MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

S. D. M. College of Engineering and Technology Dharwad-580002

Department of Mechanical Engineering CERTIFICATE

This is to certify that mini project entitled MODELING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED is a bonafied work carried out by the student team Mr. Bharat Hegde, Mr. Sushanth Shetty, Mr. Karan Pavanje, Mr. Ananth Alur in partial fulfillment for the award of degree of B.E. in Mechanical Engineering of the S.D.M. College of Engineering and Technology, Dharwad under Visvesraya Technological University during the year 2011-12. The project report has been approved as it satisfies the academic requirement with respect to the project work prescribed for 6th semester course. 1. Ananth Alur 2sd09me018 2. Bharat Hedge 2sd09me028 3. Karan Pavanje 2sd09me048 4. Sushanth Shetty 2sd09me111

Guide (Prof. S.G. Bindgi)

H.O.D (Prof. V.K. Heblikar)

Name of Examiners 1. 2.

Signature with date

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

ABSTRACT
Every one of us get fascinated when we look at the jet plane. So we decided to build what it takes for a jet plane to fly. A JET ENGINE is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. We are building a working model of a jet engine and measuring the amount of thrust developed due to the discharge of a fast moving jet.

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

ACKNOWLEDGEMENT

The satisfaction and joy that accompanies the successful completion of this project would be incomplete and short-lived, without the mention of the people who made it possible.

We wish to express our sincere gratitude to the Principal Dr. S Mohan Kumar and to the Head of the Mechanical Engineering department Prof. V.K. Heblikar for granting the permission to carry out this project and for providing us the resources.

We express our indebtedness to our project guide Prof. S.G. Bindgi who helped us in every possible aspect for the successful completion of the project.

We express our sincere thanks to the staff of the department of ME for having helped us in the successful completion of the project. Lastly we express thanks to our beloved parents, friends and seniors who gave us the support and motivated us to emerge successful.

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

CONTENTS: 1. Introduction 2. Content of the project 3. Manufacturing details 4. Images 5. Drawings 6. Future modifications and conclusion References

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

Chapter 1:

INTRODUCTION
The principle of jet propulsion was demonstrated by Hero of Alexandria as long ago as the first century AD in the earliest 'steam engine' on record, but the jet engine did not become a practical possibility until 1930 when Frank Whittle, later Sir Frank Whittle, patented the design of his first reaction motor suitable for aircraft propulsion. The early jet engines were designed solely for aircraft propulsion. However, development was rapid and the range of applications has widened to include ships, hovercraft, power stations and industrial installations, all of which benefit from the jet engine's inherent qualities of high power, small size and low weight.

1.1 How does a jet engine work..?

The jet engine or, more correctly, the gas turbine is an internal combustion engine which produces power by the controlled burning of fuel. In both the gas turbine and the motor car engine, air is compressed, fuel is added and the mixture is ignited. The resulting hot gas expands rapidly and is used to produce the power.

In the motor car engine, the burning is intermittent and the expanding gas moves a piston and crank to produce rotary or shaft power which is transmitted to the road wheels. The turbojet engine consists of four sections: compressor, combustion chamber, turbine section, and exhaust. The compressor section passes inlet air at a high rate of speed to the combustion chamber. The combustion chamber contains the fuel inlet and igniter for combustion. The expanding air drives a turbine, which is connected by a shaft to the compressor, sustaining engine operation. The accelerated exhaust gases from the engine provide thrust. This is a basic application of compressing air, igniting the fuel-air mixture, producing power to self-sustain the engine operation, and exhaust for propulsion.

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

Chapter 2: CONTENT OF THE PROJECT/DISCUSSION/RESULTS

The project undertaken by us, a jet engine, which upon input of liquid petroleum gas as fuel along with compressed air from the blower produces thrust, we theoretically

calculate thrust by calculations and practically analyse it by spring balance attached working jet engine. The theoretical calculations are shown below:

2.1 THRUST CALCULATION

A jet engine provides thrust by accelerating a fluid. Newtons second law gives that force equals mass times acceleration (F = ma). Since acceleration is the derivative of velocity, force (ma) is the time derivative of the momentum (mv). The Material Derivative, which gives a rate of change that is time and location specific with a dummy variable =m

From the Material Derivative with steady state conditions,

F=

Control surface integration over input and output areas yields

.
The continuity equation of mass,

(in)=(out)

requires

thus the force required for the acceleration of air from u1 to u2 is,

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

where m = u1A is the mass flow rate through the control surface, u1 is the fluid velocity at the intake and u2 is the exit velocity of the fluid.

For maximum thrust the thrust equation must be differentiated with respect to inlet velocity and must be equated to zero

i.e.

Therefore, maximum force is obtained at u2 = 2u1. Power, force times velocity (F* u1), is maximized at

Therefore, maximum power occurs when u2 = 1.5u1 The propulsive efficiency of the engine is

Therefore, the maximum efficiency is at u1 = u2

2.2 CONCLUSION
From the derived thrust equation, it was found that, 1. If the force is to be maximized, the exit velocity relative to the vehicle must be twice the inlet velocity.

