着火油罐燃烧特性的理论分析

本文利用自行建立的油罐火灾燃烧特性通用模型,计算得到了燃烧速度、火焰高度,火焰跳动频率和平均温度等油罐燃烧特性的变化规律,并深入探讨了油品燃烧速度在油罐直径、风速、环境温度和油位等因素影响下的变化趋势。为了验证理论计算的准确性,将计算结果与汽油和柴油储罐的燃烧实验数据进行了对比,获得了较为满意的结果。     

汽油储罐火灾燃烧特性的实验研究

本文通过对直径为1 m、 1.5 m和2.7 m的汽油储罐进行火灾实验,分析了汽油罐燃烧时不同阶段的燃烧特 性。本文重点讨论了描述燃烧特性的几个重要参数的变化规律,包括火焰脉动频率、火焰高度、倾斜角度以及火焰的温度 分布等,并将结果拟合为相应的实验关联式,以揭示油罐火灾的内在规律和预测其发展趋势。     

空间方位对木材燃烧火焰传播的影响

一、引言 在森林火灾和城市建筑火灾中,木材作为一种主要可燃物,对于火灾的发生及发展具有重要的影响。其燃烧的特性,尤其是其燃烧的火焰及火焰传播的规律,往往决定了火灾发展的方向,并左右着局部火场的燃烧状况。因此,弄清木材燃烧的火焰传播的规律,已成为揭示森林火灾及城市建筑火灾发展规律的关键。     

甲醇喷雾湍流反应流的JPDF数值模拟

喷雾湍流燃烧过程中,液滴、湍流和化学反应之间强烈耦合,物理化学机理非常复杂。本文将速度-标量-频率联合概率密度函数JPDF输运方程方法应用于两相喷雾湍流反应流问题,利用火焰面模型解耦流动和化学反应动力学的耦合关系,建立起相应的数值计算模型。采用Monte-Carlo数值计算方法,针对澳大利亚悉尼大学Masri等人以甲醇为燃料所进行的湍流喷雾燃烧值班火焰这一试验进行了数值模拟,通过与Fluent下的计算结果及试验结果的对比分析,验证了本文所建模型的准确性。     

油罐火机理的研究

本文从理论和实验两方面对油罐火的机理进行了研究并提出了一个三层模型理论。三层模型理论可较准确地说明油罐火的热交换关系,特别是中间层在油罐火燃烧中的重要作用,导出了可较精确地计算油罐火稳定燃烧时燃烧速率的公式。在直径为1.6米、高1.5米的油罐中用航空煤油进行的燃烧试验验证了理论的正确性。     

钝体驻定湍流扩散火焰的数值研究——燃烧模型比较

分别采用标量联合的概率密度函数方法、稳态火焰面模型、Euler非稳态火焰面模型和基于有限体积/Monte Carlo混合算法的完备PDF模型对钝体驻定的Sydney湍流扩散火焰HM1进行数值模拟,以比较不同燃烧模型的性能,并比较标量联合的概率密度函数方法和Euler非稳态火焰面模型对氮氧化物排放预测的差异.计算结果和实验数据的比较表明,采用概率密度函数方法计算化学反应可以得到更好的结果但计算量较大,而用火焰面模型求解计算量较小,在接近完全燃烧的情形下,其计算结果比较合理.     

