叶片弦向倾斜对损失发展的影响及叶片反弯降低损失机理的研究

早在六十年代初期,Ｓｍｉｔｈ提出了弦向倾斜叶片￣［１］。叶片的这种倾斜集叶片的后掠（叶片展向与气流不垂直）和上反（叶片表面与端壁斜交）于一身。根据理论分析可知,弦向倾斜叶片与周向倾斜叶片比较,在相同倾斜角下,它更能有效地抑制通道涡的形成和发展￣［２］。但是,到现在为止还没有实验数据证实这一计算结果。本文继文献￣［３］详细测量了弦向倾斜叶片叶栅由栅前至栅后诸截面上的气动参数。实验结果表明,弦向倾斜对损失的发展起到了与周向倾斜相类似的作用,但是前者比后者减小了叶栅进口段的流向逆压梯度,从而降低了二次旋涡损失。本文还测量了大转角常规直叶栅与反弯叶片叶栅端壁与叶片表面上的静压分布,探讨了反弯叶片降低损失的原因,认为：减小叶栅进口段流向逆压梯度,在叶片吸力面前部形成垂直于端壁的平行静压等值线、在中部形成反“Ｃ”型静压等值线,以及在流道内建立沿叶高的反“Ｃ”型静压分布,是反弯叶片降低损失的三要素。

EFFECT OF BLADE CHORDWISE LEANING ON THE LOSS DEVELOPMENT AND STUDY OF THE MECHANISM REDUCING LOSSES BY BLADE NEGATIVELY CURVING

The aerodynamic Parameters on the measurement plans arranged as three before, six in, and one after the cascades with the chordwise and circumferential lean blades and high turning angle and low aspect ratio were measured in detail. The experimental results show that the effect of chordwise lean blades on the loss development is analogous to that of circumferential lean blades, but blade chordwise leaning reduces the cascade inlet streamwise adverse pressure gradient and negative pressure gradient along blade height from the acute angle side in cascade inlet section,this leads to weaken the separation at the saddles and intension of passage vortices, thereby the secondary vortex losses are cut down. through analysis of experimental results of conventional straight cascade and negatively curved blade cascade with high turning angle and low aspect ratio, the resons reducing losses by blade negatively curving are expored. the reducing of cascade inlet streamwise adverse pressure gradient, the forming of perpendicular to the endwall on front of blade suction surface and negative shape "C" on midlle of the surface static pressure contours, and the building of negative shape "C" static pressure distribution along blade height in the passages are three essential factors reducing losses.