Course Objectives

This course covers the fundamental principles of jet propulsion systems. By the end of the course, you should be able to

1. understand the major elements of a jet engine, and the reasons for their presence

2. calculate the overall performance of a jet engine, given a few critical parameters

3. understand technological limitations on the performance of engines

4. understand the differences in design between engines intended for different applications

 

We will not attempt to teach you about the detailed parts or workings of any particular engine. Instead we will attempt to ensure that you have the capability to analyze any engine.


FUNDAMENTALS OF PROPULSION

Course Outline

 

 

Propulsion

(P)

P1. Introduction to Propulsion

P2. Review of thermodynamics

P3. Review of isentropic flow relations

P4. Thrust of a jet propulsion system

P5. Brayton cycle: cycle efficiency; choice of parameters

P6. Ideal ramjet cycle

P7. Turbojet, turbofan, and turboprop engines

P8. Optimization of propeller work fraction

P9. Gas turbine engine analysis

P10. Engine component design considerations

P11. Inlets

P12. Nozzles

P13. Burners

P14. Turbomachines

P15. Single stage analysis

P16. Multistaging

P17. Engine performance prediction using a computer spreadsheet

 

 


1: Introduction

 

 

In this course, we will learn how jet engines work, and to analyze the performance of any jet engine. We will do this by reducing the complex mechanisms of an engine to a few essential features. Shown above is a cut-away view of a modern turbofan engine. Many of the complex parts have been deleted. Starting from the left, we see a compressor system which does work on the air entering the engine, increasing its pressure. In this engine, the compressor is in two parts, running on two different shafts which can operate at different speeds. Next, we see pipes introducing fuel into the combustion chamber, where the fuel is mixed with air and burned. Thus, heat is added to the air. Next we see a turbine, which takes work out of the air leaving the combustion chamber, and uses it to run the compressor. Finally, the air leaving the turbine blows out at high speed through a nozzle. Upon closer examination, we see that some of the air entering the engine goes through the outer parts of the compressor, called a "fan", and then blow out of the engine directly without going through the combustion chamber or nozzle.

 

The net effect of the engine is that the momentum of the air leaving the engine is greater than that of the air entering the engine. The reaction to this added momentum is reflected in the thrust of the engine.

 

In this course, we will consider the features of the overall engine, and then of each of the components in turn. To understand the flow in the compressor, turbines, intakes, and nozzles, we will first learn some concepts in compressible fluid dynamics. To understand the flow in the combustor, we will first learn about combustion and reacting flows. These concepts will then be brought together to develop analysis procedures for complete engines, and to compute their performance over a range of flight conditions.

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