灭火添加剂对细水雾性质与灭火效能的影响

为了提高细水雾的灭火效能,研究了两种复合细水雾灭火添加剂G1和G2对水的物理化学性质的影响.通过试验研究了G1和G2对水溶液密度、黏度、表面张力、细水雾粒径分布以及灭火效能的影响.结果表明,G1和G2对水溶液的密度和黏度影响不大,G1使水溶液的表面张力和细水雾的雾滴粒径减小,G2使水溶液的表面张力和细水雾的雾滴粒径增大.通过清水细水雾和含G1和G2的细水雾熄灭煤油池火的试验,得到灭火效能的顺序:含G1细水雾＞含G2细水雾＞清水细水雾.分析了含G1和G2的细水雾对煤油池火的抑制熄灭机制,G1和G2中各成分之间的偶合效应提高了细水雾的综合灭火效能,含有G1的细水雾主要是通过提高细水雾蒸发吸热降温效果及气相俘获自由基的作用来提高灭火效能,而含有G2的细水雾主要通过提高大粒径雾滴穿透火羽流,冷却燃烧物表面及气相俘获自由基的作用提高灭火效能.     

含NaCl添加剂细水雾对不同燃料池火灭火性能的实验研究

为了提高普通细水雾的灭火有效性，克服不足之处，研究了含NaCl灭火添加剂的细水雾与油池火相互作用的过程。重点研究了不同质量分数、不同工作压力、不同燃料条件下，细水雾的灭火有效性。研究结果表明，向细水雾中加入NaCl，显影响其灭火性能。细水雾的灭火对间与加入的NaCl质量分数间呈现出“W”形的关系曲线；细水雾喷头工作压力和燃料性质也影响细水雾的灭火性能：工作压力越高，平均熄灭时间越短；在相同的实验条件下，含NaCl添加剂的细水雾熄灭煤油火的时间小于酒精火的时间。含添加剂细水雾的灭火有效性，存在着细水雾与灭火添加剂的最优质量分数配比关系。     

细水雾抑制障碍物遮挡气体池火的缩尺度实验研究

大型仓库等场所由于存在明显的障碍物空间遮挡情形,一旦发生火灾,障碍物势必会对细水雾灭火效果及其作用机制产生影响．通过搭建1/6缩尺度实验平台,利用平面激光诱导荧光(PLIF)及粒子图像测速(PIV)技术,获取了细水雾与障碍物遮挡火焰相互作用的火焰羟基自由基浓度分布及细水雾流场数据．结果表明,细水雾可以有效熄灭最大有效雾量比大于0.59且火焰功率小于3.93 kW的遮挡火焰．PIV拍摄视场下雾滴最大速度随细水雾施加时间的特征规律,揭示了灭火过程中雾-焰相互竞争的动力学机制．     

细水雾抑制气体扩散火焰的机理研究

应用三维LDV／APV系统和热成像方法，测量了细水雾和气体扩散火焰作用过程中的细水雾雾场、火焰温度场并研究了细水雾和气体扩散火焰的作用过程．探索了细水雾抑制火焰的机理和规律，比较了细水雾抑制气体扩散火焰时3种主要灭火机理，用数据定量表征了细水雾灭火时，水雾的蒸发潜热吸热作用、热容吸热作用以及稀释氧气作用对抑制气体扩散火焰所做的贡献，细水雾直接喷射或被卷吸进入火焰内部时，由于表面积大，吸收热量快，迅速汽化，体积扩大。大量的汽化潜热会降低火焰区及气相燃料的温度，细水雾及其蒸汽吸收部分热辐射，降低对燃料的热回馈，减少其汽化蒸发，从而降低反应区的可燃气体积分量。这些因素都会大大降低化学反应速度，抑制火灾的发展，直至扑灭火灾。     

水与K_2CO_3的协同灭火作用

实验研究了惰性灭火介质水与化学灭火介质的协同灭火作用.通过测定纯水、含K_2CO_3添加剂细水雾及K_2CO_3干粉的最小灭火浓度,分析了水与K_2CO_3的结合对两者单独使用时灭火有效性的影响.结果表明:含K_2CO_3添加剂细水雾可以分别提升纯水与K_2CO_3干粉的灭火效能,并且灭火效能随着溶液中K_2CO_3含量的增加而增强.水与K_2CO_3在火焰温度下发挥协同灭火作用的实质是水蒸气的存在对K_2CO_3有一定的活化作用,使其更容易在平衡产物中生成大量的灭火活性物质KOH.     

船舶机舱水雾灭火相似模型分析与设计

以某型3000吨级船舶机舱为原型,根据对船舶机舱火灾蔓延规律的相似理论分析,建立了小尺度船舶火灾模拟实验舱的相似物理模型;确定了船舶机舱细水雾模拟的相似准则关系,并建立了模拟机舱细水雾灭火系统相似物理模型;依据IMO相关细水雾灭火系统有效性评估的实验场景设置和相似模型设计,采用FDS（4.0）对模拟实验舱内细水雾灭火系统进行了数值模拟的实验研究.实验结果表明,在忽略热辐射作用的条件下,对细水雾灭火系统采用相似理论分析,并建立的相似缩比模型可以较好的模拟原型舱室细水雾灭火过程与规律.     

细水雾扑灭油池火的临界条件

通过模拟灭火实验发现细水雾灭火过程中由于雾特性参数的变化而形成两种相异的灭火过程,进而通过理论分析与计算得到了细水雾通过火焰冷却扑灭油池火所需的临界条件,并通过实验室尺度实验与全尺度实验对计算结果进行了验证．在实验中还发现对于下喷式系统而言,细水雾能否穿透烟气羽流层对于细水雾系统能否灭火具有至关重要的影响,为此引入了烟气羽流与细水雾的推力比这一概念,并通过实验确定了采用下喷方式时,细水雾灭火的临界推力比大致为10．     

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。     

细水雾熄灭K类火灾的全尺寸模拟实验

利用ISO 9705全尺寸多功能热释放速率测试仪在开放空间研究了细水雾作用下K类火灾的发展过程,实验中对细水雾作用下食用油火的温度、热释放速率及烟气的主要特性参数变化规律进行了测量与研究,分析了预燃时间对灭火有效性的影响,系统地阐述了细水雾作用下K类火灾关键特性参数的变化规律．实验发现,细水雾可以有效地抑制K类火灾的发展,在其作用下火焰温度及热释放速率快速降低,并可以有效地冲刷烟气,降低一氧化碳及二氧化碳的浓度,提高氧气的浓度及火场能见度．同时利用稳定火源热释放速率模型计算了K类火灾发展阶段的热释放速率,与实验测量结果比较发现,模型可准确地预测K类火灾发展阶段的热释放速率的变化规律．     

全氟己酮及细水雾灭火装置对大容量三元锂离子电池的灭火实验

本工作搭建了锂电池燃烧-抑制实验平台,以额定容量为150 A·h的三元铝壳动力锂离子电池单体为研究对象,采用电加热方法诱导其发生热失控,研究全氟己酮及细水雾灭火装置对热失控锂离子电池的灭火降温效果,测试了不同工况下的灭火时间、最高温度、质量损失、灭火效率.实验结果表明:标准设计下的全氟己酮灭火装置能够快速灭火,最大降温...     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Contents in Volume 23,2014

<正>~~     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.