Cavitation Performance Of A Mini Space Pump At Microgravity Conditions

The fueling system is one of the most significant parts of the rocket and missile ground equipment which uses liquid propellant.The core component of the filling system is the mini pump.Once the pump is out of work,it would result in delay or failure of the refueling task.It has a very high demand for its space size,stability,quality and reliability because of its application in the field of space.So it is necessary to not only take an experiment on the ground,but also to simulate under microgravity condition to study the hydraulic performance and cavitation performance.under microgravity condition,however,not only the mass force,but also the surface force(especially the surface tension of the liquid)and attach angle will change,leading cavitation performance making a significant variation.Based on the basic theory of the fluid machinery,and the hydrodynamic suspension technology,magnetic coupling technology,concept of combined impeller with motor rotor,the hydraulic design for the flow passage components of the mini pump was built.Further,to conduct the experiment successfully,the mini pump test bench is designed,including the design of test system,acquisition system and control system.The test bench is compact and easy to operate,and it can meet the need of the hydraulic and cavitation performance test,while the accuracy can reach 0.03%.The hydraulic and cavitation performance is measured through the test bench,which shows the mini pump meets the design requirements as well as stable operation,compact structure and high stability.To consider the influence of surface tension,the level-set method is introduced in this paper.The cavitating flow inside the mini pump is numerically simulated by using RANS method and a homogeneous cavitation model.For better accuracy,the attach angle on the flow passage wall is also introduced to figureout the effect of surface tension on cavitation development under microgravity operation condition.The hydraulic and cavitation performance of the mini pump are simulated and through the comparison of the simulation data and the experimental data,it shows that using level-set method has no obvious influence on the hydraulic performance,but it has a significant influence on the cavitation performance and the vortex on suction surface is also more obvious by using the method.The numerical results indicated that the mini pump impeller head operating under the microgravity condition was a little higher than that under the conventional gravity condition.However,the difference of the hydraulic efficiency under two different gravity conditions was negligible.For both gravity conditions,cavitation inception occurs along the vane suction surface near the leading edge,and the cavity inside the pump expands toward the downstream of the blade-to-blade flow passage.If the cavity size and NPSHr are considered,cavitation performance under the microgravity condition is better than that under the constant gravity condition.The reason is that the surface tension will delay the cavitation inception and accelerate the process of cavitation.