基于DDS叠加波的双频超声法测量管内煤粉参数

Measuring pulverized coal parameter in power plant pipeline based on DDS superposition ultrasonic wave

基于声散射理论,考虑煤粉不规则度对声衰减的影响,通过数值模拟分析不同物性参数的影响,得出声衰减系数随煤粉体积分数和粒度的变化关系。设计中心频率分别为40、200 kHz的一体式超声波探针,使用叠加猝发波作为信号激励源以简化实验装置。在某电厂煤粉管道开展不同深度测点的实时在线测量,进行时长1 h的连续测量实验,同步测得煤粉平均体积分数约0.11%和平均粒径约35μm。该方法能够实时在线测量管内煤粉的体积分数和粒度,有效改善磨煤机工况和提高锅炉燃烧器效率。

An acoustic method was proposed and investigated based on the sound scattering theory, taking the influence on the acoustic attenuation caused by the irregularity of the coal powder into account. Meanwhile, numerical simulations of the acoustic attenuation were conducted to analyze the influence of different physical parameters＇ variation and establish the relationship between ultrasonic attenuation and coal volume fraction, size. Two one-piece ultrasonic probes with center frequencies of 40, 200 kHz were developed, where superimposed wave was adopted as a probe excitation source reduced the complexity of the experimental setup. The on-line coal parameter experiments were then conducted in a coal-fired power plant. The in-line measurements were carried out at zones with different depths from the pipe wall, and a one-hour continuous monitoring was also conducted, yielding a mean volume fraction of 0.11% and size of around 35 μm. Therefore the proposed method can real-time online measure coal powder volume fraction and size in power plant pipelines, improve the coal pulverizers＇ working condition and increase the boiler＇ s combustion efficiency.