8.1 Introduction

This chapter is concerned with predicting the performance of a gas turbine engine and obtaining performance data similar to Figs. 1.14a 1.14e, 1.15a, and 1.15b and the data contained in Appendix B. The analysis required to obtain engine performance is related to, but very different from, the parametric cycle analysis of Chapters 5 and 7. In parametric cycle analysis of a turbojet engine, we independently selected values of the compressor pressure ratio, main burner exit temperature, flight condition, etc. The analysis determined the turbine temperature ratio it is dependent on the choices of compressor pressure ratio, main burner exit temperature, and flight condition, as shown by Eq. (7.12). In engine performance analysis, we consider the performance of an engine that was built (constructed physically or created mathematically) with a selected compressor pressure ratio and its corresponding turbine temperature ratio. As will be shown in this chapter, the turbine temperature ratio remains essentially constant for a turbojet engine (and many other engine cycles), and its compressor pressure ratio is dependent on the throttle setting (main burner exit temperature T _{t 4}) and flight condition ( M ₀ and T ₀). The basic independent and dependent variables of the turbojet engine are listed in Table 8.1 for both parametric cycle analysis and engine performance analysis.