阻尼材料对发动机薄壁件降噪效果分析

Effect of Noise Reduction on Thin-Walled Parts of Engine Using Damping Material Treatment

为降低发动机薄壁件的辐射噪声,对部分薄壁件表面增加质量或敷设阻尼材料进行对比试验.结果表明:对薄壁件表面增加质量块,表面振动幅值与共振频率降低,噪声的尖锐度会降低,而响度与粗糙度变化较小.对薄壁件敷设阻尼材料,近场噪声的各频段都有一定的抑制,尤其对于结构固有频率所对应的噪声共振带有显著的削弱,是一种很好的宽带振动噪声控制措施.其中对铝合金的气缸盖敷设阻尼材料,近场噪声的尖锐度与粗糙度变化不明显,响度在高转速(2500~3100 r/min)下降低了5 sone;对塑料正时盖罩敷设阻尼材料,随发动机转速的提高,近场噪声的响度优化效果越显著,在标定转速(3200 r/min)响度降低值可达12 sone.尖锐度在各转速下降低约为0.1 acum,粗糙度变化不明显.对于民用小功率发动机,正时盖罩敷设阻尼材料,声品质优化效果较为理想,是可实际应用的降噪措施.

An experiment was carried out on adding mass or laying damping materials on the surface of thin-walled parts of an engine in order to reduce the noise radiated by thin-walled parts.Results show that the surface vibration amplitude and resonance frequency can be reduced by adding mass.The sharpness decreases,while the loudness and roughness change little.Laying damping materials has a certain suppression effect for each frequency band and thus is a good broadband vibration and noise control measure.Especially,the noise resonance corresponding to the natural frequency of the structure is significantly weakened.The loudness of laying damping materials on cylinder head made by aluminum alloy decreases by 5 sone at high speed of 2500—3100 r/min,while the sharpness and roughness change little.When the damping material is laid on the plastic timing cover,the loudness optimization effect becomes more obvious as the speed increases.The loudness is reduced by 12 sone at the rated speed of 3200 r/min.The sharpness decreases by about 0.1 acum at each rotation speed while the roughness changes little.For a civil low power engine,the sound quality optimization of damping material for timing cover is ideal,which is a practical noise reduction measure.