CFD Analysis And Research Of Aerodynamic Noise Of Automotive Air Conditioning And Passenger Compartment System

With the growth of national economy,The automotive industry has developed rapidly.People are demanding more and more on the comfort experience of automobiles,and the noise problem is one of the main factors affecting the comfort of automobiles.The research shows that the excessive interior noise in cars not only affects the communication among crew,but also arouses human hearing fatigue leading to distraction and discomfort,even affects the safety of driving.Therefore,the noise in the car during driving is a problem that automobile manufacturers must overcome.With the continuous advancement of automotive technology,the reduction of external noise of the car and the improvement of the sealing effect of the passenger compartment,the aerodynamic noise of the air conditioning system makes the highest contribution to the noise inside the vehicle.As a consequence,it is of great significance to carry out research on reducing the aerodynamic noise of air conditioning systems.The aerodynamic noise of automobile air conditioning systems can be divided into two categories: one is the noise caused by the fan cavity during operation;the other one is the noise caused by the airway propagation process.For fan noise,the aerodynamic noise characteristics of the fan have been improved after many scholars’ efforts,however,the unreasonable air duct structure design not only affects the temperature distribution throughout,but also produces a lot of noise.People improve the aerodynamic noise characteristics of the air duct by reducing the sudden change in the structure of the air duct to reduce the pressure drop in the air duct.After the air conditioning assembly is loaded,the air conditioning system of independent research has certain limitations due to the different conditions of use and the test environment.If the research is conducted on the overall model of air conditioning pipe body and cabin based on the research of independent air conditioning lines,it will be more practical and easier to find other reasons affecting the aerodynamic noise at the human ear.The development cycle of the traditional test method is long and takes a lot of manpower and material resources.The computational fluid dynamics(CFD)application in automotive engineering allows the researchers to combine the model by computer simulation technology for research instead of the real system.It is easy to obtain the state of fluid motion and predict thegenerated noise with no limitation by test conditions and environment.Meanwhile,it can clarify the research direction,shorten development cycle and reduce waste caused by repeated trials.Specific research contents of this paper is aiming at the whole air-conditioning duct and passenger cabin of a passenger car as the research object,based on the basic theoretical analysis of flow field and sound field,a simplified model is first established,which is simulated and calculated by numerical simulation.Combining with wind tunnel test,the turbulence model with the best coincidence is selected for this paper.The internal flow field calculation model.Then,the feasibility of the AA method in calculating the noise in this paper is verified by CAA and AA methods.Finally,the simulation model of air-conditioning pipeline and passenger compartment system is established,and the distribution of flow field and sound field in the driving room,air-conditioning outlet and human ears in the compartment is analyzed.Based on the above analysis of flow field and sound field,the structure of air-conditioning pipeline is optimized and improved to achieve the purpose of noise reduction.After the improvement of the optimal scheme,the noise at the outlet and the human ear is reduced by about 4 dB.