Gas Turbine Performance

Course Overview

The gas turbine engine is a very complex device. Its high power to weight ratio has made it the propulsion system of choice in aircraft applications. It is also used extensively in the oil, gas, power and process industries. An understanding of the basic principles underpinning its design, operation and behaviour is essential for all engineers involved in the development, production, procurement and use of gas turbines.

Who should Attend

The course is intended for graduates of engineering, science or mathematics who are involved in the gas turbine or associated industries. Previous industrial experience is desirable.

Course Objectives

The aim of this course is to provide the delegate with an understanding of how different types of gas turbine produce useful power and how their output is influenced by a very wide range of operating conditions. The three major categories of gas turbine applications are covered, civil aviation, military aviation and mechanical power applications.

When completing the course the delegate should be able to understand the influence of mission on the choice of gas turbine cycle and how gas turbines behave in a very wide range of operating conditions.

Content Summary

The content is split into three main sections since, as stated in the learning outcomes, the objective of the course is to give detailed insight in three key topic areas:

• Gas Turbine Aerothermodynamics
• Design Point Performance Assessment
• Off-Design Performance

To make the learning process more efficient, the presentations of these three sections are given in a carefully selected order. The above material is complemented by several sessions given by guest speakers who may present special subjects, such as emissions, gas path analysis, engine lifing and case studies.

Gas Turbine Aerothermodynamics
This section comprises the delivery of basic gas dynamics including isentropic flow, an explanation of non-dimensional parameters and a description of the Joule Cycle. The processes of compression, combustion and expansion in turbines and nozzles are outlined, within a thermodynamics framework.
The two main applications of the gas turbine, jet engines and shaft power output, are explained. The concepts of thermal and propulsive efficiencies are introduced. The concept of the turbofan is explained.

Design Point Performance Assessment
The influence on engine output of turbine inlet temperature, overall pressure ratio, bypass ratio and fan pressure ratio is explained. This description is made by means of SFC versus Specific Thrust or Power Charts. The side-effects of the selection of these parameters are also explained and the resulting choices in suitability for a mission highlighted. The concept of growth variants of a power plant is discussed. Different engine designs are described.

Off-Design Performance
This section contains a description of component characteristics and how these components interact to determine the behaviour of the engine. This explanation is given at a simplified level for an understanding of the principles involved and at a more detailed level which is illustrative of the simulation methods in widespread use in the industry today. On a macroscopic level, the effect of different inlet conditions on gas turbine performance is explained. This includes altitude, hot day and flight speed. In addition the behaviour of the engine is discussed with reference to changes in power output.