不同初始温度对航空煤油表面火蔓延的影响

采用微细热电偶、红外热像仪、CCD摄像及纹影技术对不同初始温度航空煤油表面火蔓现象及机理进行实验研究.结果表明:当航空煤油(开杯闪点为66℃)的初始温度T0≤82.5℃时,其火焰蔓延主要受液相控制,在此阶段表面流预热作用是火焰脉动蔓延的主要控制机制,火焰蔓延平均速度随初始温度升高呈指数增长关系;当航空煤油初始温度T0＞...     

细水雾与液体燃料火焰相互作用的小尺度实验研究及简化模型

细水雾灭火技术是可以替代哈龙灭火剂的绿色灭火技术。以此为工程背景,开展了细水雾与液体燃料火焰相互作用的小尺度实验研究,结果表明:预燃时间、喷雾气压、细水雾气源种类等参数对灭火过程有重要影响。细水雾抑制熄灭液体燃料火焰的主要机理是燃料表面冷却效应。建立的液体燃料平均温度零维简化模型与实验结果吻合较好。     

细水雾灭油池火过程中火焰强化现象的实验研究

细水雾灭火初期,在短时间内会观察到剧烈燃烧的火焰强化现象。设计了多组实验对比不同燃料在不同工况下的火焰强化现象,发现液滴通过撞击油盘燃料引起的液滴飞溅可以增大燃料与空气的接触面积,强化火焰燃烧。细水雾在燃料内发生扬沸也可能强化火焰,但增益效果不明显,同时燃料气化率对于火焰强化程度有很大关系。     

矩形油池火羽流中心线的温度分布

开展了不同火源形状因子(1≤s≤3)的较大功率矩形油池火实验,测量了燃料的质量损失速率,借助编制的图像分析程序处理实验视频得到了连续火焰最大高度(Lc)和火焰最大高度(Lm).将Hasemi羽流中心线温度修正模型的理论预测值和实验值进行了对比,结果表明,随着s的增大,Hasemi理论模型预测值呈现增大的趋势,s=1时,理论预测值和实验值比较接近,两者无明显差异性;s=1.33和s=3时,理论预测值和实验值的变化趋势一致,但两者的总体偏差超过5%.     

基于火焰辐射图像的温度分布与浓度分布联合重建

讨论了基于火焰辐射图像的截面温度分布和碳粒浓度分布的重建测试方法。分析并建立了测试系统理模型和优化模型，设计了相应的求解算法，针对电站锅炉燃煤火焰进行了实际测试。计算结果与实际测试结果进行比较和分析，温度分布和浓度分布与模型重建结果比较接近，表明重建结果合理、可信。     

基于光纤测温系统的温度时空分布模型及应用

针对混凝土坝温度场仿真分析的局限性及采用离散、零星的电阻式温度计实测温度重构温度场时精度较差的问题,探讨了基于分布式光纤测温方法对混凝土坝施工期温度场进行重构。从场理论出发,应用幂级数的处理方法,并结合施工期大体积混凝土热传导理论,将周期项函数、顺河向和垂直向坐标及指数函数进行组合,建立了施工期大坝温度场时空分布模型。结合西南某在建混凝土坝工程的分布式光纤测温资料,回归确定了所建温度场时空分布模型的系数。实例应用表明,基于分布式光纤测温建立的施工期大坝温度场时空分布模型的拟合精度及中短期预测效果较好,真实反映了大坝混凝土的温度状态。     

利用面阵CCD进行火焰温度分布测量_I_二维投影温度场的测量

介绍了利用彩色面阵CCD进行火焰投影温度测量的系统结构和基本原理,并分析其主要的误差来源,针对这些误差源,分别提出了各自的解决方案或校正算法,最后进行了试验测量,结果表明,这种测温方法方便可行,具有较高的精度。     

用双色法研究汽油机燃烧火焰的温度分布

探讨了用双色法测量汽油机温度场的可行性.通过添加氧化铝粒子替代柴油机燃烧产生的碳烟颗粒,利用高速彩色CCD拍摄得到图像,采用双色法计算缸内温度分布.为验证其可行性,在稳态火焰燃烧器上同时采用双色法和热电偶对甲烷空气火焰进行温度测试对比,并讨论不同双色组合对测试精度的影响.结果表明用氧化铝粒子和RB模式的双色法可以获得较好的精度.在一台汽油进气道喷射可视化发动机上,通过向进气道喷射混合均匀的纳米氧化铝粒子,对缸内燃烧过程进行分析,获得了汽油机温度场信息.     

