Optimum Design And Performance Analysis Of Circular-Arc Gear Pump With Parabola Transition Curve

With the development of technology,gear pump is widely used in various fields because of its simple structure and low cost.It is one of the most commonly used hydraulic pumps.However,its large trapping pressure and flow pulsation greatly limit its use.As a new type of gear pump,circular-arc gear pump reduces the trapping pressure and flow pulsation to a certain extent with its unique gear profile,thus having great development prospects.The type of gear profile and the selection of parameters are the main factors affecting its performance.However,at present,the research of circular-arc gear pump is mainly focused on involute circular-arc gear pump,while the research of parabolic circular-arc gear pump is less.At present,the widely used circular-arc gear pump has some improvement over the traditional involute gear pump in flow pulsation,but it’s not enough.Relevant studies show that the advantages of parabolic gears lie in their even stress distribution and higher tooth surface strength.Therefore,combining it with circular-arc gear pump,a kind of parabolic-circular-arc gear pump with "arc-parabola-arc" as its profile is designed to further reduce its pressure pulsation and flow pulsation,which has certain theoretical research value.The main research contents are summarized as follows:(1)Based on the theory of plane coordinate transformation and the meshing principle of gear and rack,the profile equation of rack was deduced firstly,and the profile equation and meshing equation of conjugate gear were obtained,thus the end profile of circular-arc gear pump with parabola transition curve was generated.(2)Referring to the parabolic-circular-arc spur gear pump,the mathematical model of instantaneous flow and flow pulsation coefficient of the parabolic-circulararc helical gear pump was established.The variable-controlling method was used to generate the relationship curves between different tooth shape parameters and flow characteristics.The influence of tooth shape parameters on flow characteristics was analyzed,based on which the initial design parameters of parabolic-circular-arc gear pump could be obtained(3)Taking the displacement,volume and flow pulsation coefficient of the parabolic-circular-arc gear pump as the objective function,the multi-objective optimization design of the tooth profile parameters was carried out.The results show that the tooth shape parameters have a great influence on the flow characteristics.The flow pulsation coefficient of the parabolic-circular-arc gear pump before and after the optimization design is reduced by 86.14%.(4)Based on the optimal design results,the sensitivity of tooth profile parameters was analyzed by perturbation method.The results show that the sensitivity of modulus to flow pulsation coefficient is higher;the sensitivity of tooth number to volume and displacement is higher;the sensitivity of tooth width to displacement and flow pulsation coefficient is higher,and the range of variation is obvious at the boundary;and the sensitivity of pressure angle and helix angle is lower.(5)Based on the FLUENT software,the internal flow field of parabolic-circulararc gear pump with initial parameters,parabolic-circular-arc gear pump with optimized parameters and involute-circular-arc gear pump with optimized parameters were simulated respectively,thus the theoretical design and calculation got verified.The results show that the parabolic-circular-arc gear pump has good performance.Compared with the involute-circular-arc gear pump with the same parameters,the flow pulsation coefficient of the parabolic-circular-arc gear pump decreases by 47.68%,and the flow pulsation coefficient of the parabolic-circular-arc gear pump decreases by 65.49% before and after parameter optimization.