Multi-objective parameters optimization and experiments of six-blade differential pump driven by non-circular gear with free pitch curve

Abstract: In order to further optimize the performance of the differential pump, a multi-objective parameter optimization model was proposed for the six-blade differential pump driven by the non-circular gear with free pitch curve which had the flexible local adjustment ability. Based on the best 1∶3 order Fourier pitch curves driving the six-blade differential pump, the control vertex of the B-spline curve was designed. Three calculation models and coefficients of displacement, pulsation rate and maximum modulus without undercutting of differential pump were established. The evaluation function of comprehensive performance of differential pump was constructed by geometric average. The multi-objective optimization software was designed according to the efficiency coefficient method and the improved genetic algorithm. The Pareto solution of the free pitch curve was obtained by using the software. The results showed that the comprehensive performance of the differential pump was significantly improved after the multi-objective optimization. The displacement was increased by 2.4%, and the pulsation rate of the single pump was reduced 10.6% and the maximum modulus without undercutting increased by 30.0%. The optimization results preliminarily showed that the local optimization of free pitch curve was helpful to improve the comprehensive performance of differential pump. In order to verify the calculation results and carry out the investigation on before and after the optimization of the free pitch curve, the motor power of the differential pump test bed is 5 kW, the speed of the input shaft is 300 r/min, because the order ratio of the driving and driven gears is 1∶3, the average speed of the impeller is 100 r/min, and the cycle time of one revolution is 0.6 s. Due to the high frequency characteristics of pump source pulsation, at present, it is mainly based on the transient pressure sensor to measure and calculate the pulsation rate. The Aier AE-H high frequency pressure sensor was selected. The power supply is 24 V, the measuring range is 0-1 MPa, the measurement accuracy is ± 0.5%FS, and the signal voltage output is 0-10 V. The data acquisition device uses Altay's acquisition card and acquisition software. Refer to the input shaft speed range, and according to the sampling theorem, the sampling frequency of the acquisition card is 2 kHz. After optimization, the difference of pressure curve before and after optimization was obvious, and the peak width of pressure wave increases at the outlet of differential pump. The displacement per minute of the six-blade differential pump was increased by 3.3%, which can increase the effective volume cavity of the differential pump. According to the national standard series of modulus, the actual tooth profile modulus of the optimized non-circular gear was 2.5 mm, increased by 25.0%. According to the relevant theory of gear transmission, the increase of modulus can significantly improve the bearing capacity of the non-circular gear. The pulsation rate of differential pump was reduced by 3.1%, the impact of fluid was weakened, the leakage of pump clearance was reduced, and the volume efficiency was improved. It indicates that the comprehensive performance of six blade differential pump driven by free pitch curve non-circular gear can be effectively improved by multi-objective parameter optimization.