根据子午面流道的相对马赫数分布可知，在入口轮毂钝头处存在低速区，这是由于流动工质在此被阻塞减速。在流道内部叶根处存在低速区，这是由于转弯处扩压度增大，边界层内流动首先没有足够的动能克服逆压梯度，率先发生减速分离。叶顶处也因转弯剧烈和叶顶泄露流影响存在减速现象。

According to the relative Mach number distribution of the meridian channel, there is a low speed zone at the blunt head of the inlet hub, which is because the flow medium is blocked and decelerated here. There is a low speed zone at the blade root inside the flow channel, which is due to the increase of diffuser degree at the turning point, and the flow in the boundary layer does not have enough kinetic energy to overcome the inverse pressure gradient, and the deceleration separation occurs first. The tip of the blade is also decelerated due to sharp turning and tip leakage flow.