Optimized Design Of Aero-slip Pump Impeller Structure Based On NSGA-Ⅱ

As an important part of the helicopter engine accessory oil return system,the performance of the oil pump has an important impact on the reliability of the engine work.As a common type of oil pump,gear pump has the advantages of stable operation,long life and easy maintenance.The oil pump often needs to operate steadily under special conditions(high altitude,low pressure),and when the oil pump runs in a low-pressure environment,there will be insufficient oil supply,reduced efficiency and other problems,resulting in insufficient lubrication of engine parts,resulting in parts failure or even damage and other phenomena,affecting the engine performance.The single gear pump structure is difficult to meet this requirement,therefore,a helicopter oil pump uses a combination of gear pump and impeller structure to improve its performance.In order to get the oil pump that meets the design requirements and has the best performance,it is important to optimize the design of the impeller structure for a helicopter oil pump.In this paper,the hydraulic efficiency and head of two typical working conditions at high altitude are selected as the optimization targets,and the optimization variables are screened by response surface analysis method,taking the impeller structure of the slide oil pump as the research object and the low efficiency of the slide oil pump as the problem.The sample database is established by the design of experiments method,and the optimized target values of the sample database are calculated based on the computational fluid dynamics(CFD)method,and the models of the variables to be optimized as a function of hydraulic efficiency and head are fitted.The NSGA-Ⅱ genetic algorithm is used to optimize the key parameters of the impeller geometry of the slide oil pump,and the hydraulic efficiency and head of the slide oil pump before and after optimization are compared and analyzed.CFD fluid simulation and experimental methods were used to verify the optimization results.The results show that the design point head of the optimized slide oil pump is increased by 2.6m and the hydraulic efficiency is increased by2.86%.The main research work and results of this paper are as follows.(1)For the optimization of the impeller structural parameters of the slick oil pump,the optimized parameters are reasonably selected according to the design requirements and the range of variables is determined;the design of experiment(DOE)method is used to design the test sample database;the mesh irrelevance test is completed to verify the accuracy of the numerical simulation;based on CFD fluid simulation,the hydraulic efficiency and head values of the target parameters are calculated,and the database is improved according to the calculation results.The large range of variation of the database sample values proves the reasonableness of the impeller parameters selection and the room for further optimization of the impeller.(2)According to the established sample database,the response surface analysis method is used to fit the function model of the parameters to be optimized and the target parameters of hydraulic efficiency and head;the constraints are determined according to the range of optimized parameter values,and the NSGA-II genetic algorithm is used to find the optimal parameters for the target function,and the optimal parameter Pareto solution set is obtained;the TOPSIS analysis decision method is used to evaluate the solutions in the Pareto optimal solution set The parameter combinations of the optimal solutions are obtained by evaluating and ranking the solutions in the Pareto optimal solution set using TOPSIS analytical decision method.The performance values predicted by the optimal solutions are compared with the original model performance values,and the advancedness of the optimized model is demonstrated.(3)The hydraulic efficiency and head values were calculated based on the obtained inlet pressure,outlet pressure and flow rate parameters of the slide oil pump,and compared with the result values of the optimization algorithm,and the errors were found to be small and within the acceptable range,which proved the reliability of the optimization.(4)The solid model of the impeller was machined according to the optimized parameters,assembled with the rest of the components and then conducted experiments;the experimental procedure was designed and the experiments were conducted using the test bench of the cooperative unit,and the inlet and outlet pressures of the slip oil pump were measured by the pressure transducer respectively;the outlet flow rate was measured by the flow meter.The obtained experimental results model prediction results were compared and analyzed.The results show that the error between the experimental value and the predicted value of the optimized oil pump performance is small,which further proves the reliability of the optimized results.