射流火焰形态和辐射场的细水雾控制机理研究

Safe and effective disposal of jet flame formed by leakage from gas line or vessel is an urgent problem in the field of safety. Since fine water mist can dominate flame pattern and weaken the thermal radiation intensity of the flame, it is promising to serve as an effective technology to control jet flame by reducing the fire damage and creating more favorable conditions for rescue and plugging. In response, this project devotes to uncover the control mechanisms of jet flame’s shape and thermal radiation field by water mist as following strategies: (1) By virtue of the measured jet flame temperature, find out how the stability of the jet flame is altered by the fine water mist. Also, based on the temperature contour resolved by infrared thermal imager, establish the criteria for determining if the jet flame is secure, viz., being within the stable combustion zone. (2) Investigate the dependences of the flame shape and the thermal radiation field on factors such as atomization particle size, droplet velocity, gas composition, combustion power, horizontal wind velocity, etc., and elucidate the hydraulic and chemical kinetic mechanisms for the varying jet flame shape and the diminishing thermal radiation intensity due to the presence of the fine water mist. (3) With advanced mathematical optimization tool such as Support Vector Machines and neural networks, develop optimization method to select the operating parameters that lead to either the greatest reduction in radiation within the targeted region or the swinging angle of the jet flame kept at the set value. (4) Develop numerical model to predict with accuracy the jet flame shape and the thermal radiation field under the control of the water mist.

燃气管路或容器泄漏射流火焰的有效控制是安全生产领域亟待解决的难题之一。采用细水雾控制射流火焰可以干涉火焰形态和削弱火焰热辐射强度，在减少火灾危害的同时，也为抢险堵漏创造有利的条件。本项目针对细水雾控制射流火焰形态和热辐射场的机理展开如下研究工作：（1）从射流火焰温度信息入手研究细水雾对射流火焰稳定性影响规律，以红外热成像仪拍摄的温度云图数据为基础，构建射流火焰是否处于稳定燃烧安全区间的判定条件；（2）针对雾化粒径、雾滴速度、燃气成分、燃烧功率、水平风速等对火焰形态和热辐射场的影响规律展开实验和理论研究，揭示细水雾作用下射流火焰形态变化和热辐射强度衰减的流体与反应动力学成因；（3）采用支持向量机、神经网络等数学工具，建立以最大辐射衰减量或以射流火焰摆动到设定角度为目标的操作参数选择优化方法；（4）建立细水雾作用下射流火焰受控燃烧数值仿真模型，准确预测射流火焰形态和热辐射场。

燃气在能源消耗中的比例逐年增加，因燃气管道或容器破裂形成的射流火灾事故时有发生，且射流火具有温度高、辐射范围广、破坏力巨大等特点，对周边人员和财产安全构成极大威胁。细水雾可以干涉火势蔓延方向、控制火焰形态和削弱火焰辐射强度，故本项目针对细水雾作用下射流火焰形态和热辐射场控制机理展开研究，完成的主要研究内容包括：（1）实验研究了细水雾在顶喷、侧喷和底喷作用下圆形、矩形、三角形三种不同喷口结构射流火火焰形态、火焰温度、火焰热辐射能力、火焰熄灭时间的变化规律，以及含细水雾环境风对火焰特征的影响规律。（2）建立了二维CH4-AIR扩散火焰模型，定量研究了水雾直径对CH4-AIR扩散火焰燃烧反应的影响；将细水雾作为一种拟气体物质，详细对比了细水雾作用下的不同总包机理，并提出了改进方法；通过CFD模拟研究了雾滴尺寸对射流火焰的影响及侧喷时细水雾与射流火焰相互作用。（3）通过Mie散射理论、Rosin-Rammler模型、黑体辐射函数，获得水雾区域辐射光谱透射率关键参数，将修正的两通量辐射模型和射流火焰轨迹方程等整合到一起得到修正线型源辐射模型，从而构建出水雾遮蔽喷射火热辐射的工程快速计算方法。研究成果能为细水雾控制消减射流火的危害提供数据和理论支撑，具有一定的工程应用和学术价值。