主流压力梯度对气膜孔流量系数影响机理

测量了主流零压力梯度、正压力梯度及负压力梯度条件下气膜孔流量系数,分析了主流压力梯度对气膜孔流量系数的影响机理.结果显示:正、负压力梯度的存在对气膜孔流量系数的影响幅度最大值分别为22%及26%.主流压力梯度会对喷出气流施加弯转作用及挤压作用,同时也会改变喷出气流与近壁面主流的掺混作用,从而影响气膜孔流量系数.挤压作用使喷出气流管变细而增加喷出气流的流动损失;弯转作用主要影响喷出气流的流动轨迹,正压力梯度下弯转作用使喷出气流的轨迹靠近壁面而远离其自由喷射方向增加流动损失,负压力梯度的作用则相反;掺混作用会增加喷出气流的动量消耗,正压力梯度对掺混有抑制作用,从而减少喷出气流用于掺混的动量损失,负压力梯度则相反.

Influence physics of mainstream pressure gradient on film hole discharge coefficient

Film hole discharge coefficients at different mainstream pressure gradients (zero pressure gradient, positive pressure gradient and negative pressure gradient) were tested, and influence physics of mainstream pressure gradient on film hole discharge coefficient was analyzed. Result shows that the maximum amplitude of effect on film hole discharge coefficient of mainstream positive and negative pressure gradients are 22% and 26% respectively. At different mainstream pressure gradients, bending effect and crushing effect of mainstream on jet are different, together with the changed interaction of jet with mainstream, and therefore the film hole discharge coefficient will be different. Crushing effect makes jet narrower and enhances the jet flow loss. Bending effect can change jet flow track; the positive pressure gradient makes jet flow close to the wall but far away from the free ejection direction, resulting in more flow loss; to the contrary, the negative pressure gradient may decrease the flow loss. The mixing effect enhances the momentum dissipation of jet, while at positive pressure gradient, the mixing effect is restrained and then momentum dissipation of jet decreases, however, the rule is opposite at negative pressure gradient.