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).

The burner, reheat burner, and afterburner are the only components through which energy is added to the gas turbine.

A nozzle is sometimes called the exhaust duct or tail pipe, and is the last component of a jet engine through which the air passes. Up to two parallel nozzles are present on an engine: primary and fan (or secondary). In this chapter, both converging and converging– diverging (CD) nozzle types are discussed, and the two nozzles can be any combination of the two types (i.e., converging and converging–diverging, converging and converging, etc.). Recall that the functions of the nozzles are to convert high-pressure, high-temperature energy (enthalpy) to kinetic energy and to straighten the flow so that it exits in the axial direction. It is from this conversion process that the thrust is derived. Because of the high temperatures that a nozzle experiences, materials used in nozzle construction are usually a nickel-based alloy, titanium alloy, or ceramic composite. In Chapter 2, the nonideal effects of nozzles are discussed. The reader is also encouraged to review Appendix C as many of the fundamentals are covered therein. In this chapter, these effects are covered in more detail along with other design considerations.

As discussed in Chapters 2 and 4, the basic operating principle of a compressor is to impart kinetic energy to the working fluid by the means of some rotating blades and then to convert the increase in energy to an increase in total pressure. Axial flow compressors are covered in Chapter 5. These compressors are used on large engines and gas turbines. However, for small engines – particularly turboshafts and turboprops – centrifugal (or radial) compressors are used.

Two remaining components that affect the overall performance of a turbofan engine are the bypass duct and mixer, as shown in Figure 11.1. Applications have previously been presented in Figures 2.42 and 2.44. These are relatively simple compared with the other components but should be included because they both generate losses in total pressure. Because the length-to-flow-width ratio of the bypass duct is moderate, the duct can incur significant losses. Also, it is desirable to have a uniform temperature gas entering the afterburner or nozzle so that these components operate near peak efficiency. Mixing of two fluid streams at different temperatures is a highly irreversible process, and a mixer consists of 3-D vanes in both the radial and circumferential (annular) directions. Thus, with good mixing of the low-temperature bypassed air and high-temperature primary air, further significant losses can occur. Owing to the temperatures exiting from the turbine, mixers are generally fabricated from a nickel-based alloy. With these losses the thrust and TSFC will both be compromised.

A generalization of the classical theory of flight dynamics is presented that includes quasi-steady aeroelastic effects using residualization approach. This is then used to investigate static stability of the aircraft, which may result in torsional divergence, as well as its controllability, which results in a metric for control effectiveness and potentially control reversal. Several illustrative problems are finally considered: a simplified model for the dynamics of a aircraft with a rigid fuselage, the aeroelastic trim of an aircraft with high-aspect ratio wings, and roll control with aeroelastic effects.