and the kind of prototype you will be getting as an
output:
 Dremel DigiLab 3D45 3D Printer
 Form labs Form 2
 MakerBot Replicator+
 Original Prusa i3 MK3S
 Ultimaker S5 3D Printer
 LulzBot Mini 2
 Flash forge Finder 3D Printer

10. About my project
I have chosen to design and develop a prototype of a Turbojet in view of the
importance assumed by these turbojets in the modern-day developments of
the humankind. And I have chosen 3D modelling software Fusion 360 for its
commendable versatility as a designing software and utility for using in 3D
printing technology the latest development tool for manufacturing.
The turbojet is an airbreathing jet engine typically used in aircraft. It consists
of a gas turbine with a propelling nozzle. The gas turbine has an air inlet, a
compressor, a combustion chamber, and a turbine (that drives the
compressor). The compressed air from the compressor is heated by burning
fuel in the combustion chamber and then allowed to expand through the
turbine.

14. All about turbojet engine
The turbojet is an airbreathing jet engine, typically used in aircraft. It
consists of a gas turbine with a propelling nozzle. The gas turbine has an air
inlet, a compressor, a combustion chamber, and a turbine (that drives the
compressor). The compressed air from the compressor is heated by burning
fuel in the combustion chamber and then allowed to expand through the
turbine.
While the turbojet was the first form of gas turbine power plant for aviation,
it has largely been replaced in use by other developments of the original
concept. In operation, turbojets typically generate thrust by accelerating a
relatively small amount of air to very high supersonic speeds,
whereas turbofans accelerate a larger amount of air to
lower transonic speeds. Turbojets have been replaced in slower aircraft
by turboprops because they have better specific fuel consumption. At medium
to high speeds, where the propeller is no longer efficient, turboprops have
been replaced by turbofans. At these transonic speeds, the turbofan is quieter
and has better range-specific fuel consumption than the turbojet. Turbojets
can be highly efficient for supersonic aircraft.
Turbojets have poor efficiency at low vehicle speeds, which limits their
usefulness in vehicles other than aircraft. Turbojet engines have been used in
isolated cases to power vehicles other than aircraft, typically for attempts
on land speed records. Where vehicles are "turbine-powered", this is more
commonly by use of a turboshaft engine, a development of the gas turbine
engine where an additional turbine is used to drive a rotating output shaft.

15. Components of a turbojet engine
 Fan
The fan is the first component in a turbofan. The large spinning fan sucks in
large quantities of air. Most blades of the fan are made of titanium. It then
speeds this air up and splits it into two parts. One part continues through the
"core" or center of the engine, where it is acted upon by the other engine
components.
The second part "bypasses" the core of the engine. It goes through a duct that
surrounds the core to the back of the engine where it produces much of the
force that propels the airplane forward. This cooler air helps to quiet the
engine as well as adding thrust to the engine.
 Compressor
The compressor is the first component in the engine core. The compressor is
made up of fans with many blades and attached to a shaft. The compressor
squeezes the air that enters it into progressively smaller areas, resulting in an
increase in the air pressure. This results in an increase in the energy potential
of the air. The squashed air is forced into the combustion chamber.

16. Components of a turbojet engine
 Combustor
In the combustor the air is mixed with fuel and then ignited. There are as
many as 20 nozzles to spray fuel into the airstream. The mixture of air and
fuel catches fire. This provides a high temperature, high-energy airflow. The
fuel burns with the oxygen in the compressed air, producing hot expanding
gases. The inside of the combustor is often made of ceramic materials to
provide a heat-resistant chamber. The heat can reach 2700°.
 Turbine
The high-energy airflow coming out of the combustor goes into the turbine,
causing the turbine blades to rotate. The turbines are linked by a shaft to turn
the blades in the compressor and to spin the intake fan at the front. This
rotation takes some energy from the high-energy flow that is used to drive the
fan and the compressor. The gases produced in the combustion chamber move
through the turbine and spin its blades. The turbines of the jet spin around
thousands of times. They are fixed on shafts which have several sets of ball-
bearing in between them.
 Nozzle
The nozzle is the exhaust duct of the engine. This is the engine part which
produces the thrust for the plane. The energy depleted airflow that passed the
turbine, in addition to the colder air that bypassed the engine core, produces a
force when exiting the nozzle that acts to propel the engine, and therefore the
airplane, forward. The combination of the hot air and cold air are expelled
and produce an exhaust, which causes a forward thrust. The nozzle may be
preceded by a mixer, which combines the high temperature air coming from
the engine core with the lower temperature air that was bypassed in the fan.
The mixer helps to make the engine quieter.

