Size Effect On Axial Flow Compressor Performance Research

To a small flow rate compressor, compared with large size fan /compressor, it is more difficult to keep the tip clearance to chord ratio in a relative small scope during manufacture and test rig due to its relatively small size.It leads to more complex vortex structures especially in the tip clearance of the compressor. One of the major vortex structures is the tip leakage, which is induced by the flow from blade pressure side to the suction side through the tip clearance. The interaction between tip leakage, boundary layer, secondary flows and shock waves has a great effect on the flow filed inside the compressor passage. It results in blockage and choking in the blade tip area, higher losses and SFC, lower efficiency and a smaller surge margin of the compressor.In a high speed axial compressor, even a very small leakage at the stator root could bring a significant reduction of rotor performance.Besides the flow rate of the leakage, the circumferential velocity component of the leakage also is a very important factor. Generally, the higher circumferential velocity, the worse rotor performance.Con-sideration of security, machining and rig, the axial gap of the small flow rate compressor is not so small when compared with the large si-ze compressor. When airflow passes through the axial gap at blade root, part of it enters the stator root plenum. There is a high momentum l-oss due to these phenomena which could affect the working ability of the compressor and leads to a reduction of efficiency. More seriously, the compressor could enter the unstable operating conditions.In this paper, an investigation of effects of stator root plenum and rotor tip clearance on compressor performance has been undertaken in a GTE small flow rate compressor by using 3D CFD numerical simulation which based on test data. The results could provide a theoretical basis about how to choose the related parameters during a small size compressor design.