压力旋流式细水雾喷头的优化设计及灭火有效性研究

发布时间：2019-03-19 15:24

【摘要】：自从人们发现传统的哈龙灭火剂对臭氧层有着不可修复的破坏性之后,细水雾灭火技术越来越受到重视。细水雾灭火技术不仅在民用建筑、公共建筑和船用领域上受到广泛应用,在能源领域和工业领域中更是发挥了重要作用。一直以来,人们都致力于提升细水雾灭火性能的研究。但喷雾速度过低,流量过小,喷头尺寸过大等问题仍然没有得到解决。本文将针对以上问题,对压力式细水雾喷头进行结构优化,将优化后的细水雾喷头应用到室内泄漏的天然气所引起的火灾中去,并对其灭火有效性进行探究。采用FLUENT数值模拟软件对压力式细水雾喷头进行内部流场数值模拟,分析该喷头的雾滴粒径分布情况,检验粒径是否符合正态分布,完成结构准确性判定。划分网格并进行无关性验证,讨论分析喷头几何结构参数对细水雾喷雾效果的影响。着重考察出口数量,进口直径比和出口长径比对喷雾速度以及喷雾压力的影响。经模拟发现,三者均对喷雾效果产生影响,进口直径比对喷雾效果的影响尤为突出。对优化后的压力旋流式细水雾喷头进行外部流场数值模拟研究。打开离散相追踪模型,完成湍流模型、边界条件、初始条件以及求解方法的选择和设置。捕捉喷雾形态随时间的变化,对比分析不同截面处、不同压力下细水雾液滴的粒径分布情况和速度变化规律。经模拟发现,提高喷雾压力,不仅有利于扩大喷雾保护范围,还可以提高液滴穿透火焰的能力;在距离喷嘴出口竖直距离30mm处,细水雾液滴的破碎已基本达到平衡状态;当喷射压力达到0.5MPa时,液滴接近完全破碎。建立细水雾作用于室内泄漏的天然气所引发火灾的气/液两相数值计算模型。采用通用有限速率燃烧模型和涡耗散湍流与化学反应相互作用模型模拟火焰的稳定燃烧,开启细水雾DPM离散相模型,对细水雾与火焰之间的相互作用过程展开分析和记录。对比分析细水雾作用前后火焰的动态变化以及流场温度、生成物浓度的变化情况。讨论细水雾粒径、流量和速度对灭火效果的影响。经模拟发现,优化后的细水雾喷头可以有效抑制室内天然气泄漏引发的火灾,合理设置细水雾粒径、流量和速度对灭火至关重要。
[Abstract]:Since it was found that the traditional halon extinguishing agent has irreparable damage to the ozone layer, water mist fire extinguishing technology has been paid more and more attention. Water mist fire extinguishing technology is not only widely used in civil buildings, public buildings and marine areas, but also plays an important role in the field of energy and industry. All along, people are devoted to improving the performance of water mist fire fighting. However, the spray speed is too low, the flow rate is too small, the nozzle size is too large and other problems have not been solved. In view of the above problems, the structure optimization of pressure water mist sprinkler is carried out in this paper. The optimized water mist nozzle is applied to the fire caused by indoor leakage of natural gas, and the fire extinguishing effectiveness of the optimized water mist sprinkler is discussed. The internal flow field of the pressure water mist nozzle is simulated by using FLUENT numerical simulation software. The droplet size distribution of the nozzle is analyzed, and whether the particle size conforms to the normal distribution is checked, and the accuracy of the structure is determined. The effects of nozzle geometry parameters on the spray effect of water mist are discussed and analyzed. The effects of outlet quantity, inlet diameter ratio and outlet length to diameter ratio on spray velocity and spray pressure were investigated. The simulation results show that all of them have influence on the spray effect, especially the inlet diameter ratio. The external flow field of the optimized pressure swirl water mist nozzle is numerically simulated. The discrete phase tracking model is opened to complete the selection and setting of turbulence model, boundary condition, initial condition and solution method. After capturing the change of spray morphology with time, the particle size distribution and velocity variation of water mist droplets at different cross sections and under different pressures were compared and analyzed. The simulation results show that increasing spray pressure can not only enlarge the spray protection range but also improve the ability of droplets to penetrate the flame. At the vertical distance from the nozzle outlet 30mm the breakup of water mist droplets has basically reached the equilibrium state. When the injection pressure reaches 0.5MPa, the droplet is nearly completely broken. A numerical model of gas / liquid two-phase fire caused by natural gas leakage caused by water mist is established. The steady combustion of flame was simulated by general finite rate combustion model and interaction model of vortex dissipation turbulence and chemical reaction. The DPM discrete phase model of water mist was opened and the interaction process between water mist and flame was analyzed and recorded. The dynamic change of flame, the temperature of flow field and the concentration of product before and after the action of water mist were compared and analyzed. The effects of particle size, flow rate and velocity of water mist on fire fighting effect are discussed. It is found by simulation that the optimized water mist nozzle can effectively restrain the fire caused by natural gas leakage in the room, and it is very important to set the particle size, flow rate and speed of water mist to extinguish the fire.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU892

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