【作者】 王磊；

【导师】 郜冶；

【作者基本信息】 哈尔滨工程大学 ， 一般力学与力学基础， 2021， 博士

【摘要】 煤炭是我国最基础的能源,在能源生产消费市场上占据着主导地位。随着当前煤矿开采深度的逐渐增加,地质条件越来越复杂,特大事故频繁发生,而其中尤以瓦斯爆炸灾害最为突出。煤矿瓦斯爆炸事故对人员及设备设施的危害主要来源于爆炸火焰(高温气流)、冲击波和有毒有害气体等。煤矿井下条件复杂,构筑物众多,如通风设施、支护设施、运输设施、提升设施等。这些构筑物形状、尺寸差异明显,在爆炸过程中起到了障碍物的作用,并对爆炸流场起到扰动作用。一旦井下发生爆炸,爆炸火焰和冲击波在经过障碍物时,其传播规律会受障碍物影响而发生变化,火焰传播速度随着湍流强度的增加而增大,造成更大的危害。另外,火焰和压力波的相互作用也会对爆炸强度、波及范围等产生重要影响。上述波的传播及相互作用等都属于典型的力学问题。因此,无论从煤矿安全生产还是从社会效应等角度出发,都应在数学和力学分析的基础上开展瓦斯爆炸传播规律方面的研究,以便为煤矿井下瓦斯爆炸事故预防与控制提供技术支持。本文采用实验研究和数值模拟相结合的方法,以火焰和压力波相互作用机制研究为主线,将小型管道和大型巷道实验串联起来,在对瓦斯爆燃传播规律、障碍物对火焰和压力波的影响规律研究的基础上,深入分析压力波对火焰结构、火焰速度的影响,以及火焰对压力波的影响过程,主要工作内容及结论如下:首先,根据小型管道实验重复性高、便于观测测试的特点,利用规格尺寸为200mm×200mm×6500mm的钢制管道,进行全管道充满瓦斯情况下的爆燃传播实验。利用纹影仪、高速摄影系统、压力传感器、火焰传感器等测试手段,对瓦斯爆燃压力波、火焰的传播规律进行研究,重点对压力波超压、火焰传播速度、火焰在观察窗口区域的变化特性等进行详细分析,并对沉积煤尘参与反应过程进行可视化研究。研究发现:同样的初始条件下,左端点火的最大压力峰值与最大压力上升速率峰值与中部点火基本相当,但略大于后两者;中部点火时瓦斯爆燃的进程(即各测点达到最大压力的呈现时间)要大于左端点火的进程;湍流火焰、化学反应作用能力与反射压力波的相互博弈是造成火焰传播速度变化的主要原因;研究了火焰和压力波诱导沉积煤尘参与反应的过程,发现沉积煤尘扬起是压力波和火焰共同作用的结果,湍流火焰是诱导煤尘扬起的主力军,扬尘高度与湍流强度有直接的关系;探讨了本实验条件下最大压力上升速率经验公式。其次,本文利用断面为7.2m~2、长度为896m的大型试验巷道开展研究工作,对不同体积量的瓦斯爆燃传播规律及尺度效应、火焰和压力波相互作用机制等开展研究。研究发现,瓦斯体积量的大小,决定了爆燃反应的强度,也影响了爆燃压力沿巷道的传播过程,气体体积越大,爆燃威力越强;火焰的传播速度在爆燃过程中是先逐渐增大,后又减小的变化趋势。最大压力随传播距离变化曲线在瓦斯积聚区和火焰减速区近似呈一元四次函数关系,在火焰加速区和无火焰区近似呈一元九次函数关系;这主要与瓦斯体积量以及火焰和压力波的相互作用有关。研究还发现在爆燃反应初期,巷道和管道装置的尺度差异对于火焰速度的影响不大,最大爆燃压力差距不大;但在爆燃快速发展期,尺度效应开始显现,参与反应的可燃物量不同,以及实验装置内部结构形成的湍流,是造成尺度效应的主要原因。第三,通过在管道观察段内布置矩形(R)、梯形(T)和球形(S)等三种不同类型的障碍物,对爆燃火焰通过障碍物时的传播行为进行实验研究。研究发现,无障碍物时爆燃火焰前锋阵面在达到观察窗后半段时,前端阵面趋于平整;有障碍物时,火焰明显分为前锋、中锋和尾锋三种情况,且前锋的速度最快,尾锋最慢,在火焰阵面前锋和尾锋之间产生较大的横向偏差距离,且a_R>a _S>a _T。无障碍物时,火焰传播速度与反射压力波有关,反射压力波会诱导火焰前锋出现湍流火焰,开始褶皱变形,造成火焰传播速度发生变化。障碍物能对流场造成扰动,对于障碍物的前后压力峰值来说,梯形是最低的,矩形最高,但球形障碍物前后压力峰值最为接近,差值仅为9.54kPa。矩形障碍物前测点相对更早地达到压力峰值,而梯形和球形障碍物的后测点压力达到峰值的时间领先于障碍物前方测点。最后,本文基于ANSYS FLUENT软件,通过数值模拟的方法,研究障碍物存在的条件下,压力波对火焰传播速度的影响,并与实验结果进行了对比。采用基于雷诺时均(RANS)的湍流模型,近壁面采用缩放型壁面函数,燃烧模型采用通用有限速率模型,几何模型采用简化的二维模型,离散方程组的求解采用SIMPLE算法。研究发现,无障碍物时火焰传播速度呈现周期性变化,火焰出现逆向传播,这是由反射压力波造成的;有障碍物存在时,火焰传播的这种波动特性得到抑制,火焰前锋向未燃烧区域的传播较为平稳,且障碍物的存在加快了火焰在障碍物处的传播速度。无障碍物和球形障碍物条件下,整个过程中压力波动都较为剧烈,压力波动振幅遵循增大-减小-再增大过程;矩形和梯形障碍物条件下,初始阶段的压力波动较大,而火焰经过障碍物之后,压力波波幅快速减小。更多还原

【Abstract】 Coal is the most basic energy source in China,and it occupies a dominant position in the energy production and consumption market.With the gradual increase of the current coal mining depth,the geological conditions are becoming more and more complex,while extremely serious accidents have occurred frequently,among which gas explosion disasters are the most prominent.The hazards of coal mine gas explosion accidents to personnel,equipment,and facilities mainly come from the explosive flame(high-temperature gas flow),shock waves,and toxic and harmful gases.The underground conditions of coal mines are complex and there are many structures,such as ventilation facilities,supporting facilities,transportation facilities,and lifting facilities.These structures have obvious differences in shape and size,which acted as obstacles during the explosion process and disturbed the explosion field.Once an explosion occurs underground,when the explosion flame and shock wave pass through obstacles,their propagation law will change due to the impact of obstacles.The flame propagation speed increases with the increase of turbulence intensity,causing greater harm.In addition,the interaction between flame and pressure wave also has important influence on the intensity and sweep range of explosion.The propagation and interaction of the wave mentioned above are typical