Turbofan Jet Engine

By Alex King

Abstract. I recently built a model of a turbofan jet engine with a cross section down the length of the engine cut out to see the different sections of the engine. Although I thoroughly enjoyed building the model and constructing the different parts of the engine, that’s all it was, constructing. I felt there was a significant lack of context and explanation as to what I was building. So, in response I decided to write this document with the intention of gaining a much better understanding of the inner workings of a commercial jet engine by visualising and describing the sections, their components and how they work from a mechanical and thermodynamic perspective (such that it somewhat ties into my degree).

Table of Contents

1. Introduction
2. Low Pressure Compressor
3. High Pressure Compressor
4. Combustion Chamber
5. High Pressure Turbine
6. Low Pressure Turbine
7. Nozzle
8. Fan
9. Types of Turbofan Engine
10. Trails
11. Conclusion

Introduction

Most modern passenger and military aircraft are powered by gas turbine engines, otherwise known as jet engines. Although there are different types of gas turbine engines, most have components and processes in common. The standard stages for a commercial engine are as follows:

1. Low-Pressure Compressor
2. High-Pressure Compressor
3. Combustion Chamber
4. High-Pressure Turbine
5. Low-Pressure Turbine

A turbofan works by sucking in air through the large fan blades at the front of the engine and dividing the air through two main paths. The division of air is based on something called the bypass ratio, which determines the amount of air that travels through the bypass stream (funnel outside the engine core) and through the engine core. Commercial turbofan engines normally have quite a high bypass ratio, meaning most air that is sucked in gets routed around the engine core. For the air that gets sent through the engine core, it first encounters the low-pressure compressor, which increases the pressure of the air and sends it into the high-pressure compressor. The high-pressure compressor is then able to increase the temperature of the air so significantly that when the air comes into contact with the fuel in the combustion chamber, the combustion process starts itself. The combusted air-fuel mixture then enters the high-pressure turbine,

Low Pressure Compressor

High Pressure Compressor

Combustion Chamber

High Pressure Turbine

Low Pressure Turbine

Nozzle

Fan

The fan of a turbofan engine is located at the front of the engine and helps the engine to generate thrust. The purpose of the fan is to draw large amounts of air inside the engine.

Types of Turbofan Engine

Low-bypass Turbofan

High-bypass Turbofan

Turbojet

Zero bypass

Afterburn Turbofan

Trails

Conclusion