无外部扰动的均直巷道风速和风压测不准机理实验研究

Experimental study on uncertainty mechanism of mine airvelocity and pressure with non-external disturbance

井下风速和风压的波动通常被认为是由外部扰动引起的,但是,即使在实验室条件下对可能的外部扰动给予充分的控制,风速和风压的示值仍始终呈现不规则的波动,即测不准现象。对此,从湍流角度出发对这一现象的产生机理进行了研究。利用激光多普勒测速仪和数字式微压差计测量了中低风速下巷道模型风速和静压的时间序列。结果显示,在无外部扰动的均直光滑巷道内,风速和压力依然存在波动,其大小和方向均发生剧烈变化,总体上呈现出在一平均值附近的随机脉动;当平均风速和平均压力分别为2.57 m/s和17.1 Pa时,风速和压力的最大脉动幅度分别达到了1.19 m/s和4.9 Pa。风速和压力的脉动信号服从正态分布,平均脉动幅度分别与速度和速度平方成正比,但测不准现象与风速大小关系不大仅受湍流强度影响。实验表明,即使在无外部扰动的条件下,井下风速和风压也是测不准的,测不准的本质是井下湍流随机脉动特性所致。而湍流具有规则的统计平均结果,是可以精准测量的。为了获得井下风流的精准参数,风速及风压等测试仪器应基于湍流的统计平均特性来设计研发。

Fluctuations of mine air velocity and pressure are generally considered to be caused by external disturbances. But even if external disturbances are fully controlled in a lab environment,the indicated values of velocity and pressure still present irregular fluctuations which is known as uncertainty phenomenon. Mechanism which causes the uncertainty phenomenon was studied from the turbulent theory. Time-series data of air velocity and static pressure in a tunnel model were measured by laser dopper anemometer（ LDA） and digital differential manometer. The results show that the fluctuations still exist in both magnitude and direction,which generally present a random fluctuation around an average value. The maximum pulsating amplitude of air velocity and pressure reach 1. 19 m / s and 4. 9 Pa respectively when their average values are 2. 57 m / s and 17. 1 Pa respectively. Both velocity and pressure fluctuation signals followa normal distribution. Their average pulsating amplitudes are respectively proportional to velocity and its square,but the uncertainty phenomenon is only affected by turbulence intensity instead of velocity. Experiments show that mine air velocity and pressure are uncertainty even with non-external disturbances which is essentially caused by turbulence fluctuations. Yet,turbulence can be measured accurately because it has regular statistical average value. To get accurate parameters in the tunnel airflow the development of test instruments should be based on the statistical average value of turbulence.