基于低频声波的空气温度测量研究  

Research on air temperature measurement using low frequency sound waves

作　　者：郭淼[1] 闫勇[1,2] 卢钢[2] 胡永辉[1] Guo Miao;Yan Yong;Lu Gang;Hu Yonghui(School of Control and Computer Engineering, North China Electric Power University, Beijing 102206, China;School of Engineering and Digital Arts, University of Kent, Kent CT2 7NT, UK)

机构地区：[1]华北电力大学控制与计算机工程学院,北京102206 [2]英国肯特大学工程与数字艺术学院肯特CT27NT

出　　处：《仪器仪表学报》2018年第1期75-83,共9页Chinese Journal of Scientific Instrument

基　　金：中央高校基本科研业务费专项资金(2015XS64);留学基金委(201506730012)项目资助

摘　　要：低频声波可以用来实现对空气温度的非侵入式测量。现有的基于低频声波的测温方法精度较低,如何建立有效的声学测温机制从而提高测量精度需要进一步研究。描述了一个基于低频声源和传声器的新型空气温度测量系统,通过测量空气中的声速达到测量空气温度的目的。首先根据温度、湿度、大气压和空气成分与声速的关系提出了一种通过计算空气密度来计算声速的方法。由于空气的湿度、大气压和空气成分也会影响声速,为了提高测温精度,分别从理论上分析了这3个因素对声学测温结果的影响并给出了相应的技术解决方案。为了测量声速,选择宽度为0.1 s的200～1 500 Hz线性扫频信号作为声源信号,通过对上下游两个传声器接收到的扫频信号进行互相关,计算出声波在两个传声器间的传播时间。为了提高声速测量精度,通过参照温度试验获得了不同温度下的声波传播时间并代入校准方程,使用最小二乘法估计出了等效声波路径长度和系统时延。得到这两个参数值后,系统测量出的声速更加接近同温度下的理论声速值。验证试验以K型热电偶测量的温度作为对比,在23.5℃～54.2℃的温度范围内,声学测温的相对误差在3.2%以内,标准差在0.2%以内。Low frequency sound waves can be utilized to measure air temperature non-intrusively.The existed air temperature measurement approaches are low-precision.How to establish an effective mechanism for more accurate temperature measurement needs to be further investigated.In this paper,one kind of new air temperature measurement system based on low frequency sound waves and acoustic sensors is proposed.Air temperature measurement is achieved by measuring the sound speed in the air.Based on the relationship among the temperature,humidity,pressure and constituents of air and sound speed,the approach of determining the sound speed through the calculation of air density is proposed.Sound speed is also influenced by humidity,pressure and constituents of air.To increase the temperature measurement accuracy,a theoretical analysis is conducted to investigate the influence of these three factors on temperature measurement results and corresponding technical solutions are provided.To measure the sound speed,a linear chirp signal with 0.1 s duration from 200 Hz to 1 500 Hz is used.By cross-correlating the chirp signals of two acoustic sensors,the travel time of the sound wave between the two sensors is calculated.To increase the accuracy of the sound speed measurement,sound travel times under different air temperatures are acquired through temperature reference experiments and are further improved by the calibration equation.The least squares method is used to estimate the equivalent sound path length and systematic delay.In this way,the measured sound speed is closer to the theoretical value with these two parameters.Compared with the reference temperature measured from a K-type thermocouple,the relative error of the measured temperatures using the acoustic system is no larger than ± 3.2% with a standard deviation of within 0.2% over the temperature range from 23.5℃ to 54.2℃.

关 键 词：声学 线性扫频信号 空气温度 低频声波 互相关 

分 类 号：TH89[机械工程—仪器科学与技术]