Study Of Heat Transfer Characteristics Of Turbo Blades Surfcae

Turbine blade profile heat transfer calculation is very important for the optimization of the cooling structure and geometric shape of the real blade.There are many factors affecting the heat transfer of the leaf surface,such as the Reynolds number of import and export,turbulence,leaf curvature,boundary layer transition,etc.The research shows that the wall temperature also has an effect on the heat transfer of the turbine blades.True temperature ratio experiment of the wall temperature and the total temperature of mainstream are not only expensive,but also the error caused by the experimental measurement.In order to discuss the heat transfer characteristics of turbine blade surface,numerical simulation method was used to study the Nusselt number and velocity distribution of blade profile,when the pressure ratio between inlet and outlet of the blade grid is 2 and the wall temperature to gas ratio are 0.7,0.8 and 0.9,respectively,and to study the blade surface heat transfer coefficient when the leaf surface roughness were 0mm,0.01 mm,0.02 mm,0.03 mm,respectively.Study on the effect of temperature ratio of wall to gas on the heat transfer of turbine blade profile shows that the bigger the temperature ratio is,the smaller the dimensionless excess temperature near the wall and the Nusselt number on the leaf surface are.The maximum difference of the Nusselt number is up to 32% between the temperature ratio 0.7 and 0.9.With the increase of the temperature ratio,the position of the suction surface separation bubble is closer to the leading edge and the distance between the flow and the direction of the separation is increased.The Nusselt number of the blade surface rises sharply in the main direction in the range from x/d=0.836 to x/d=0.884,due to the separation and reattachment of the turbulent boundary layer caused by the separation bubble.The study of the effect of surface roughness on the heat transfer of the turbine blade surface shows that as the roughness increases,the surface heat transfer coefficient of the blade increases.Compared with the smooth surface,the average heat transfer coefficient with surface roughness of 0.01 mm to 0.03 mm increased by 103.88%,145.37% and 166.91% respectively.The greater the roughness,the closer the pressure surface and suction surface transition to the leading edge,the greater the heat transfer coefficient after turning.The increase of the surface roughness,effectively reduces the impact of boundary layer separation.The greater the roughness,the closer the starting point of the separation bubble to the tail edge,and the shorter the separation bubble.Compared with the smooth surface,the starting point of the separation surface from the surface roughness of 0.01 mm to 0.03 mm lagged 50.1%,77.2% and 111.7% of the bubble length along the mainstream direction,and the maximum value of the heat transfer coefficient decreased by 20.13%,38.13%,50.73%,respectively.