【作者】 邹高万；

【导师】 周允基；

【作者基本信息】 哈尔滨工程大学 ， 动力机械及工程， 2005， 博士

【摘要】 船舶火灾在世界上被公认为最难扑救的火灾之一,它是船舶海难中较常见且危险性较大的一种事故。船舶火灾不仅威胁船舶本身、船上人员、货物等的安全,严重的还会导致人身伤亡和巨大的财产损失,甚至造成无法估量的环境破坏。 机舱是船舶的动力源,是船舶的心脏,船舶的推进以及船上其它所有设备和系统所需要的各种能源均来自机舱。机舱内有各种运转着的机器和电器设备,又有大量油料及其它可燃物,如若不慎,很容易导致火灾。机舱内一旦着火,由于设备管线众多、通道狭窄,探火和扑救都非常困难,极易失去控制而造成重大损失。进行船舶机舱火灾的研究,对预防和扑救机舱火灾具有十分重要的意义。 本论文以NIST开发的FDS程序为平台,采用LES方法对船舶机舱火灾热流场特性和规律进行了研究。主要完成以下几项工作: 首先,建立适用于火灾计算的数学物理模型。火灾场内的流动属于多组分、低马赫数浮力流,依据这一特点对描述质量、动量和能量输运的通用方程组进行合理地简化和变形。对火的描述采用混合分数燃烧模型,模型中忽略燃烧过程中的反应机理,应用了层流扩散火焰理论和单步不可逆快速反应假定。辐射模型中把火焰和烟气视作灰体,离散后辐射输运方程采用FVM方法进行求解。模型方程组的离散采用限差分法和交错网格系统,时间项的离散采用显式格式,空间项的离散采用二阶精度的有限差分格式。 其次,搭建了火灾实验平台,进行了室火轰燃的实验研究。采用耗氧原理测量火灾场的释热速率来研究室内火灾轰燃现象,得到了不同通风因子下轰燃的临界释热速率。实验结果与经验公式计算出的结果进行了比较,说明采用耗氧原理获得火灾场释热速率的方法对轰燃进行研究是可行的,且试验中能直接得到轰燃的临界释热速率。 第三,为验证程序的可靠性与通用性,对室火轰燃和其它两个有代表性和针对性的实验进行了模拟计算。室火轰燃的模拟计算中,研究了C_S的取值对计算结果的影响,当滤波宽度△=0.1m时,取C_S≈0.20较为合适:两相邻房间(舱室)内火灾情况下的模拟计算中,依据模拟结果对起火房间竖直壁面更多还原

【Abstract】 It is obvious that ship fire is one of the most difficult fires to control. Ship fires occurred frequently and there might be dangerous disasters. Life safety, property protection, cargoes on the ship, and the ship safety itself are the concerns. Lost of lives, damages to property and environmental pollution might be resulted from the fires.Engine plant room is the power source of a ship, regarded as the main core. Power for driving the ship and operating all other equipments and systems are supplied from there. In addition to the operating machines, equipments and wiring in the engine room, there are liquid fuel and other combustible items. Therefore, a fire is likely to occur in the ship engine room. Once a fire occurs, locating the fire and fighting against it are difficult due to obstructions by so many equipments and pipes. An engine room fire can grow to a very big size and become uncontrollable, causing big damages. Preventing and fighting engine room fires on ship vessels should be studied in more detail.Based on the advanced Computational Fluid Dynamics package Fire Dynamics Simulator released by the National Institute of Standards and Technology in the U.S.A., thermal flow field characteristics induced by a ship engine room fire were studied by the Large Eddy Simulation (LES) method. Key works performed in this thesis are:Firstly, mathematical and physical models commonly applied in fire simulations were developed. Fluid flow driven by a fire is a multi-species, low Mach number buoyant flow. The conservation equations on mass, momentum and energy are simplified and reduced to a form suitable for describing fluid flow driven by a fire. The fire was modeled by the mixture fraction combustion method with chemical reaction mechanisms neglected. Laminar diffusion flame theory with one-step irreversible fast reactions is assumed. Flame and smoke were taken as gray medium in the thermal radiation model. The radiative transport equationwas solved using techniques similar to those for convective transport in Finite Volume Method for fluid flow. The governing equations were discretized by finite difference method with stagger grids. Spatial derivatives were approximated by second-order central differences. The flow variables were updated in time using an explicit second-order predictor-corrector scheme.Secondly, an experimental facility was built to carry out experiments on flashover in a chamber. The minimum heat release rate for flashover under different ventilation factors were measured by the oxygen consumption method. Experimental results were compared with the empirical formula reported in the literature. It is demonstrated that oxygen consumption calorimetry can be used to measure the heat release rate. In fact, the minimum heat release rate for flashover in a room was measured directly.Thirdly, two other experiments with a two-room structure were carried out for studying flashover. In simulating flashover, the results will be affected by different values of a constant Cs in using LES. cs of value 0.2 will be acceptablewhen the filter width is 0.1 m. For the two-room structure, the equation of air mass flow rate induced by the fire through a vertical opening was derived. In simulating fires occurring in a sealed chamber, the change of pressure in the chamber was studied. Simulation results show that the numerical simulation program developed can be applied to study ship engine room fires.Finally, real ship fire scenarios were simulated with the developed numerical simulation program. Fluid flow field was predicted for fires at the same source and same place under different ventilation conditions. The study was repeated for fires occurred at different locations with the same source and ventilation condition.The results achieved and the conclusion drawn in this thesis are of great importance and applicable in fire prevention and fire fighting against ship engine room fires or other similar cabin fires.更多还原