Numerical Simulation of High Temperature Air Combustion Flames Properties

High temperature air combustion (HTAC) is an attractive technology of saving energy and controlling environment. The mathematical models of turbulent jet flame under the highly preheated air combustion condition are conducted in the paper. The mixture fraction/probability density function model is employed. The results show that the maximum flame temperature is decreased, the temperature in the HTAC furnace is more uniform than that in the conventional furnace, and the NO x emission is low. The numerical results are partially validated by some experimental measurements.

Study on the Flame-retardant Properties of High Flame-retardant Acrylic Fiber Knitted Fabrics

This paper involved five kinds of weft-knitted fabrics made from high flame-retardant acrylic/cotton(0/100,30/70,50/50,70/30,100/0).The article adopted the vertical burning method,limiting oxygen index method and Cone Calorimeter test method for testing fabric flame retardant property.By comparison with these five fabrics,the effects on the properties of high flame-retardant acrylic fiber knitted fabrics due to the content of high flame-retardant acrylic fiber were analyzed.

基于FLAMES和HLA的导弹分队作战仿真系统

研究了基于FLAMES和HLA导弹分队作战仿真。首先介绍了系统架构及工作流程,然后剖析了基于FLAMES和HLA进行导弹分队作战中的仿真实体之间的信息交互机制,最后探讨了基于FLAMES和HLA的开发过程,验证了基于FLAMES和HLA开发的导弹分队作战仿真的实用性,为以后分队作战智能化仿真研究提供借鉴。

Numerical Investigation of Fuel Dilution Effects on the Performance of the Conventional and the Highly Preheated and Diluted Air Combustion Furnaces

This numerical study investigates the effects of using a diluted fuel （50% natural gas and 50% N2） in an industrial furnace under several cases of conventional combustion （air with 21% O2 at 300 and 1273 K） and the highly preheated and diluted air （1273 K with 10% O2 and 90% N2） combustion （HPDAC） conditions using an in-house computer program. It was found that by applying a combined diluted fuel and oxidant instead of their uncombined and/or undiluted states, the best condition is obtained for the establishment of HPDAC＇s main unique features. These features are low mean and maximum gas temperature and high radiation/total heat transfer to gas and tubes; as well as more uniformity of theirs distributions which results in decrease in NOx pollutant formation and increase in furnace efficiency or energy saving. Moreover, a variety of chemical flame shape, the process fluid and tubes walls temperatures profiles, the required regenerator efficiency and finally the concentration and velocity patterns have been also qualitatively/quantitatively studied.

Measurement of Breakdown Electric Field Strength for Vegetation and Hydrocarbon Flames

A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the high-voltage transmission system. In any case, the wildfire plumes provide a conductive path. The electrical conductivity is due to intense heat in combustion zone of the fire which creates ion and electrons from flame inherent particulates. Increase in the ion concentration increases the electrical conductivity of the fire plume. The main purpose of this study was to measure dielectric breakdown electric field for vegetation and hydrocarbon flames. The experimental data is needed for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. In this study, hydrocarbon and vegetation fuels were ignited in a cylindrically shaped steel burner which was fitted with type-K thermocouples to measure flame temperature. The fuels consisted of dried weeping wattle (Peltophorum africanum) litter, butane gas and candle wax. Two pinned copper electrodes supported by retort stands were mounted to the burner and energized to a high voltage. This generated a strong electric field sufficient to initiate dielectric breakdown in the flames. Breakdown electric field strength (Ecrit) obtained from the experiment decreased from 10.5 to 6.9 kV/cm for the flames with temperature range of 1003 to 1410 K, respectively.

Thermal and Thermo-oxidative Degradation of Flame Retardant High Impact Polystyrene with Triphenyl Phosphate and Novolac Epoxy Resin

Thermal and thermo-oxidative decomposition and decomposition kinetics of flame retardant high impact polystyrene （HIPS） with triphenyl phosphate （TPP） and novolac type epoxy resin （NE） were characterized using thermo-gravimetric experiment. And the flammability was determined by limited oxygen indices （LOI）. The LOI results show that TPP and NE had a good synthetic effect on the flame retardancy of HIPS. Compared with pure HIPS, the LOI values of HIPS/NE and HIPS/TPP only increased by about 5%, and the LOI value of HIPS/TPP/NE reached 42.3%, nearly 23% above that of HIPS. All materials showed one main decomposition step, as radical HIPS scission predominated during anaerobic decomposition. TPP increased the activity energy effectively while NE affected the thermal-oxidative degradation more with the help of the char formation. With both TPP and NE, the materials could have a comparable good result of both thermal and thermal-oxidative degradation, which could contribute to their effect on the flame retardancy.

