湍流脉动影响下巷道平均风速单点统计测量方法

Method for air velocity measurement with single-point under the influence of turbulent fluctuation

巷道断面上各点风速不同,每点的瞬时风速又具有随机脉动性,准确获取一点的风速时均值并将其转换为断面的平均风速值是矿井通风领域中的一项技术难题。根据巷道湍流定常非均匀特征,建立了巷道断面上任一点时均风速u和断面平均风速V的统计测量模型,并对u与V之间的转换机制进行了理论和实验研究。理论研究表明,湍流充分发展的圆形巷道内,u与V之间呈非线性正相关,但在很宽的风速变化范围内,可近似为正比关系。实验结果表明,在井下常见风速范围内,湍流非充分发展的非圆巷道断面无量纲速度场结构近似恒定,u与V之间亦呈正比关系,比值k为常数,亦即无量纲速度场结构恒定时,系数k的大小和分布也是恒定的。k值与风速大小无关,仅取决于巷道的方向、断面形状、断面积以及支护方式等边界条件的变化。只要获得巷道断面k的分布以及任一点的时均风速u就可获得巷道断面的平均风速V。根据统计测量模型给出了恒定速度场结构下k值的首次标定准则,提出单点瞬时风速的时均化原则为时间平均尺度大于湍流各态遍历假设。新型智能传感器应提高数据采集频率以满足风速时均化要求。

Air velocities over the roadway section vary from point to point, and instantaneous velocities are allpulsing at the same time, so it＇s a technical problem in field of mine ventilation to measure air velocity of apoint and convert it to the mean velocity accurately- Statistical measurement models for a certain point velocity（ u） and means （V） are described,according to the characteristics of turbulent roadway flow, and also conver-sion mechanism between u and V is investigated theoretically and experimentally in this paper- The theoreticalstudy of fully developed turbulent in circular tunnel indicates that non-linear relationships are shown betweenu and V, which can be approximated as linear ones over a broad range of velocity changes- The experimentalresults show that,dimensional flow field structure of non-fully-developed turbulent in non-circular tunnel isnearly constant, and proportional relationship is still remain between u and V, and the ratio k is constant- Inother words, the value and distribution of the ration are fixed when the flow field structure is constant- The kvalues are independent on velocity and are only relevant to boundary conditions such as direction, shape basalarea and support pattern of the roadway, Once time-averaged velocity and k value of any point on the roadwaysection are obtained, the mean velocity can be get- Furthermore, a method for k value calibration under con＇stant flow field structure is provided, and the time-averaged principle of instantaneous velocity is put forwardthat the time-average-scale should greater than ergodic hypothesis- Thus, new sensors should improve thedata acquisition-frequency to satisfy the time-averaged requests.