空调室外机钣金结构辐射噪声分析与优化

Analysis and optimization of radiation noise from sheet metal structure of air conditioner outdoor unit

针对空调室外机背面位置处在压缩机5280 r/min转速下的出现两倍频(176 Hz)噪声峰值异常高的问题,基于双转子压缩机工作原理,计算双转子压缩机吸排气过程的两倍频转动力矩;建立空调室外机整机有限元模型,施加两倍频转动力矩,应用模态线性叠加法计算整机的频率响应,经过模态测试确定在176 Hz附近整机钣金存在共振,导致测点位置处两倍频异常高。基于间接边界元法,将整机频响计算结果导入声学仿真软件中,进一步计算钣金框体6个部位对测点位置处的声学贡献量,最终确定背板、中隔板、前面板共振导致测点位置两倍频过高。基于形貌优化技术,重点优化背板的压型,将固有频率从172 Hz提高至201.5 Hz,避免背板共振;同时前面板增加压型凸包,中隔板局部贴附阻尼,将整机176 Hz的两倍频峰值从55.74 dB(A)降低至45.11 dB(A),有效地提升了空调室外机的声品质。

Aiming at the problem of abnormally twice fundamental frequency(176 Hz)noise peak at the back of the AC outdoor unit when the compressor speed is of 5280 r/min,based on the working principle of the dual-rotor compressor,calculate the twice fundamental frequency torque of the double-rotor compressor in the suction and discharge process.Establish a finite element model of the outdoor unit,apply twice fundamental frequency torque,calculate the frequency response of the unit using the modal superposition method.Using the modal testing and analysis,it is preliminarily determined that there is resonance at the metal structure near 176 Hz,resulting in an abnormally twice fundamental frequency at the measuring position.Based on the indirect boundary element method,the frequency response calculation result of the finite element model is imported into the acoustic simulation software,and the acoustic contribution of the 6 parts of the sheet metal frame to the measuring point is further calculated,and it is finally determined that the resonance of the back plate,partition plate,and front panel causes excessively high frequency peak at the measuring point.Based on the topography optimization technology,optimize the profile of the back plate to increase the natural frequency from 172 Hz to 201.5 Hz,which in turn avoids resonance of back plate;at the same time,the front panel is provided with a profiled convex hull,and the partition plate is partially attached with damping,making the peak of twice fundamental frequency(176 Hz)reduced from 55.74 dB(A)to 45.11 dB(A),effectively improving the sound quality of the AC outdoor unit.