\r刘正先，王生玲\r
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AuthorsHTML:\r刘正先，王生玲\r
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AuthorsListE:\rLiu Zhengxian，Wang Shengling\r
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AuthorsHTMLE:\rLiu Zhengxian，Wang Shengling\r
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Unit:\r天津大学机械工程学院，天津 300350\r
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Unit_EngLish:\rSchool of Mechanical Engineering，Tianjin University，Tianjin 300350，China\r
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Abstract_Chinese:\r在叶轮失速流场中，由于小流量工况下回流而导致部分通道阻塞，单通道计算无法真实反映失速发生过程，因此为了识别离心叶轮失速信号，首先采用数值方法对Eckardt 离心叶轮设计工况和失速工况实施全通道非定常流场计算．对比分析设计工况和失速工况三维流场流动涡分布，离心叶轮由于径向折转和叶片扭转，在设计工况下就存在低速二次涡，而失速工况下在入口存在4 个对称分布的通道涡，造成叶轮阻塞并导致失速．进一步采用空间傅里叶分析方法对不同叶高、不同流向位置周向压力信号进行定量分析，结果表明：①设计工况下流道中仅存在受叶片通过影响的20 阶扰动，而失速工况下4 阶扰动振幅最大，并存在振幅逐渐减小的倍数阶扰动，即此时叶轮中存在4 个失速团；②引起叶轮失速的流动涡首先出现在入口近叶顶区域，导致叶轮入口阻塞，并逐渐发生涡脱落、破碎进而形成新的流动涡，并向流道下游移动；③通过对振幅最大的4 阶扰动相位变化分析，得到失速团周向运动速度约为0.62～0.73 倍叶轮转速．最后通过与不同流向位置静压信号时间傅里叶分析结果对比，确定空间傅里叶分析能准确识别叶轮中失速团个数及周向传播速度，可有效应用于失速信号识别和进一步对叶轮流场失速信号的实时监测、主动控制和优化设计．\r
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Abstract_English:\rUnder a low flow rate condition，the reversed flow is likely to cause some passages to choke. The stall process cannot be accurately reflected by simulating the single passage. To recognize the stall signal in a centrifugal impeller，the full-annual unsteady-flow simulation was carried out under the design and stall conditions of the Eckardt impeller. After analyzing the flow vortex distribution，results revealed a trailing secondary vortex under the design condition due to the strong meridian and circumferential twist，along with four passage vortices at the impeller inlet region under the stall condition. The pressure signals on several streamwise and span lines were analyzed by spatial Fourier transform method，and several conclusions were obtained. ①There only exists 20th order perturbation influenced by blade pass frequency in design condition，but the amplitude of the 4th order perturbation is at the maximum under the stall condition，such that four stall cells exist in the impeller. ②The flow vortex causing the stall first occurs on the blade leading edge near the shroud endwall，and gradually sheds，breaks down，and moves
downstream. ③Analyzing the phase variation of the 4th order perturbation of the maximum amplitude，results indicated that stall cells move at about a 0.62—0.73 rotor speed along the circumference. Compared with the Fourier transform results of the pressure time series at different streamwise positions，the spatial Fourier method can exactly identify the number of stall cells and propagation speed along the circumference. It can be effectively applied to the recognition of stall signals，which can improve the real-time monitoring，active control and optimal design of the impeller flow field.\r
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Keyword_Chinese:离心叶轮；全通道非定常流场；空间傅里叶分析；失速信号\r

Keywords_English:centrifugal impeller；full-annual unsteady flow field；spatial Fourier transform(SFT)；stall signal\r


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