17. Design of Turbojet Engine
 Overall efficiency of a jet propulsion engine:
𝜼𝒐𝒗𝒆𝒓𝒂𝒍𝒍 = 𝜼𝒕𝒉𝒆𝒓𝒎𝒂𝒍 * 𝜼𝒑𝒓𝒐𝒑𝒖𝒍𝒔𝒊𝒗𝒆
The thermal efficiency is defined as the ratio of the net power out of the
engine to the rate of thermal energy available from the fuel.
According to the T-s diagram of an ideal turbojet engine, the thermal
efficiency simplifies to:
𝜼𝒕𝒉𝒆𝒓𝒎𝒂𝒍 = 1-
𝑻𝟎
𝑻𝟑

18. Design of Turbojet Engine
The propulsive efficiency is defined as the ratio of the useful power output
(the product of thrust and flight velocity, 𝑽𝟎) to the total power output (rate of
change of the kinetic energy of gases through the engine). This simplifies to
𝜼𝒑𝒓𝒐𝒑𝒖𝒍𝒔𝒊𝒗𝒆 =
𝑭∗𝑽𝟎
𝑾𝒐𝒖𝒕
=
𝟐
𝑽𝒆
𝑽𝟎
+𝟏
𝑾𝒐𝒖𝒕 =Total power output
F =Thrust
𝑽𝟎 =Flight Velocity
𝑽𝒆 =Exit Velocity
𝒎𝒇 =Mass of fuel
𝒎𝒂 =Mass of air, 𝑷𝒔 = Shaft power
Fuel air ratio,
f =
𝒎𝒇
𝒎𝒂
Thrust specific fuel consumption,
TSFC =
𝒎𝒇
𝑭
=
𝒎𝒇
𝒎𝒂[ 𝟏+𝒇 𝒖𝒆−𝒖]
Brake specific fuel consumption,
BSFC =
𝒎𝒇
𝑷𝒔

19. Design of Turbojet Engine
PARAMETRS VALUE
Mach number 3.0
Altitude (km) 21.0
Bypass ratio 0.7
Fan pressure ratio 1.30
Fan efficiency 0.84
Compressor efficiency 0.84
Compressor pressure ratio 3.10
Cooling air ratio 0.24
Turbine inlet temperature (k) 2000
Burner efficiency 0.995
Burner total pressure lost coefficient 0.06
High pressure turbine efficiency 0.85
Low pressure turbine efficiency 0.88
Bypass total pressure loss coefficient 0.04

20. The Brayton Cycle
 The Brayton cycle depicts the air-standard model of a gas turbine power
cycle. A simple gas turbine engine is comprised of three main
components: a compressor, a combustor, and a turbine. According to the
principle of the Brayton cycle, air is compressed in the turbine
compressor. The air is then mixed with fuel and burned under constant
pressure conditions in the combustor.
 The resulting hot gas is allowed to expand through a turbine to perform
work. Most of the work produced in the turbine is used to run the
compressor and the rest is available to run auxiliary equipment and
produce power.
 The gas turbine is used in a wide range of applications. Common uses
include stationary power generation plants (electric utilities) and mobile
power generation engines (ships and aircraft).
 In power plant applications, the power output of the turbine is used to
provide shaft power to drive a generator, a helicopter rotor, etc. A jet
engine powered aircraft is propelled by the reaction thrust of the exiting
gas stream. The turbine provides just enough power to drive the
compressor and produce the auxiliary power.
 The gas stream acquires more energy in the cycle than is needed to drive
the compressor. The remaining available energy is used to propel the
aircraft forward.

22. Dynamic analysis of industrial rotors
The Finite Element Method is commonly used in industry.
 1D-model (beam elements): the most used for pilot-studies.
 2D-model (plane or axisymmetric shell elements): practical interest for
projects.
 3D-model (volume elements): used for detailed analyses.

23. Dynamic analysis of industrial rotors
 Equations of motion
1) 𝑲𝒔 + 𝜴 ∗ 𝑪𝑨𝑺 + 𝑲𝒍 (𝜴)
2) Mq +C(𝛀)*q +K(𝛀)q + f (q,q,𝛀) = g(t)
3) 𝑪𝒔 + 𝛀𝑮 + 𝑪𝒍 (𝛀)
Where,
 𝑲𝒔 is Structural stiffness matrix
 𝛀 ∗ 𝑪𝑨𝑺 is Matrix of circulatory forces
 𝑲𝒍*𝛀 is stiffness matrix of localized elements
 M is the mass matrix
 F is the vector of non-linear forces
 G(t) is the vector of excitation forces
 𝑪𝒔 is the Structural damping matrix
 G*𝛀 is the gyroscopic matrix
 𝑪𝒍 (𝛀) is the damping matrix of localized elements