An Empirical Relation for Vegetation Fuel Flames Breakdown Electric Field Strength

The compulsion to provide reliable electric power for sustenance of socio-economic development is vital for most of southern Africa states. The demand for the resource in the region is anticipated to escalate in the next couple of decades. However, there is a deleterious effect of fire-induced power disruption which is observed in many countries. The mechanism through which the disruption occurs is currently a subject of current research in electric power distribution. It has been observed that streamer initiated conduction channel provides a means of high voltage electric power flashover. The main purpose of this study is to determine the empirical expression for breakdown electric field strength of vegetation fires. The breakdown field was measured from vegetation fuel (Peltophorum africanum) flames at different combustion temperatures. The data is essential for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. In this study, Peltophorum africanum fuels were ignited in a cylindrically shaped steel burner which was fitted with a Type-K thermocouple to measure flame temperature. The fuels consisted of dried fine twig (≤0.8 mm Ø) and limb wood (≥10 mm Ø) litter. Two copper pinned-electrodes supported by retort stands were mounted to the burner and energized to a high voltage. This generated a strong electric field sufficient to initiate dielectric breakdown in the flames. The measured electric field strength was plotted against flame temperatures and fit with a non-linear relation to give the empirical relation.

A multiple flame-retardant,early fire-warning,and highly sensitive thread-shaped all-fabric-based piezoresistive sensor

In the artificial intelligence age,multifunctional and intelligent fireproof fabric-based electronics are urgently needed.Herein,a novel thread-shaped all-fabric-based piezoresistive sensor(denoted as TAFPS)with properties such as flame retardancy,firewarning,and piezoresistivity is proposed,which is composed of an inner nickel-plated fabric electrode,a multifunctional double helix fabric,and an external flame-retardant encapsulation fabric.Owing to the multiple flame-retardant properties of glass fiber tubular fabric,aminated carbon nanotubes(ACNTs),and ammonium polyphosphate,the char residue of the TAFPS reaches40.3 wt%at 800℃.In addition,the heat-sensitive effect of ACNTs during combustion causes a rapid decrease in the TAFPS resistance,triggering the fire alarm system within 2 s.Additionally,benefiting from the force-sensitive behavior of the double helix layer and tightly wrapped pattern of the external heat-shrinkable tubular fabric,TAFPS demonstrated a high sensitivity of4.40 kPa^(-1)(0–5.81 k Pa)and good stability for 10000 s.Considering its excellent flame resistance,high sensitivity,and agreeable stability,the developed TAFPS can be integrated into fire suits to monitor the exercise training process and the external fire environment.This work offers a novel approach for fabricating all-fabric-based piezoresistive sensors in the future for fire prevention and fire alarms,with promising applications in fire protection,the Internet of Things,and smart apparel.

A New Process for Preparing Fine-ceramic-containing Composite Coatings──Flame Spray Synthesis

Flame spray synthesis (FSS), a combination of the flame spray technology and Self-propagation High-temperature Synthesis (SHS) was developed for preparing fine-ceramic-containing composite coatings. It can simplify the preparations of powder to synthesize and deposit the desired materials in one step. The preliminary results obtained from TiC-Fe cermet coatings by FSS process are reported. The peculiar microstructure of the composite coatings, which contains very fine (<1m) and round TiC and alternate TiC-rich (Hv=11€*13GPa) and TiC-poor layers (Hv=3.0 -6.0GPa), is expected to play an important role in their tribological properties.

Sulfolane‑Based Flame‑Retardant Electrolyte for High‑Voltage Sodium‑Ion Batteries

Sodium-ion batteries hold great promise as next-generation energy storage systems.However,the high instability of the electrode/electrolyte interphase during cycling has seriously hindered the development of SIBs.In particular,an unstable cathode–electrolyte interphase(CEI)leads to successive electrolyte side reactions,transition metal leaching and rapid capacity decay,which tends to be exacerbated under high-voltage conditions.Therefore,constructing dense and stable CEIs are crucial for high-performance SIBs.This work reports localized high-concentration electrolyte by incorporating a highly oxidation-resistant sulfolane solvent with non-solvent diluent 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether,which exhibited excellent oxidative stability and was able to form thin,dense and homogeneous CEI.The excellent CEI enabled the O3-type layered oxide cathode NaNi_(1/3)Mn_(1/3)Fe_(1/3)O_(2)(NaNMF)to achieve stable cycling,with a capacity retention of 79.48%after 300 cycles at 1 C and 81.15%after 400 cycles at 2 C with a high charging voltage of 4.2 V.In addition,its nonflammable nature enhances the safety of SIBs.This work provides a viable pathway for the application of sulfolane-based electrolytes on SIBs and the design of next-generation high-voltage electrolytes.

