Study On The Clearance Flow Mechanism Of Micro Turbine Rotor-Stator Cavity

In order to ensure the connecting shaft in the shaft passage can work normally under high temperature,high pressure and high load,and to protect the gap passage from the influence of the main stream invasion,usually through the rotor-stator cavity into the gas.However,when the clearance flow is injected vertically into the main flow field of the turbine,it will cause the loss of the main flow field,especially near the wall of the main flow,the secondary flow structure formed by boundary layer separation will affect the turbine flow.In this paper,the flow mechanism and the main flow intrusion characteristics of the clearance flow in the rotorstator cavity of a turbine are revealed within the calculation range of considering the heat transfer characteristics of the turbine,and the flow law of the clearance flow is summarized,based on the deformation of disk cavity under multi-load coupling,a method for pmadicting the clearance deformation is proposed.First of all,this paper simplifies the turbine cold air inlet model,through the simplified flow tube model calculation,in this paper,the flow characteristics of turbine inlet mixing region under different pressure gradients,Reynolds number and inlet blowing ratio are compared.The results show that the effect of the variable blowing ratio on the gap flow is the most obvious.When the blowing ratio is between 0.025 and 0.1,the effect of the gap flow on the main flow is small.Secondly,based on the real multi-physical field environment,the whole-cycle turbine model is numerically modeled,and the high-precision fluid-heat-solid coupling model is established,the aerodynamic parameters in the flow field can be combined with the solid domain.The influence of clearance flow on the main flow and its flow mechanism under the heat transfer characteristics are investigated.Finally,the passage and the main flow area of the turbine rotor-stator cavity are analyzed by numerical method,and the flow relationship between the gap flow and the main flow is further explored,the influence of blowing ratio on main stream invasion and turbine performance is summarized.A method for predicting the clearance deformation of the impeller is proposed.The boundary deformation of the impeller is calculated by using the multi-physical field calculation method,the accuracy of the model is verified by the results of multi-mode flow-thermo-solid coupling.The results show that when the blowing ratio is greater than 0.08,the sealing efficiency is greater than 90% at all angles near the exit,but the overall relative error is within a certain range,and the maximum error is less than 10%.