竖通道内热浮力旋转流相关特性研究

发布时间：2019-05-24 17:50

【摘要】：火旋风因其强大的卷吸力和浮升力，而比普通火灾具有更快的燃烧速度、更高的火焰温度和更大的破坏力，随着建筑空间的增大及开口形式的多样化，火旋风在建筑火灾尤其在建筑物的中庭及竖井型通道中出现的可能性也日渐增大，给人们的生命和财产安全带来严重威胁。近年来，建筑内火旋风巨大的破坏性得到了国内外研究人员的重视，研究火旋风的形成机制、运动形态以及由于火旋风而形成的热流场，是控制室内火旋风发生发展的一个主要内容，对保障社会安定具有重要意义。进行火灾热流场相关研究的方法主要有实验研究、数值模拟及理论分析三种，本文主要采用这三种方法对一有侧开缝的竖通道内浮力旋转火焰及热流场的相关特性进行深入研究，具体工作内容如下：首先，归纳了热浮力旋转流场的数学模型，给出了适用于火灾场的多组分、低马赫数、有粘性、热驱动浮力流的数学模型，包括控制方程组，混合分数燃烧模型和有限容积（FVM）辐射模型；介绍了大涡模拟(LES)的主要思想并对模型方程组进行了滤波；在动量方程的基础上研究了涡量方程、涡量场的动力学特性、旋转系统中流体的运动方程以及火灾场中的涡量方程。其次，搭建了一个有侧开缝的方形竖通道，进行热浮力旋转流的实验研究，发现无量纲侧开缝宽度在某一临界范围内时，火焰的旋转最为剧烈、火焰高度最高、燃料燃烧速度最快；随后在临界无量纲侧开缝宽度条件下，进行了三种不同直径及燃料用量的火旋风实验，分别对旋转火焰纵向和径向温度分布、燃料的燃烧速率、热释放速率及火焰高度等特性进行了详细研究，并对文献中提出的普通汽油池火燃料失重速率及火焰高度计算经验式中的部分参数在本文研究的旋转火焰条件下进行了修正。第三，应用火灾场模拟软件FDS并采用LES方法对竖通道内热浮力旋转流实验进行了模拟计算，得到了三种不同尺寸及热释放速率火源形成的浮力旋转流物理场的分布规律、火焰中轴线纵向温度分布、火焰不同高度径向温度分布及火焰的高度，利用实验结果对所选模型的有效性进行了验证；进而对浮力旋转火焰的周向速度及轴向速度分布进行预测，并对三种情况下旋转火焰的最大轴向速度与周向速度比值的变化情况进行了研究。第四，在详细地总结和分析几种典型的涡旋流动精确解形式及特性的基础上，，针对这些精确解普遍存在的问题，并依据本文实验所观察到的现象，重新构造了旋转涡量的形式。通过引入半经验系数，给出了旋转涡量沿火焰径向和周向旋转速度沿火焰纵向及径向衰减规律的级数近似解的表达式。再根据本文的数值模拟结果，确定了半经验系数的取值，进而得出了基于实验和数值计算结果的热浮力旋转流旋转涡量和周向旋转速度的级数近似解。本文的研究成果和结论在建筑物内火旋风的预防和扑救方面具有重要的意义及实用价值。同时，为进一步开展旋转火焰及其热流场的相关研究工作奠定了基础。
[Abstract]:The fire cyclone has a faster combustion speed, higher flame temperature and greater destructive power than a common fire due to its strong volume suction and uplift force, and with the increase of the building space and the diversification of the opening form, The possibility of the fire cyclone in the building fire, especially in the atrium of the building and the shaft-type channel, is also increasing, which poses a serious threat to the safety of people's life and property. In recent years, the great destructiveness of the fire cyclone in the building has been paid more and more attention by the researchers at home and abroad, the forming mechanism of the cyclone, the movement form and the heat flow field due to the fire cyclone are the main contents for controlling the development of the indoor fire cyclone. It is of great significance to guarantee social stability. In this paper, the related characteristics of the buoyancy rotary flame and the heat flow field in a side-slotted vertical channel are studied in detail by the three methods, such as the experimental research, the numerical simulation and the theoretical analysis. In this paper, the mathematical model of the hot-buoyancy rotary flow field is summarized, and the mathematical model of the multi-component, low-Mach number, viscous and heat-driven buoyancy flow for fire field is given, including the control equations, the mixed-fraction combustion model and the finite volume (FVM). The main idea of the large eddy simulation (LES) is introduced and the equations of the model are filtered. On the basis of the momentum equation, the vorticity equation, the dynamic characteristic of the vorticity field, the motion equation of the fluid in the rotating system and the vortex in the fire field are studied. In this paper, a square vertical channel with side slit is set up, and the experimental study of the hot-buoyancy rotary flow is carried out. The flame's rotation is the most severe when the non-dimensional side slit width is within a certain critical range. The flame height is the highest, and the fuel is burning. The burning speed is the fastest, and three different diameters and fuel consumption are carried out under the condition of the critical dimensionless side slit width, and the longitudinal and radial temperature distribution of the rotating flame, the combustion rate of the fuel, the heat release rate and the flame height are respectively carried out. A detailed study is made and some of the parameters in the empirical formula of the weight loss rate and the flame height of the ordinary gasoline pool in the literature are studied in this paper. In the third part, a fire-field simulation software FDS was applied and a LES method was used to simulate the rotational flow of the internal heat buoyancy in the vertical channel. The distribution law of the physical field of the buoyancy rotary flow formed by three different size and heat release rate sources was obtained, and the central axis of the flame The longitudinal temperature distribution of the line, the radial temperature distribution at different heights of the flame and the height of the flame, the effectiveness of the selected model is verified by the experimental results, and the circumferential speed and the axial speed of the buoyancy rotary flame are further improved. the prediction of the degree distribution and the change in the ratio of the maximum axial velocity and the circumferential velocity of the rotating flame in three cases In the fourth part, on the basis of the detailed summary and analysis of several typical forms and characteristics of the vortex flow, the problems that are common to these exact solutions are discussed, and the phenomena and re-structures observed in this paper are reconstructed. In this paper, the form of rotational vorticity is built. By introducing the semi-empirical coefficient, the longitudinal and radial decay of the flame in the radial and circumferential direction of the flame are given. Based on the numerical simulation results of this paper, the value of the semi-empirical coefficient is determined, and the rotational vorticity and the circumferential rotation of the hot-buoyancy rotary flow based on the experimental and numerical results are obtained. A series of approximate solutions to the speed of revolution. The research results and conclusions of this paper are used in the prevention and suppression of fire and cyclone in buildings. It is of great significance and practical value, and at the same time, to further carry out the rotating flame and the heat flow field,
【学位授予单位】：哈尔滨工程大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU998.1

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