A review on research of fire dynamics in high-rise buildings

Since serious fire occurred frequently in recent years, fire safety of high-rise building has attracted extensive attention. A National Basic Research Program （973 program） of China has been set up by Ministry of Science and Technology （MOST） of China in 2012 to meet the research requirements of fire safety in high-rise buildings. This paper reviews the current state of art of research on fire dynamics of high-rise buildings, including the up-to-date progress of this project. The following three subjects on fire dynamics of high-rise buildings are addressed in this review： the ejected flame and fire plume behavior over facade out of the compartment window, the flame spread behavior over facade thermal insulation materiMs, and the buoyancy-driven smoke transportation characteristics along long vertical channels in high-rise buildings. Prospective future works are discussed and summarized.

Analysis of Aluminum Dust Cloud Combustion Using Flame Emission Spectroscopy

In this study,aluminum flame analysis was researched in order to develop a measurement method for high-energy-density metal aluminum dust cloud combustion,and the flame temperature and UV-VIS-IR emission spectra were precisely measured using a spectrometer.Because the micron-sized aluminum flame temperature was higher than 2 400 K,Flame temperature was measured by a non-contact optical technique,namely,a modified two-color method using 520 and 640nm light,as well as by apolychromatic fitting method.These methods were applied experimentally after accurate calibration.The flame temperature was identified to be higher than 2 400 Kusing both methods.By analyzing the emission spectra,we could identify AlO radicals,which occur dominantly in aluminum combustion.This study paves the way for realization of a measurement technique for aluminum dust cloud combustion flames,and it will be applied in the aluminum combustors that are in development for military purposes.

Development of low-cost high-strength stainless steel for new-energy bus frames

Along with strict environmental regulation, new-energy vehicles are becoming increasingly popular due to their low emissions, and they will inevitably replace existing fossil-fuel-based buses in China. To achieve a lightweight bus body ,high-strength steels are commonly used for the bus frame,but these grades are susceptible to corrosion. From the perspective of ＂lower life-cycle cost＂, high-strength stainless steel is a better bus structure choice than high-strength carbon steels, since stainless steel bus frames last 10-15 years without requiring any maintenance. The low-cost high-strength stainless steels developed by Baosteel are introduced,the yield and tensile strengths of which can be controlled to within the range of 350-700 MPa and 900-1 200 MPa,respectively, and the elongation values are above 30%. Measurements of the toughness and fatigue resistance of these high-strength stainless steels and their joints indicate that the structural integrity requirements for bus frames can be met. The results of salt spray corrosion studies indicate that stainless steels will substantially increase the service life of bus frames in wet and icy winter conditions where deicing with CaC12 is necessary for road safety. The results of our investigation clearly indicate that high-strength stainless steel is a potential bus-frame material that makes it possible to achieve substantial weight savings, excellent corrosion resistance, and prolonged operational life.

马赫数10条件下冲压发动机内氢气燃烧特性试验

针对高马赫数超燃冲压发动机面临的高效燃烧组织挑战,本文提出了一种凹腔后缘激波强化的高马赫数超声速燃烧组织技术,并设计了一套燃烧室采用双侧对称布置凹腔结构的三维发动机试验模型。采用OH*基化学发光光谱诊断与壁面测压相结合的试验手段,在自由活塞驱动激波风洞的名义Ma=10流场中,对凹腔上游横向氢气射流的燃烧特性进行了研究,并讨论了模拟流场的重复性,给出了氢气燃烧演化特征、火焰稳定结构及释热特性。不同车次的总压等流场参数表明试验流场具有较高的重复性,可保障氢气燃烧特性的可复现性。通过观察试验过程中OH*基动态发光特征发现,在高焓激波风洞发动机试验中采用燃料提前喷注的方法使发动机流道在空气主流到来之前充盈大量的氢气,进而在主流到达发动机内的瞬间形成所谓“激波管流动-燃烧”效应,使来流空气与氢气接触面发生自点火与剧烈燃烧,产生显著不同于发动机正常工作情况下的点火与燃烧机制,但随着主流趋于平稳,“激波管流动-燃烧”效应消失,在高总温气流的自点火效应与凹腔后缘的X型激波耦合作用下,火焰稳定在凹腔上游近壁面区的氢气射流尾迹区和凹腔后缘附近的全流场中。通过分析壁面压力分布特征发现,凹腔后缘的X型激波实现了燃烧的强化与火焰的稳定,并获得了最显著的释热压升。这些结果表明高马赫数冲压发动机可利用凹腔后缘X型激波强化燃烧和稳定火焰。

