On The Aerodynamic Design And Aerothermal Performance In Different Dimensions Of Axial Flow Turbine With High And Low Reaction

Axial flow turbine is one of the three core components of an aeroengine.Among them,aerodynamic design is at the initial stage of the whole design process of turbine components,which has a crucial impact on the final shape and reliability of turbines.In order to better master the aerodynamic design of a single-stage transonic turbine and related issues on aerothermal performance.In this dissertation,two turbines with reaction degrees of 0.25 and 0.43 are systematically completed from one dimension to three dimension,and steady and unsteady numerical simulation studies are carried out on blade profile design and modification,rotor blade tip leakage flow and aerothermal performance of turbine rotor blades in the presence of film cooling.In order to explore the influence of preliminary design parameters on aerodynamic design of axial flow turbines,and improve the existing aerodynamic design system,three one-dimensional calculation strategies are established,which are respectively applied to Smith graph with variable specific heat,the calculation of the relation between reaction and relative total temperature at rotor inlet,and calculation of feasible region of preliminary design parameters under multi-constraint conditions.Based on these tools,relevant research is designed and analyzed respectively;in addition,it is pointed out that the fidelity of CIAM loss model is good,but the accuracy is insufficient.In view of the influence of reaction degree on turbine tip leakage flow,in order to master the aerothermal characteristics of tip structure and effectively control the leakage loss and tip heat load.Experimental and numerical results show that the open groove tip structure can effectively reduce the leakage loss.The results of transonic TTM turbine stages with low reaction degree show that the open groove tip structure is effective in reducing the leakage losses and the heat loads of rotor and casing.The study shows that the turbine stage efficiency is 0.33% and 0.42% higher than that of closed groove tip and flat tip at 0.5mm clearance,respectively,and the heat loads of casing are reduced by 10%.Through the entropy production rate and the velocity triangle analysis of the leakage flow,the reasons that the open groove tip is beneficial to reduce the leakage loss and the heat load of the casing are determined.When the boundary of turbine inlet is non-swirling and non-uniform,the stage efficiency with open groove tip is 0.22% higher than that of closed groove tip.When the boundary of turbine inlet is swirling,the stage efficiency with open groove tip is 0.33% higher than that of the closed groove tip.As a key parameter to match the stator and rotor blades,the reaction degree directly determines the flow Mach number and flow angle of the stator and rotor blades,which has a significant influence on the profile design and rotor-stator interaction.In order to master the blade profile design with the concepts of low loss,low heat load and low aerodynamic fluctuation amplitude,this dissertation firstly studies the aerothermal characteristics of turbine leading edge through leading edge reconstruction and modification.Secondly,unsteady numerical simulations are carried out to study the aerothermal performance and aerodynamic force of rotor blade with different kinds of aerodynamic loads.The results show that different blade leading edge reconfiguration and modification have significant influence on the heat load and aerodynamic performance of the blade,and the design criterions of leading-edge profile are proposed accordingly.The blade profile with forward load design is beneficial to the reduction of profile loss,blade profile heat load and amplitude of aerodynamic force fluctuation.In the preliminary design phase of a single-stage transonic turbine with an expansion ratio of 3.5,the difference in reaction degree will lead to significant differences in turbine rotor blade geometry and inflow conditions,resulting in changes in turbine stage aerodynamic losses,cooling air mixing,cooling effect and aerodynamic force fluctuation.In order to understand the influence of reaction degree on all aspects of one-dimensional aerodynamic scheme design from the perspective of high dimension and multiple disciplines.First of all,the aerodynamic design of two transonic turbines with pressure reaction of 0.25 and 0.43 is completed systematically and normatively from one dimension to three dimensions.Secondly,the influence degree of coolant on aerodynamic performance is studied.Finally,the differences between the two turbines in terms of loss,rotor-stator interaction,mixing of the cool film with the main flow,external heat transfer of the rotor blade tip casing and aerodynamic force are compared and analyzed under the condition of the rotor blade with or without film cooling.The results show that for two turbines with high and low reaction,the efficiency of the turbine stage decreases by 0.84%and 0.49% with the increase of 1% of the stator coolant,and 1.67% and 1.93% of the turbine stage efficiency with the increase of 1% of the rotor coolant.In addition,the reaction of the high reaction turbine increases three times as much as that of the low reaction one,and the increase of the tip leakage flow loss caused by cooling air is more obvious.The results show that the shock wave system in the two turbine passages is obviously different due to the different reaction degrees,and the intensity of "effective throat" effect is also different,which leads to the fluctuation amplitude of fluctuating pressure on the suction surface and pressure surface of the leading edge of the low reaction turbine.The difference of the time-averaged heat transfer coefficient distribution between the two turbine blades and the casing is relatively small.Under the disturbance such as rotor-stator interaction,the film hole flow presents different pulsating characteristics.In the high reaction turbine,the reverse flow phenomenon of hot gas exists in the film hole of blade root under the rotor-stator interaction,and the flow fluctuation amplitude of film mass flow is as high as 100%.In the low reaction turbine,the fluctuation amplitude of film hole flow is alleviated at higher disturbance frequency.In terms of aerodynamic force,the axial thrust of the rotor blade in the high reaction turbine is twice that of the low reaction one,and the absolute value of the fluctuation amplitude is roughly the same.