Elements of gas turbine propulsion part 2
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Elements of gas turbine propulsion part 2
CHAPTER8ENGINEPERFORMANCEANALYSIS8-1 INTRODUCTIONThis chapter is concerned with predicting.the performance of a gas turbine engine and obtaining perfo Elements of gas turbine propulsion part 2 ormance data similar to Figs. 1-14« through l-14e, 1-15«, and 1-156 and the data contained in App. B. The analysis required to obtain engine performance is related to, but very different from, the parametric cycle analysis of Chaps. 5 and 7. Tn parametric cycle analysis of a turbojet engine, wc inde Elements of gas turbine propulsion part 2 pendently selected values of the compressor pressure ratio, main burner exit temperature, flight condition, etc. The analysis determined the turbine tElements of gas turbine propulsion part 2
emperature ratio—it is dependent on the choices of compressor pressure ratio, main burner exit temperature, and flight condition, as shown by Eq. (7-1CHAPTER8ENGINEPERFORMANCEANALYSIS8-1 INTRODUCTIONThis chapter is concerned with predicting.the performance of a gas turbine engine and obtaining perfo Elements of gas turbine propulsion part 2 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 settin Elements of gas turbine propulsion part 2 g (main burner exit temperature TtA) and flight condition (Mo and Tn). The basic independent and dependent variables of the turbojet engine arc listedElements of gas turbine propulsion part 2
ỉn Table 8-1 for both parametric cycle analysis and engine performance analysis.Th parametric cycle analysis, we looked at the variation of gas turbiCHAPTER8ENGINEPERFORMANCEANALYSIS8-1 INTRODUCTIONThis chapter is concerned with predicting.the performance of a gas turbine engine and obtaining perfo Elements of gas turbine propulsion part 2 ic cycleEngine performanceFlight condition (Af0, Tv. and p„)IndependentIndependentCompressor pressure ratio JT,IndependentDependentMain burner exit temperature 7]4IndependentIndependentTurbine temperature ratio T,DependentConstantconditions were specified via the design inputs: Tn, Mữ, Tụ, and R>. I Elements of gas turbine propulsion part 2 n addition, the engine cycle was selected along with the compressor pressure alio, the polytropic efficiency of turbomachincry components, etc. For thElements of gas turbine propulsion part 2
e combination of design input values, the resulting calculations yielded the specific performance of the engine (specific thrust and thrust specific fCHAPTER8ENGINEPERFORMANCEANALYSIS8-1 INTRODUCTIONThis chapter is concerned with predicting.the performance of a gas turbine engine and obtaining perfo Elements of gas turbine propulsion part 2 ion or design input values is referred to as the engine design point or reference point. The resulting specific engine thrust and fuel consumption are valid only for the given engine cycle and values of Tn. Af0, Tq, Ke, t,, ->ic, etc. When we changed any of these values in parametric cycle analysis, Elements of gas turbine propulsion part 2 we were studying a “rubber” engine, i.c., one which changes its shape and component design to meet the thermodynamic, fluid dynamic, etc., requiremenElements of gas turbine propulsion part 2
ts.When a gas turbine engine is designed and built, the degree of variability of an engine depends upon available technology, the needs of the principCHAPTER8ENGINEPERFORMANCEANALYSIS8-1 INTRODUCTIONThis chapter is concerned with predicting.the performance of a gas turbine engine and obtaining perfo Elements of gas turbine propulsion part 2 iable Tn, and sometimes variable Ta and exhaust nozzle throat area). In a simple constant-tlow-area turbojet engine, the performance (pressure ratio and mass flow rate) of its compressor depends upon the power from the turbine and the inlet conditions to the compressor. As we will see in this chapte Elements of gas turbine propulsion part 2 r, a simple analytical expression can be used to express the relationship between the compressor performance and the independent variables: throttle sElements of gas turbine propulsion part 2
etting (Trt) and flight condition (Af0. Tq. Pq).When a gas turbine engine is installed in an aircraft, its performance varies with flight conditions aCHAPTER8ENGINEPERFORMANCEANALYSIS8-1 INTRODUCTIONThis chapter is concerned with predicting.the performance of a gas turbine engine and obtaining perfo Elements of gas turbine propulsion part 2 le and indirectly by changing flight conditions. The thrust and fuel consumption will thereby change. In this chapter, we will look at how-specific engine cycles perform at conditions other than their design (or reference) point.There are several ways to obtain this engine performance. One way is to Elements of gas turbine propulsion part 2 look at the interaction and performance of the compressor-burner-turbine combination, known as the pumping characteristics of the gas generator. In tElements of gas turbine propulsion part 2
his case, the performance of the components is known since the gas generator exists. However, in a preliminary design, the gas generator has not been CHAPTER8ENGINEPERFORMANCEANALYSIS8-1 INTRODUCTIONThis chapter is concerned with predicting.the performance of a gas turbine engine and obtaining perfo Elements of gas turbine propulsion part 2 n such a case, the gas generator performance can be estimated by using first principles and estimates of the variations in component efficiencies. In reality, the principal effects of engine performance occur because of the changes in propulsive efficiency and thermal efficiency (rather than because Elements of gas turbine propulsion part 2 of changes in component efficiency). Thus a good approximation of an engine’s performance can be obtained by simply assuming that the component efficElements of gas turbine propulsion part 2
iencies remain constant.The analysis of engine performance requires a model for the behavior of each engine component over its actual range of operatiCHAPTER8ENGINEPERFORMANCEANALYSIS8-1 INTRODUCTIONThis chapter is concerned with predicting.the performance of a gas turbine engine and obtaining perfo Elements of gas turbine propulsion part 2 ents and constant total pressure ratio of the other components) used in this textbook gives answers that are perfectly adequate for preliminary design, it is important to know that the usual industrial practice is to use data or correlations having greater accuracy and definition in the form of comp Elements of gas turbine propulsion part 2 onent “maps.” The principal values of the maps arc to improve the understanding of component behavior and to slightly increase the accuracy of the resElements of gas turbine propulsion part 2
ults.NomenclatureThe station numbering used for the performance analysis of the turbojet and turbofan is shown in Fig. 8’1. Note that the turbine is dCHAPTER8ENGINEPERFORMANCEANALYSIS8-1 INTRODUCTIONThis chapter is concerned with predicting.the performance of a gas turbine engine and obtaining perfo Elements of gas turbine propulsion part 2 re compressor (station 2.5 to 3), and the low-pressure turbine drives the fan (station 2 to 13) and low-pressure compressor (station 2 to 2.5).The assembly containing the high-pressure turbine, high-pressure compressor, and connecting shaft is called the high-pressure spool. That containing the low- Elements of gas turbine propulsion part 2 pressure turbine, fan or low-pressure compressor, and connecting shaft is called the low-pressure spool, in addition to the r and It values defined inElements of gas turbine propulsion part 2
Table 5-1, the component total temperature ratios and total pressure ratios listed in Table 8-2 arc required for analysis of the above gas turbine enCHAPTER8ENGINEPERFORMANCEANALYSIS8-1 INTRODUCTIONThis chapter is concerned with predicting.the performance of a gas turbine engine and obtaining perfo Elements of gas turbine propulsion part 2 s_ p'2.5pữt, = — eL Taz"tZn’L=p^CHAPTER8ENGINEPERFORMANCEANALYSIS8-1 INTRODUCTIONThis chapter is concerned with predicting.the performance of a gas turbine engine and obtaining perfoGọi ngay
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