高强度玻璃纤维对阻燃增强PET性能的影响

研究了高强度玻璃纤维对阻燃增强聚对苯二甲酸乙二酯(PET)材料性能的影响,并制备了综合性能优良的高性能阻燃增强PET材料,同时分析了高强度玻璃纤维和普通无碱玻璃纤维在PET材料中的尺寸分布。结果表明:高强度玻璃纤维的表面处理可以有效提高阻燃增强PET材料的性能;阻燃增强PET的性能随着玻璃纤维含量的增加而提高,高强度玻璃纤维比普通无碱玻璃纤维能更好地改善PET材料的综合性能。

基于5 kHz平面激光诱导荧光的射流火焰局部熄火时空特性分析

基于高频光学测量手段研究射流火焰局部熄火的分布特性,对于分析燃烧场不稳定性机理有重要意义。建立5 kHz的平面激光诱导荧光测量系统,对高速射流火焰开展实验研究,并获得火焰结构的动态发展过程;将双边滤波、竖直滑窗局部自适应阈值等图像处理方法引入平面激光诱导荧光图像的预处理,在局部断裂结构数量特征的基础上,提取局部断裂结构长度和空间位置等特征;基于上述特征深入解析局部熄火的时空分布特性,进一步完善高频平面激光诱导荧光诊断与分析方法。研究表明:双边滤波算法处理后,图像峰值信噪比为34.3 dB,结构相似度为0.93,噪声水平显著降低,获得了较好的去噪效果;使用竖直滑窗局部自适应方法进行图像分割的F1分数达到93.30%;断裂结构累计数量随时间线性增加,当射流马赫数由0.5增至1.6时,单侧图像断裂结构的每秒累计数量从790.7增至9 217.2,并且局部熄火频率与射流马赫数呈指数关系;断裂结构主要分布区域为火焰臂及上侧中央燃料区。本研究进一步拓展了高频平面激光诱导荧光技术的应用能力,证明了高频平面激光诱导荧光技术用于局部熄火时空分布特性研究的可行性。

不同结构因子下带连廊高层建筑外墙火竖向蔓延数值模拟

目的 研究带连廊高层建筑发生火灾时火焰蔓延的变化规律,为该类建筑的防火设计提供参考。方法 应用火灾数值模拟软件FDS建立一个33层带连廊建筑模型,分别改变结构因子、窗口数量两种因素进行模拟,分析该模型在不同条件下的温度分布等温线和温度曲线。结果 结构因子为0.4、0.8、1.2,窗口数量为二、三、四时,达到危险温度540℃,火焰融合高度随结构因子和窗口数量增加而上升;随着结构因子的增加,火焰融合高度提高了0.25~12.5 m;随着窗口数量的增加,火焰融合高度上升了0.9~6.37 m;结论 带连廊高层建筑外墙火焰蔓延高度受结构因子和窗口数量影响;随着窗口数量增加,结构因子对火焰融合高度影响越大,结构因子越大,火焰融合高度越高;建议带连廊高层建筑连廊部分结构因子小于0.8,并选用结构因子为0.8时的火焰融合高度作为外部蔓延防火阻隔区高度。

某中储式锅炉水冷壁高温腐蚀特征分析

对某中储式制粉系统锅炉的高温腐蚀特点进行了详细分析,包括腐蚀区域、煤粉刷墙情况、煤粉未燃尽情况以及运行人员的习惯运行方式等.研究发现:该锅炉腐蚀最严重区域位于三次风喷口下方,而不是燃尽风喷口下方,这是与直吹式制粉系统锅炉发生高温腐蚀的一个显著区别点.另外,该锅炉腐蚀还有一个特点是沿着一次风逆时针切圆方向,从上游到下游区域,腐蚀在水冷壁管出现的位置依次为向火侧腐蚀、管中间腐蚀、管两侧腐蚀.煤粉大面积刷墙和水冷壁区域的高H2S浓度是严重腐蚀的主要原因.在刷墙处抽烟气获得的未燃尽煤粉燃尽率73.5%~80%,煤粉经炉内高温后,黄铁矿硫基本分解完毕,剩余硫主要以有机硫为主.

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)。

高附着轻质复材用防护涂料的研制

为提升碳纤维/环氧复合材料的防护性能,降低其吸水率,延长复合材料的使用寿命,采用不同相对分子质量的聚四氢呋喃醚二醇(PTMG)对环氧树脂进行改性,设计合成了高性能改性树脂作为成膜物,制备了复材用防护涂料。同时,进一步调控了涂料的颜基比,系统研究了涂层的耐候性、附着力、耐水性及阻燃性等性能。结果表明:当采用相对分子质量为800和2 000的PTMG且二者质量比为3∶2时,得到的改性树脂性能最佳。当涂料颜基比为1.1时,制备的涂层具有良好的耐环境适应性、耐水性,吸水率低至0.6%,氧指数为25.8%,拉开法附着力可达25.33 MPa,能够为复合材料提供良好的防护能力,具有广阔的应用前景。