Experimental study on cavitation characteristics of mixed-flow pump during startup
CHEN Zonghe1, SHI Weidong1,2*, ZHANG Dengsheng1, ZHANG Junjie3, ZHANG Zhiwei1
1. National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu 212013, China; 2. School of Mechanical Engineering, Nantong University, Nantong, Jiangsu 226019, China; 3. Shanghai Institute of Quality Inspection and Technical Research, Shanghai 200072, China
Abstract：A high-speed photographical experiment was carried out on a mixed-flow pump with 0.25 mm tip clearance during its startup period to study cavitation characteristics of the pump at various flow rates, inlet pressures and startup times. The cavitation phenomena in the pump were observed at 0.80Qd,0.90Qd,1.00Qd and 1.05Qd flow rates and 10 s, 15 s and 20 s startup times. During the initial stage of startup process, since the rotating speed is so low that the pressure in the impeller eye does not reach the saturated vapor pressure of water, no cavitation appears at all. As startup process arrives at its stable stage, cavitating bubbles appear at the impeller tip firstly, then propagate into impeller passages to result in severe cavitation. At the same flow rate, the lower the inlet pressure(cavitation number)is, the more serious cavitation occurs. At the same inlet pressure and flow rate, the degree of ca-vitation in the pump is gradually intensified with startup advancing, and the most serious degree of ca-vitation occurs in the stable stage at different startup times.
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