基于扇形孔的实验数据,提出了一种预测气膜冷却效率的新关联式.综合考虑孔形参数和孔内外流动条件对气膜冷却效率的影响,构建关联式特征系数的代理模型.结果表明:通过实验设计(DOE)获得的优化孔与采用特征系数代理模型获得的优化孔的气膜冷却效率和最优孔形参数基本一致;应用新关联式加速气膜孔形的多置信度优化或优化多气膜孔阵列的具体布局具有显著的工程应用价值.

Under the condition of cross-flow inlet, the effects of cross-flow ratios of 0,0.2 and 0.4 and inlet blockage（ upstream and downstream sides of cross-flow） on the film cooling characteristics of fan-shaped holes under different blowing ratios were studied based on the film cooling plate experiment. Results show that when the crossflow ratio decreases from 0.4 to 0.2, the film deflection of the fan-shaped hole is reduced and the film performance is improved. But when the crossflow ratio approaches zero, the coolant deflects to the opposite side with performance decline. Blockage on the downstream side aggravates the film deflection and reduces the cooling effectiveness. Blockage on the upstream side reverses the coolant deflection direction and raises the coolant coverage. Effects of inlet blockage on film cooling effecive depend on the hole location and the coolant serving flow conditions.

A flat plate film cooling experiment was conducted to investigate the effects of near-wall vortex on the film cooling performance of a fan-shaped hole. A vane-shaped vortex generator was installed upstream of a fan-shaped hole to simulate a near-wall vortex. Infrared thermography was used to measure the cooling effective-ness and heat transfer coefficient for the blowing ratios from 0.5 to 2.5. Inlet flow properties of turbulence in-tensity and boundary layer thickness were varied to set up different freestream conditions. Results show that the vortex affects the film cooling to varying degree under different freestream conditions. In case of low inlet turbulence, upstream boundary layer thickness is a significant factor on the film cooling performance. With a thin boundary layer, vortex intensifies the mixing of freestream and coolant jet. The decrease in lateral-average film cooling effectiveness ranges from 0.02 to 0.06 depending on the blowing ratios and relative positions of the vortex. The heat flux through the test plate is significantly increased by 20%. Thickened boundary layer pro-motes coolant jet to penetrate the freestream flow, which degrades the film cooling performance. However, thick boundary layer restrains the vortex disturbance on the freestream flow, and the heat flux of the test plate is only increased by 5.6%. In the case of high turbulence intensity, boundary layer plays an insignificant role. The near-wall vortex dissipates quickly and exerts little impact on the film cooling effectiveness and surface heat transfer coefficient.

Fan-shaped hole is a typical shaped hole frequently used in gas turbine film cooling, which may operate in a complex vortical flow environment of turbine blade rows. It is critical to understand the destructive mechanism of the film cooling by near-wall vortex on the endwall surface. A vortex generator (VG) was installed in front of a discrete fan-shaped hole to produce a vortical environment on a flat plate. Heat transfer effects were experimentally studied for mainstream velocities of 20m/s by measuring the adiabatic film cooling effectiveness at blowing ratios M = 0.5 to 2.5. Fluid dynamics effects of vortical upwash and downwash movements were numerically analyzed. Results show that near-wall streamwise vortex destroys the film flow and intensifies the mixing of hot gas and coolant flow, which leads to the deterioration of film cooling performance. Film coverage area varies remarkably with respect to the positions of streamwise vortex. An efficient blowing ratio has a strong ability to mitigate the influence of near-wall vortex. At M = 2.5, streamwise vortex can restrain liftoff tendency of coolant jet and retard the decrease of film cooling effects.

Fan-shaped hole is a typical shaped hole frequently used in gas turbine film cooling, which may operate in a complex vortical flow environment of turbine blade rows. A vortex generator (VG) was installed in front of a single row of fan-shaped holes to produce streamwise vortex on a flate plate to simulate the vortical flows environment of the gas turbine. Effects of streamwise vortices on the film cooling effectiveness of a discrete fan-shaped hole were experimentally studied. Results show that streamwise vortices intensify the mixing of mainstream and coolant jet, the film cooling effectiveness decrease sharply, the maximum reduction of the area-averaged-film cooling effectiveness is 63%. At the high blowing ratio M=2.5, streamwise vortices can restrain lift-off tendency of the coolant jet and retard the decrease of film cooling effectiveness. Also of importance are the changes of the film cooling distributions and coverage area, which occur as the lateral position of the vortex is changed.