混合动力低地板车冷却风机降噪试验研究

摘要

混合动力低地板车采用氢燃料电池为清洁能源,冷却风机是确保其正常工作的关键部件之一.冷却风机噪声作为混合动力低地板车静置乃至低速运行时的主导声源,其减振降噪是混合动力低地板车噪声控制的关键所在.为探寻其低噪声设计方法或高效降噪措施方案,基于试验测试研究,系统研究和对比分析冷却风机在不同运行工况(转速、风机数量、栅格影响)和减振降噪控制措施(不同降噪处理方案)下的辐射噪声响应特性.结果表明:冷却风机噪声呈现为显著的纯音加宽中频频谱特性,纯音成分由旋转基频在内的前3阶旋转频率主导,宽中频噪声由风机气动和箱体振动声辐射噪声组合而成;随着风机转速增加,旋转基频和A计权总声压级线性增长.在保证冷却效果的前提下,尽量降低风机转速是控制其噪声响应的有效手段.风机数量减半,辐射噪声仅下降2 dB(A),说明箱体振动声辐射对总辐射噪声影响显著;栅格对辐射噪声影响很小,去掉栅格,辐射噪声仅降低0.4 dB(A);最佳的降噪方案为在底板、侧板和边板粘贴降噪和吸声材料,可降低噪声2.6 dB(A).相关测试分析结果对冷却风机噪声和车外噪声控制具有一定的参考价值.%Hydrogen fuel cell is used as a clean energy source in hybrid low-floor vehicles. Cooling fan is one of the key components to ensure the normal operation of the vehicles. Cooling fan noise is the dominant noise source of the hybrid low-floor vehicles whenever they are stationary or travelling at a low speed. So, diminution of vibration and noise of cooling fans is essential for the noise control of the hybrid low-floor vehicles. In this paper, the low noise design method and the efficient low noise control method are studied. Based on the experiments, the noise radiation properties of the cooling fans under different operation conditions, such as speeds, fan numbers and grid influences, and different noise-reduction schemes are studied systematically. The results show that the noise of the cooling fans is characterized by the pure tone and wide mid-frequency spectrum. The pure tone component is mainly caused by the rotational frequencies of the first three orders, and the wide-mid frequency spectrum noise is composed of the aerodynamic noise and the radiation noise of the fan-box vibration. As the fan's speed increases, the fundamental rotating frequency and the total A-weighted sound pressure level grow linearly. Under the essential prerequisite of ensuring the cooling effect, reducing the fan speed is an effective means to control the noise response. When the number of fans is halved, the radiated noise is only reduced by 2 dB(A). It indicates that the vibration of the fan-box has a significant effect on the total radiated noise. The influence of the grating on the radiated noise is very small. When removing the grate, the radiated noise is only reduced by 0.4 dB(A). The best noise reduction measures are to paste noise-reduction materials and sound-absorbing materials on bottom panels and side panels, which can reduce the noise by 2.6 dB(A). The results of the relevant test analysis have some reference value for the control of cooling fan noise and exterior noise.