Numerical Study On The Inter-Stage Bleeding In A High-Pressure Compressor

As one of the core components of aero gas turbine engine, the efficiency and stability of axial compressor significantly influence the performance of the engine. In order to keep the normal work of the einge and meet the requiremnt for air during the flight, air should be bleeded from the high-pressure compressor. The air can be used to supply the customer, cool high temperature engine components, control leakage flows, pressurize drum cavities, bearing chamber and so on. At off design conditions, bleed flows can be used for preventing the occurrence of rotating stall and surge. Bleed will certainly change compressor's working condition, thereby affect the operating state of the engine. Thus, in order to guarantee the normal work of the engine, it is necessary to study the effects of the bleed on the compressor.A high-pressure compressor model containing three and a half stages was studied in this article with the using of numerical simulation software, aiming at study the influence on the compressor of the bleeding structure, bleeding place and bleeding rate.First of all, in order to ensure the stability of numerical calculation process and the accuracy of results, a comprehensive study of the grid scale, grid topology, difference scheme and turbulence model was conducted to decide the grid, difference scheme and turbence model used in further study.Secondly, the performance of the compressor model and the flow field inside with and without bleed were studied by numeciral simulation. The results showed that the bleed resulted in increasing of the mainstream in-flow flow rate, decreasing of the manstream out-flow flow rate, increasing of the isentropic efficiency and decreasing of the total pressure ratio; the bleed sucted away the hight entropy flow, reduced the total pressure loss near the adjacent blades'tip. The bleed changed the attack angle of the blade downstream, therefore change the matching condition between stages.Then, in order to explore the effects of the bleeding structure and bleeding place, the slots with same flow area, but different inlet profile and location were constructed. The results showed that the bleeding place had a great influence on the performance of the compressor. Among the various bleeding place, the place at the downstream of trailing edge is the best, the place near the pressure surface is the worst. Bleeding in the cascade tunnel is harmful to the performance of compressor.Finally, the effects of the bleeding flow rate on the change of performance and flow field were investigated. The results showed that the effects were decided by the operating state of the compressor. At high rotating speed, the improvement caused by the bleed was obvious; at low rotating speed, the improvement was little.