Effect Analysis And Modeling Research Of Endwall Film Cooling On Flow Loss In Turbine End Region

In order to improve the performance of gas turbines,the inlet temperature of the high-pressure turbine continuously increases in recent years.Cooling the end wall with coolant film is a common way to protect the end wall.Secondary flow near the turbine end wall is very complex,and the addition of coolant jet also increases the flow complexity in this region.Therefore,analyzing the effect of coolant on the flow in the end wall region is of great help to the turbine design.In this thesis,the first stage guide vane of the E~3 engine high-pressure turbine is studied by approach of numerical computation.Different film hole design parameters and coolant aerodynamic parameters are used.This thesis contains three main parts.Firstly,the influence of the coolant on the flow in the end wall region under different working conditions is analyzed,and it is found that the cooling jet has a good coverage effectiveness on the hub end wall when the mass flow ratio is relatively low,but the coolant is affected by the pressure gradient in the channel and impacts the cascade near the trailing edge,forming an impact vortex.In addition,if the mass flow ratio is relatively low and the position of the hole is very close to the pressure side leading edge of the cascade,the coolant will be greatly deflected by the impact of the pressure side branch of the horseshoe vortex,and the coolant will leave the wall surface earlier.Secondly,through comparative analysis of the numerical computation results,based on the loss scheme and the loss coefficient calculation method of the K-O model,the hub end wall film cooling correction factor is developed.It has been calculated that for all considered operating conditions,the developed hub end wall film cooling correction factor can reduce the prediction error rate of the K-O model from 20%to less than 3%.Finally,the fluid-solid conjugate heat transfer between the end wall solid domain,the coolant fluid domain and the mainstream fluid domain is taken into account,and the effect of heat transfer on the cooling of the end wall and the airflow is analyzed.The study found that the secondary flow intensity near the end wall zone,especially the vortex strength of the suction side branch of the horseshoe vortex,was smaller than that without the solid heat transfer;the pressure gradient in the channel could begin to change the outflow direction of the coolant at the outlet position of the holes;and the jet separation vortex is more difficult to form when the mass flow was relatively low.When the holes are in the area with a high mainstream Mach number,a reasonable mass flow ratio is important.Low mass flow can only get poor cooling effects,but high coolant mass flow may lead to ultrasonic coolant jets,resulting in shock wave loss,thereby reducing the efficiency of the turbine.