Transient Numerical Investigation Of Blade Row Interaction In A High Performance Test Turbine

The internal flow of turbo-machinery is intrinsically three-dimensional, viscous and unsteady, the unsteady characters of the internal flow have an important influence on the thermal power conversion, and investigate the unsteady interactions in turbine cascade is meaningful for improving the performance of high loading turbine. So its study and research related to the development of turbo-machinery directly. In this paper a transonic high-pressure turbine stage was modeled and simulated using domain scaling method, structured grid, dual time step method, standard k-epsilon turbulence model and sliding interface to analyze the three-dimensional unsteady flow in the High Performance Test Turbine stage.Traditional methods of turbo-machinery design have made a great success. These methods are based on such an important assumption that rotors and stators operate in relative steady flow conditions. As the unsteady fluctuation of flow field is neglected, deviation from real case is thus raised by the steady design methods particularly in the case of high-load and of design condition. Turbine stages of the unsteady flow field numerical simulation is at the present stage of the important areas of computational fluid dynamics research. The work in the present dissertation aims at exploiting unsteady flow phenomena to extract useful information for unsteady design methods. The paper presents the investigation of the effects of blade row interaction on the aerodynamics of the turbine stage in detail. The unsteady phenomena include the shockwave, wake, shedding vortex, endwall vortex, passage vortex and leakage vortex, etc. Periodic flow is observed for each vane passing period. A stator trailing edge shock appears as the turbine stage is operating at transonic conditions. The shock alters the flow condition in the rotor section periodically. The vortex simulated in this article include the shedding vortex induced by the vane trailing edge boundary layer, the endwall vortex generated by the endwall boundary layer interaction, the passage vortex generated by the rotor rotation, and the leakage vortex generated by the tip clearance flow. The same patterns in tip leakage flow structures were observed in both unsteady and steady simulations. The upstream wake-passage vortex interactions in turbine cascade were simulated, and the flow mechanisms were analyzed. Numerical simulations were applied as main tool to study unsteady flow phenomena. Numerical results indicate that periodic upstream wakes can enhance the vorticity of passage vortex, which increases losses. On the other hand, upstream wakes can suppress the streamwise vorticity development of passage vortex to some extent, which reduces losses. The combined unsteady effect in the endwall region depends on the balance of above two factors.The CFD code used to simulate the fluid field is the commercial software Ansys-CFX. Through the numerical simulation, it can make a qualitative looking of unsteady flow in the turbine stage and the numerical result can provide an objective for the unsteady optimization and the design of turbines.