受限空间油池火燃烧特性的实验研究

通过理论分析和实验研究的方法来研究油池火在受限空间的燃烧特性。初步总结了受限空间油池火燃烧的特性及其规律，给出了在实验条件下油池火在受限空间和开放空间燃烧速率以及燃料吸收热量的差异。讨论了通风条件和油池燃烧面积以及通风口高度对于燃料的燃烧速率的影响，初步确定了受限空间中油池火燃烧速率与油池面积、通风因子的关系。     

通风因子对有机玻璃燃烧速率的影响

通过小规模火灾实验,研究通风因子对有机玻璃燃烧速率的影响,拟合得到在SNHZ-01型火灾实验箱内有机玻璃燃烧速率随通风因子变化的函数关系式,同时对实验结果进行了分析讨论,为进一步的火灾研究和防火、灭火实践提供参考和指导。     

基于CFD的开放空间油池火燃烧速率和热辐射研究

采用混合组分燃烧模型和有限体积辐射模型,通过液体表面蒸发模型对液态燃料和火羽流进行耦合,建立开放空间油池火模型.利用CFD方法分别对不同直径的庚烷油池火进行模拟,研究其燃烧速率、热释放速率随直径的变化以及火焰中轴上的温度和单位体积热释放速率(HRRPUV)分布,并得出油池表面的热辐射反馈以及油池外部水平和垂直方向的热辐射强度分布规律.部分模拟结果与实验进行对比,验证该模型的适用性和有效性.     

变压器油池火非稳态燃烧特性实验研究

为研究变压器油的非稳态燃烧特性,搭建变压器油燃烧实验平台,开展不同油池直径的池火实验,系统分析油池直径对变压器油非稳态燃烧的影响,定性、定量研究不同油池直径对燃烧速率、火焰脉动频率等的影响。结果表明：变压器油池火燃烧过程可以划分为：初期增长阶段、充分发展阶段和衰减阶段。其中充分发展阶段又可以根据燃烧速率的变化特征分为准稳态燃烧阶段和沸腾燃烧阶段。燃烧速率随油池直径的增大而增大。准稳态燃烧阶段中,火焰脉动频率与油池直径呈负相关,油池直径越大,火焰脉动频率越小。     

自由燃烧下油池火灾的燃烧特性研究

通过对93#汽油、0#柴油和95％的乙醇的自由燃烧试验,得出了3种燃料的燃烧特性,包括液层温度、质量损失速率、燃烧速度、密度、热释放速率、火焰温度等,并结合理论公式拟合热释放速率随油盘直径变化的曲线.质量损失速率与火焰高度汽油＞柴油＞乙醇;汽油、柴油、乙醇燃烧时的液面温度分别为125、310、80℃;3种燃料都在2 min以后达到稳定燃烧状态.     

纵向通风下障碍物对隧道火灾燃烧速率的影响研究

采用模型隧道实验的方法,研究不同纵向通风速度和障碍物距离下池火燃烧速率的变化规律。结果表明,在纵向通风的条件下,障碍物的距离为5 cm时池火的燃烧速率最高。在障碍物距离一定时,池火的燃烧速率随纵向通风速度增加而增加。障碍物距离在一定范围内,池火的燃烧速率高于无障碍物的情况,而障碍物距离超出一定范围时,池火燃烧速率与无障碍物的情况相差不大。障碍物的存在对池火燃烧速率的影响主要归因于侧壁辐射效应和气流场的变化。纵向通风对池火燃烧的影响更为明显。当障碍物距离改变时,气流场会改变火焰的倾斜方向,进而改变侧壁辐射效应。这些发现对于深入理解隧道火灾特性、优化消防安全设计以及制定有效的火灾防控措施具有一定的指导意义。     

流淌火与油池火燃烧特性对比实验研究

建立流淌火燃烧特性实验研究平台,采用93#汽油进行油池火与流淌火的对比燃烧实验,研究在不同斜面角度条件下流淌火与油池火灾在质量损失速率、火焰温度、火焰热辐射等特性参数上的差异,并分析其原因.结果表明,流淌火的火焰高度较低而且非对称分布,火焰波动较大,质量损失速率较小,温度较低,热辐射值较小.可为建立与完善流淌火燃烧理论模型和热辐射危害模型提供参考依据,同时对大型油罐区消防安全设计及灭火救援也具有重要意义.     

