Research On Aerodynamic Noise Analysis Of A Car Air Intake Pressurization System

Currently,small and high-efficiency internal combustion engines have become the main development tendency of fuel engines.As the main technology for achieving high efficiency,supercharging technology has been widely used in automotive internal combustion engines.So far,although the research on the prediction and control of the intake system noise of naturally aspirated engines has been very deep,the research on the noise of the turbocharged intake system especially relates to its unique compressor aerodynamic noise and pressure relief noise.Research still needs to strengthen.In this paper,the finite volume method,broadband noise method and acoustic analog method are used to analyze the flow field and sound field characteristics of the compressor.The causes of noise in the intake pressurization system are discussed.The flow field and sound field characteristics of the intake pressurization system under the pressure relief condition is studied,and the system is improved on this basis.Firstly,on the basis of verifying the correctness of the finite element model and boundary conditions in this paper,the overall flow field characteristics of the compressor and the local flow characteristics of key components are discussed,and the influence of flow rate and rotational speed on the flow field of each component is analyzed.The results show that the airflow enters the impeller passage as laminar flow,and the airflow velocity increases.After flowing into the diffuser and volute,the airflow velocity decreases continuously until it flows out in a spiral shape.And the change of pressure is from the inlet of compressor to the volute outlet first decreased and then increased.There is an obvious negative pressure zone near the leading edge of the blade suction surface.As the compressor speed increases,the negative pressure at the inlet of the impeller becomes larger and larger,and the negative pressure zone takes up a larger proportion in the entire blade.A low-speed zone is formed in some area of the shroud where is close to the main flow blade.With the increase of flow rate,backflow phenomenon begins to appear,and the low-speed zone gradually increases.The volute tongue is prone to airflow obstruction under the condition of high flow,so it should avoid that the compressor is close to the blocking line in the common working conditions.Secondly,based on the above research,the broadband noise method and the acoustic analog method are used to investigate the causes and distribution characteristics of the aerodynamic noise of the compressor.The results show that the impeller motion is the main source of compressor aerodynamic noise,followed by the air movement of the volute region.The aerodynamic noise in the impeller region is a wideband noise mixed with obviously discrete harmonic peaks corresponding to the passage frequency of the blade and its harmonic frequency.The aerodynamic noise in the middle and front of the impeller is mainly affected by the main flow blade,while in the middle and rear of the impeller,it is affected by the combined action of the main flow blade and the splitter blade.In the middle region with the largest spacing between the main flow blade and the splitter blade,aerodynamic noise similar to "buzz noise" is generated.The aerodynamic noise generated at the volute tongue is distributed in the frequency range of 0~10 kHz.Finally,the noise source and its distribution characteristics of the intake pressurization system under the pressure relief condition are discussed.The results show that the main noise sources are the impeller motion and the airflow motion of the pressure relief components.Before and after the pressure relief valve is opened and closed,the sound pressure level spectrum at the inlet of the pressure relief valve shows no discrete characteristics,but the broadband characteristic is obvious,which are mainly distributed in 0.5~7 kHz.By improving the arrangement of the pressure relief components under the pressure relief condition,the pressure relief noise is controlled,and the total sound pressure level of 0.5~7 kHz of the pressure relief noise is improved from 97.0 dB to 93.6 dB,and the acoustic performance is effectively improved.