25. CURA
 Cura is an open-source slicing application for 3D printers. It was created
by David Bram who was later employed by Ultimaker, a 3D printer
manufacturing company, to maintain the software. Cura is available
under LGPLv3 license.
 Cura was initially released under the open source Affero General Public
License version 3, but on 28 September 2017 the license was changed
to LGPLv3. This change allowed for more integration with third-party
CAD applications.
Technical specifications:
 Ultimaker Cura works by slicing the user’s model file into layers and
generating a printer-specific g-code. Once finished, the g-code can be sent
to the printer for the manufacture of the physical object.
 The open-source software, compatible with most desktop 3D printers,
can work with files in the most common 3D formats such
as STL, OBJ, X3D, 3MF as well as image file formats such
as BMP, GIF, JPG, and PNG.
Plugins:
 Release 3.0 introduced plugin capability. Users can develop their own
plugins or use plugins commercially available. Plugins simplify workflow
for users by allowing them to quickly perform tasks like opening a file
from a menu or exporting a file from an application. Starting with
Release 4.0, users can rate plugins using a star system.
 Current plugins include SolidWorks, Siemens NX, HP 3D Scanning,
Make Printable, Autodesk Inventor.

27. G CODES
 What is a G-code?
G-code is a language that humans use to tell a machine how to do something.
With 3D printing, g-code contains commands to move parts within the
printer. G-code consists of G- and M-commands that have an assigned
movement or action.
The Ultimaker GitHub page has a list of these commands and their
corresponding movements. You create a g-code by slicing a file in Cura and
saving it. The saved file will be converted to g-code, the language the printer
understands and uses to create a 3D print.
How are G-codes built?
First and foremost, thing we do is to save the 3d cad model in .stl format.
Second thing we are doing is placing the saved .stl format model in the
Ultimaker Cura software machine. Then we edit and remodel the same 3d cad
model as per the need and once the editing and remodeling work is done, we
save this file in .gcode format where we get the g-codes automatically for the
operations we have performed in the Ultimaker Cura software.

29. What does each G-code mean?
 G00: Rapid Positioning
 G01: Linear Interpolation
 G02: Circular interpolation, clockwise
 G03: Circular interpolation, counterclockwise
 G04: Dwell
 G05: High-precision contour control (HPCC)
 G06: Non uniform rational B-spline (NURBS)
 G07: Imaginary axis designation
 G09: Exact stop check, non modal
 G17: XY plane selection
 G18: ZX plane selection
 G19: YZ plane selection
 G33: Constant pitch threading
 G34: Variable pitch threading
 G40: Tool radius compensation off
 G41: Tool radius compensation left
 G42: Tool radius compensation right
 G43: Tool height offset compensation negative
 G44: Tool height offset compensation positive

30. Pros and Cons of 3d printing technology
 Pros:
1) Flexible Design
2) Rapid Prototyping
3) Print on Demand
4) Strong and Lightweight Parts
5) Minimising Waste
6) Cost Effective
7) Ease of Access
8) Environmentally Friendly
 Cons:
1) Limited Materials
2) Restricted Build Size
3) Large Volumes
4) Reduction in Manufacturing Jobs
5) Design Inaccuracies

31. Conclusions
 It is generally accepted that 3D printing will be a revolutionary force in
manufacturing, whether positive or negative. Despite concerns over
counterfeiting, many companies are already using the technology to
repeatably produce intricate components, for example in automotive and
aerospace manufacturing.
 As 3D printers become more affordable, they will inevitably be used for
local, small scale manufacturing, largely eliminating supply chains for
many types of product. Consumer units for home use will even become
feasible, allowing end users to simply download a design for the product
they require and print it out.
 There will be major challenges for the conventional manufacturing
industry to adapt to these changes. The opportunities for technology and
engineering are clearly huge, however, and the creative possibilities in
product design and printing material formulation are nearly endless.

32. REFERENCES
 "Ceramic 3D Printing: A Design Case Study" - Peter Walters, UWE
 "Integrated 3D-Printed Reactionware for Chemical Synthesis and
Analysis" - M.D. Symes et al, Nature Chemistry 2012.
DOi: 10.1038/nchem.1313
 "3D Printing in Color: Technical Evaluation and Creative Applications"
– P. Walters et al, Impact 6 International Printmaking Conference, 2009.
 "Could 3D Printing Change the World?" - Atlantic Council Strategic
Foresight Report
 "7 Things You Should Know About 3D Printing" - Educause
 https://www.sciencedirect.com/topics/engineering/campbell-diagram
 https://builtin.com/3d-printing
 https://www.diva-portal.org/smash/get/diva2:974874/FULLTEXT01.pdf
 https://aerospaceengineeringblog.com/jet-engine-
design/#:~:text=When%20optimising%20the%20jet%20engine,produce
%20a%20unit%20of%20thrust.
 http://www.ltas-
cm3.ulg.ac.be/AERO00231/ConceptionMecaTurbomachine.pdf
 https://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node8
5.html

33. THANK YOU AND
HAVE A NICE DAY