圆周运动移动火源扩散火焰图像特征及其规律

发布时间：2018-10-04 20:45

【摘要】：目前，随着交通工具行驶速度和使用密度的不断加大，行驶中发生火灾事故也日趋增多。这类火灾的火源点往往处于运动状态且与空气产生相对运动，从而形成移动火源。移动火源扩散燃烧火焰特征的研究是准确评估这类火灾发展趋势的基础工作，对火灾的预测、防范和救援具有实际应用价值和理论指导意义。同时该领域的研究有助于丰富和完善移动火源扩散火焰理论体系，对移动火焰燃烧的能源高效利用等方面具有指导意义。但目前国内外学者对移动火源扩散火焰的基础研究较少，至今仍未很清楚了解移动火源扩散火焰的内在本质和物理规律。本文通过移动火源扩散火焰在无限大空间圆周运动的实验获得火焰图像，从火焰力场和热量的角度分析了火焰图像平均灰度、火焰面积、火焰倾角与火焰线速度、火焰距离转轴半径之间的关系，以揭示移动火焰扩散火焰的燃烧机理和影响规律。文中搭建了无限大空间圆周运动移动火源实验台，通过Lightning RDT高速摄像仪以及同步测量控制计算机获得火焰照片，并在Matlab软件下对火焰图像进行预处理。通过研究表明，先用电视工业的标准灰度化处理图片，后利用中值滤波法来消除噪声干扰，再使用Canny算子检测出火焰边缘图像，可以得到较好的图像处理效果。在图像预处理的基础上，对移动火源扩散火焰图像特征进行提取和变化规律总结。实验结果显示，火焰在不同半径位置时，火焰图像平均灰度值随火焰线速度的变化而先下降后上升，再大幅下降；火焰面积随火焰线速度的变化呈现先增大后减小；随着火焰线速度的增加，刚开始阶段火焰倾角增大得很快，而到达某个临界值之后增大的幅度变缓慢。究其原因认为，第一阶段线速度不大时，气流散热大于生成热量，火焰温度略有下降，火焰图像平均灰度值随之稍微减少，气流扰动增加加剧燃料与空气的混合程度以及火焰温度稍微下降导致火焰面积增大；第二阶段火焰线速度一定程度时，生成热量大于气流散热，，火焰温度略有上升，火焰图像平均灰度值随之稍微增加；第三阶段在移动火源运动速度达到较大时，气流过大带走燃料使燃烧量大幅减少，火焰温度大幅下降，火焰图像平均灰度值随之也减少；第二和第三阶段里燃料与空气混合程度达到极限以及过大的气流会带走更多热量和燃料导致火焰面积减少。而火焰倾角由于空气阻力增大并起拉伸作用，开始时火焰倾角增大得很快，后到达临界值后火焰面积减少抵消火焰线速度的影响，火焰倾角增大幅度相对平缓。以上的研究，实现了对移动火源运动下火焰特征提取与规律分析，为移动火源的机理研究提供了一定的实验和理论基础。
[Abstract]:At present, with the increase of vehicle speed and use density, fire accidents are also increasing. The fire source of this kind of fire is usually in the state of motion and is in relative motion with the air, thus forming the moving fire source. The study of the flame characteristics of moving fire source diffusion combustion is the basic work to accurately evaluate the development trend of this kind of fire. It has practical application value and theoretical guiding significance for fire prediction, prevention and rescue. At the same time, the research in this field is helpful to enrich and perfect the theoretical system of mobile flame diffusion flame, and has guiding significance for the efficient use of energy in mobile flame combustion. However, there are few researches on the basic research of mobile flame diffusion at home and abroad, so far there is still not a clear understanding of the inherent nature and physical laws of mobile flame diffusion. In this paper, the flame image is obtained by the experiment of moving fire source diffusion flame in an infinite space. From the angle of flame force field and heat, the average gray scale, flame area, flame inclination angle and flame linear velocity of flame image are analyzed. In order to reveal the combustion mechanism and influence law of the moving flame diffusion flame, the relationship between the radius of the rotating axis and the distance between the flame and the flame is revealed. In this paper, an infinite space experimental platform of moving fire source with circular motion is set up. Flame photos are obtained by Lightning RDT high-speed camera and synchronous measurement control computer, and the flame images are preprocessed under Matlab software. The results show that the standard grayscale image processing in television industry, the median filter method to eliminate noise interference, and the Canny operator to detect the flame edge image can get a better image processing effect. On the basis of image preprocessing, the characteristics of moving flame diffusion image are extracted and summarized. The experimental results show that the average gray value of flame image decreases first and then rises and then decreases significantly with the change of flame linear velocity, and the flame area increases first and then decreases with the change of flame linear velocity. With the increase of the linear velocity of the flame, the angle of flame inclination increases rapidly at the beginning, but the amplitude increases slowly after reaching a certain critical value. The reason is that when the linear velocity of the first stage is not large, the heat dissipation of the air flow is greater than the heat produced, the flame temperature drops slightly, and the average gray value of the flame image decreases slightly. The increase of air disturbance intensifies the mixing degree of fuel and air, and the flame temperature decreases slightly, which results in the increase of flame area. In the second stage, when the linear velocity of the flame is to a certain extent, the heat generated is larger than the heat dissipation, and the flame temperature rises slightly. In the third stage, when the moving velocity of the flame source reaches a higher speed, the amount of combustion is greatly reduced, the flame temperature is greatly decreased, and the average gray value of the flame image is also reduced when the gas flow takes away the fuel greatly, and the flame image grayscale value increases slightly. In the second and third stages, the mixture of fuel and air reaches its limit and too much air will take away more heat and fuel to reduce the area of the flame. The flame inclination angle increases rapidly at the beginning due to the increase of air resistance, and then decreases to offset the influence of flame linear velocity after reaching the critical value, and the increase of flame inclination angle is relatively flat. The above research realizes the extraction and analysis of the flame characteristics under the moving fire source motion, and provides a certain experimental and theoretical basis for the study of the mechanism of moving fire source.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：X951;TP391.41

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