气液两相入流条件下离心泵内部流动诱导特性实验研究

Tests for flow induced characteristics of a centrifugal pump under air-water two-phase inflow condition

搭建了泵送气液两相流实验台,以比转速n_s=132.2的离心泵为模型进行气液两相入流条件下的流动诱导特性研究,获得了在不同进口含气率下的外特性和压力脉动、振动信号的频谱和概率密度图。研究结果表明:气液两相入流条件下,离心泵在小流量工况时的性能对气体更加敏感;模型泵在入流含气率超过8%以后,性能急剧下降且可测试的工况范围变窄并比较紊乱,能达到的最大入流含气率为10%;气液两相入流条件下,泵出口压力脉动主频仍为叶频,叶频处幅值随着进口含气率的增大而增大,含气率越大低频区的宽频特性越明显;压力脉动信号和振动信号均服从正态分布,随着进口含气率的不断增大,压力脉动的概率密度函数(PDF)幅值逐渐减小而压力幅值跨度逐渐变宽,振动的PDF幅值呈先增大,然后减小,在进口含气率为5%时达到最小(仍大于纯水工况),然后再增大的趋势,两者均可作为流态监测的重要依据。

A two-phase flow pumping test platform was built to study flow induced characteristics of a centrifugal pump under air-water two-phase inflow condition. The pump characteristics were measured when its ratio rotating speed ns=132.2. Under different flow rates and inlet air voids, the pump’s outer characteristics, pressure pulsation, vibration signal frequency spectra and their probability density figures were obtained. The study results showed that the performance of the centrifugal pump is more sensitive to air under the conditions of small flow rate and air-water two-phase inflow;its performance drops sharply when inflow air void is more than 8%,and the range of working conditions that can be tested becomes narrower and more chaotic, the maximum air void of the pump can reach 10%;the main frequency of the pump outlet pressure pulsation is the blade frequency under air-water two-phase condition, vibration amplitude at the blade frequency increases with increase in inlet air void;the larger the inlet air void,the more obvious the broadband characteristics of the low frequency field;pressure fluctuation signals and vibration signals obey the normal distribution;with increase in inlet air void, the probability density function (PDF) amplitude of pressure pulsation decreases gradually, while its span becomes wider gradually;the PDF amplitude of vibration increases firstly and then decreases, and reaches the minimum when inlet air void is 5%, furthermore it has a rising trend;both pressure fluctuation and vibration variations can be used as important bases for flow state monitoring.