湍流脉动影响下巷道平均风速单点统计测量方法
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摘要
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 all pulsing at the same time,so it's a technical problem in field of mine ventilation to measure air velocity of a point 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 conversion mechanism between u and V is investigated theoretically and experimentally in this paper. The theoretical study of fully developed turbulent in circular tunnel indicates that non-linear relationships are shown between u and V,which can be approximated as linear ones over a broad range of velocity changes. The experimental results show that,dimensional flow field structure of non-fully-developed turbulent in non-circular tunnel is nearly constant,and proportional relationship is still remain between u and V,and the ratio k is constant. In other 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 basal area and support pattern of the roadway. Once time-averaged velocity and k value of any point on the roadway section are obtained,the mean velocity can be get. Furthermore,a method for k value calibration under constant flow field structure is provided,and the time-averaged principle of instantaneous velocity is put forward that the time-average-scale should greater than ergodic hypothesis. Thus,new sensors should improve the data acquisition-frequency to satisfy the time-averaged requests.
Air velocities over the roadway section vary from point to point,and instantaneous velocities are all pulsing at the same time,so it's a technical problem in field of mine ventilation to measure air velocity of a point 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 conversion mechanism between u and V is investigated theoretically and experimentally in this paper. The theoretical study of fully developed turbulent in circular tunnel indicates that non-linear relationships are shown between u and V,which can be approximated as linear ones over a broad range of velocity changes. The experimental results show that,dimensional flow field structure of non-fully-developed turbulent in non-circular tunnel is nearly constant,and proportional relationship is still remain between u and V,and the ratio k is constant. In other 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 basal area and support pattern of the roadway. Once time-averaged velocity and k value of any point on the roadway section are obtained,the mean velocity can be get. Furthermore,a method for k value calibration under constant flow field structure is provided,and the time-averaged principle of instantaneous velocity is put forward that the time-average-scale should greater than ergodic hypothesis. Thus,new sensors should improve the data acquisition-frequency to satisfy the time-averaged requests.
引文
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[2]黄元平.矿井通风[M].徐州:中国矿业大学出版社,1986.
[3]王英敏.矿内空气动力学与矿井通风系统[M].北京:冶金工业出版社,1994.
[4]王翰锋.基于Fluent巷道断面平均风速点定位监测模拟研究[J].煤炭科学技术,2015,43(8):92-96.
[5]丁翠,何学秋,聂百胜.矿井通风巷道风流分布“关键环”数值与实验研究[J].辽宁工程技术大学学报(自然科学版),2015,34(10):1131-1136.
[6]王军,陈开岩,黄帅.基于CFD数值模拟的矿井巷道平均风速单点测法[J].煤矿安全,2013,44(3):144-146.
[7]罗永豪,赵阳升.煤矿井下不同粗糙度巷道内风速分布的风洞模拟[J].太原理工大学学报,2015,46(2):235-237.
[8]王丙建,罗永豪,赵阳升.输送机布设矩形巷道断面风速分布特征风洞模拟[J].煤矿安全,2013,44(5):42-45.
[9]宋莹,李雪冰,王施惠,等.基于LDA的矩形巷道测风站风速测定与校正实验研究[J].中国安全生产科学技术,2016,12(1):169-175.
[10]周西华,孟乐,李诚玉,等.圆形管道风速测定与校正方法实验[J].辽宁工程技术大学学报(自然科学版),2012,31(6):801-804.
[11]郝元伟,陈开岩,蒋中承,等.基于CFD模拟的巷道风速监测值修正处理[J].煤矿安全,2011,42(2):1-4.
[12]齐庆杰,黄伯轩.均压灭火自动监测与调节系统中风速传感器显示值修正系数的确定[J].东北煤炭技术,1997(2):42-52.
[13]刘铁城.国外矿井通风监测及今后发展[J].煤矿安全,1983(10):55-65.
[14]吴望一.流体力学(下册)[M].北京:北京大学出版社,1983.