CFD CODE VALIDATION & QUALITATIVE STUDY OF EFFECTS OF TIP CLEARANCE VARIATION ON PERFORMANCE OF TRANSONIC AXIAL COMPRESSOR ROTOR

The main objective of this work is the validation of Computational Fluid Dynamics (CFD) code used for analysis of transonic axial compressors. NASA Rotor 35 is used here as test case for validation. In this work, computations are performed using parallelized RANS code, to predict the transonic axial compressor rotor flow characteristics. Advection Upstream Splitting Method (AUSM) scheme has been used. A Multiple Frame of Reference approach has been used to model the rotor passage. Spalart-Allmaras turbulence model is used to model turbulence. Multiblock Structured mesh is used. Performance characteristics for the entire range of operation, from maximum mass flow rate till maximum pressure ratio, have been simulated. The results obtained are comparable with experimental data within 5-10% error. Investigations have been carried out to study the effect of varying tip clearance in NASA Rotor 35. The present work is intended to study the clearance flow trajectory as a function of varying tip clearance. The effects of shock/vortex interaction in tip clearance region are also studied. The effects of tip clearance size on the generation and evolution of the end-wall vortical structures are discussed by investigating their evolutionary trajectories. By this study, it is observed that as tip clearance reduces, clearance flow trajectory moves downstream. From this it can be concluded that if tip clearance increases, tip clearance vortices expand. This may help in casing-treatment or tip-treatment to mitigate the loss in the performance, if the tip clearance increases.