高高原受限空间内小尺度油池火燃烧特性试验研究

为研究我国高高原地区的受限空间内液体燃料小尺度油池火燃烧特性,在高高原康定机场自主搭建受限空间内油池火的试验平台。共选取3类典型液体燃料(航空煤油、航空汽油、正庚烷)进行燃烧试验,测量火焰高度、火焰温度和烟气成分等变化规律,研究了高高原受限空间内小尺度油池火行为。研究发现：在高高原地区,正庚烷稳定燃烧阶段的平均火焰高度可以通过模型L/D=k+0.254Q^2/5/D表示,其中,火焰高度与压力之间的关系式为L/D～p^-2/9。3种燃料的火焰最高温度均超过600℃,而羽流轴线温升与火焰高度呈现-5/3的指数关系。产烟速率则表现出对环境压力的依赖性,其关系可表示为：v～p^-1/3。     

小尺度变压器油池火灾燃烧特性的实验研究

开展了直径20～50 cm 的圆形变压器油池火实验,分别测量并研究了火焰形态、燃烧速率、火焰轴心温度等燃烧特性。结果表明：在变压器油燃烧的3 个阶段中,稳定燃烧阶段持续时间最长,而衰减熄灭阶段要明显短于起始燃烧阶段。在燃烧速率方面,油池的直径越大,变压器油燃烧速率越快,燃烧时间越短,变压器油的液位下降速度也越快。变压器油的单位面积燃烧速率与经典辐射模型具有良好的一致性,单位面积燃烧速率与油池直径呈现幂函数形式。在火焰温度方面,油池中心线温度呈现距离液面的垂直高度越大其火焰温度越低的趋势,液面上方火焰温度最高可达700～800 ℃,同时油池火尺度对火焰最高温度的影响不大。     

小尺度沸溢油池火灾燃烧速率特性试验研究

使用胜利原油对小尺度沸溢火灾燃烧速率特性进行了试验研究。分别记录了直径为0.1、0.15、0.2 m的原油沸溢油池火灾的燃烧过程,测量了燃烧速率和温度随时间的变化。根据燃烧速率和火焰高度变化对沸溢火灾燃烧进行阶段划分。探讨了不同直径及初始油层厚度对沸溢火灾燃烧速率的影响,在燃烧速率基础上建立沸溢强度模型。结果表明:沸溢火灾燃烧可以分为预燃、准稳态燃烧、沸溢燃烧、火焰熄灭4个典型燃烧阶段;沸溢燃烧阶段的燃烧速率和火焰高度显著大于准稳态燃烧阶段;沸溢火灾各阶段燃烧速率均随油池直径的增大而增大,且沸溢燃烧阶段的增幅明显大于准稳态燃烧阶段的增幅;准稳态燃烧阶段的稳定燃烧速率与初始油层厚度无关,随油池直径的增大而增大;沸溢强度随初始油层厚度的增加及油池直径的减小而增大,并与初始油层厚度和油池直径间的比值成正比。     

不同燃料液面深度的变压器套管油池火燃烧特性数值模拟

以某典型变压器油浸纸套管火灾事故为对象,利用FDS研究了燃料液面深度对套管油池火燃烧速率和火焰高度的影响.结果表明:随着燃料液面深度的增加,油池火的质量损失速率和热释放速率呈指数衰减,燃烧效率呈先减小后增大的变化规律,同时提出了耦合套管尺寸和燃料液面深度的无量纲火焰高度预测模型.     

两种防火分区方式的技术经济比较

提出“面防火分区”和“体防火分区”两种防火分区方式的概念，通过工程实例，按两种方式进行防火分区设计，从经济，技术角度进行比较，指出根据建筑物的使用功能采用“体防火分区”方式进行防火分区设计的设计方法，有其经济技术上的优点，对研究建筑防火与建筑经济，技术之间的关系有着重要的现实意义。     

Experimental study of natural roof ventilation in full-scale enclosure fire tests in a small compartment

An analysis of full-scale fire test experimental data is presented for a small compartment (3×3.6×2.3 m). A square steady fire source is placed in the center of the compartment. There is an open door and a horizontal opening in the roof, so that natural ventilation is established for the well-ventilated fire. A parameter study is performed, covering a range of total fire heat release rates (330, 440 and 550 kW), fire source areas (0.3×0.3 m and 0.6×0.6 m) and roof ventilation opening areas (1.45×1 m, 0.75×1 m and 0.5×1 m). The impact of the different parameters is examined on the smoke layer depth and the temperature variations in vertical direction in the compartment. Both mean temperatures and temperature fluctuations are reported. The total fire heat release rate value has the strongest influence on the hot smoke layer average temperature rise, while the influence of the fire source area and the roof opening is smaller. The hot smoke layer depth, determined from the measured temperature profiles, is primarily influenced by the fire source area, while the total fire heat release rate and the roof opening only have a small impact. Correlations are given for the hot smoke layer average temperature rise, the buoyancy reference velocity and the total smoke mass flow rate out of the compartment, as a function of the different parameters mentioned. Based on the experimental findings, it is discussed that different manual calculation methods, widely used for natural ventilation design of compartments in the case of fire, under-predict the hot layer thickness and total smoke mass flow rate, while the hot layer average temperature is over-estimated.     

