Vibration And Noise Control Of Vehicle Reciprocating Electric Air Compressors

As an important part of the pneumatic braking system of electric bus,the vehicle electric air compressor often causes abnormal vibration and excessive noise due to its structural characteristics,which seriously affects the NVH(Noise,Vibration and Harshness)performance of the vehicle.In this paper,the reciprocating electric air compressor is taken as the research object.By designing the intake muffler,balance mechanism and vibration isolation system,the vibration and noise reduction of the air compressor can be realized,and the ride comfort of the electric bus can be improved.Firstly,analyze the performance of the basic muffler unit to provide a basis for the muffler design.Based on Virtual.Lab Acoustics and FLUENT,the effects of structural parameters such as expansion length,expansion diameter,inlet and outlet offset distance and intubation length on the acoustic and aerodynamic performance of the basic muffling unit were studied.Secondly,according to the noise characteristics of the air compressor,the structure design of the intake muffler is completed.The noise spectrum characteristics of air compressor are obtained by noise testing,and the target of muffler is determined.According to the plane wave theory,the preliminary structural parameters of the muffler are determined.Considering the acoustic and aerodynamic performances,several basic silencing units are reasonably combined to optimize the internal structure of the muffler,and the design scheme is determined.The experimental results show that the muffler can effectively reduce the noise of air compressor.Thirdly,according to the balance state of the air compressor,the design of the balance mechanism is performed.Based on the kinematics and dynamics analysis of the single-cylinder air compressor,the unbalanced force and torque of the two-cylinder air compressor are calculated.The preliminary scheme design is carried out by using asymmetric balancing gear,and the final scheme is determined by further optimizing the balancing mechanism according to its balancing effect.The simulation results show that the final balance scheme can achieve an effective balance of the air compressor.Finally,the influence of different vibration isolation parameters on the vibration intensity is analyzed,and the original vibration isolation system of the air compressor is optimized.The mathematical model of single-layer vibration isolation system of air compressor is established,and the natural frequency of the system is calculated by using MATLAB.It shows that the excitation frequency of air compressor is far from the natural frequency and will not cause resonance.The number of support points and the stiffness are optimized by single variable principle,and the optimization scheme of vibration isolation system is determined.Vibration test results show that the vibration isolation effect of the optimized scheme is significantly improved.