雾状钠火钠滴燃烧比率的模拟及应用

将雾状钠火中钠滴的燃烧分成预燃阶段和燃烧阶段,利用雾状钠火程序计算得到钠滴燃烧比率和时间的关系曲线,分别用幂函数、指数函数和线性函数对曲线进行拟合,拟合效果较好。拟合函数中包含钠滴下落时间和钠滴最大燃烧比率等参数,这些参数可通过钠滴下落燃烧试验或雾状钠火程序计算得到。通过推导得到了雾状钠火燃烧和单个钠滴燃烧的关系,钠滴燃烧比率的拟合函数被用来模拟雾状钠火燃烧的过程,包括用于计算已燃烧的钠质量、空气中未燃烧的钠质量、进入钠池的钠质量和雾状钠火的燃烧速率。当雾状钠火燃烧过程中钠泄漏流量恒定不变时,空气中未燃烧的钠质量和钠泄漏流量呈正比,雾状钠火的燃烧速率和钠泄漏流量呈正比。雾状钠火的燃烧速率和钠火造成的事故工艺间内的温度与压力变化直接相关。雾状钠火的燃烧速率被用来求解钠气溶胶的生成速率、钠燃烧火焰层和空气之间的传热、钠燃烧火焰层和墙壁之间的传热。总之,使用简单的函数模拟钠滴的燃烧比率曲线,将雾状钠火燃烧当成事故工艺间的热源和钠气溶胶源作为输入,便可模拟雾状钠火的整个燃烧过程,计算得到工艺间温度、压力和钠气溶胶浓度的变化。钠滴的燃烧比率曲线、雾状钠火的燃烧速率曲线还可与试验数据进行对比验证后作为雾状钠火模拟的输入,这种模拟方法可用于钠火事故安全分析中雾状钠火的模拟。     

单个钠滴燃烧理论分析及实验设计

深入研究单个钠滴的燃烧对研究雾状钠火具有十分重要的意义。本文介绍了单个下落钠滴的燃烧、运动及热传递模型,设计了单个钠滴下落的试验装置,为我国开展钠滴燃烧行为的实验研究提供了基础,并简述了在试验装置上可开展的试验及目的。     

钠工艺间钠雾火模型适用性分析

钠冷快堆钠泄漏事故中,泄漏的钠以液滴形式在抛射过程中与空气剧烈反应,发生钠雾火现象。通过桑迪亚国家实验室（Sandia National Laboratories,SNL）的T3钠雾火实验结果,以及原子国际（Atomics International,AI）的J1～J4钠雾火实验结果,对改进的Tsai钠雾火模型适用性进行了评估。针对Tsai模型高估实际工况钠喷雾燃烧速率的问题,将Tsai模型中钠液滴下落模型改为单一速度模型,同时将喷雾燃烧对空间的影响改为瞬发。在T3实验中分析了钠雾火阶段对改进模型适用性的影响,在J1～J4实验中分析了初始氧气浓度对改进模型适用性的影响。结果表明：改进的钠雾火模型能够很好地预测空气中钠喷雾燃烧的升温升压现象以及钠消耗量,可以应用于预测钠工艺间内钠泄漏事故后发生在空气中的钠雾火行为。     

钠滴着火特性和预燃模型综述

与碳氢化合物燃料液滴着火特性不同,液态钠滴在常温空气中会自发着火,钠滴着火延迟时间及着火极限受着火前的预燃阶段控制.预燃阶段钠滴主要发生表面氧化反应,该阶段的特性及表面氧化的速率模型是钠滴燃烧研究的一个重点.目前国内用于快堆雾状钠火安全分析程序的预燃模型是通过氧气向钠滴表面传输来控制表面氧化反应速率,着火延迟时间由钠滴...     

钠火压力缓解和钠气溶胶专用探测性能试验研究

<正>在钠安全综合试验设施(F204)配管间内开展了工程应用规模的钠火综合性试验。约200kg温度达316℃的液态金属钠以1.3kg/s的流速从钠管道破口处泄漏,泄漏时间为150s,钠在密闭的配管间内迅速燃烧,测量了流量、温度、压力和钠气溶胶等参数,验证了钠火事故缓解装置和钠气溶胶专用探测装置的性能。钠泄漏钠火事故模拟的配管间1体积约为120m3,相邻配管间2约为91m3,钠火压力缓解     

池式钠火事故下燃烧产物气溶胶行为研究

在钠冷快堆的安全评估中,分析钠泄露导致的池式钠火事故下燃烧产物的气溶胶行为尤为重要。本文采用将池式钠火燃烧模型与气溶胶动力学模型耦合的方式,开发了池式钠火事故下燃烧产物气溶胶行为分析程序REBAC-SFR,基于该程序模拟了SAPFIRE-D1和ABCOVE池式钠火实验,并与实验数据进行了对比。结果表明,本文开发的程序具有良好的可靠性和正确性,可为钠工艺间内池式钠火事故下燃烧产物气溶胶行为分析研究提供理论工具。      

