| With the improvement of people's living standard,and at the same time,the car industry has also been greatly developed,as a result,more and more people are beginning to pay attention to the comfort of the vehicle.Noise is the main factor affecting the comfort of an automobile.Automobile noise mainly consists of two types,one is the aerodynamic noise,the second is the vibration noise caused by the engine and other exciting sources,the aerodynamic noise has become the main factors affecting the comfort of the vehicle.In this paper,the aerodynamic noise produced by the automobile HVAC system is studied.Through the analysis of the previous car noise experiment in the paper found that leakage noise is the main way to affect the comfort of the vehicle.The reason for choosing the noise of automobile HVAC system in this study mainly on account of automotive air conditioning is directly connected with the cab,the noise produced by HVAC system can be propagated through the ventilation pipe directly into the cab and have a great influence on the cab noise,Therefore,the size of the noise produced by the automobile HVAC system has a direct impact on the comfort of the car cab.In this paper,the fluid software STAR CCM+ coupled with the acoustic software VIRTUAL.LAB is used to simulate the flow field and sound field of the automobile HVAC system.In numerical simulation,the steady simulation analysis has focused on the internal flow mechanism of automobile HVAC system,including the flow of differences between different areas and flow inducement are analyzed and explained,and the main components of internal automotive HVAC system and its influence on the flow field also made a detailed analysis.During transient simulation analysis,the emphasis is on the fluctuation of pressure in special position and the relationship between pressure and density on different sections.At the same time,the relationship between total pressure,static pressure and dynamic pressure is introduced and analyzed in detail.In the acoustic field simulation analysis,the mainresearch direction includes two parts,one is to study the sound pressure situation of the key position of HVAC system by direct calculation method and make a comparative analysis with the corresponding pressure changes.At the same time,the distribution of surface sound sources is analyzed.The second is the study of the far field noise propagation using boundary element method,make the key analysis on pressure nephogram of different sites on the grid,at the same time to the human ear position of the sound pressure level is predicted and analyzed.When conducting research on the propagation of far-field sound pressure,the detailed analysis is made on the respective roles of the sound sources of the fans and the sound sources of the housings and the mutual influence between them.Finally,the specific scope of the sound sources is determined through comparative analysis.In the process of structural optimization,five main schemes are made according to the distribution of the flow field and the sound field.They are: adding the shark fin structure to the fan blade,adopting the unequal distance blade,the local smooth transition of the shell,adding the convex part at the back of the vortex tongue and increasing the reflecting air flow structure.In terms of noise reduction in human ear,the five optimization schemes have better noise reduction effect,especially in the fan blade,adding shark fin structure,adding the convex part at the back of vortex tongue and increasing the reflecting airflow structure,the effect is very significant,which can achieve the 2-4dB level of noise reduction. |
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