Predicting the heat release rates of liquid pool fires in mechanically ventilated compartments

In this paper we perform predictive simulations of liquid pool fires in mechanically ventilated compartments. We show that steady state burning rates are accurately predicted using a detailed model for the liquid phase heat transfer. The effect of lowered oxygen vitiation on the burning rate of pool fires is correctly captured. Simulations were done using the Fire Dynamics Simulator and the experiments considered were conducted in the OECD PRISME project. The main difference between the present study and previous simulation studies is the use of a detailed liquid evaporation model and the direct calculation of the vitiation and thermal environment interactions through the CFD solver.     

An experimental study on the effect of ventilation velocity on burning rate in tunnel fires—heptane pool fire case

The 1/20 reduced-scale experiments using Froude scaling are conducted to investigate the effect of longitudinal ventilation velocity on the burning rate in tunnel fires. The n-heptane pool fires with heat release rate ranging from 3.71 to 15.6 kW are used in this study. A load cell is used to measure the mass loss rate of burning fuel and the temperature distributions are measured by K-type thermocouples in order to investigate smoke movement. The ventilation velocity in the reduced-scale tunnel is controlled by the wind tunnel through an inverter. The increases in ventilation velocity lead to enhance burning rate of n-heptane fuel. The reason is that the oxygen supply effect prevails rather than the cooling effect as the ventilation velocity increases. As a result, the heat release rates in experiment are larger than constant heat release rates by 4.45–11.3 times in the n-heptane pool fires. Also, it is found that non-dimensional critical ventilation velocity is proportional to one-third power of non-dimensional heat release rate.     

Experimental study based on large-scale smoke propagation fire tests through a horizontal opening connecting two mechanically ventilated compartments

This work describes an experimental study of the flow through a horizontal opening (also referred to as a vent), applicable to specific situations typically encountered in nuclear installations. The configuration consisted of two rooms, which were mechanically ventilated and connected to each other by a horizontal opening, the fire being located in the lower room. The flow was governed by buoyancy due to the heat release from the fire, inertia resulting from the mechanical ventilation, and local momentum from the ceiling jet. Two flow regimes (bi-directional and uni-directional) were encountered depending on the fire power and the ventilation set-up. This study presents 17 large-scale fire tests, investigating the behaviour of the flow at the horizontal opening according to several fire scenario parameters: the fire heat release rate, the fire location, the ventilation configuration and the ventilation flow rate. This range of parameters enabled us to focus on different flow regimes, from pure natural convection (bi-directional) to forced convection (uni-directional). The new set of data obtained, based on detailed flow measurements, offers new insights for understanding the flow and developing sub-models to be used in zone codes.     

Pool fires under atmosphere and ventilation in steady-state burning (part I)

Modeling based on Spalding's theory was undertaken to obtain information on a solvent pool fire under atmosphere and ventilation in steady-state burning. The model comprised the modified B-number with burning parameters governing the burning rate of solvent. Mass loss rate and burning rate of solvent from the burning pan were governed by heat conduction through the pan wall for small pans and by turbulent free convective heat transfer for large pans.This paper will be published inFire Technology in two parts. Part II will appear in the August 1987 issue. Reference: Gunji Nishio and Satoru Machida, Pool Fires under Atmosphere and Ventilation in Steady-State Burning, Part I,Fire Technology, Vol. 23, No. 2, May 1987, pp. 146–155.     

Critical velocity and burning rate in pool fire during longitudinal ventilation

Since the prediction of ‘critical velocity’ is important to control the smoke in tunnel fires, many researches have been carried out to predict critical velocity with various fire sizes, tunnel shape, tunnel slope, and so forth. But few researches have been conducted to estimate critical ventilation velocity for varied burning rate by longitudinal ventilation, although burning rate of fuel is influenced by ventilation conditions. Therefore, there is a need to investigate the difference of upstream smoke layer (e.g., backlayering) between naturally ventilated heat release rate and varied heat release rate by longitudinal ventilation.In this study, the 1/20 reduced-scale experiments using Froude scaling are conducted to examine the difference of backlayering between naturally ventilated heat release rate and varied heat release rate by longitudinal ventilation. And the experimental results obtained are compared with numerical ones. Three-dimensional simulations of smoke flow in the tunnel fire with the measured burning rates have been carried out using Fire Dynamics Simulator; Ver. 406 code, which is developed by National Institute of Standards and Technology. They show a good degree of agreement, even if some deviation in temperature downstream of the fire is evident. Since ventilation velocity had a greater enhancing effect on the burning rate of fuel due to oxygen supply effect, the critical ventilation velocity should be calculated on the basis of varied HRR by ventilation velocity.     

Pool fires under atmosphere and ventilation in steady-state burning (part II)

Two pool fire tests for solvent burning were made to obtain the burning rate and the mass loss rate from burning pans under atmosphere and ventilation in a cell. From the data, burning parameters for the Spalding's modified model reported in Part I were determined in steady-state pool burning.Part I of this paper was published in the May 1987 issue ofFire Technology. Reference: Gunji Nishio and Satoru Machida, Pool Fires under Atmosphere and Ventilation in Steady-State Burning, Part II,Fire Technology, Vol. 23, No. 3, August 1987, pp. 186–197.