CS2燃烧火焰光谱辐射模型的构建与特征污染产物浓度反演研究

CS₂在当今化工等领域占据了重要地位,而CS₂火灾污染事故危害性极大。通过研究CS₂燃烧火焰光谱辐射以探究其火灾污染特性极为必要。搭建了CS₂燃烧火焰光谱测试平台,采用黑体辐射源对VSR仪器进行了标定,通过多用途傅里叶变换(VSR)红外光谱辐射仪测试了5,10和20 cm三种燃烧尺度下CS₂燃烧的火焰光谱,并通过热电偶测试了整个燃烧时间段内不同燃烧时刻下的火焰温度,以及在火焰上方安装了烟气分析仪对火焰中的燃烧产物浓度进行监测。测量了CS₂整个燃烧时间段内火焰温度,以及不同燃烧时间、不同燃烧尺度下的火焰光谱、燃烧产物组分信息。测试结果表明,CS₂火焰中主要含有高温SO₂,CO₂,CO气体和空气中卷入的H₂O分子,并获取了特征污染产物SO₂的浓度。由于现有光谱仪测量分辨率有限,室内实验测量的火焰尺度有限,为了能实现火灾在线监测需要建立一个火焰光谱辐射模型来反演CS₂火灾时的污染物浓度相关信息。基于HITRAN数据库可知在2.7 μm附近为高温水蒸气的发射峰,4.2 μm附近特征峰为高温CO₂气体的发射峰,4.7 μm附近有CO微弱的发射峰,在7.4 μm附近特征峰为高温SO₂气体的发射峰,并获得了CS₂燃烧时产生的SO₂,CO₂,CO和H₂O气体在火焰燃烧相同温度下的吸收系数,通过计算得到了CS₂燃烧时产生的SO₂,CO₂,CO和H₂O混合气体的透过率与发射率,并结合气体辐射传输方程、气体吸收系数等方程,创建了CS₂燃烧的火焰光谱辐射模型。利用该光谱辐射模型反演了不同燃烧时间下特征污染产物SO₂的浓度,并与实验测得的数据进行了对比分析。结果表明,该模型精度高,可用于燃烧产物浓度的定量化反演,SO₂分子含量在燃烧时间20,40,60和80 s时的反演精度分别是89.5%,82.5%,85.6%和86.5%。为遥感反演CS₂型大尺度火灾中燃烧产物的浓度奠定基础。     

湍流扩散燃烧的数值研究-PDF方法和火焰面模型的性能比较

采用标量概率密度函数(PDF)方法、稳态和非稳态火焰面模型三种方法对一个值班湍流CH_4/O_2/N_2射流扩散火焰(Sandia Flame D)进行数值计算,以比较不同燃烧模型的性能。PDF方法通过计算反应标量的PDF输运方程来得到标量分布,而火焰面模型只求解单标量混合物分数的PDF方程,组分和温度分布通过火焰面方程的求解或者火焰面数据库的插值得到。计算结果和实验数据对比表明PDF方法计算结果最好但计算量相当大,稳态火焰面模型则反之。综合而言,非稳态火焰面模型的预测结果相对稳态模型有了非常大的改进,而计算量仍然容易接受,非常适合工程应用。     

乙腈池火燃烧场分析与特征产物浓度的定量反演研究

乙腈广泛应用于医药、化工等领域,而乙腈属于易燃易爆化学品,其引发的火灾事故具有极大的危害。研究乙腈燃烧的温度场与浓度场、火焰辐射光谱以探究其火灾污染特性具有重要实用价值。首先采用平面激光诱导荧光技术(PLIF)与Fluent数值模拟方法,获取了5 cm尺度乙腈池火燃烧产物NO在20、 40、 60和80 s时刻的空间浓度值,并结合CFD与FDS仿真模拟获取了不同时刻下乙腈燃烧温度场与浓度场信息。其次,采用所获取的乙腈火焰温度场和浓度场数据(将火焰划分为6个热力学平衡区域),并基于HITRAN数据库内高温气体分子吸收系数与火焰总体辐射传输方程构建了乙腈火焰光谱辐射模型。再次,将所得乙腈浓度场与温度场数据代入火焰光谱辐射模型,模型模拟计算结果与相同条件下乙腈火焰光谱实测数据进行对比,以验证模型精度,然后再与Radcal模型进行精度对比。最后,利用自行构建的火焰光谱辐射模型对燃烧特征污染产物NO进行了浓度反演。结果表明：(1)5 cm尺度乙腈池火火焰温度范围为400～1 000 K,在池火上方60～80 mm区域温度较高,最高温度为945 K。(2)在20、 40、 60和80 s时刻下5 ...     

