| Plastic centrifugal pumps are widely used in petroleum,chemical and other industrial fields due to their excellent quality and low price.Because the material of the flow parts is polymer plastics with weak strength,the overall antideformation ability of the centrifugal pump under dynamic conditions is not strong,which causes vibration easily.The transmission system of pump shaft is the key link in the power input of the plastic centrifugal pump.The stability of the system’ structure is directly related to the working state of the centrifugal pump.However,the current design of the transmission system mostly refers to the design method of the metal pump transmission system,and fails to correlate the dynamic and static characteristics of the plastic centrifugal pump with the structural parameters of the pump shaft.Under the premise of ensuring the performance of the plastic centrifugal pump,this paper studied the influence of the structural parameters of the transmission system on the dynamic and static performance of the pump,and the problem of improving the system’s ability to resist torsional vibration.The main research contents of this dissertation are as follows:(1)According to the given parameters,the structural parameters of the plastic centrifugal pump were calculated,and the main hydraulic components of the centrifugal pump were designed.The three-dimensional models and twodimensional engineering drawings of the impeller and the volute chamber were completed by the software.(2)The composition of radial force and axial force generated by the plastic centrifugal pump was analyzed.The flow field of the plastic centrifugal pump was simulated under ideal conditions based on ANSYS fluent software.The results of the axial force and radial force on the plastic centrifugal pump were calculated and corrected.(3)Based on the application principle of singular functions in mechanics,a mathematical model of the deflection of the pump shaft transmission system was constructed.The key factors affecting the deflection of the pump shaft were analyzed.Taking the minimum disturbance and the maximum first-order critical speed as the objective function,an optimization model of the transmission system was established.The structural parameters of the pump shaft were optimized with multiple objectives,and the ratio of the optimal span to the cantilever of the pump shaft was 1:0.75.(4)Taking the torsional vibration of the pump shaft transmission as the research object,the single-mass free torsional vibration model and the forced torsional vibration model of the pump shaft were established,and the vibration is damped by a silicone oil damper,and a silicone oil shock absorber was used to reduce the vibration of the models.The dual-mass forced torsional vibration model with the shock absorber was established,and the optimal damping coefficient of the silicone oil shock absorber and the kinematic viscosity of the silicone oil were calculated.The structural design of the silicone oil shock absorber was completed,and the three-dimensional model and two-dimensional parts drawing of the shock absorber were completed.(5)The ZT-3 rotor test device was used as a platform to verify the influence of the ratio of the span to the cantilever on the dynamic performance of the rotor.Three groups of different ratios(1:1,1:0.75 and 0.8:1)were selected in the experiment,three observation points were set for each group of experiments,and twelve groups of deflection values at different speeds were recorded.The conclusion that the optimal ratio was 1:0.75 was verified by comparing the data.(6)Through the processing of experimental data,a mathematical model between rotation speed and deflection was established.Taking the single-span cantilever structure as the research object,the deflection values of the cantilever from 400r/min to 4000r/min at equal intervals(100r/div)were sampled,and the mathematical polynomial of speed-deflection and its corresponding were obtained by polynomial fitting data.The main innovations of this article are:(1)Based on the application principle of singular functions in mechanics,a mathematical model of the shaft deflection of the plastic centrifugal pump was deduced.Using the NSGA-Ⅱ multi-objective optimization algorithm,the structure of the transmission system of plastic centrifugal pump was optimized,and the optimal structure parameters of the transmission system were obtained.Compared with the traditional design model,the optimized pump shaft deflection was reduced by 52.35%,and the first-order critical speed was increased by 42.77%.(2)A pump shaft transmission system with a silicone oil shock absorber was constructed,and an equivalent model of torsional vibration of the system was established.The optimal damping coefficient when the silicone oil shock absorber was working was calculated to be 0.22,and the effective kinematic viscosity of the silicone oil was calculated to be 1.79m2/s.Compared with the transmission system without the shock absorber,the natural frequency of the model was increased by 10.45%,and the maximum amplitude was decreased by 49.29%.(3)Using polynomial fitting as a mathematical tool,37 groups of speeddeflection values collected in the experiment were analyzed,and the mathematical expression of the speed-deflection relationship of the pump shaft at the first-order critical speed and the corresponding function curve were obtained. |
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