Study On Flow Pulsation And Noise Reduction Of Involute External Gear Pump

In the current hydraulic industry,the development and application range of external gear pumps are severely constrained by the fact that their noise is too large.Although the gear pump has the advantages of compact structure,light weight,reliable operation,insensitivity to pollutants,it is rarely used in applications such as precision transmission and indoor machinery.Therefore,how to reduce its noise has become a urgent problem to solve.At present,it is weak that the theoretical research foundation and positive product development capability of the domestic gear pump industry in terms of noise reduction.Therefore,in order to improve the level of domestic noise reduction,the flow pulsation of the gear pump was carried out to strengthen theoretical foundation in this paper.Secondly,two measures were proposed for the main noise sources,such as flow pulsation and oil trapping.The RC filter is used to reduce the gear pump flow pulsation and a new structure of groove is used to solve the oil-trapped phenomenon of gear pump.In the study of flow pulsation,based on the meshing principle of the involute external gear pump,a new formula for accurately calculating the instantaneous flow of the gear pump was proposed.The flow pulsation of gear pump was analyzed using this formula,and then the displacement of various gear pumps was calculated to verify the correctness of the formula.Finally,after analyzed the flow pulsation characteristics,the formula of flow pulsation unevenness coefficient and frequency were obtained.These laid the foundation for the subsequent analysis of the effects of noise reduction measures.In the research of RC filter,the principle and structure was explained firstly.The outlet flow pulsation of gear pump equipped the filter can be decreased.Then dynamic characteristics of the filter were analyzed.In order to deeply analyze the influence of three parameters of filter damping,accumulator cross-sectional area and accumulator volume on flow pulsation,the system was simulated by MATLAB software.Then the fmincon optimization function was used to optimize the result of reducing the gear pump pulsation.Theoptimization results show that for the CBH-G5**-*F** gear pump,when accumulator cross-sectional area and accumulator volume are 5 square centimetre and 47 ml respectively,flow pulsation unevenness coefficient is as low as 0.8%.The research shows that: 1.Damping parameters will constrain the noise reduction effect;2.Although the two parameters of the filter cross-sectional area and volume are small,the filtering effect is great,and the flow pulsation becomes larger after deviating from the optimal value.3,RC filter to reduce the flow pulsation is very obvious,and the gear pump pulsation unevenness coefficient can be reduced to below 3%.Afterwards,in order to solve the oil-trapped phenomenon more completely,a new structure of unloading groove was proposed,which connects the two parts of the oil-trapped area to the suction chamber of the gear pump.In this paper,the parameters of CBH-G5**-*F** gear pump were taken as an example.Firstly,the position selection of the unloading groove was analyzed in the CAD software.Then the MATLAB model was built to analyze the impact of unloading groove on gear pump oil-trapped pressure and flow quality.The research shows that: 1.After the reasonable design,the new groove can ensure the sealing of the oil suction chamber and the oil discharge chamber;2.The unloading groove can avoid the problem that the oil-trapped phenomenon cannot be completely eliminated due to the small gap of the tooth side;3,The unloading groove has little effect on the displacement,but it will increase the flow pulsation of the gear pump.In order to better reduce the noise,the RC filter can be used in combination with the new groove.The former can reduce the flow pulsation,and the latter can better solve the oil-trapped phenomenon.Suppressing the two major noise sources of the gear pump,the noise of the gear pump can be reduced.