The Performance Estimation of Transonic Turbine at Design and Off-Design Conditions

Abstract

A performance estimation method has been developed for the transonic turbine. This method can be used for the calculation of gasdynamic parameters of turbines at design and off-design conditions. In this paper a group of simultaneous equations including the S2 stream surface equation, the simplified flow correlation between blade and blade, the loss equations and the deviation angle correlation are solved (Wu, 1950, 1950, 1965; Marsh, 1966; Smith 1973; Novak and Hearsey, 1977.) Solving these equations, the turbine performance can be obtained. The essential difference in treating the sub-critical, critial and super-critical flow conditions is researched. The correlation between entropy and losses is deduced in this paper. For the choking flow calculation, a unified approach to solve these equations is developed. On the basis of the above research, the false choking condition will not occur and convergence will be reached rapidly with this method. A computer program was then compiled with this method and has been used for the performance calculation of transonic turbines at design and off-design conditions. Several examples have been calculated. Satisfactory results are obtained and the reduced flow rate, efficiency and expansion ratio are fairly consistent with the experimental results. The difference between the computational results and experimental data is within 1% near the design condition.