Research On NVH Characteristics Of Engine Intake System

With the improvement of living standards,users and enterprises have higher and higher requirements for engine NVH performance,and engine NVH performance is mainly reflected by combustion noise,mechanical noise and aerodynamic noise.Since the intake system is closer to the passenger compartment,the NVH of the intake system The characteristics have an important influence on the passing noise inside and outside the vehicle.The NVH characteristics of the intake system are mainly reflected by aerodynamic noise and component(air filter)radiation noise,both of which are directly related to the flow state of the intake air.The research on aerodynamic noise is based on the piping system before the intake manifold or throttle.There are few research results aimed at the overall intake system and considering the influence of the flow field on the structural radiation noise.There are few research results on the probability distribution of aerodynamic noise in consideration of manufacturing and assembly errors.Based on the softwares of GT-Power,Fluent and LMS Virtual Lab,this paper uses the co-simulation method to simulate and analyze the aerodynamic noise and structural radiation noise(air filter)of an engine’s intake system under steady-state conditions.The generation mechanism and influencing factors(modality,transmission loss,intake pressure pulsation)of aerodynamic noise and radiation noise are studied,At the same time,the probability distribution of aerodynamic noise under manufacturing and assembly errors is also studied.Completed the establishment and calibration of the engine model according to the main technical parameters of the engine and related test data.Based on the calibrated engine model in GT-Power and the fluid domain model of the intake system in Fluent,a three-dimensional CFD calculation is performed on the internal flow of the intake system.Through the systematic analysis of the pressure,velocity,and turbulent kinetic energy distribution in the flow field,to study the influence of the air filter element on the flow field and the generation and distribution of vortices in the intake system.The wall pressure data output during the calculation of the flow field can provide accurate boundary conditions for the analysis of the acoustic characteristics of the intake system.The simulation model of aerodynamic noise in intake system is established by importing the wall pressure calculated by flow field into LMS virtual lab as dipole sound source,and the aerodynamic noise spectrum curve of the intake system is calculated by the method of acoustic finite element.The aerodynamic noise test of the air intake system is carried out.The verification of the accuracy of the co-simulation calculation results is verified by the comparison of simulation and test results.Based on the calculation principle and method of the acoustic madel and transmission loss,the acoustic madel and transmission loss of the intake system are simulated and analyzed,and the influence of the acoustic madel frequency on the transmission loss is studied.Using the simulation results of acoustic madel,transmission loss,intake pressure pulsation noise(GT-Power simulation result),and aerodynamic noise,the influence of acoustic mode frequency and vibration shape,transmission loss,and intake pulsation frequency on aerodynamics is studied.The finite element model of the air filter is established,the structural modal analysis of the air filter is carried out,and the accuracy of the finite element model is verified through the modal test.The result of the pressure on the inner wall of the air filter is used as the excitation force,combined with the result of restrained madel,modal superposition method and MATV method are used to establish the modal participation factor of the air filter vibration response and the radiation noise simulation model.Based on the calculation results,the effects of restrained madel and intake pressure pulsation frequency on the radiated noise of the air filter are studied.The orthogonal test is used to analyze the influencing factors of aerodynamic noise,and the main influencing factors of aerodynamic noise are obtained.Combined with the response surface method,a response surface model based on the main influencing factors is established,and the The accuracy of the model is verified,and the interaction relationship between the main influencing factors of aerodynamic noise is obtained.Assuming that manufacturing and assembly errors obey normal distribution,The main influencing factors of aerodynamic noise are randomly sampled by Monte Carlo method and calculated by engine model.The probability analysis and evaluation of aerodynamic noise under the condition of design value error of each factor are carried out.The influence law of main influencing factors on the probability distribution of aerodynamic noise is studied.The paper presented a method for the probability analysis and evaluation of aerodynamic noise considering the manufacturing and assembly errors.