湍流值班火焰点火数值计算

本文用惰性气体热射流模拟值班火焰的热效应,对其点火过程进行数值计算. 用K-ε湍流模型和拉切滑(SCASM)湍流燃烧模型完成了对控制微分方程组的封闭。引入了最佳寻查方法计算点火的临界条件;阐述了建立跟踪火焰的网格系统的思想和方法,并进行了实际计算,计算结果合理。     

A novel combustion system for liquid fuel evaporating and burning

To utilize sustainable biofuel, the current study proposes a novel combustion technique that directly burns liquid ethanol without a spray system. Two swirling air flows are induced by tangentially injected the gas from two concentric tubes at different stages. The liquid ethanol is fed by a liquid tank at the center. At the beginning methane flame assists in preheating the system to vaporize liquid ethanol and ignite the vapor. Thereafter methane is switched off, and liquid ethanol can be continuously vaporized through self-burning released heat. The heat and mass transfer processes are examined to illustrate such self-sustained burning–heating–evaporating system. The ethanol flow rate is gradually increased to provide different heat output. The flame structures, temperature distributions and pollutant emissions are carefully examined. The results show that the ethanol can be steadily burned to provide heat output between 0.7 and 2.5?kW. Generally a blue flame is obtained, and the NO_x and CO concentrations are ultralow. By increasing ethanol flow rate to exceed 8?mL/min, an unsteady, sooting flame is observed owing to incomplete evaporation and poor mixing. A parametric study is conducted to evaluate the influences of liquid tank position, flow rate and tip structure on the combustion characteristics. Additionally, an optimal operation condition is proposed. The current study provides a promising method to burn low-boiling liquid fuel in a clean, efficient and compact way.     

基于光谱分析的油料池火内部传热特性研究

油料池火焰内部分为不同燃烧区域,目前对油池火内部传热特性研究较少。针对油池火内部传热特性研究不足的现状,构建了红外火焰光谱测试系统,研究分析了92#汽油、95#汽油及润滑油池火焰红外光谱特性,对油池火焰不同燃烧区域的光谱信息进行了提取分析,结果表明：三种油料池火焰光谱特征相似,存在多个CO₂,H₂O及炭黑颗粒等燃烧产物的特征发射波段,3.4 μm处C—H伸缩振动峰明显;火焰烟气区主要光谱特征为4～4.5 μm波段范围内高温CO₂发射峰,该区域火焰与空气换热剧烈,温度变化不稳定,火焰脉动频率较高;火焰间歇区的光谱特征是4～4.5 μm波段范围内高温CO₂发射峰,与烟气区相比,火焰间歇区脉动频率相对较低;与烟气区及间歇区相比,火焰连续区燃烧较为稳定,该区域的光谱特征明显,在2.5～3 μm波段范围内炭黑粒子发射光谱强度较高,且在3.4 μm处存在C—H伸缩振动峰,表明油料池火焰光谱3.4 μm处的特征峰由高温油蒸汽产生。油池火焰不同燃烧区域光谱特征分析表明,油池火焰液态油表面的“富燃料层”吸收火焰传热,引起3.4 μm附近油蒸汽分子能级的改变。油池火焰不同燃烧区域发射光谱强度计算表明,火焰连续区的强度最大,其次为间歇区,火焰烟气区与空气对流强烈,测得的发射光谱强度最低。研究结果为火焰—油料传热模型的修正提供了参考。     

Physical aspects of polymer combustion and the inhibition mechanism

The characteristics of polymer combustion were studied. The contributions from the conductive, convective, and radiation components of the total heat flow from the flame to the polymer surface were determined. The influence of inhibitors on the rate of chemical reactions in the preignition zone and on the rate of heat and mass exchange between the flame and the burning surface was estimated. It was shown that a change in the heat balance and heat and mass exchange accompanied by changing the optical properties of the flame and burning surface has a pronounced effect on the combustion rate at the flame edge. The formation of a protective coke layer reduces heat flow to the surface of a nonreacted polymer, leading to a decrease in the rate of evolution of the volatile combustible polymer-destruction products into the gas phase. As a result, the flame temperature decreases and it is extinguished.     

