全尺寸墙角火实验中木工板表面火蔓延研究

对木工板表面火蔓延进行了全尺寸墙角火实验研究，实验是在符合ISO9705标准的ISO ROOM全尺寸实验装置内进行．通过测量材料表面的温度来研究火蔓延的情况，同时还将火蔓延与火灾过程中的重要参数如热释放速率、热流密度和室内温度等进行了比较，分析了相互之间的关系．研究结果为火灾安全设计和计算机数值模拟提供了实验依据．     

胶合板室内火灾行为全尺寸实验研究与模拟分析

选择4种典型的胶合板作为研究对象,即三厘板、五厘板、九厘板和十二厘板,在ISO 9705标准的全尺寸燃烧间(3．6m×2．4m×2．4m)内对其进行全尺寸火灾实验模拟,从热释放速率方面研究了胶合板的火灾行为并获得了室内轰燃发生的时间,分析比较了材料厚度对于胶合板室内火灾过程的影响．同时将顺流(Wind-Aided)火蔓延的理论引入到室内墙角火蔓延中,对胶合板的表面火蔓延进行模拟,得到了胶合板室内火灾的热释放速率和轰燃发生时间．通过比较发现,五厘板、九厘板和十二厘板的计算结果与实验测量结果吻合得比较好,三厘板的计算结果与实验测量结果吻合得比较差些．     

拉萨和合肥环境下不同厚度保温材料XPS的火蔓延特性

分别对不同厚度保温材料XPS在高原地区拉萨和平原地区合肥进行一系列小尺寸火蔓延实验.通过分析在水平放置时,不同厚度保温材料在两地火蔓延过程中一些重要特性参数(火蔓延速度、平均池火长度、火焰侧面积和最高气相火焰温度等)的变化规律,定性地揭示了高原和平原环境对不同厚度保温材料XPS火蔓延特性参数的影响.结果表明,在拉萨火蔓...     

薄片可燃物火蔓延速率的测量与计算

固体可燃物火蔓延速率对于火灾的蔓延有重要的影响。以此为背景，采用热电偶瞬态测温技术，测量了牛皮纸、硬纸板的火蔓延速率。探讨了对流环境下风速的大小对薄片可燃物火蔓延速率的影响，并建立了经验公式。在实验研究基础上建立了薄片可燃物火蔓延速率的简化模型，理论计算与实验结果较为吻合。     

林火蔓延初期的增长模型与室内模拟实验研究

分析了均匀水平燃料床从一个点火源的着火过程,建立了林火蔓延初期的增长模型,采用数值法计算了蔓延初期的加速度与速度的变化趋势,并通过室内模拟实验,在燃料床上测取了林火初期蔓延速度。通过对着火后１００ｓ的实验数据与计算结果的比较,说明所使用的初期蔓延过程的增长模型在物理上是合理的。从实验结果分析看出,在着火后２０ｓ以内,及在着火的８０ｓ－１００ｓ锥形火焰向环形火焰转化时,火蔓延速度与加速度剧烈地波动。     

高原环境下木材表面火蔓延特性的实验研究

在拉萨高原地区和合肥平原地区开展了一系列木材表面火蔓延对比实验研究,通过对火蔓延过程中一些重要特性参数(固相热解温度、气相火焰温度、燃烧区长度和燃烧速率等)的测量,分析了高原地区的火灾危害特性.结果表明,高原地区的固相热解温度与平原差别不大,但是气相火焰温度要略高一些.火蔓延过程中高原地区的燃烧区长度比平原的小,而且两...     

上山火加速过程的模拟计算与实验研究

通过对林火蔓延过程的理论分析,建立了模拟林火进入斜坡后的计算模型,采用数值法计算了林火在斜坡上蔓延的加速度以及初期蔓延过程。同时,在燃料床上进行模拟实验,测取了林火自水平燃料床进入倾斜燃料床后的火蔓延速度和加速度。通过对理论计算与实验结果的比较,说明理论模型是合理的。由实验与理论分析可知,木火灾一旦蔓延进入山坡之后,在大约１到２ｍｉｎ之内,火蔓延的加速度很快达到最大值,随着坡度的增加,火蔓延加速度达到最大值所需要的时间减少。达最大值之后,加速度逐渐减小,直到稳定的蔓延速度。同时发现,林火进入斜坡之后,大约需要２５ｍｉｎ才能达到稳定的蔓延速度,这个结论是通过计算得到的,在实验室内模拟这个过程是很困难的。     

基于红外热像的热塑性材料二维火蔓延速率

利用红外热像技术,对受限空间内热塑性材料熔融燃烧过程中初始发展阶段的固体样品表面的二维火蔓延速率进行了实验研究,分析样品与其下部油盆的间距对样品表面火蔓延速率的影响.在ISO 9705燃烧室内,针对6,mm厚聚丙烯板,考虑了0,cm、5,cm、10,cm、15,cm、25,cm和35,cm共6种不同间距,开展了6组全尺寸火灾实验,记录了样品表面的温度场数据,得到了样品表面火蔓延速率的变化规律.结果表明,由于液体油池火的影响,固体表面二维火蔓延速率随时间呈指数增长关系,且其增长速率随间距的增加而降低.     

微重力燃烧及固体表面火蔓延的研究

本文对微重力条件下单滴燃烧和固体可燃物表面火焰传播过程的研究作了简要评述。微重力条件下单滴燃烧的研究对于认识燃烧过程的物理机理具有重要价值。对于微重力条件下固体可燃物表面的火焰传播过程,指出其主要物理机制是气化表面的“表面燃料喷射”效应,文中还给出了作者对火蔓延过程进行的三维非稳态数值模拟得到的部分计算结果。     

城市危险源对地震次生火灾影响的计算机模拟

城市危险源分布范围较广,有些还以线状和网络状分布在人口、公共设施集中的区域.在地震的作用下,城市中潜在的危险源对地震次生火灾的起火和蔓延都有着重要的影响.着重研究了城市中危险源对地震次生火灾起火的影响,并建立了基于元胞自动机的城市区域火蔓延概率模型.模拟结果再现了火蔓延的过程,不仅提高了人们对城市区域火蔓延危害的认识,而且为城市危险源纳入城市布局和城区建设规划设计提供了依据.     

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

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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.