流道喷涂对双吸离心泵压力脉动特性影响研究

Effect of flow passage coating on pressure fluctuation characteristic for a double suction centrifugal pump

流道喷涂技术能有效提高水泵过流部件抗磨损能力并降低水力损失,但其对压力脉动特性的影响并不明确。本文采用试验的方法,对一双吸离心泵流道喷涂前后的压力脉动进行同台测试,并分析了混频幅值和频谱特性。结果表明:流道喷涂处理降低了流道粗糙度,减小了水力损失,提高了效率,但同时也改变了水泵固有的压力脉动特性。对于吸水室,喷涂处理缩小了压力脉动稳定区的范围,使小流量工况区的压力脉动峰峰值达到喷涂处理前的2.8倍,加剧了水泵在小流量工况下运行的不稳定性。对于压水室,喷涂处理使靠近隔舌区域在小流量区的压力脉动明显增加,使远离隔舌区域在大流量区的压力脉动增加。而在设计流量区域,喷涂对各个位置压力脉动影响不明显。为了使喷涂技术发挥综合效果,保证水泵运行稳定,应该尽量避免喷涂后的水泵在偏离设计流量工况运行,特别是严格避免水泵在低于0.75倍设计流量工况运行。

Flow passage coating can effectively improve the resistance to wear, and reduce the hydraulic loss. However, the effect of the flow passage coating on pressure fluctuations for double suction centrifugal pumps has not been understood yet. The experiments for a centrifugal pump with and without flow passage coating were carried out. The fluctuating pressure signals were obtained and recorded at various operating conditions, then time and frequency domains of the signals were analyzed by using the Fast Fourier Trans- form method. The results show that the flow passage coating decreased the surface roughness, reduced the hydraulic loss and eventually increase the efficiency. However, flow passage coating had changed the pres- sure fluctuation characteristics. For the suction chamber, the operating range of pump stability was nar- rowed. And the peak to peak value of pressure fluctuation in suction chamber with coated surface may reached 2.8 times as large as that with original one, which enhanced the operating instability at partial flow rates. For the volute region, the pressure fluctuation at the monitoring location relatively closed to the volute tongue remarkably increased at the partial flow rates. While the pressure fluctuation at the monitor- ing location relatively far from volute tongue increased at high flow rates. The effect of flow passage coating on pressure fluctuation was not obvious on the design flow rate. To develop the synthetic benefits of flow passage coating technology and ensure the stable operation of pumps, the pump with flow passage coating should not operate at the flow rates that are derived from the design flow rate, especially at the flow rates below 75 % of design flow rate.