Based on the Reynolds-Averaged Navier-Stokes equations and mass transfer model,an approach,where a three-component cavitation model is proposed,is presented to simulate ventilated cavitating flow as well as natural cavitation.In the proposed cavitation model,the initial content of nucleus in the local flow field is updated instantaneously,and is coupled with the Rayleigh-Plesset equation to capture the cavity development.The proposed model is applied to simulate the cavitating flow around an under-water vehicle in different cavitation conditions.The results indicate that for the natural and ventilated cavitation simulation,the predicted cavitation characteristics including the cavity length,cavity diameter and cavity shape agree satisfactorily with the analytic and experimental results,for the ventilated cavitation,the proposed methods reproduce the special behavior that the axial line of the cavity bends and rises at the tail part.The study concludes that the ventilated flow rate of the non-condensate gas influences the development of natural cavitation as well as ventilated cavitation,and the vapor cavity is suppressed remarkably by the gas cavity with the increase of the gas ventilation.
JI BinLUO Xian-wuPENG Xiao-xingZHANG YaoWU Yu-linXU Hong-yuan
A novel double suction shaft-less mini pump was developed for heat control of small energy systems in this study.The mini pump impeller with an exit diameter of 40 mm was combined with the motor rotor supported by the hybrid dynamic bearing.The specific speed of the pump was 125 min-1 m3 min-1 m.The hydraulic performance of the pump was investigated experimen-tally under four rotational speeds.From the test results,it was recognized that the pump could provide a flow discharge of 5 L/min and head of 1.5 m,which are applicable for the heat control system of a 3 kW fuel cell.A three-dimensional turbulent flow simulation in the pump was also conducted near the design point.The numerical results showed that the average hydraulic performance of the mini pump was predicted reasonably.From the internal flow simulation,it was revealed that the favorable inflow condition upstream of impeller inlet could be attained by applying the double suction shaft-less design for the mini pump.