煤垛温度分布的研究

本文针对横截面为梯形的成型煤堆进行了理论分析和计算,并通过现场实测验证了理论分析的正确性。为堆煤场煤垛的自然问题提供了理论基础及解决的途径。     

基于生物柴油制取航空燃料研究的分析

分析了生物质燃料的特征和理化性质。对比分析了生物质航空燃料与传统航空燃料的差异,提供了生物柴油改性的方向,并综述了目前有的几种主要的生物质柴油制取航空燃料的方法。介绍了生物质燃料的发展现状与研究进展,分析了目前生物质航空燃料发展面临的几个关键问题。     

基于不确定度的辐射测温优化分析

将基于标定模式的双色测温拓展为基于非标定模式的三色比值辐射测温,以此为出发点,考虑测量不确定度的影响,开展辐射测温的反演算法、光谱组合等优化分析。研究了非标定模式的比值辐射测温与标定模式的双色测温的优劣,对于非标定模式的比值辐射测温,当测量不确定度较大时,通过比较分析,提出了推荐采用的反演算法。同时,针对于具有应用优势的非标定比值辐射测温模式,讨论了光谱组合优化选择的问题,采用遍历模拟的方式,得到了特定条件下的优化光谱组合结果。给辐射测温方法与技术的改进与应用提供重要的指导。     

Online impedance spectrum measurement of fuel cells based on Morlet wavelet transform

An online impedance calculation method for fuel cells is proposed in this paper. A periodic square wave is selected as the standard excitation current and injected into a fuel cell. Then, the impedance spectrum is obtained by converting the excitation current and response voltage to the frequency domain with the Morlet wavelet. The accuracy of the calculated impedance is firstly tested offline under the stand excitation current condition, and the relative errors of the real part and imaginary part are within 5% and 10%, respectively. To calculate the impedance automatically, a search method is proposed to locate the position of the translation parameters autonomously. Besides, this paper investigates the effects of the stable time and the excitation current form on the calculation results and recommends the excitation current parameters. Finally, an implementation scheme for online impedance measurement is given.     

Evidence of soot superaggregates in a turbulent pool fire

We report experimental observations of extremely large, 10–100 μm, soot aggregates in a blended methanol/toluene fueled turbulent pool fire, which are believed to be the first observation of “superaggregates” in a turbulent flame. Laser-induced incandescence images of soot volume concentration, at the center of the fire plume and at a height within the active flaming region, reveal the appearance of large-scale particle-like features across a broad range of apparent volume fraction, which emit at an intensity that is comparable with that of the laser-heated soot particles. We argue that the features in the incandescence images result from very large soot aggregates. This observation is supported by scanning electron microscope imaging of extracted soot that reveals large soot structures composed of much smaller chains of individual primary particles. Analysis of the soot aggregate structure from the electron-microscope images reveals a 1.8 fractal dimension at micron scales, comparable with commonly reported soot aggregate sizes from hydrocarbon flames. At larger scales of 10s of microns, comparable with the total aggregate size, a larger volume-filling fractal dimension of 2.5–2.6 is observed. This type of fractal structure is consistent with reported, but apparently rare, observations of soot superaggregates in heavily sooting laboratory laminar diffusion flames, but is encountered in the much larger meter-scale pool fire at much lower soot volume concentrations.     

The structure and radiation of an ethanol pool fire

The structure of the flame above a burning 0.5 m diameter pool of ethanol has been examined. The average concentration of CO₂, CO, H₂O, and hydrocarbons, the mean and standard deviation of temperature, and the mean velocity are reported from the surface up to 1.5 diameters downstream. The local soot absorption coefficient has been found to be less than 0.7 m⁻¹ everywhere in the fire using a fiber optic laser attenuation probe. Instantaneous temperatures measured simultaneously at 11 positions along the diameter show no correlation between fluctuations on the centerline and at the edge of the fire, and moderate correlation between thermocouple pairs located at similar radial positions across the fire. In all cases the cross-correlation is maximum where the time delay is zero for any given height. The temperature probability distribution and a measured dominant flickering frequency of 1.96 Hz are consistent with observations made in other moderate sized pool fires of various fuels. The radiative loss in the first 0.75 m is 19% of the 72.8 kW thermal input. Measurements of radiant intensity distributions from the fire are compared to values predicted from nonisothermal radiation models. When account is taken of the low frequency, large scale fluctuations in temperature, concentration, and soot absorption coefficient, predictions of intensity are in closer agreement with experiment than predictions from models based only upon time mean temperature and composition. The data reported here provide a comprehensive basis for evaluation of other fire and radiation models as well.     

基于燃料电池膜水分传递特性研究的温度与湿度控制

质子交换膜燃料电池(PEMFC)中保持膜的适度湿润性非常重要.模拟了质子交换膜的水环境,采用西门子S7-300PLC和力控组态软件设计了温度湿度控制系统;应用PID调节原理分别控制三种不同空气流量(1、6、10 g·s-1)情况下空气加热器和水加热器的温湿度.由数据分析可得到结论:1 g·s-1流量引起的湿度波动较大,10 g·s-1流量在高温高湿情况下出现异常.     

细水雾对油池火热释放速率影响的初步研究

热释放速率是反映火场规模与发展的最重要的基础参数,利用ISO9705实验台进行细水雾灭火有效性的影响因素及相关机理研究,不仅能营造出一个真实的室内火灾环境,而且能够得到火场的热释放速率。对汽油池火的初步实验表明：热释放速率曲线能直接反映出细水雾对火源的作用;细水雾作用下燃烧总的热释放量减少很大;开启水雾的时间不同,细水雾对热释放速率峰值的削减程度不同。