环境风作用下输油管道泄漏油料火蔓延传热传质机制及关键灾害参数研究

The safety of oil pipeline is an important factor to meet the development of our country’s economy and realize the strategy of energy security. However, in the oil pipeline leakage accident, flame spread over liquid fuel is a typical phenomenon that is easily influenced by the environmental wind. In this project, experimental investigation, theoretical analysis and numerical simulation will be used to: (1) study the influence of initial fuel temperature and pool size on the critical disaster parameters of flame spread (including the flame length, the flame inclination, the flame spread rate, and the flame radiation) under various environmental wind conditions, reveal the mechanism of flame spread regime transformation, and establish the critical criterion of flame extinction; (2) analyze the heat transfer through subsurface convection flow, gas-phase convection, pool side-wall conduction and flame radiation and the respond mechanism of pool size and wind speed, clarify the transient relationship between the oil surface temperature and fuel vapor concentration or subsurface flow velocity, and reveal the mechanisms of heat and mass transfer on the basis of the gas- and liquid-phase mass transfer theory and the special boundary conditions; (3) establish some predicting models for critical disaster parameters of flame spread under multi-factor coupling conditions (wind speed, wind direction, initial fuel temperature, and pool size, etc.). Then, these models will be validated and correctted by comparison with the experimental data of flame length, flame inclination, temperature and radiation intensity. This project can enrich people’s understanding of the oil pipeline spilling fire in the early stage, and provide some basic data and analysis basis for the fire protection design and the safety distance calculation of the oil pipelines.

保障输油管道安全是满足我国经济发展，实现能源安全战略的重要前提，而火蔓延是输油管道泄漏事故中典型的火灾现象，且其发展特性会受到环境风的影响。本项目拟通过实验、理论分析和数值模拟相结合的方法：（1）研究环境风作用下，初始温度和油池尺寸对泄漏油料火蔓延关键灾害参数（火焰长度、火焰倾角、火蔓延速度和热辐射等）的影响规律，揭示火蔓延模式突变机理和建立火焰熄灭的临界判据；（2）分析表面流传热、气相对流传热、油池侧壁面传热和火焰热辐射等对油池尺度效应及环境风的响应机制，解明油面温度与蒸气浓度、表面流速度的瞬态对应关系，结合气液传质理论和特殊边界条件，揭示火蔓延传热传质机制；（3）建立多参数耦合作用下泄漏油料火蔓延关键灾害参数预测模型，基于火焰形状、速度、温度和辐射强度的实验结果，验证和修正模型。本项目可丰富人们对输油管道泄漏油料火灾早期发展规律的认识，为输油管道防火设计以及安全距离的确定提供理论参考。

燃油泄漏环境往往伴随环境风，其能够携带燃烧所需氧气，且可能拉长火焰，直接点燃相邻的泄漏口或扩大对周围物体的热辐射。本项目采用实验和理论分析方法，（1）研究了环境风作用下航空煤油火蔓延过程中火行为特性（火焰倾角、火焰高度和火蔓延速度）。随着风速的增加，火焰高度的下降速率逐渐减小，火焰高度最终接近一个临界值。将无量纲参数油池特征尺度比引入Welker模型和Oka模型，分别得到改进的火焰倾角模型和火焰高度模型，与实验数据十分吻合。（2）开展了环境风作用下液体火蔓延气-液流体动力学研究。无论是顺风还是逆风环境，液体火蔓延表面流主要受表面张力驱动，浮力的作用相对较弱。火焰脉动与火焰前锋的气相涡旋紧密相关。顺风条件下，存在临界风速，当强制对流大于临界风速时，火焰前方不能形成气相涡旋，火焰以稳定模式蔓延；反之，当强制对流小于临界风速时，能够形成气相涡旋，火焰以脉动模式蔓延。逆风条件下，火焰均以脉动方式蔓延。（3）建立了耦合液相对流传热、火焰辐射传热以及底部面的对流散热的火蔓延传热模型。逆风和低风速顺风火蔓延，液体火蔓延主要传热方式为液相热对流，这与无风时的火蔓延传热机制相同；强顺风火蔓延，液体火蔓延为火焰热辐射和液相热对流耦合传热控制。（4）分析了正丁醇水平流淌动力学特征和流淌火行为。发现油膜主要受到重力、惯性力、表面张力和摩擦阻力的作用，且连续泄漏正丁醇燃料流动主要经历了“重力-惯性”扩散阶段和“重力-粘性”扩散阶段。建立了定常流动液体燃料的流动模型，发现正丁醇泄漏速率和流速满足幂函数关系，流速和油层厚度的平方根满足线性关系。将流淌火蔓延划分为四个阶段，随着流速增加，逆流流淌火蔓延分为：抑制蔓延阶段和无法蔓延阶段；顺流流淌火蔓延分为：加速蔓延阶段和火焰脱离阶段。（5）建立了正丁醇水平定常流淌火蔓延表面流传热模型。定量计算了表面流总热流、液体温升显热和流淌槽下垫面及侧壁的热损失，发现模型计算结果与实验数据十分吻合。对于小尺度的流淌火灾，液体燃料的蒸发潜热可以忽略，表面流总热流主要由液体温升的显热和流淌槽下垫面及侧壁的热损失构成。