Analogy Principle For Overall Cooling Effectiveness Between Engine And Laboratory Condition And Numerical Validation

The actual temperature of metal determines whether the hot components work properly.The overall cooling effectiveness?was an important parameter for conjugate heat transfer analysis of gas turbines,it represents the distribution of dimensionless temperature of gas turbines surface.The temperature of gas turbines surface could provide reference for the design of cooling.Thus the studies of the overall cooling effectiveness has gradually become the focus of the researcher's.Firstly,the analogy principles of the overall cooling effectiveness have been studied with three cooling structures,including impingement/effusion configurations,single internal cooling structure and the thermal barrier coating(TBC)structure.The mainstream side Biot number Bi_g and the heat transfer coefficient ratioh_g/h_c are the same analogy principles for all above three cooling structures.The adiabatic cooling effectiveness?and warming factor?were another important parameter for impingement/effusion configurations.The ratio of TBC to turbine hot components thermal resistances was an important parameter for the TBC structure.Meanwhile,this paper also provides a reliable matching principle of the overall cooling effectiveness from theory under laboratory condition.Matching mainstream side Biot number can be converted to match the ratio of air thermal conductivity and solid material thermal conductivity.Thus,the mainstream side Biot number can be matched easy by choosing suitable solid material.If the mainstream side Biot numberBi_g,Reynolds number Re_g,temperature ratioT_g T_c and blowing ratio M are matched between engine condition and laboratory condition,the overall cooling effectiveness and related analogy parameters will be matched well.When the temperature ratio T_g T_c is mismatched,the adiabatic cooling effectiveness and heat transfer ratio will also be mismatched.However,matching momentum flux ratio will reduce the difference of the adiabatic cooling effectiveness and heat transfer ratio between engine condition and laboratory condition.In order to verify the conjugate heat transfer analogy principles described above,the numerical simulation of impingement/effusion plate and turbine guide vane were studied.The analogy principles were studied on the impingement and film cooling plat model under engine and laboratory condition by numerical simulations.The match methods have been validated by numerical simulations.The mainstream side Biot number can be matched well by matching Reynolds number of mainstream and choosing suitable solid material.If the temperature ratio and blowing ratio M was matched between engine condition and laboratory condition,the other analogy parameters can be also matched easy.Thus the overall cooling effectiveness was nearly same on both the values and distributions between engine and laboratory conditions.If the temperature ratio is mismatched,matching momentum flux ratio will reduce the difference of the adiabatic cooling effectiveness and heat transfer ratio between engine condition and laboratory condition.Thereby,the overall cooling effectiveness under laboratory condition was similar with that under engine conditions.However,the results of matching blowing ratio and velocity ratio were obviously different with that of engine condition.The simulation results also verified the ratio of coolant side Biot number between engine and laboratory conditions.The analogy principles were also studied on the turbine guide vane with complicated impingement cooling structure under engine and laboratory condition by numerical simulations.This paper compared the overall cooling effectiveness under engine condition with that under laboratory with three different temperature ratio.The matching methods were further validated.The mainstream side Biot number can be approximately matched by matching Reynolds number of mainstream and choosing suitable solid material,but there were slightly difference around the film hole between engine condition and laboratory condition which mismatched the temperature ratio.When the temperature ratio and blowing ratio M was matched between engine condition and laboratory condition,the overall cooling effectiveness and other analogy parameters can be also matched easy.The advantage of matching temperature ratio further verified on the turbine vane.If the temperature ratio is mismatched,the heat transfer ratio can be matched well between engine condition and laboratory condition,and the distribution trend of adiabatic cooling effectiveness can be also matched.The results also shown that,as the temperature ratio of laboratory was closer to that of engine condition,the adiabatic cooling effectiveness and heat transfer ratio of laboratory were also closer to that of engine condition.