相对马赫数云图中，低马赫数区域与熵增区域基本重合，低能流体具有高熵、低速的特征。可以发现，优化方案的低相对马赫数区域有所增加，但相对马赫数最小值变大。在x/s_m=1.0位置处，叶顶位置的低相对马赫数区随着型线修改和优化设计逐渐减小。在优化方案叶片尾缘位置，由于叶片的消失出现局部加速程度增加，流体速度增加造成的熵减现象也是后两种方案效率提高的因素之一。静压分布结果表明流场的压力梯度均匀，工质在无叶扩压器中静压继续提高。

Compared with the Mach number cloud image, the low Mach number region basically coincides with the entropy increasing region, and the low energy fluid has the characteristics of high entropy and low speed. It can be found that the low relative Mach number region of the optimization scheme is increased, but the relative Mach number minimum is larger. At the x/s_m=1.0 position, the low relative Mach number region at the tip position gradually decreases with the modification of the profile and the optimization design. At the trailing edge of the optimized scheme, the local acceleration of the disappearance of the blade increases, and the entropy reduction caused by the increase of fluid velocity is also one of the factors that improve the efficiency of the latter two schemes. The static pressure distribution results show that the pressure gradient of the flow field is uniform, and the static pressure of the working medium in the vaneless diffuser continues to increase.