NUMERICAL INVESTIGATION OF THE EFFECT OF MOVING ENDWALL AND TIP CLEARANCE ON THE LOSSES IN A LOW SPEED AXIAL FLOW COMPRESSOR CASCADE

摘要

This paper explores the effect of the tip-clearance in presence of the endwall motion, incident at 10°, on a rectilinear cascade of C4 blade. The width of the moving endwall considered here was 120% of an axial chord to represent the operating conditions close to that of an actual rotor in subsonic condition at peak load. The flow coefficient was varied from 0.3 to 0.6. The cascade was analysed computationally using ANSYS Fluent ©. The validation of numerical results of the cascade was done with the experimental result for no tip gap condition. The results agreed well with the experimental data. Detailed analysis of the numerical results was then carried out to explore the complex flow features, which was a consequence of the combined influence of the endwall effect, tip clearance and moving endwall. With no tip-gap, the endwall effects were substantial and extended up to 40%span of the blade and nearly 60% of the pitch whereas the flow coefficient does not alter the distribution along the span. The tip leakage flow counteracts the endwall flows and helps in minimizing them in the region towards the tip. The endwall motion does alter the pressure distribution at the blade tip but the relative variations in blade loading at the tip were not appreciable. Lower flow coefficient at 1% tip clearance gives the optimum pressure rise with reduced total pressure loss in the wake.