着火油罐辐射热传递过程实验研究

通过对直径D=1 m、 1.5 m、2.7 m全掀顶油罐着火特性实验研究,分别得出汽油、柴油的火焰形状,及距油罐1D、1.5D的火焰辐射强度和温度动态分布数据,对直径1 m的相邻油罐,得出在火灾辐射场中其壁面温度分布和罐体内部压力及温度动态变化曲线,研究内容对修订我国相关消防规范和工程设计提供参考,同时为开展数值模拟提供参照标准。     

Analytical predictions of shapes of laminar diffusion flames in microgravity and earth gravity

Flame shape is an important observed characteristic of flames that can be used to scale flame properties such as heat release rates and radiation. Flame shape is affected by fuel type, oxygen levels in the oxidiser, inverse burning and gravity. The objective of this study is to understand the effect of high oxygen concentrations, inverse burning, and gravity on the predictions of flame shapes. Flame shapes are obtained from recent analytical models and compared with experimental data for a number of inverse and normal ethane flame configurations with varying oxygen concentrations in the oxidiser and under earth gravity and microgravity conditions. The Roper flame shape model was extended to predict the complete flame shapes of laminar gas jet normal and inverse diffusion flames on round burners. The Spalding model was extended to inverse diffusion flames. The results show that the extended Roper model results in reasonable predictions for all microgravity and earth gravity flames except for enhanced oxygen normal diffusion flames under earth gravity conditions. The results also show trends towards cooler flames in microgravity that are in line with past experimental observations. Some key characteristics of the predicted flame shapes and parameters needed to describe the flame shape using the extended Roper model are discussed.     

Processing of thermogram sequences to determine the rotation rate of a vortex flame

We study vortex flame radiation in laboratory conditions. A fire torch was burning from a tank, which was fixed at the axis of uprising swirl airflow. Ethanol was used as a fuel. Processing of a sequence of thermograms of a swirling torch is described. The vortex flame revolutions were calculated using FFT of time pulsations of a signal from a thermal imaging system.     

多光谱辐射测温技术测量火工烟火药剂燃烧温度

利用瞬态光谱辐射仪分析了火工烟火药剂燃烧火焰辐射光谱分布,介绍了多光谱辐射测温技术的工作原理。结合火工烟火药剂燃烧火焰特征光谱分布状况设计研制了具有12个工作通道的多光谱辐射测温系统,测试者可根据被测火焰光谱辐射分布状况选择合适的工作通道进行分析计算。该系统由光学部分,电路部分,数据采集部分及数据处理部分组成。文章以黑火药为例,应用该系统对其燃烧火焰的辐射能量进行了测定,经过迭代计算后给出黑火药燃烧温度随时间的变化曲线。实验证明,在分析被测火焰特征光谱分布的前提下,选择合适的光谱工作通道,多光谱辐射测温系统能够很好地应用于火工烟火药剂燃烧温度的测定,为火工烟火药剂燃烧输出特性的研究奠定了基础。     

Modelling of candle burning with a self-trimmed wick

As an example of a coupled gas-phase diffusion flame with porous media flow, a candle burning model with a porous wick is offered in this paper. The porous media analysis includes capillarity-induced liquid flow, liquid vaporisation, vapour motion and re-condensation and multi-phase heat transfer. Coupling with the gas phase flame is through the conservation of mass, momentum and energy at the wick surface. The steady state solutions obtained not only yield the flame structure but also the detailed flow pattern and saturation distributions inside the wick. One of the novel features of the present model is the capability to address the self-trimming phenomena of candle burning. The self-trimming wick length and the associated flame characteristics have been computed as a function of gravity level, wick permeability and wick diameter.