钠冷快堆中池式钠火的计算分析

文章论述了根据池式钠火的特点建立了理论模型 ,编制了SPOOL程序。该程序模拟钠燃烧过程中钠和氧气的化学反应 ,钠燃烧热在各种介质中不同方式的传递 ,钠气溶胶的产生、沉积 ,以及在各种通风条件下多种介质的质量和能量交换等瞬态过程 ,描述了钠燃烧过程中各种特征参数随时间的变化。其主要的计算参数包括房间内气体的压力和温度、房间建筑结构的温度、钠气溶胶质量浓度等等。用俄罗斯别洛雅尔斯克核电站实验和法国卡桑德拉 3号实验的数据 ,对SPOOL程序进行验证的结果表明 ,该程序的计算结果可信。该程序为国内钠冷快堆中池式钠火事故的安全分析提供了分析方法     

喷射钠火的初步分析及实验方法研究

以交换器入口端和蒸发器出口端的管道为例,研究管道中液态钠泄漏所产生喷射钠火的成因和影响后果,研究实际泄漏情况下钠的泄漏流速和形成钠滴的大小,比较模拟水喷射下的水流速和水滴大小,理解液滴在不同流量下和不同大小喷嘴的喷射形式和相互关系,选择合适的钠喷射喷嘴开展钠喷射实验,获得喷射钠火的相关数据,帮助理解钠喷射燃烧现象。     

钠滴氧化燃烧特性的实验研究

液态钠泄漏和燃烧是钠冷快堆在运行中一多发的常见事故。本文主要针对液态钠滴在不同初始温度(140~370℃)和氧浓度(4%~21%)条件下的氧化燃烧行为进行实验研究。实验通过1套钠滴燃烧装置和高速摄像机使钠滴的氧化燃烧行为可视化。实验结果表明:钠滴的初始温度和氧浓度越低,钠滴表面产生的柱状氧化物越长;在相同氧浓度条件下,钠滴初始温度越高,越易着火燃烧;钠滴初始温度在200℃以下时很难点燃,当有扰动破坏了表面的氧化层结构时,钠滴也会逐渐燃烧;钠滴初始温度在140~370℃的条件下,氧浓度≥12%时,钠滴能燃烧充分,最高温度基本可升至600~800℃;氧浓度12%时,燃烧并不充分,燃烧的最高温度均在600℃以下。这些结果对柱状流及雾状钠火的研究有重要的指导意义。     

钠冷快堆中喷雾钠火的计算分析

根据钠冷快堆中喷雾钠火的特点建立了理论模型，编制了SSPRAY程序。该程序模拟钠喷雾燃料过程中钠滴的运动、钠和氧气的燃烧反应、热量传递和质量传递等瞬态过程。用该程序计算了气体和墙壁温度、气体压力、氧气摩尔份额、喷雾流燃烧速率和热量热递速率等主要参数。利用AI实验数据和美国SPRAY－3A的计算结果对程序进行了验证，结果符合较好。     

Response Surface Modeling of Aerosol Release Fraction in Sodium Pool Combustion

A response surface model has been proposed to evaluate an aerosol release fraction during sodium pool fire in a liquid metal fast reactor (LMFR). Air containing aerosols are radiative and they influence the allocation of combustion heat from the flame to atmospheric gas or sodium pool. Hence, the aerosol release fraction needs to be quantified based on the behavior of the aerosols and physics of mass and heat transfer. However, the aerosol release fraction is one of user-specified parameters of computer codes for the sodium fire safety analysis of the LMFR. In the present study, a response surface model of the aerosol release fraction has been developed based on numerical experiments of aerosol dynamics. For developing the model, aerosol dynamic equation has been solved coupled with thermal-hydraulics and chemical reaction. The authors obtained good agreement of the aerosol release fraction between the numerical experiments and the past experiments. Therefore, the aerosol behavior model has been validated with regard to the pool combustion phenomena and is reasonably applicable to the numerical experiment. Three influential variables on the release fraction are identified as pool temperature, gas temperature and oxygen molar fraction in the air. The proposed response surface model is a quadratic expression of the influential variables and can be easily employed in the sodium fire analysis code.     

钠冷快增殖堆钠雾火分析计算

在钠冷快增殖堆假想事故中 ,由于管道破裂 ,钠喷出到有氧的房间引起钠雾火 ,导致房间内温度及压力的上升。在NACOM单个液滴燃烧模型的基础上 ,考虑燃烧钠液滴的运动以及由于钠液滴与气体的热平衡关系 ,并忽略由于液滴间的相互作用影响 ,编制程序SPCOM。对钠雾火过程中涉及的液滴运动、液滴燃烧、喷雾燃烧以及质量热量传递问题进行了模拟。计算了钠雾火引起的房间的温度及压力瞬变 ,并与实验进行了比较 ,符合良好     

