标题：Numerical analysis of acoustic and resistance performance of muffler in refrigeration compressor's discharge pipe
作者：Kong, Xiangqiang ;Chen, Lijuan ;Li, Ying
作者机构：[Kong, Xiangqiang ;Chen, Lijuan ;Li, Ying ] College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Qingdao; 更多
来源：Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering
摘要：The noise level has become an important index to evaluate the quality of air conditioners, and the refrigeration compressor is a major noise source of an air conditioners' outdoor unit. In order to reduce the noise of an air conditioner, by means of the theories that the noise is spread by fluid and the acoustics impedance mismatch occurs in the pipe with variable cross sections, a muffler was set in a refrigeration compressor's discharge pipe. The finite element model of a refrigerant in the muffler was established, based on which, the transmission loss could be numerically simulated by acoustics software Virtual Lab Acoustics, as well as the resistance performance by the computational fluid dynamics software Fluent. The effect of various structural parameters on the transmission loss and pressure loss of the muffler was investigated, including the length of the expansion chamber, and the position and the inner diameter of the orifice plate. The simulation results showed that the transmission loss curve of the muffler gradually moved to the higher frequency as the length of the expansion chamber decreases, which could also expand the effective acoustic attenuation frequency range, but it had little effect on the pressure loss of the muffler. To effectively reduce the noise of the compressor, the length of the expansion chamber should be appropriately selected. When the length of the expansion chamber was bigger than 140 mm, the noise of 2000-3000 Hz was effectively reduced, and the frequency of more than 2000 Hz was the main frequency region of the rotary compressor noise, so the length of expansion chamber was suggested to be bigger than 140 mm, but the length cannot be too big for decreasing the pressure loss of the muffler. For middle and high frequency noise, the position of orifice plate had a great influence on the acoustic attenuation performance of the muffler. As the orifice plate moved from the center of expansion chamber to its inlet surface, the acoustic attenuation performance for the frequency of 2000-2400 Hz gradually became better, while the pressure loss of the muffler decreased and the declination rate gradually increased, so the orifice plate should not only deviate from the center of the expansion chamber, but also get as close to the inlet of the muffler as possible within the permitted range. Moreover, the muffler could achieve better acoustic attenuation performance along with the decrease of the inner diameter of orifice plate, but the pressure loss of the muffler increased gradually with its increase rate tending to be bigger. As a result, in order to achieve an effective noise reduction and reduce the pressure loss of the muffler, the inner diameter of the orifice plate should not be too small. If the pressure loss of the muffler is required to less than 600 Pa, the inner diameter of the orifice plate should be bigger than 6 mm. In the design of the muffler, in addition to obtaining better acoustics attenuation performance, the pressure loss of the muffler needs to be considered, so that the performance of an air conditioner system cannot be greatly influenced. The research results would be able to provide a theoretical base for the noise reduction of air conditioners.
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