基于LDA的均直巷道断面突扩风速分布规律实验研究

风速分布是计算井下巷道瓦斯、火灾气体、粉尘运移规律，温度、湿度分布，传热传质过程的基础，对风速传感器布置及测风仪表研制具有重要意义。针对传统的接触式瞬时速度测量方法的局限性，采用非接触式激光多普勒测速仪（LDA）对均直巷道的稳定流动及断面突扩后风流状态进行实验测试。在平均风速为4 m/s左右的条件下，得出即使是均直巷道的稳定流动，其瞬时风速的大小及方向也呈现极度的湍流脉动性，平均脉动幅度可达平均风速值的33%左右，测点风速大小及风向均服从正态高斯分布；在突扩区域有大涡存在，漩涡区风流方向极不规则，各向均有分布，其风速平均绝对值在0.1~0.2 m/s左右波动，表明井下工程测风可有条件地忽略湍流大涡区域。受突扩影响均直巷道断面风速分布呈近似均等的动态的波浪线分布而非拟抛物线型，壁面光滑的实验巷道边界层厚度在5 mm左右，风速以跃迁方式“突变”达到均值。实验表明，传统的测风原理及方法仅能满足一般的工程需要，但是不能满足以湍流为特征的巷道瓦斯、火灾气体、粉尘运移规律，温度、湿度分布，传热传质等过程的计算要求。

Experimental study on wind speed distribution of the straight roadway and sudden enlarged sections based on LDA

Wind speed distribution is a fundamental basis for calculating the migration of gas,gas fire,dust,temperature,humidity,heat and mass transfer processes within the underground roadway.It also plays a significant role in the arrangement of wind speed sensors and the development of wind instruments.In order to overcome the limitations of traditional contact instantaneous velocity measurement methods,a non-contact technology of LDA is used to test the steady flow in underground roadway and the airflow state at a sudden enlarged section.Under an average wind speed of 4 m/s,it can determine the extreme turbulence pulsations in the wind speed.With steady flow in the straight roadway,the average pulsation amplitude reaches 33% of average speed.The velocity vector and its direction display a normal Gaussian distribution.A large eddy can form in the sudden enlarged area with highly irregular airflow fluctuating around 0.1 m/s-0.2 m/s.This suggests that the turbulence vortex area can be neglected when considering airflow during the process.Affected by the sudden enlargement,the roadway wind speed resembles the distribution of equal dynamic wavy lines rather than the quasi parabolic distribution.The thickness of the boundary layer of the experimental roadway with smooth surface is about 5 mm with the wind speed reaching the mean value via a transitional “mutation”.Experiments show that the traditional measurement principle and method of wind can only satisfy the needs of general requirements,but cannot meet the other computing requirements,such as gas,gas fire,movement rules of dust,temperature and humidity distribution,and heat and mass transfer process under turbulent conditions in underground roadway.