Study On Control Of Tip Clearance Flow In Compressor

Tip clearance flow is one of the important components of complicated flow structure in cascade passage, which plays a vital role in compressor efficiency and stability. The formation and evolution of tip clearance flow have been studied thoroughly. Combined with the knowledge of characteristics of various passive/active flow control methods, synthetic jet was adopted to control the tip clearance flow in this paper. This active control method was beneficial to improve the tip clearance flow field, reduce the total pressure loss coefficient at exit of the cascade passage, and increase compressor stability.The numerical calculation model was based on NACA64-A905 airfoil profile. The vibration of synthetic jet top wall was performed by dynamic mesh while the relative motion between casing and cascade was performed by slide mesh. Unsteady numerical simulation method was carried out to study the effects of synthetic jet excitation amplitude and excitation frequency on tip clearance flow control in detail. The effects of synthetic jet on total pressure loss coefficient and leakage ratio were analyzed emphatically.The results demonstrate that the flow control effects of multi-row synthetic jet cavities are significant. Synthetic jet is able to reduce total pressure loss coefficient and helpful to drive more fluid near the casing wall. The larger the excitation amplitude, the better the control effects. Total pressure loss coefficient was reduced by 3.2% when the excitation amplitude was up to 0.4mm; increasing excitation frequency makes a difference in leakage vortex trace, total pressure loss coefficients were reduced by 0.6% when the excitation frequencies were 5000 Hz and 6000 Hz.