基于声学参数的OGFC沥青混合料吸声性能优化

Optimization of Sound Absorption Performance of OGFC Asphalt Mixture Based on Acoustic Parameters

多孔材料吸声系数的唯象模型考虑了声波在空隙结构中传播产生的能量耗散,构建基于声学参数的模型,可对吸声系数进行较好的预测。为了准确获取OGFC沥青混合料的5个声学参数(孔隙率、流阻率、曲折因子、黏性/热效特征长度)以构建声学模型,首先,通过实测与反演结合的方法制备了不同孔隙率、不同级配类型的OGFC沥青混合料,使用驻波管测试了吸声系数;其次,开发了适用于混合料的流阻率测量设备,利用实测的空隙率、吸声系数和流阻率,基于遗传算法编写反演程序对OGFC的曲折因子、黏性/热效特征长度进行反演;再次,建立驻波管的有限元模型验证了声学参数的正确性,分析了声学参数单因素对吸声性能的影响;最后,基于声学参数对吸声性能进行了优化。结果表明:OGFC的空隙率越高和公称最大粒径越大,平均吸声系数和峰值吸声系数均越大;所构建的模型能够较好体现混合料的吸声特性,峰值吸声系数及出现的频率与实测值吻合;空隙率、黏性特征长度和热效特征长度增大,以及曲折因子减小,均有利于提高吸声性能,根据声学参数对混合料吸声性能的优化结果,最佳的吸声性能应将空隙率控制在22%左右。

In the phenomenological model,the sound absorption coefficient of porous materials was used to explain takes into account the energy dissipation generated by the propagation of sound waves in the void structure.A model based on acoustic parameters was constructed to predict the sound absorption coefficient.In order to accurately obtain the five acoustic parameters(porosity,flow resistance rate,tortuosity factor,viscous/thermal characteristic length)of OGFC asphalt mixture to construct the acoustic model,the OGFC asphalt mixture with different porosity and different gradation types was prepared by the combination of measurement and inversion,and the sound absorption coefficient was tested by standing wave tube.The flow resistance measurement equipment suitable for mixture was developed.Based on the measured porosity,sound absorption coefficient and flow resistance,the inversion program was written based on genetic algorithm to invert the tortuosity factor and viscous/thermal effect characteristic length of OGFC.Secondly,the finite element model of standing wave tube was established to verify the correctness of acoustic parameters.The influence of single factor of acoustic parameters on sound absorption performance was analyzed.Finally,the sound absorption performance was optimized based on acoustic parameters.The results showed that the higher the porosity of OGFC and the larger the nominal maximum particle size,the larger the average sound absorption coefficient and the peak sound absorption coefficient.The model constructed could better reflect the sound absorption characteristics of the mixture,and the peak sound absorption coefficient and the frequency of occurrence were consistent with the measured values.The increase of porosity,viscous characteristic length and thermal effect characteristic length,and the decrease of tortuosity factor would be beneficial to improve the sound absorption performance.The optimization results of the sound absorption performance of the mixture based on the acoustic parameters showed that the porosity should be controlled at about 22%for the best sound absorption performance.