Abstract: Based on constant specific heat, a simplified solution is proposed for land and flight gas turbine performance and its four significant pressure ratios, I. E. for optimum thrust or work, for optimum core turbine outlet pressure and reheat, for optimum thermal efficiency and for hitherto not analytically analysed optimum specific fuel consumption. The sea level static and strate flight illustrative results are compared with two variable specific heat accurate computations with either isentropic or polytropic compressor and turbine efficiencies kept constant. It is not strange to see the simplified method deviate in absolute values of performance. Yet it is interesting to note this much simplier and quicker method predicting the trends of performance variation with pressure ratio and the four optimum pressure ratios as well as the trends of component and flight conditions effects on these optimum pressure ratios and their performance fairly well, being thus appropriate to be used for preliminary estimate in design. It may serve as a start for accurate solutions too. Besides, it would probably be helpful in analysing complex cycles and also in searching for new cycles. Notably, the static results are directly applicable to more general cases of gas turbine engines, e. g. stationary power units or mobile engines utilizing shaft power, with specific thrust value representing the square root of twice shaft work, and the variation of thermal efficiency just equivalent to the variation of reciprocal of specific fuel consumption on shaft power basis. The paper deals only with cycle analysis. Practical choice of compressor pressure ratios will be a compromise between the various optima, with due considerations given to off-design performance and a series of concrete engineering requirements.

Key words: 简化解, 燃气轮机, 最佳压比