Study on Dynamic Response Including Rotating Stall of a Rotor Blade Row

在改善轴流风机低流量特性和探索旋转失速开始的项目中，揭示了以下几点：1.低能流体向转子空心区压力侧积聚是旋转失速开始的原因。这种低能流体的去除极大地改善了风机的低流量特性。在叶顶间隙较大的通风机中，低能流体的积聚是由叶尖间隙的泄漏涡引起的。在近失速流速区，即使改变风机流量，静压升也几乎保持不变。动叶排内相对速度的减速导致的动压差对风机流量的变化非常敏感。流量下降幅度较小时，阻力差变大，叶片排损失大大增加。在这种流量方案下，入口速度分布对筛网也很敏感。利用非定常Bernoulli方程计算了叶片的瞬时排损失，并将其绘制为瞬时进气角的函数。在旋转失速起始阶段，旋转失速是从叶尖开始的。细胞的旋转速度在整个发育过程中保持不变。细胞在转子旋转四到五周后完全发育。这一级内的流场变化很大，在转子半桨距运动时不同，文[4]中所得的瞬时叶排损失必须在以后的旋转失速数值模拟中加以验证。

In the project of improving the low flow rate characteristics of an axial flow fan and exploring the onset of rotatin stall, the followings are revealed:1. The low energy fluid accumulated toward the pressure side of rotor blased is responsible for the onset of rotating stall. The removal of this low energy fluid improves low flow rate characteristics of the fan perfectly.2. In a fan with relatively large tip clearance, the accumulation of the low energy fluid is caused by leakage vortices through tip clearance.3. In the near stall flow rate regime, the static pressure rise remains almost constant even if the fan flow rate is changed. The dynamic presure difference due to the deceleration of relative velocity through the rotor blade row is, on the contrary, sensitive to the change of fan flow rate. The difference becomes large with a small decrease in flow rate and causes much increase in blade row losses. The inlet velocity distribution is also sensitive to the screen in this flow rate regime.4. The instantaneous blade row losses calculated from the above data using the unsteady Bernoulli equation are plotted as a function of instantaneous inlet angle.5. In the initiation of rotating stall, it starts from the blade tip. The rotating speed of the cell remains constant throughout its development. The cell completely develops in four or five rotations of the rotor. The flow field in this stage is so changeable that it differs during the period of half pitch movement of the rotor.The instantaneous blade row losses obtained in 4. must be verified by using them in a numerical simulation of rotating stall which is going to be carried out hereafter.