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

在改善轴流风机小流量特性和探讨旋转失速起始点的项目中，揭示了以下内容：1。低能量流体向压气机压侧聚集是导致旋转失速的主要原因。这种低能量流体的去除完美地改善了风扇的低流速特性。在叶尖间隙较大的风扇中，低能流体的积聚是由通过叶尖间隙的泄漏涡引起的.在近失速流率状态下，即使风扇流率改变，静压升也几乎保持恒定。动叶排相对速度减速引起的动压差对风机流量变化敏感。流量小幅度降低时，这种差异就变大，导致叶排损失大幅度增加。在此流速范围内，入口速度分布对筛网也很敏感.根据上述数据使用非定常伯努利方程计算的瞬时叶栅损失绘制为瞬时入口角的函数。5.在旋转失速的起始阶段，它是从叶尖开始的。细胞的旋转速度在整个发育过程中保持恒定。细胞在转子的四到五次旋转中完全发育。该级的流场是变化的，在转子半变桨期间流场是不同的。必须通过将它们用于以后将要进行的旋转失速的数值模拟来验证。

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.