Study On Internal Flow And Cavitation Characteristic Of Jet Centrifugal Pump

The internal flow of jet centrifugal pump is complex, in the large flow rate condition, the pipes cavitation causes head sharp decline. For in-depth understanding of centrifugal jet pump internal flow and cavitation characteristics, a Zhejiang enterprises JET750 jet centrifugal pump is selected as the main object of study in this paper, based on experiment and numerical simulation research methods, the internal flow of jet aerator and impeller are analyzed, and the effect of geometrical parameters of jet to jet centrifugal pump cavitation performance is studied. At the same time, LES method was used to analyze the root cause of the jet centrifugal pump head breaking point and the characteristics of the transient static pressure distribution, and compared with the results calculated by k- SST. The main research contents of this paper are as follows:1) The CFX software is adapted to simulate the JET750 jet centrifugal pump flow field,and the external characteristic test is carried out at the same time. Analysis found that the jet nozzle flow decreases with the jet centrifugal pump flow increasing, however, the total flow has been increased with the jet centrifugal pump; The jet centrifugal pump inner ejector performance curve and the jet pump performance curve versus show the same trend; The determinants of jet centrifugal pump flow lift curve slope is jet area ratio.2) Numerical simulation shows that the same flow field parameters distribution along flow direction inside the jet device has certain difference. In general, the more close to the jet boundary layer flow field the information change more turbulent; Vorticity analysis found that the vorticity maximum occurs in high and low speed fluid interaction area, where the flow field information changes dramatically; the same flow field parameters distribution curve along flow direction inside the jet device have migration trend to move to the downstream in large flow condition; Due to the high-speed jet flow, the turbulent kinetic energy and turbulent kinetic energy dissipation rate of the impeller inlet is big, the impeller inlet pressure is higher, which inhibits the occurrence of cavitation inside the impeller.3) It is found that when the nozzle cylindrical length is 2 mm, throat diameter 1.5mm, the pump cavitation performance is improved, and head break point move to the large flow rate,design performance can meet the design requirements; The increasing of the jet area ratio can increase the flow rate of the head break point, but the area ratio should not be too large.4) The steady-state simulation simulated is selected as the initial condition, The transient flow characteristics of head break point in the jet centrifugal pump are studied by using the LESand k- SST turbulence model, which shows that the LES numerical simulation can calculate the transient static pressure of the head breaking point better and reveals that the strong entrainment vortex may be the cause of the transient pressure and the cavitation. At the same time, it is found that the radial static pressure distribution of throat pipe is non-symmetric and the pressure distribution of the flow direction changes dramatically with the LES simulation, and the k-omega SST simulation gets the radial static pressure of throat pipe is symmetrically distributed the static pressure distribution curve of the flow direction is a smooth curve.