mechanical problems.Therefore,whether from the perspective of coal mine safety production or social effects,research on the law of gas explosion propagation should be carried out to provide technical support for the prevention and control of underground coal mine gas explosion accidents on the basis of mathematical and mechanical analysis.In this paper,a combination of experimental research and numerical simulation was adopted,based on the study of the interaction mechanism between flame and pressure wave,the experiment of small pipe and large tunnel was connected in series.On the basis of the propagation law of gas explosion and the influence law of obstacles on flame and pressure wave,the influence process of pressure wave on flame structure and flame velocity as well as the influence process of flame on pressure wave was deeply analyzed.The main work content and conclusions are as follows:First of all,according to the characteristics of high reproducibility and easy to observation and testing of small pipeline experiments,a steel pipeline with a specification size of200mm×200mm×6500mm was used to conduct a deflagration propagation experiment under the condition that the entire pipeline is filled with gas.Using test methods such as schlieren,high-speed photography system,pressure sensor,flame sensor to study the propagation law of gas deflagration pressure wave and flame.Focusing on detailed analysis of the overpressure,flame propagation speed,and flame characteristics in the observation window area,etc.Visualizing the participation of deposited coal dust in the reaction process.The study found that under the same initial conditions,the maximum pressure peak value and the maximum pressure rise rate peak of ignition at the left end are the same as those in the middle,but slightly greater than the latter two;the process of gas deflagration during ignition in the middle(that is,the presentation time of each measuring point reaching the maximum pressure)is longer than the ignition process at the left end;the mutual game of turbulent flame,chemical reaction ability and reflected pressure wave is the main reason for the change of flame propagation speed.From the process of flame and pressure wave induced deposited coal dust to participate in the reaction,it was found that the rising of deposited coal dust is the result of the combined effect of the pressure wave and flame,the turbulent flame is the main force that induces the rising of coal dust,and the height of dust is directly related to the intensity of turbulence.This paper also discussed the maximum pressure rise rate formula under the experimental conditions.Secondly,a large-scale test roadway with a cross-section of 7.2 m~2 and a length of 896 m was used to carry out research work to study the propagation law of gas deflagration of different volumes,the scale effect,and the interaction mechanism of flame and pressure waves.The study found that the size of the gas volume determines the intensity of the deflagration reaction and also affects the propagation process of the deflagration pressure along the tunnel.The larger the gas volume,the stronger the deflagration power.The flame propagation velocity first gradually increases and then decreases during the deflagration process.The variation curve of the maximum pressure with the propagation distance is approximately a quaternary function relationship in the gas accumulation zone and the flame deceleration zone,and approximately