Analysis And Research On Pressure Relief Noise Of A Car Air Intake Pressurization System

In order to improve emission characteristics,the power and fuel economy of the automotive engines,booster technology has been widely used in automotive engines.However,the high speed operating characteristics of turbochargers also bring new noise problems,which are mainly reflected in the intake system.So far,the research on the noise of turbocharged intake system is mostly focused on the aerodynamic noise generated by the compressor under steady-state operating conditions,and there are few studies on the pressure relief noise under continuous transient operating conditions.In this paper,the commercial software Fluent is used to analyze the flow and sound fields characteristics of the compressor and the pressure relief valve.Then,the pressure relief flow channel model of the compressor is established,and the pressure relief noise under continuous transient conditions is analyzed and optimized.Firstly,this paper establishes a compressor flow channel model to simulate the flow field inside the compressor under steady-state conditions,and analyzes the flow field characteristics of the compressor,diffuser and volute region.Based on the steady flow field,the broadband noise source model method is used to calculate the acoustic power distribution.The results show that the impeller area is the main noise source of the compressor under steady-state conditions,and the maximum sound power is distributed at the blade leading edge and tip near the compressor housing.In order to analyze the noise spectrum characteristics of different points in the compressor,unsteady calculations are carried out in combination with the acoustic analog method.It is found that all receiving points have obvious discrete characteristics,which are mainly represented by "Buzz-saw" noise and blade passing noise.Then,the flow channel model of the pressure relief valve is established to analyze the flow field characteristics under different opening degrees and boundary conditions.According to the results,the average outlet velocity and mass flow rate are both related to the minimum flow area,and the calculated results are in good agreement with the theoretical values.By combining the steady-state results with the broadband noise source method,it is found that the dipole source and the quadrupole source are both the main noise sources at the low opening degree.As valve core opening increases,the quadrupole source gradually weakened,while the dipole source gradually strengthened to become the main noise source,and the intensity is related to the mass flow.In order to optimize the pressure relief noise,the structure of the pressure relief valve was improved to control noise from the perspective of noise generation.Finally,on the basis of compressor and pressure relief valve,the pressure relief flow channel model including the intercooler and pressure relief pipe is established to analyze the flow and sound fields under continuous transient conditions.The analysis results show that the pressure relief noise presents broadband characteristics,and the intensity continues to decrease over time.According to the results,compared with original structure,the minimum flow area of optimized the structure is smaller,the mass flow is reduced under the same opening degree,the internal flow field changes less in the same time,and the flow is more stable.The total sound pressure level of the optimized pressure relief noise is reduced by 24 d B on average in each time period.The test results show that the optimized pressure relief noise is reduced by 6.4 d B,and the acoustic performance is improved,which verifies the reliability of the scheme.