Research On Thrust Characteristics Of Miniature Water Jet Propulsion Pump

Water jet propulsion is a special way of propulsion for ships,underwater gliders and other fields,which has the advantages of smooth operation,low noise,good control performance and shallow water operation.Its core component is a water jet propulsion pump.The water jet propulsion pump usually changes its operating condition by changing the flow rate or changing the speed.However,the miniature water jet propulsion pump is limited by its own size and can only change the operating condition by controlling the speed and it is difficult to operate at design condition.It will cause a decline in thrust,efficienc and the time of continuously sailing.It is found that the structural parameters of over current components will also affect the thrust and efficiency of water jet propulsion pump.Therefore,it is of great significance to study the thrust characteristics and performance optimization of the miniature water jet propulsion pump.Based on theoretical analysis,numerical simulation and model test,the numerical simulation of the water jet propulsion pump at open boundary conditions is carried out first,and the thrust,outlet flow rate and distribution of internal flow field at different speeds are studied.Then,the influence of design of cross section line of the nozzle and blade thickness on the hydraulic performance of the water jet propulsion pump are studied.At last,a new method of measuring the thrust and flow rate of the water jet propulsion pump is proposed in this paper.And the test bench was set up to measure thrust and outlet flow rate.The main conclusions are as follows:(1)At the condition of open operation,the outlet flow rate and thrust of the water jet propulsion pump are gradually increased as the speed increases.And the magnitude of thrust increase becomes larger at high speed.The change of surface pressure on the blade surface is obvious and the range of high pressure area is gradually expanding.(2)When the cross section line of the nozzle is a smooth curve with large contraction angle,the thrust and outlet flow rate reached the maximum at each speed.There is partial high speed area near the contraction section of the nozzle and the range of low turbulent kinetic energy area is large.(3)As the blade thickness increases,the thrust and outlet flow rate increase first and then decrease.When the relative thickness of the blade flange is 4% and the relative thickness of the hub is 11%,the thrust and outlet flow rate of the miniature water jetpropulsion pump reached the maximum.And the surface pressure distribution of the blade is well-distributed.(4)The difference of the calculated value and the experimental value of the thrust and outlet flow rate are within 5% at each speed,which proved that the numerical simulation of this paper is reliable.It also shows that the test method for measuring the thrust and outlet flow rate of miniature water jet propulsion pump is feasible.