3 - Non-ideal Cycle Analysis

Summary

Introduction

Chapter 2 has included a review of the ideal thermodynamic processes of different components, ideal cycle analyses for various types of engines, and a discussion of performance trends. All of the components were assumed to operate without any losses, and the gas was assumed to be perfect and to have constant specific heats throughout the entire engine. The objectives of this chapter are to relax these assumptions, to explain the physical conditions that lead to losses, and to review the nonideal thermodynamic processes from, for example, Keenan (1970) or Wark and Richards (1999) and the gas dynamic processes from, for example, Anderson (1982), Zucrow and Hoffman (1976), or Shapiro (1953). Efficiency levels and losses are included for the different components so that more realistic predictions can be made for overall engine performance. Even though most components operate with individually with relatively high efficiencies (upwards from 90%), when all the components are coupled the overall engine performance can be reduced drastically. However, in general, the performance trends do not change. Also, note that simple single- or two-term expressions are used to model the losses in each component in this chapter for simplicity. Each component is covered separately and in detail. At this stage these 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.