高负荷叶片弯曲对壁面流动的影响

测量了低展弦比高负荷涡轮直叶片和正、反弯叶片叶栅端壁和叶片表面静压及流道内损失沿流向的发展, 并对端壁和叶片吸力面上的流动进行了墨迹显示。实验结果表明:叶片正弯增大了叶栅进口段逆压梯度, 并在叶片吸力面前部形成反“C”型静压等值线, 加剧了叶片前缘的鞍点分离和吸力面分离线向叶栅中部的收敛。叶片反弯减小了叶栅进口段逆压梯度, 在吸力面进口形成垂直于端壁的静压等值线, 不仅削弱了鞍点分离, 而且造成吸力面上的自由涡层型分离, 避免了吸力面上、下分离线相交, 因此二次旋涡损失大为降低。 

EFFECT OF CURVING OF HEAVY DUTY BLADES ON WALL FLOW

Static pressures on endwalls and blade surfaces and growth of the losses along flow direction were measured,and the flow visualizations of the endwall and blade suction surface with ink traces were also made.The experimental results show that the positive curving of the blade increases the streamwise adverse pressure gradient in the cascade inlet and makcs isobars on the front part of the blade suction surface into opposed C shape,thereby the saddle point separation near the blade leading edges and convergence of separation lines on the suction surface to the cascade middle are intensified.The negative curving of the blade reduces the adverse pressure gradient in the cascade inlet and makes isobars perpendicular to the endwall on the front part of the blade suction sarface.As a result not only the separation flow near saddle point weakens,but also the separation flow on the suction surface turns into free vortex laminal separation so as to aviod interception of the upper and lower separation lines.In consequence,the secondary vortex losses are decreased greatly.