a ninth-fold function relationship in the flame acceleration zone and the flameless zone.This is mainly related to the volume of gas and the interaction between flame and pressure wave.The study also found that in the initial stage of the deflagration reaction,the difference in the size of the tunnel and the pipeline device has little effect on the flame speed,and the maximum deflagration pressure gap is not large;but in the rapid development period of the deflagration,the scale effect begins to appear.The amount of combustibles involved in the reaction is different,and the turbulence formed by the internal structure of the experimental device is the main cause of the scale effect.Third,the propagation behavior of the deflagration flame when passing through the obstacles was studied experimentally by arranging three different types of obstacles such as rectangle,trapezoid,and spherical in the observation section of the pipeline.The study found that when the front of the deflagration flame reaches the second half of the observation window without obstacle,the front of the flame tends to be flat;when there are obstacles,the flame is divided into three situations:forward,center,and tail,the forward is the fastest and the tail is the slowest.There is a large lateral deviation distanceσbetween the flame front and the tail,andσ_R>σ_S>σ_T.When there are no obstacles,the flame propagation speed is related to the reflected pressure wave.The reflected pressure wave will induce a turbulent flame at the front of the flame and begin to fold and deform.Obstacles can cause a disturbance in the flow field.For the front and rear pressure peaks of the obstacle,the trapezoid is the lowest and the rectangle is the highest,but the spherical obstacle is the closest to the front and rear pressure peaks,with a difference of only 9.54 k Pa.The front measuring point of the rectangular obstacle reaches the pressure peak relatively earlier,while the pressure peak of the back measuring point of the trapezoidal and spherical obstacles is ahead of the measuring point in front of the obstacle.Finally,based on the ANSYS FLUENT software,this paper uses numerical simulation to study the influence of pressure waves on the flame propagation speed in the presence of obstacles and compares them with the experimental results.The turbulence model based on Reynolds Time Average(RANS)is adopted,the near-wall surface adopts a scaling wall function,the combustion model adopts a general finite rate model,the geometric model adopts a simplified two-dimensional model,and the solution of discrete equations adopts the SIMPLE algorithm.The study found that the flame propagation speed changes periodically when there are no obstacles,and the flame propagates backward,which is caused by the reflected pressure wave;when there are obstacles,the fluctuating characteristics of flame propagation are suppressed,the flame front spreads more smoothly to the unburned area,and the existence of obstacles accelerates the spread of flame at the obstacle.Under the conditions of obstacle-free and spherical obstacles,the pressure fluctuations in the whole process are relatively severe,and the amplitude of the pressure fluctuation follows the process of increasing-decreasing-increasing;under the conditions of square and trapezoidal obstacles,the pressure fluctuations in the initial stage are relatively large,after the flame passes the obstacle,the pressure wave amplitude decreases rapidly.更多还原