Fundamentals of Jet Propulsion with Power Generation Applications

Chapter 1 identified the basic engine types and defined the important operating performance parameters of gas turbines. That chapter also briefly reviewed the fundamental thermodynamics of cycles and established that gas turbines consist of several important components. This chapter covers all basic jet engine and power generation configurations. Both ideal and nonideal components were considered in Chapter 2. Ideal implies that there are no losses in the components. Nonideal includes such losses. Components are now assembled in a “cycle analysis” to make it possible to predict the overall engine performance. As will be seen, the ideal cycle analysis results in closed-form equations for the engine characteristics and final equations are summarized in this chapter. Developing these equations (Appendix H) serves three purposes. First, doing so allows the reader to see how the equations are assembled to model an engine without having to deal with numerical details. Second, and more importantly, developing the equations allows the reader to observe how detail parameters affect the overall performance of an engine without parametrically varying numbers. Third, in some cases, analytically optimizing a performance characteristic is possible. On the other hand, nonideal cycle analysis does not result in closed-form equations owing to the increased complexity of the component equations of the engine. Nonideal efficiency levels and losses are included for the different components so that more realistic predictions can be made for overall engine performance. Also, note that the simple single- or two-term expressions used to model the losses in each component in Chapter 2 are used. Even though most components operate with individually with relatively high efficiencies (upwards from 90 percent), when all the components are coupled the overall engine performance can be reduced dramatically. However, in general, parametric studies and the performance trends are similar for both ideal and nonideal cases. This chapter presents quantitative examples to demonstrate the analysis and to give the reader a physical understanding of characteristics. Trend studies are also discussed to show the dependence of the overall characteristics on individual component parameters. At this stage the loss terms are specified a priori even though, in a real engine, the different component losses are dependent on the engine operating point and are thus dependent on each other. This advanced topic is the subject of Chapter 12, which addresses component matching. More complex and refined analyses of the component losses are presented in each of the component chapters (Chapters 4–11).