Response Tests on the Unsteady Fluid Forces for the Oscillating Centrifugal Impeller

第一年致力于从非定常压力测量值估算旋进叶轮围带上的流体力矩。结果表明，不稳定区域增加的增加是泄漏流量，造成的泄漏流的平均切向速度的增加。还发现外径处的阻力增加导致力测量值增加。基于整体流动模型进行了数值分析。结果表明，解析法可以模拟实验中的大多数重要方面.第二年，对前一年设计制造的开式压气机叶轮进行了直接测力实验。为了识别叶轮旋转和涡动运动的相位关系，将主轴和涡动套筒的两个触发信号输入到AND电路中，当旋转和涡动信号同时开启时，输出一个触发信号，并利用该触发信号开始对力信号进行FFT累加，得到了一个有趣的结果，表明了前向和后向涡动不稳定性的可能性。得到了然而，对波动力的详细检查表明存在意外的轴振动。因此，我们应该继续实验，以获得更可靠的数据。

The first year was devoted to the estimation of the fluid force moment on the shroud of precessing impeller, from unsteady pressure measurements. It was shown that the destabilizing region increases as the increase is leakage flow rate, caused by the increase in the mean tangential velocity of the leakage flow. It was also found the increase of resistance at the outerradius causes the increase in the force measurements. A numerical analysis based on the bulk flow model was made. It was found that analysis can simulate most of important aspects experiments. It was also made clear that the leakage flow can be basically treated as a 2-D inviscid unsteady flow within variable clearance.In the 2nd year, direct force measurements on a whirling open-type compressor impeller which was designed and manufactured in the preceding year. To identify the phase relationship of the impeller rotation and the whirling motion, two triggering signals from the main shaft and the whirling sleeve was put in an AND circuit and a triggering signal was put out when the rotational and whirl signal were both on. The triggering signal was used to start accumulating the force signal in a FFT.An interesting result which suggests the possibility of both forward and backward whirl instability was obtained. However, a detailed inspection of the fluctuating force suggests the existence of unexpected shaft vibration. Hence we should continue the experiments to obtain more reliable data.