Elements of Propulsion: Gas Turbines and Rockets
With worked examples, numerous homework problems, illustrations and pictures, this book provides a complete introduction to gas turbine and rocket propulsion for aerospace and mechanical engineers.
TABLE OF CONTENTS Elements of Propulsion: Gas Turbines and Rockets
Chapter 6: Component Performance
6.1 Introduction
In Chapter 5, we idealized the engine components and assumed that the working fluid behaved as a perfect gas with constant specific heats. These idealizations and assumptions permitted the basic cycle analysis of several types of engines and the analysis of engine performance trends. In this chapter, we will develop the analytical tools that allow us to use realistic assumptions as to component losses and to include the variation of specific heats.
6.2 Variation in Gas Properties
The enthalpy h and specific heat at constant pressure c p for air (modeled as a perfect gas) are functions of temperature. Also, the enthalpy h and specific heat at constant pressure c p for a typical hydrocarbon fuel JP-8 and air combustion products (modeled as a perfect gas) are functions of temperature and the fuel/air ratio f. The variations of properties h and c p for fuel/air combustion products vs temperature are presented in Figs. 6.1a and 6.1b, respectively. The ratio of specific heats ? for fuel/air combustion products is also a function of temperature and of fuel/air ratio. A plot of ? is shown in Fig. 6.2. These figures are based on Eq. (2.64) and the coefficients of Table 2.2. Note that both h and c p increase and ? decreases with temperature and the fuel/air ratio. Our models of gas properties in the engines need to include changes in both c p and ?
Copyright The American Institute of Aeronautics and Astronautics, Inc. 2006 under license agreement with Books24x7
