NVH Performance Analysis Of Internal Gear Pump

With the gradual development of the automotive industry technology,the NVH problem of auto parts has attracted more and more attention from researchers.The internal gear pump is an energy conversion device that can convert the mechanical energy transmitted by the power unit into hydraulic energy.It is widely used in hydraulic systems and lubrication systems in automobiles.The internal flow field of the internal gear pump is relatively complicated,often accompanied by problems such as basic performance and NVH performance.In recent years,with the development of high pressure and high displacement of gear pumps,large output flow pulsations and significant NVH problems have become the main disadvantages of gear pumps.In this paper,an internal cycloid pump of an automatic transmission is taken as the research object.The combination of CFD simulation and acoustic simulation is used to analyze the internal flow field flow characteristics and noise generation mechanism,and to find an effective way to improve the NVH performance of internal gear pump.The main research work and results of this article are as follows:The CFD analysis model of the internal gear pump is established for flow field simulation calculation.The validity of the model is verified by comparing the simulated flow value with experimental values ??and theoretical values.The pressure distribution and pressure pulsation of the internal gear pump are analyzed with emphasis.Based on the pressure cloud diagrams at different speeds and the pressure pulsation curves at different monitoring points,it is found that the gear pump pressure at the trapped oil volume is the largest,and the main factors affecting the gear pump pressure pulsation are the meshing frequency fundamental frequency and the second-order harmonic frequency;The Pumplinx cavitation model simulates the cavitation of internal gear pumps.The analysis shows that the cavitation-prone area is the oil-gearing gear meshing area.The increase in outlet pressure has a certain inhibitory effect on the cavitation phenomenon.The method of combining flow field simulation and acoustic simulation is used to numerically simulate the internal gear pump flow noise.Based on the Lighthill acoustic analog method,the results of CFD simulation calculations are interpolated into the acoustic grid as variables to perform acoustic calculations.The cloud maps of the sound source and sound field of the gear pump at different frequencies and the noise signal spectrum curvesof the monitoring points were obtained.The research found that among the frequency components of gear pump flow noise,the discrete noise dominated by the meshing frequency was the dominant factor;as the frequency increased,the broadband noise became more significant;the relationship between pressure pulsation and flow noise was studied.The results show that the noise frequency component of the internal gear pump is mainly discrete noise,and the pressure pulsation is the main excitation source of the oil pump noise.Considering the influence of structural factors,fluid flow and service conditions on the NVH performance of internal gear pumps,acoustic calculations of various factors were carried out,and the noise spectrum curves of monitoring points under different factors were obtained.The research shows that under conditions of high volumetric efficiency,the smaller the speed,the better the NVH performance;the existence of the cavitation phenomenon increases the oil pressure pulsation and aggravates the vibration noise of the gear pump;for this research object,the method of deepening the unloading tank can be effective Reduce the trapped oil pressure to reduce the noise of the internal gear pump.At the same time,the effects of other factors on the NVH performance of the internal gear pump are outlined,and related improvement measures are elaborated to provide a technical reference for the subsequent design of low-noise gear pumps.