Research Of Acoustics And Dynamic Stiffness Characteristics On Connecting Pipe Of Automobile Air Conditioning

In order to reduce the influence of vibration and noise of the automobile air conditioning on the automobile interior environment, besides the normal ways of reducing vibration and noise of the compressor and fan, the transfer routes of vibration and noise should also be considered. As the refrigerant transmission channel between the compressor, evaporator and condenser, the connecting pipe also transferes vibration and noise of the compressor to the car. This paper is aimed at studying the characteristics of acoustic and the dynamic stiffness of the air conditioning pipings for a certain company.In order to reduce the noise transmission through the connecting pipes, the acoustic transmission loss of the connecting pipes will be increased. In this paper, theoretical studies on muffling mechanism of muffler had been done. For the dominant frequency of the compressor noise ranges from100to2000Hz, based on the theoretical analysis and acoustic simulation with the LMS Virtual lab, the muffler performance of the pipes had been improved by changing the structure of the muffler given the condition that the invariable pipeline structure path should be guaranteed. In order to evaluate the reliability of the simulation results and measure the acoustic characteristics of the tube conveniently, an experimental device for measuring acoustic transfer functions of the pipes was designed. Then the transfer functions of the pipes were measured successfully and the results of the simulation analysis were verified.Dynamic transfer stiffness is the most appropriate parameter for describing the vibro-acoustic transfer properties. In order to reduce the noise and vibration transmission through the connecting pipes, with the comparison and analysis of various dynamic stiffness measuring methods, and the consideration of the actual air conditioning connecting pipes installing and working conditions, an experimental platform of direct measurement method was designed to measure the dynamic stiffness of the connecting pipes, and the experiments were carried out to verify the rationality of the experimental platform. With experiments each testing point’s dynamic stiffness was measured, its vibro-acoustic transfer properties was known based on the dynamic stiffness of each frequency range, And based on the results some improvement approaches were given, and at the meantime, it also provided a new method to evaluate the vibro-acoustic transfer properties of elements other than resilient supports.