5 - Engine Performance

Summary

Overview

In this chapter we present a basic analysis for three key gas-turbine engine architectures: high by-pass turbofan, turboshaft and low by-pass turbojet with thrust augmentation. We consider general gas turbine engine architecture (§ 5.1), the thrust and power ratings (§ 5.2), the turbofan model (§ 5.3), the turboprop engine (§ 5.4) and the low by-pass engine model (§ 5.5).We briefly mention the methods of generalised engine performance (§ 5.6). We finally discuss the role of the auxiliary power unit (§ 5.7). An important aspect of the presentation is the strategy for the determination of the design point of the engine in absence of reliable data. In all cases we discuss the calculation of the engine state as a function of the main operational parameters.

KEY CONCEPTS: Gas Turbine Engines, Thrust/Power Ratings, Engine Derating, Turbofan Engines, Engine Design Point, Engine Simulation, Rubber Engines, Effects of Contamination, Turboprop Engines, Turbojet Engines, Auxiliary Power Units.

Gas Turbine Engines

The term gas turbine is associated with a jet engine consisting of a compressor, a combustion chamber, a turbine and an exhaust nozzle, although the name refers to both jet-thrust engines and shaft-power engines. The main types of gas turbine engines are the turbojet, the turbofan and the turboprop. The gas turbine is the core of the engine. However, there are other parts whose function is essential (inlet, fuel lines, fuel nozzles, sensors, collectors, thrust reverser).