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

2. If the power is to be maximized, the exit velocity must be one and a half times the inlet velocity. 3. Maximum propulsive efficiency occurs when the inlet velocity is equal to the exit velocity.

The result of the maximum thrust, power and efficiency occurring at different points makes jet engine parameters and design dependent upon the expected function of the engine. The internal characteristics of the jet engine control the relationship between inlet and exit velocities. When the lowest cost is required such as in a commercial transport jet, the engine selected needs to have an exit velocity near the inlet velocity for maximum efficiency and lowest fuel burn cost. In comparison, a fighter jet needs to have an engine which is required to provide maximum power regardless of the loss in efficiency. Thus, jet engines must be selected with the operating functions and expected parameters known.

2.3 THRUST PRODUCED BY OUR JET ENGINE-THEORETICAL

Velocity at inlet = V= 15.8 m/s Velocity at exhaust = V = 33.036 m/s C/S area at inlet = A = 2.026x C/S area at exhaust = A = 1.266x Mass flow rate of air at inlet = m = VA = 1.226 x 15.8 x 2.026x = 0.0392 kg/sec. Mass flow rate of fuel (taking air to fuel ratio as 8:1) = Mass flow rate of fluid at exhaust = m = m + = 0.00490 kg/sec

= 0.0441 kg/sec.

Theoretical thrust produced F = m x V - m x V = (0.0392 + 0.00490) x 33.036 - 0.0392 x 15.8 = 0.837 kg F = 8.21 N

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

Chapter 3: MANUFACTURING DETAILS Table 3.1

Component details:
COMPONENT Spark plug Fuel injector Reduction Sleeve Mid joint Coupler Nipple cap Pipe U-PVC pipe Flexible pipes Flow valve T- joint Trolley 2 inch dia Miscellaneous Total cost = G.I Steel 1 1
165*1=165 200*1=200

DIMENSION inch X 3/8 inch 2 inch OD 2 inch ID 2 inch to 12mm ID 0.5 feet long, 2 inch OD 2 inch 1 inchX1 feet -

MATERIAL Brass G.I G.I G.I G.I PVC Plastic PVC

QTY 1 1 1 2 1 2 1 1 1 1

COST (in Rs) 60*1=60

90*1=60 40*1=60 55*2=110 115*1=115 90*2=180 110*1=110 48*1=48 30*1=30 90*1=90

regulating

500 Rs.1728

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

3.1 Combustion chamber:

The main core of the engine i.e. the combustion chamber should be perfectly designed because of the high pressure produced hence we chose to use standard pipe fittings which are more reliable than the chamber manually fabricated by us, which may have some manufacturing flaws.

3.2 Fuel injector:

The fuel we are using is liquid petroleum gas which is a highly flammable fuel so high rate of safety is required for handling this fuel, hence we have used a standard fuel injector and a perfectly sealed reduction sleeve for a perfectly safe fuel injection.

3.3 Ignition assembly:

The ignition assembly used by us to ignite the air fuel mixture includes a setup consisting of a rectifier unit, an induction coil, a high tension unit and a spark plug. The spark plug is fixed to the combustion chamber using perfectly drilled and tapped hole in the chamber and the external threading in the plug.

3.3.1 Spark plug circuit

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

3.4 Air compression assembly:

The compressed air is introduced into the combustion chamber using a centrifugal blower and regulated using a globe valve setup.

3.5 Thrust production unit:

The thrust is produced using a simple cross section reduction setup at the exhaust of the engine.

3.6 Practical thrust measuring unit:

The thrust generated is measured by a simple setup consisting of a locomotive stand on which our engine is mounted. The stand has a provision for the attachment of a spring balance from which we can directly measure the thrust generated by the engine.

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

Chapter 4:

IMAGES
4.1 FUEL INJECTION SYSTEM

4.2 MID JOINT

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

4.3 COMBUSTION CHAMBER WITH SPARK PLUG

4.4 T-JOINT TO MIX AIR AND FUEL

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

4.5 COUPLER

4.5 NIPPLE

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

4.6 ASSEMBLY

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

Chapter 6:

FUTURE MODIFICATIONS AND CONCLUSION

The jet engine modeled by us has a lot of scope for future improvement or modifications so as to produce more thrust which then can be installed on any UAVs. But as we had to manage and restrict ourselves to a limited budget no further modification could be made. Modifications like installing a fuel mass flow rate increaser, which would have given us a much better result, a perfectly designed venturi or nozzle at the exhaust. And a major modification would be to install a turbocharger at the exhaust which will increase the efficiency of the engine by a huge margin. The final conclusion is that by taking up this project we have learnt a lot of things not only from the mechanical subjects but also electrical circuits, time management, financial management and team work.

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MODELLING OF JET ENGINE AND MEASUREMENT OF THRUST PRODUCED

REFERENCES:
1) http://www.junkyardjet.com/ 2) JET ENGINE PERFORMANCE Charles Robert ONeill School of Mechanical and Aerospace Engineering Oklahoma State University 3) Flight operations engineering-Boeing 4) Wikipedia

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