低温地板辐射供暖节能作用分析

低温地板辐射供暖地板与外围护结构内表面存在辐射换热，散热器供暖房间的散热器附近以及散热器上部热气流与外围护结构存在热流短路。文章在低温地板辐射供暖室比散热器供暖房间室内设计温度降低2℃的情况下，分别对三个典型地区这两种供暖方式在上述情况下造成的房间热负荷和供暖季平均耗热量进行计算。结果表明此条件下，低温地板辐射供暖房间的热负荷可降低10％～15％，节能率约为15％～20％。     

抛罩-展开期间航天器太阳电池阵温度场的数值模拟

将太阳电池板中发生的辐射-传导复合传热过程等效为一个无内热源的三维瞬态热传导问题。根据实测数据得出太阳电池板的三维等效导热系数。针对任意两相邻电池板表面间的热辐射交换规律，构造适用于这两个表面内节点温度的离散方程系数。研究折叠状太阳电池阵边界节点的热特点时，仔细考虑了地球红外辐照、太阳辐射加热、航天器舱体几何遮挡、深冷环境散热、飞行轨道高度及航天器在太阳-地球系中不同位置等造成的影响。采用SIP算法，对离散方程进行了求解。比较了考虑和不考虑地球红外辐射电池阵温度分布的影响。该文的分析对折叠状太阳电池阵展开时刻的认定有重要 的参考价值。     

内插式太阳能真空管空气集热器性能分析

建立了内插管式真空管空气集热器管内空气流动与换热的三维瞬态模型,该模型能够反映真空管吸热层表面辐射热流随时间和各微元位置不同而变化的特点。对不同工况下集热器的主要性能参数及内插管与真空管吸热体表面的温度分布进行预测。同时对横双排内插管式真空管空气集热器进行实验研究,理论和实验相结合,分析了不同工况下集热器的集热温度、瞬时集热效率、热损系数等性能参数,该集热器春夏季在30～80℃的集热温度范围内,集热效率在50%～70%之间,热损系数集中在2～6W/(m~2·K)的范围内。     

周期热作用下房间辐射传递函数实验研究

为了更加准确地计算大空间分层空调辐射转移负荷,本文通过壁面对流辐射分离的实验方法获得房间在周期热作用下,变房间换气次数和变壁面发热量时的辐射得热和辐射负荷,并采用最小二乘法求得房间辐射传递函数系数。采用传递函数法也可求得辐射负荷,对比分析两种方法获得的辐射负荷与热平衡实验辐射负荷结果,前者采用对流辐射分离实验方法获得的辐射负荷与热平衡实验结果比较,完整周期内平均相对误差7.4%,而后者传递函数法计算获得的辐射负荷在完整周期内各工况平均相对误差为10.5%。上述结果表明,两种变参数条件下,辐射传递函数受壁面热流与换气次数变化的影响均可忽略,且房间各壁面辐射负荷变化规律相似,其中加热面对立面的辐射负荷最大,且其在完整周期内的辐射负荷均值随壁面热流增加呈非线性增加,随换气次数增加近似线性降低,进一步验证了通过实验获得房间辐射传递函数方法的可行性,为大空间辐射转移负荷的研究奠定了实验基础。     

形状记忆复合材料可展桁架在轨热分析

传统星载桁架结构需通过驱动器实现展开/收拢动作,应用形状记忆复合材料可突破该限制。对新型可展桁架各组件进行热控方案设计,基于I-DEAS/TMG软件建立热分析数值模型,对桁架各组件在轨外热流以及温度场变化进行计算分析。结果表明:最外端桁架在轨运行4个周期后其温度场呈周期性变化特征;不同多层隔热材料(multi-layer insulation material,MLI)表面辐射特性对内/外端纵杆温度影响明显;热控方案能实现有效的在轨温度控制。     

柴油机缸内瞬态辐射换热实验研究

本介绍了作研制的内燃机缸内瞬态传热研究应用的总热流与辐射热流传感器。应用过渡状态的测试方法，尽可能减少了燃烧室内积碳对传感器的污染，从而提高了瞬态辐射热流的测试精度。实测单缸风冷柴油机缸内局部瞬态辐射热流的结果表明，瞬态辐射热流主要发生在压缩上止点及之后５０°ＣＡ￣７０°ＣＡ；循环平均辐射热流与实测总热流平均值比较，辐射热流占总热流的相对值可达２０％以上；随柴油机负荷增大，其相对值呈上升趋势。     

两相流喷雾冷却持续散热表面的方法研究

针对固体激光设备、电子设备以及能源系统热管理系统热流密度过高、换热效率较低以及耗能较大的难题,提出两相流喷雾冷却新方案。利用控制变量法,通过模拟与实验研究喷雾冷却过程中热沉表面温度变化趋势、热沉表面温度分布规律、换热系数变化规律。研究表明：气液两相流喷雾可以实现快速均匀的冷却;热沉表面温度随被冷却物体底面热流密度的增加而增加,底面的热流密度为20 W/cm²时,热沉表面温度最低,为35.6℃;热沉表面的换热系数随被冷却物体底面热流密度值的增加而增大,底面的热流密度为90 W/cm²时,热沉表面换热系数最高,为13 165.9 W/(m²·K)。     

冷辐射地板系统的实验研究

为了研究冷辐射地板系统的热工性能，测试了地板辐射供冷系统的运行工况，得到了地板表面的最低温度、室内的实感温度、热流密度等参数，并初步探讨地板辐射供冷系统结露现象及防治措施，通过实验分析指出这是一种舒适、节能的供冷方式。     

常热流密度矩形管内层流对流换热系数的数值计算

利用数学模型的数值计算探讨了常热流密度条件下矩形管内层流对流换热表面传热系数随流速的变化规律。通过一个算例计算,并给出了该算例的表面传热系数与水流流速的拟合式。根据计算结果发现,对流换热表面传热系数随管长逐渐减小,之后稳定在某个数值,其分布类似外掠平板层流对流换热;流速也影响表面传热系数的大小;而热流密度对换热效果没有影响。把算例的结果与传统的等效直径圆管算法比较,发现后者的误差较大。     

太阳能烟囱强化自然通风实验研究

实验探讨了高2000mm,长1000mm的竖直集热板屋顶式太阳能烟囱模型,在改变宽度及热流密度的情况下,研究其诱导的空气量及内部空间气流温度场和速度场的变化.结果表明,在研究范围内自然通风量随烟囱宽度、热流密度的增加而增大,气流速度随热流密度的增加而增大,随烟囱宽度的增加而降低.气流温度及速度在烟囱热壁近壁面处高于其在远离壁面处,在热壁近壁处形成了温度和速度边界层.     

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。     

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.     

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.