Research On Turbine Blade Profile Design Method Under Wide Operating Conditions

Aeroengine and marine gas turbine often work in off-design conditions,resulting in turbine efficiency attenuation,which is specifically shown as follows:with the change of working conditions,the blade exit Mach number（spanning Ma₂=1 working condition）and incidence angle changes in a wide range.At present,domestic researches on turbine wide operating conditions are few and very scattered,which lack the design methods of turbine blade profile under a wide range of variable working conditions（variable exit Mach number and incidence angle）.Therefore,in order to adapt to the tactical indicators of excellent performance in the wide operating range of aeroengines and marine gas turbines,it is of great significance to carry out the optimization and design research of turbine blades in wide operating conditions.First of all,this paper selects the range of 0.6～1.4 exit Mach number and-40°～20°incidence angle,and studies the flow field characteristics and loss variation laws of two typical turbine blade profile:convergent and convergent-divergent blade profile.The results show that the loss of the convergent blade profile increases with the increase of exit Mach number,and the loss of the convergent-divergent blade profile first increases,then decreases and then increases with the increase of exit Mach number;the incidence angle mainly affects the front load distribution of the blade profile;the loss of both convergent and convergent-divergent blade profile first decreases and then increases with the increase of incidence angle.Secondly,according to the loss analysis,the unguided turning angle,trailing edge wedge angle and trailing edge thickness,leading edge radius and leading edge wedge angle are selected as the key parameters,and the direct method is used to optimize the blade profile.The optimization results show that the average loss of the optimized blade profile is reduced by 1.95%in the range of Ma₂=0.6～1.4,and by 3.04%in the range of-40°～20°incidence angle.Then,the basic characteristics and parameter selection rules of turbine blade profile under wide operating conditions are revealed.The results show that larger leading edge radius and smaller leading edge wedge angle should be selected to enhance the adaptability of incidence angle;the curvature from leading edge to throat of suction side should be increased and the curvature from throat to trailing edge should be decreased by reducing unguided turning and trailing edge wedge angle;the strength of shock wave and vortices can be weakened by choosing a smaller value of trailing edge thickness.Finally,based on the summary of the selection rules of blade profile parameters for turbine wide operating conditions,the newly designed turbine rotor blades are analyzed under variable working conditions,and the internal flow and loss distribution of the turbine blades under wide operating conditions are explored.The results show that:when rotor blade is designed for wide operating conditions,midspan can still be selected according to the blade profile parameters of the turbine wide operating conditions;tip profile must consider the effect of leakage flow,and adopt a larger leading edge radius and leading edge wedge angle,smaller unguided turning and trailing edge wedge angle.Compared with turbine blade profile in wide operating conditions,the structure has the feature of“more convex front and flatter back”on suction side,which can reduce leakage loss while ensuring better performance in variable working conditions.In this paper,the basic blade profile characteristics and parameter selection rules obtained in wide operating condition of turbine are studied,which can provide certain reference for aerodynamic design of wide operating condition turbines of aeroengine and marine gas turbine.