离心泵空化下的转速瞬变特性试验研究

通过安装轴编码器获取了离心泵空化过程的转速瞬变信号,利用时域和频域分析手段进一步探索在不同空化程度下转速瞬变的特点和规律。分析结果表明:当离心泵内刚发生空化时,离心泵的转速变化范围最大,以标准差衡量转速的波动程度也最大,严重空化时转速的波动程度高于未空化时的波动程度;在频域上,试验用离心泵—电机系统的转速的固有频率为2.9 Hz,空化条件下泵转速的主频也是轴频,不随流量和空化程度的改变而改变,但是同一流量下,空化初生时主频的幅值最高,严重空化时次之,未空化时最小;而不同流量下空化初生主频处的幅值则随着流量的增加先增大后减小,在设计流量下空化初生时主频处的幅值达到最大;在时频域上,通过小波分析的方法对转速的特征进行了分析,发现在空化下转速的能量主要集中在39~46.9 Hz,并且在空化初生时转速的能量最大。

Tests for rotating speed transient characteristics of centrifugal pump under cavitation

Transient rotating speed signal of centrifugal pump cavitation process was acquired through installing shaft encoder,and its characteristics and law under different levels of cavitation were further explored by means of time domain and frequency domain analysis.The analysis results showed that when cavitation just occurs in centrifugal pump,its rotating speed has the largest variation range,and fluctuation degree of rotating speed measured with standard deviation is also the largest,and the fluctuation degree of rotating speed under severe cavitation is higher than that without cavitation;in frequency domain,the natural frequency of the rotating speed of the centrifugal pump-motor system used in tests is 2.9 Hz;under cavitation condition,the main frequency of the pump rotating speed is also the shaft frequency,it does not change with the variation of flow rate and cavitation degree,but under the same flow rate,the amplitude of the main frequency is the highest during initial cavitation,followed by that during severe cavitation,and that is the minimum without cavitation;under different flow rates,the amplitude of the main frequency during initial cavitation firstly increases and then decreases with increase in flow rate,it reaches the maximum under the designed flow rate;in time-frequency domain,rotating speed characteristics are analyzed with wavelet analysis,its energy mainly concentrates in the range of 39-46.9 Hz under cavitation,and the rotating speed energy is the largest during initial cavitation.