Numerical Analysis of Influence of Tip Clearance Width on Tip Vortex Characteristics in Axial Flow Pump
In order to solve the problem of the tip vortex characteristics of axial flow pump with different tip clearance widths,taking an axial flow pump as the research object,the tip leakage vortex characteristics under three different tip clearance widths(0.15 mm,0.45 mm and 1.20 mm)were studied by numerical simulation method.The results show that when the tip clearance width increases from 0.15 mm to 1.20 mm under the same flow rate,the tip clearance separa-tion vortex area increases and the intensity of the vortex core increases at the same plane position.Under different tip gap widths,the distribution trend of turbulent kinetic energy in the tip gap region is similar,that is,the turbulent kinetic en-ergy increases first and then decreases along the radial direction from the tip entrance to the shroud,and reaches the max-imum near the formation of the separation vortex.In addition,the vorticity of the leakage vortex core along the leakage vortex trajectory decreases and the pressure increases,indicating that cavitation is easy to occur near the leading edge.For a very small tip of 0.15 mm,most of the main flow can not pass through the clearance,and the tip separation vortex only occurs in the pressure side corner of the blade.For the tip of 1.20 mm,the tip separation vortex with high turbulent ki-netic energy occurs in the gap region.The separation vortex is connected with the shear layer and detached from the blade,and then winds around the outside of the vortex core,and is finally ensnared by the leakage vortex.There are dif-ferent vorticity layers near the tip that can inject turbulence into the leakage vortex.The research results can provide ref-erence for the hydraulic optimization design of the axial flow pump.
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