Analysis On Cavitation Characteristic In Multistage Centrifugal Pump On Two-Phase Flow

Multistage centrifugal pump may be happen cavitition which is hydraulic machinery peculiar phenomenon when it running. Cavitation changes the velocity distribution of the flow channel, so that the efficiency of centrifugal pump down, head lower, causing machine vibration, but also will damage the impeller, seriously affecting the performance and prevent proper operation. Therefore, how to accurately predict cavitation performance of pumps to prevent the occurrence of cavitation is an important research direction.Cavitation is complexity and difficulty of measurement and its difficult to accurate quantitative analysis it. With the computational fluid dynamics (CFD) technology in the internal flow field of hydraulic machinery is used widely in, CFD as an important tool for optimal design. Therefore, the numerical simulation of multi-stage centrifugal pump cavitation can predict the performance of pump cavitation, the cavitation phenomenon of accurate quantitative analysis has become possible.In this paper, I used RNG k-turbulence model and the SIMPLEC algorithm of CFX software, and Raylcigh-Plcsset cavitation model to simulate head multistage centrifugal pump impeller. Analysis of the pressure field and velocity field, obtained at different pressures, different flow rate of the bubble distribution and velocity vector distribution.9 flow conditions also carried out a complete impeller cavitation simulation, from no cavitation, cavitation born to cavitation developed. I found NPSH critical point and NPSH-Q curve, and then made the simulation curve compared with the experimental curves.This paper conclusion is as follows:1. In order to verify the accuracy of simulation software and models, the first two levels of multi-stage centrifugal pump impeller and guide vane of single-phase flow were simulated with cavitation-free model. The simulation results were compared with experimental results. The simulated curves and experimental curve of the trend line, the error is small. The simulation prove the effectiveness and feasibility. The simulation results show that the lowest pressure of pump multi-stage centrifugal pump at the entrance of the impeller blades, for the following work to lay the foundation.2. The heads of multi-stage centrifugal pump impeller cavitation were simulated. We obtained pressure and velocity vector distribution, knew the location of cavitation born later in the leaves at the back of imports. We adjusted the outlet pressure and flow rate, got the chart of cavitation changing with the pressure and flow. Cavitation primary can be observed, primary point of cavitation can be found by simulation that it has important significance to prevent cavitation of the centrifugal pump.3.9 flow conditions carried out a complete impeller cavitation simulation. We found NPSH critical point and NPSH-Q curve, and then made the simulation curve compared with the experimental curves. Consistent with the trend of two curves, high flow conditions has the larger error. In the low flow conditions, special in rated conditions, simulated and experimental results are close to. It shows that the simulation can accurately predict the performance of centrifugal pump cavitation, it also shows that numerical simulation prediction can replace the cumbersome and complex pump cavitation experiment.