Numerical investigation of cavitating flows in bulb tubular pump and its performance prediction
TANG Xue-Lin, HUANG Wei, WANG Fu-Jun, WU Yu-Lin, LIU Zhu-Qing
(1.College of Water Resources ＆ Civil Engineering, China Agricultural University, Beijing 100083, China; 2.State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China)
Abstract：Under the design operating condition, the RNG k-ε turbulence model and the full cavitation model were employed to investigate cavitating flows in a bulb tubular pump model with lowhead and predict its cavitation performance curve by using Fluent. The cavitating flow patterns in the pump under six operating conditions, where the cavitation inception, 3% head drop point and severe cavitation condition were included, were compared and analyzed. The static pressure and vapor volume fraction contours on the suction side of blade of the impeller and the fraction distributions in various planes located at different axial positions were obtained under different available NPSH. It was showed that a cavity occurs in the suction side of blade immediately behind the blade leading edge initially at a constant flow rate, and then it expands along the suction side with lowered available NPSH; such a cavity expansion affects the pump performance eventually. The onethird net crosssectional area of flow passages at the Z=-20 mm axial location has been occupied by the vapor with more than 10% volume fraction at the 0.81 m available NPSH, causing a serious blockage effect in the impeller passages. All the predicted results might be helpful in hydraulic and structural optimization for the bulb tubular pump in future.
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