声波法测量电站锅炉烟气流速的实验研究

Experimental Study on Acoustic Measurement of Flue Gas Flow in Power Boilers

对声波法测量电站锅炉烟道流速的方法进行了冷态模拟．根据时差法求气体流速的原理，实验采用可听声为信号源，结合Fluent流场模拟功能获得声源的较佳布置点，并使用直接互相关算法和经PHAT加权的广义互相关算法对声波飞渡时间进行估计，并通过涡街流量计直接测量风道的气体流速，来验证结果的正确性．结果表明：声波法测量结果与涡街流量计直接测量结果在一定程度上吻合较好，6000~8000Hz的扫频信号是较为理想的声源信号，PHAT算法在准确性和灵敏性上均优于直接互相关算法；声波法测量气体流速能达到较高的精度，可作为电站锅炉烟气流速在线监测的有效方法．

Cold simulation was performed to acoustic measurement of flue gas flow in power boilers, during which the gas flow rate was measured based on time-difference method by taking audible sound wave as the signal source and using flow field simulation of Fluent to find the optimum arrangement of loudspeakers. The sound travel-time was estimated respectively by direct cross-correlation algorithm and the generalized cross-correlation algorithm weighted by PHAT. To validate the simulation results, vortex shedding flowmeter was adopted to directly measure the gas flow rate in the flue duct. Results show that the data obtained by acoustic method agree well with actual measurements by vortex shedding flowmeter, and the sweep signal of 6 000-8 000 Hz is proved to be ideal. The algorithm weighted by PHAT is superior to that based on direct cross-correlation in terms of accuracy and sensitivity. The acoustic measurement of flue gas flow can reach a high accuracy, which therefore may serve as a reference for online monitoring of flue gas flow in power boilers.