A Zonal Coupling Simulation For Turbine Stage Mainstream/Disk Cavity Interaction

High-pressure turbine is one of the important parts of aero-engine, which has great influence on the engine performance, structural integrity and reliability. With the continuous progress of aviation technology, the performance of engine continues to be improved and the inlet temperature of high-pressure turbine is also rising. The high temperature gas flowing through turbine does not do harm to blades but also bring huge negative effect to disc cavity. For the relative motion of rotor and stator, there must be a clearance between them. The pump effect of rotor disc and the differential pressure can make the hot gas flowing in the mainstream way enter disc cavity. The hot gas which invade into disc cavity may make the turbine disk overheated, which will lead to the thermal fatigue of components, short the life of high-pressure turbine rotor and even damage the structural integrity to end in accident. In order to maintain the cavity in normal working temperature, on one side we design sealing structure to reduce the gas exchange between inside and outside of the clearance, on the other hand, some cool air is introduced into the cavity to cool the turbine disc and then flow to mainstream through rim seal. The amount of cooling air has an important influence on engine performance. Too much cooling air will reduce the performance of engine, but not enough cooling air can't seal gas, which will reduce the life of turbine disc. Finding the optimum amount of cooling air become one of the most concerned technical problems in air system design. The air exchange passing through rim clearance make the mainstream gas and disc cavity secondary flow become a coupling system. To accurately predict the best amount of cooling air, we need to consider the complex interaction between the two kinds of flow. This article is mainly about the coupling numerical simulation of mainstream gas and secondary flow in high-pressure turbine.Because the flow characteristics of turbine mainstream gas and secondary flow are quite different, the best turbulence model for them may be different. Accordingly, we use contrast tests to evaluate the turbulence models which contain one equation and two equation of six models for these two kinds of flow. The result shows that S-A model is best for typical mainstream and SST k-? model is best for disc cavity secondary flow. On the basis, in order to use two section's fittest turbulence model respectively, we analyse the flow characters of this coupling flow and evaluate the existing coupling method. A partition coupling algorithm is proposed to solve this problem and we also use Python language and Fluent to construct coupling simulation platform. Then we use two examples to test coupling algorithm and platform. The results show that algorithm can realize the process control and data exchange two major functions required by platform and do simulation of the mainstream gas and secondary flow high efficiently, which is better than any kind of single turbulence model. It demonstrate the potential of this method.