Study on the Loss Characteristics and Flow Mechanism of Cantilevered Cascade With Moving Endwall Under the Influence of Upstream Wake

Abstract In multi-stage small-core compressors, the inflow conditions of cantilevered cascades exhibit considerable complexity. It is characterized by a larger ratio of tip clearance size to chord length and a larger ratio of wake width to pitch. These factors make it challenging to clarify the key influence of upstream wakes on large-clearance leakage flows within multistage environments. To take this challenge this paper incorporate realistic wake inflow and endwall rotation boundary conditions into the cascade simulations. Based on the wake observations of the multistage compressor (SJTU-LSRC), two sizes of cylinders were designed and positioned upstream of the controlled diffusion airfoil (CDA) cascade to generate two distinct types of inflow wakes. One wake width is comparable to the multistage compressor wake width, and the other with an expanded width. By employing an unsteady numerical simulation method, the interaction between wake and cantilever cascade clearance leakage is decoupled and elucidated. The effects of different wakes on cascade losses and secondary flows are thoroughly examined. It mainly includes the influence of wake effects on the evolution of tip clearance leakage flow. The flow mixing in the mid-span and the flow separation change near the suction side of the hub end wall are also included. The results indicate that both wake widths exert a stabilizing influence on the two clearance leakage flows. However, the wider wake induces substantial mixing losses in the mid-span region of the blade, leading to an entropy increase loss coefficient for the cascade that is 0.68 times (for large tip clearance) and 0.94 times (for small tip clearance) higher than that of the small wake. This paper provides critical insights into small-core compressor flow mechanisms, aiding performance optimization and advancing research understanding.