在煤粉制备、运输及储存过程中，堆积煤粉通常暴露于氧化环境中，当外界温度过高时极易发生自燃。低频声波具有衰减低、传播距离长的特点，以其作为声源的声学测温方式可有效弥补常规热电偶滞后预警的问题，实现实时测量，显著提升发电过程的智能化水平。主要探究了堆积煤粉的声吸收特性以及低频声波（频率在200～2 000 Hz）在堆积煤粉中的传播特性，试验以福泉煤矿的烟煤为研究对象，制备了4种不同粒径的煤样，研究了不同粒径煤粉以及堆积高度下的声吸收特性，发现堆积煤粉的声吸收曲线存在多峰值现象。进行了不同频率下低频声波在堆积煤粉中的传播特性试验，结果表明在1 000～2 000 Hz声衰减系数下降趋势明显；在实验室环境温度下，堆积煤粉的声速在142.261～142.851 m/s，试验标准差约0.1%，结果较稳定，验证了声学测量堆积煤粉温度分布的可行性。

In the process of preparation,transportation and storage of pulverized coal,the accumulated pulverized coal is usually exposed to oxidation environment. When the external temperature is too high,it is very easy to spontaneous combustion. The low frequency sound wave has the characteristics of low attenuation and long propagation distance. The acoustic temperature measurement method using low frequency sound wave as sound source can effectively make up for the lag warning of conventional thermocouple and realize real-time measurement,and significantly improve the intelligent level of power generation process. The sound absorption characteristics of the accumulated pulverized coal and the propagation characteristics of low-frequency sound waves (frequency in 200-2 000 Hz) in the accumulated pulverized coal were mainly explored. Four kinds of coal samples with different particle sizes were prepared from the bituminous coal produced by Fuquan coal mine. The sound absorption characteristics of pulverized coal were mainly studied from two aspects of different particle sizes and stacking height. The results show that the sound absorption curve of stacked pulverized coal has multi-peak phenomenon;experiments on the propagation characteristics of low-frequency sound waves in accumulated pulverized coal at different frequencies were carried out. The results show that the acoustic attenuation coefficient has an obvious downward trend in the range of 1 000-2 000 Hz. The velocity measurement results show that the range of sound velocity is 142.261-142.851 m/s,and the standard deviation is about 0.1%. The results are more stable. The feasibility of acoustic measurement of temperature distribution of accumulated pulverized coal is verified.

0 引言

1 堆积煤粉声学测温模型

2 煤粉低频声波吸收特性

   2.1 试验原理

   2.2 试验条件

   2.3 试验过程及结果分析

3 煤粉低频声波传播特性

   3.1 试验原理

   3.2 试验步骤

   3.3 试验结果及讨论

4 结论与展望