| The fuel cell system needs a hydrogen circulation pump to transfer the unreacted hydrogen to achieve the purpose of recycling.Hydrogen circulation pump is an important part of fuel system.Fuel cell system has strict restrictions and requirements on the size and weight of hydrogen circulation pump.At present,small roots vacuum pump is mostly used as hydrogen circulation pump for circulating hydrogen.In order to meet the design requirements of the system for hydrogen circulation pump,it is necessary to change the design method and manufacturing method of the traditional roots pump.The more complex rotor profile of the hydrogen circulation pump is studied and designed by parametric modeling,and then the different effects of various structural parameters on the performance of the hydrogen circulation pump are explored.Fluent dynamic grid technology is used to calculate the internal flow field of hydrogen circulation pump in this paper.The motion characteristics of the internal flow field of hydrogen circulation pump are studied,and the influence of different rotor profile,different blade number and different pressure difference on the internal flow field of hydrogen circulation pump is explored.The main contents of this paper are as follows:(1)First,Creo is used to establish the three-dimensional model of the hydrogen circulation pump,and the three-dimensional calculation model is imported into the mesh generation software ICEM.In order to prevent mesh distortion at the gap and improve the accuracy and reliability of the final calculation of the pump model,tetrahedral mesh is used to mesh the model,and more than five layers of mesh are ensured at the gap.The obtained mesh is smoothed and verified for mesh independence,The grid file meeting the requirements is imported into the CFD software for pre-processing and numerical simulation of the three-dimensional model.(2)Based on the fact that the internal flow field of hydrogen circulation pump is the flow of strong medium,RNG k-ε Model is used as its turbulence model,Fluent dynamic grid technique is used to simulate the transient flow field in hydrogen circulating pump.The pressure field,velocity field and outlet mass flow diagram of hydrogen circulation pump were obtained,which truly reflected the complex gas flow in the process of impeller rotation of hydrogen circulation pump.The distribution characteristics of gas flow pulsation and its influence on exhaust flow during operation period were explored,which provided reference for further research on its working performance and noise reduction design.(3)Through the analysis of the calculation results of different transient simulation,the influence of the change of rotor profile on the internal flow field of hydrogen circulation pump is explored,and the influence of the change of rotor profile on the flow pulsation and volumetric efficiency of hydrogen circulation pump is obtained,which provides the basis for the further optimization design of the rotor.(4)According to the design requirements of hydrogen circulation pump,the model structure and rotor clearance are preliminarily selected.In order to reduce the gap between rotors and improve the performance of hydrogen circulation pump,this paper compares and analyzes the advantages and disadvantages of several traditional multi factor optimization schemes,and finally determines to use the quadratic regression orthogonal combination experimental design method.In order to explore the influence of various structural parameters on the performance of hydrogen circulation pump and optimize its design,the volumetric efficiency and flow non-uniformity coefficient of hydrogen circulation pump are taken as the evaluation factors of pump performance,and the impeller length L and rotor clearance are selected δ、 four parameters such as the impeller length L,rotor clearance δ,blade number z,inlet and outlet diameter D,were taken as the influencing factors,and each factor was taken at three levels to design the orthogonal test scheme.The CFD software Fluent was used to carry out three-dimensional unsteady numerical simulation of nine groups of hydrogen circulation pump models.The optimal combination of four structural parameters of hydrogen circulation pump was finally determined through regression analysis and variance analysis.(5)The mixture multiphase flow model was used to simulate the hydrogen circulation pump with liquid content of 1%,2% and 4%,respectively;Keeping the inlet pressure boundary condition unchanged,by changing the outlet pressure boundary condition to control the inlet and outlet pressure difference,three-dimensional unsteady numerical calculation was carried out for the hydrogen circulation pump with inlet and outlet pressure difference of 10 k Pa,20 k Pa,30 k Pa and40 k Pa respectively,and the influence law of different inlet and outlet pressure difference on the internal flow field of the hydrogen circulation pump was studied.The volumetric efficiency and flow non-uniformity coefficient of the above numerical simulation results were calculated,and the influence of different liquid holdup and different inlet and outlet pressure difference on the performance of hydrogen circulation pump was analyzed.(6)The transient motion process of hydrogen circulating pump under linear start-up mode,exponential start-up mode and normal start-up mode is calculated by numerical simulation method,the transient flow characteristics inside the hydrogen circulating pump under different start-up modes are obtained,and the influence law of start-up mode on the internal operation performance of the pump is studied and analyzed. |
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