Numerical Analysis Of Backflow Cavitation In Inlet Of Centrifugal Pump With Inducer

Inducer being installed in high-speed centrifugal pump can suppress the pump's cavitation. However, Inducer cavitation performance is determined mainly by the entry conditions. In this paper,Using RNG k -εturbulence model and Rayleigh-Plesset cavitation model, the cavitation flow was calculated in the whole flow passage of the inducer. Cavitation performance had been systematically carried out with different tip clearance and casing shape. The major work completed.First, the flow in the inducer with three different tip clearance were calculated. The results show that, With the inlet pressure decreases, the cavitation region will be increased.When the cavition number dropped to around 0.04, the head coefficient begans to rapidly decline. there is larger relative velocity and smaller pressure at the outer edge of blade imports, and cavitation happens easily this location.the volume of vapor phase under low flow conditions significantly greater than that under conditions of high flow. The axial length of the vortex extends longer under different working conditions.With the flow rate increases, the axial length of vortex decreases and the radial length of vortex expands larger.Under rated flow, Analysis of pressure fluctuation is calculated around import and export of the region. The results show that,The value of pressure fluctuation of big tip clearance is lager than that of small tip clearance.For 0.8mm and 1.0mm tip clearance,showed the frequency of 1164Hz, which value is about 0.075 times than value of blades frequency. All of the pressure fluctuation in inducer with 1.2mm tip clearance are more than the frequency of 110.76Hz.On the basis of the above, The calculation of shroud modification was further applyed to inducer with modified casing (type A,B,C).We can acquire that modified casing improve cavitation performance,but the efficiency and head both declined slightly. Static pressure value is significantly lower for type B,C,particularly the import of the blade,the areas of the minimum pressure obviously decrease.Modified shroud,the affected region of back leakage vortex increases.The use of modified casing reduces the share of blade on the vapor phase/out there appear some bubble on the surface of the blade in inducer.