| In recent years,as a clean energy,fuel cell has been widely used in new energy vehicles,aviation industry,unmanned aerial vehicles,underwater vehicles and other fields.As the core component of fuel cell gas supply system,gas circulating pump has gradually become a hot issue in the research of key equipment.At present,the fuel cell gas circulating pump mainly adopts centrifugal type,cam type(roots type),screw type,vortex type,turbine type and other structures.Cam gas circulating pump has become one of the best configuration schemes for fuel cell gas circulating pump due to its small volume,low maintenance cost,high pressure ratio,good performance and long service life.As the core component of cam type gas circulating pump,the optimization design of its profile and rotor geometric parameters is the key to improve the aerodynamic performance and reliability of the pump.In order to promote the development trend of cam rotor towards multi blade,spiral,low noise and low pulsation characteristics,improve the aerodynamic performance of gas circulating pump,and more comprehensively understand the internal flow of gas circulating pump under different geometric parameters,this paper analyzes the aerodynamic performance of cam rotor under different geometric parameters from the aspects of pulsation characteristics,rotor force and internal flow characteristics.The practical conclusion is obtained,which provides a theoretical basis for the development of gas circulating pump with low noise,low pulsation and more stable operation.Based on this,by selecting the arc involute arc rotor profile,this paper deduces the profile equations of multi blade,spiral rotor and rotor with different diameter to pitch ratio,and establishes a three-dimensional model based on RNG k-εturbulence model and dynamic grid technology,the three-dimensional unsteady numerical analysis of rotor clearance,blade number,helix angle,diameter-to-distance ratios and other geometric parameters are performed to reveal the effect of rotor shape parameters on the aerodynamic performance of the gas circulation pump.The results show that:(1)When the rotor clearance increases from 0.10 mm to 0.30 mm,the outlet flow rate and volumetric efficiency of different blade number rotors show a downward trend,and the decrease range of 3-blade rotor is the largest,with a decrease of0.0094kg/s and 28.6%respectively,while that of 5-blade rotor is the smallest,with a decrease of 0.0064kg/s and 14.67%respectively;Meanwhile,the flow pulsation coefficient of 3-blade and 4-blade rotor is the smallest at 0.15 mm,and that of 5-blade and 6-blade rotor is the smallest.The flow pulsation coefficient of 5-blade rotor is smaller than that of other blades,which indicates that 5-blade rotor can restrain flow pulsation better.(2)With the increase of the number of rotor blades,the average flow rate of the pump outlet decreases from 0.0387kg/s of the three blade rotor to 0.0235kg/s of the 6blade rotor,but the flow pulsation intensity and pressure pulsation intensity of the 6blade rotor are relatively the lowest,and the gas pressurization process in the cavity is more stable.In addition,compared with other rotors,the distribution of the radial excitation force F_r is the most concentrated and the force is the smallest.At the same time,with the rotor blade number increasing from 3 to 6,the pulsation characteristics of the radial excitation force component along the x direction of the rotor are significantly reduced,but the influence of the blade number on the pulsation characteristics in the y direction is not significant.(3)As the helix angle of the rotor increases from 0°to 120°gradually,the outlet flow rate,outlet pressure and volumetric efficiency of the five blade rotor pump decrease by 0.013 kg/s,0.050k Pa and 25.21%respectively.This is because the larger the helix angle is the more serious the gas backflow at the outlet and the lower the gas flow rate are.But the larger the helix angle is,the lower the flow pulsation and pressure pulsation are,which effectively improves the stability of the pump;the maximum absolute values of the radial excitation force components F_x and F_y of the120°helical rotor are 82.28%and 10.03% lower than those of the straight blade rotor,respectively.It can be seen that the helical rotor can effectively weaken the excitation force in the x and y directions,but the axial force components will be generated along the y direction quantity.(4)The results show that different diameter to distance ratio rotors have significant influence on the aerodynamic performance of the pump.With the diameter to distance ratio of rotors decreasing from 1.29 to 1.20,the average flow rate,pressure and volumetric efficiency at the outlet decrease by 0.0092kg/s,0.075k Pa and14.61%respectively,but the pulsation intensity at the outlet also decreases gradually.At the same time,the maximum pressure pulsation peak value decreases by 0.18k Pa and the pressure pulsation coefficient decreases by 44.37%when the diameter to distance ratio is 1.29.When the diameter to distance ratio is reduced to 1.20,the maximum value of the excitation force fluctuation amplitude is reduced by 50.86%.(5)Based on the gas circulating pump test-bed,four different inlet and outlet pressure differences were selected to test the external characteristics of the five blade rotor gas circulating pump.The results show that the average flow rate at the outlet of the pump is inversely proportional to the inlet and outlet pressure difference,and the error between the experimental results and the numerical simulation results is controlled within 3%.In this paper,the influence of geometric parameters such as rotor clearance,blade number,helix angle and diametral distance ratio on the performance of gas circulating pump is studied.We established a quantitative relationship between the geometric parameters of the rotor and the aerodynamic performance of the pump.The flow characteristics,pressure characteristics,velocity characteristics and radial excitation force distribution of rotor are expounded.The advantages and disadvantages of each shape of rotor are analyzed from various angles.The optimal design of the rotor and the selection of the cam type gas circulating pump provide a certain theoretical basis. |
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