Sodium Fire Code SFIRE1C for Pool Fire Characteristics

Sodium pool fire code, SOFIRE II, written for the constant value of stoichiometric combustion ratio and heat of reaction is used to compute the buildup of pressure and temperature in a containment. In the SOFIRE II model, for the formation of a mixture of Na₂O and Na₂O₂ in the sodium pool, the input stoichiometric combustion ratio and heat of formation values need to be varied to corresponding values admissible for the mixture. In the present work, the SOFIRE II one-cell model is revised and the present version SFIRE1C (Sodium FIRE 1 Cell model) accounts for the formation of Na₂O in an early stage of the fire and shifts to the formation of Na₂O₂ at a later stage. Thus SFIRE1C computes in a more realistic manner the reaction products which are formed in the pool. The model for sodium oxide aerosol release is also modified in this version, by incorporating a more appropriate aerosol release rate equation. The calculated values using the SFIRE1C one-cell model are compared with sodium pool fire experimental results.     

Numerical investigation of multi-dimensional characteristics in sodium combustion

Multi-dimensional sodium combustion behavior has been numerically investigated in the present paper. A new computer code AQUA-SF has been developed for this purpose. The code includes two sodium combustion models (so called ‘spray combustion’ and ‘pool combustion’), a mass and heat transfer model considering a six-flux gas radiation and a coagulation and sedimentation model of sodium oxide and hydroxide aerosols. The sodium spray combustion rate is evaluated by a summation of the combustion rate of each sodium droplet with an individual diameter. A flame sheet model is applied to situations where sodium spreads out on the floor and a pool combustion takes place. The model assumes an infinitely thin flame above the pool surface and is based on a mass and energy balance in the flame. As the results of numerical analyses of a sodium spray combustion test, a location of high-temperature core region and a maximum temperature agrees with the experiment. Good agreements of an overall transient behavior are obtained in a large-scale sodium combustion test analysis. The numerical analyses also demonstrate that the distributions of temperature and chemical species concentration vary with sodium combustion modes. If sodium scatters and the spray combustion is dominant, the distributions vary in space. When a large amount of sodium exists on a floor and the pool area is enlarged, the distributions are more uniform in space.     

钠雾火试验结果及与雾火程序计算的比较分析

钠雾火试验在一个体积为2.4 m~3的封闭容器内进行,用于分析雾状钠火的热动力学后果。250℃的液态钠在电磁泵的驱动下经过直径为2.4mm的喷头呈液滴喷出形成雾状钠火,喷头与容器底部的距离为1.35m,钠喷射流量约14.85g/s,喷射持续78s,试验测得容器内的气体在78s时达到最高压力41kPa,113s时达到最高温度190℃。将试验数据和利用基于雾状钠火计算程序(NACOM)编制的计算程序计算得到的数据进行了对比和分析。结果表明:当将钠喷射的流量修正为3.83g/s、容器壁的总传热系数修正为9.6 W/(m~2·K)时,钠喷射期间,计算压力大于试验压力,钠喷射结束后,计算的压力变化曲线和试验所得的压力变化曲线吻合较好;而计算所得的温度曲线和试验测得的温度曲线有较大差异,理论上容器内的温度在第78s时达到最大值303℃,分析认为是因为热电偶测量的温度存在滞后现象。     

钠滴燃烧仿真模型研究

对钠冷快堆喷雾钠火计算中使用的传统球状钠滴模型进行了改进,采用表面带有锥状突起的钠滴新模型,使模拟更接近于燃烧实际现象。根据钠滴燃烧过程中表面氧化、预燃和燃烧3个阶段的不同规律,分别建立了数学模型,通过引入单位时间内参与氧化反应与发生气化的钠的质量比γ,模拟计算了钠滴在不同初始温度(200～500 ℃)和不同氧气浓度(4%～20%)下的燃烧温度特性。仿真结果与实验数据吻合较好,并分析了γ的变化规律。     

A numerical study of radiation heat transfer in sodium pool combustion and response surface modeling of luminous flame emissivity

A response surface model of the luminous flame emissivity of sodium pool fire has been proposed for use in safety analysis computer codes of a liquid metal fast reactor. The liquid sodium burns in air resulting in not only heat generation but also release of sodium oxide aerosols of sub-micron diameters. Aerosols levitating in air are radiative and they influence the allocation of combustion heat from the flame to atmospheric gas or sodium pool. The emissivity of the flame needs to be quantified, as it is one of user-specified parameters of the computer codes for the sodium fire analysis. The response surface model of the flame emissivity is developed based on numerical experiments on the physics of mass and heat transfer and behavior of the aerosol. Thermal-hydraulic equations have been solved coupled with aerosol dynamics and chemical reaction. Three influential variables on the emissivity are identified as pool temperature, gas temperature and oxygen molar fraction in the air. It has been found that the emissivity is calculated reasonably as a function of the three variables. The proposed response surface model can be easily employed in the sodium fire analysis codes because it is a simple quadratic expression. For the safety evaluation of the sodium fire, combined use is recommended of the proposed model and the lumped-mass zone model code.