PERFORMANCE IMPROVEMENT THROUGH INDEXING OF TURBINE AIRFOILS .2. NUMERICAL-SIMULATION

An experimental/analytical study has been conducted to determine the p erformance improvements achievable by circumferentially indexing succe eding rows of turbine stator airfoils. A series of tests was conducted to experimentally investigate stator wake clocking effects on the per formance of the space shuttle main engine (SSME) alternate turbopump d evelopment (ATD) fuel turbine test article (TTA). The results from thi s study indicate that significant increases in stage efficiency can be attained through application of this airfoil clocking concept. Detail s of the experiment and its results are documented in part 1 of this p aper. In order to gain insight into the mechanisms of the performance improvement, extensive computational fluid dynamics (CFD) simulations were executed. The subject of the present paper is the initial results from the CFD investigation of the configurations nad conditions detai led in part 1 of the paper. To characterize the aerodynamic environmen ts in the experimental test series, two-dimensional, time-accurate, mu ltistage, viscous analyses wee performed at the TTA midspan. Computati onal analyses for five different circumferential positions of the firs t stage stator have been completed. Details of the computational proce dure and the results are presented. The analytical results verify the experimentally demonstrated performance improvement and are compared w ith data whenever possible. Predictions of time-average turbine effici encies as well as gas conditions throughout the flow field are present ed. An initial understanding of the turbine performance improvement me chanism based on the results from this investigation is described.