Effect Of Jet Velocity Ratio And Guide Leaf Area Ratio On Performance Of Axial Flow Waterjet Propulsion Pump

Compared with the traditional propeller propulsion,the waterjet propulsion device has the advantages of small vibration and noise,easy operation and stable operatio n,and is widely used in ships and new submarines.At present,with the substant ia l increase of tonnage of new ships in various countries,the demand of jet propuls io n pump is increasing,and its performance has a higher standard.Therefore,this paper designs a set of axial flow jet propulsion pump for a large submersible model,and carried out multi-condition numerical simulation on the jet velocity ratio and guide leaf area ratio of the propulsion pump.Analyzed the effects of jet velocity ratio and guide vane area ratio on external characteristics,internal flow filed and cavitat io n performance and the pumps’ injection performance in the whole basin.The specif ic research contents are as follows :(1)According to the relationship between thrust and resistance of the submersible,the conditional parameters are selected,and the hydraulic parameters are calculate: rotational speed,specific rotational speed,flow rate and head.A set of axia l flow jet propulsion pump is designed according to streamline method,and the water body model is meshed.(2)The definition of jet velocity ratio k is introduced.Referring to the existing variation law of propulsion efficiency and jet velocity ratio of propulsion pump,and considering the differences of submersibles and the selection of assumed parameter s,the six jet velocity ratios studied in this paper are selected as 1.31,1.43,1.46,1.52,1.57 and 1.76,respectively.Through numerical simulation,it is found that with the increase of k,the injection performance and cavitation performance of the propuls io n pump first increase and then decrease.At the same time,the propulsion efficie nc y shows an open-down quadratic function form,that is,there is an optimal range of jet velocity ratio k = 1.52 ～ 1.57,and the propulsion efficiency reaches the maximum when k= 1.57.(3)The guide leaf area ratio A is defined by referring to the diffuser degree of the guide vane of axial flow pump and the inlet and outlet area of the flow passage components of the propulsion pump.To compare guide vane models with differen t expansion and contraction forms,A values were 0.72,0.86,0.92,1.01,0.11,1.18,respectively.Numerical simulation analysis shows that the cavitation performance of diffusion vane propulsion pump is better when A > 1.The internal streamlin e distribution of the flow components of the contraction guide vane pump with A < 1 is regular,and the pressure distribution is uniform.The external characteristics and propulsion performance are the best,and the cavitation performance is also improve d compared with the initial model.When A=0.92,the internal loss of the guide vane is the smallest.(4)Change of Linear Curvature of Guide Vane Shell with Area Ratio A = 0.86.The numerical simulation analysis shows that under the same area ratio,the differe nc e in the external characteristics of the linear propulsion pump with different curvature guide vane shells is small,but compared with zero curvature and positive curvature,the hydraulic performance of the linear propulsion pump with negative curvature guide vane shells is improved.Due to the increase of curvature,the retained fluid in the guide vane channel increases,the flowability is poor,and the flow loss increases.Therefore,the internal hydraulic loss of the negative curvature guide vane with contraction is the smallest,which can effectively reduce by 11.7 %,and the thrust coefficient and propulsion efficiency are increased by 1.49 % and 1.15 %,respectively.