北京地区太阳紫外辐射的长期变化趋势及分析

对实际天气条件下北京地区1990年1月至1992年8月太阳辐射预测资料进行了详细分析。得到实际天气条件下到达地面的太阳紫外辐射的计算公式。结果表明,计算值与预测值吻合得比较好,利用该式计算了北京地区1979年1月-1996年6月的太阳紫外辐射,讨论了1979-1996年北京地区太阳紫外辐射的变化趋势及不同因子（臭氧、水汽、气溶胶等）对太阳紫外辐射的影响。     

黑龙江漠河地区太阳紫外辐射的统计计算方法

在实际天气下对黑龙江省谟河县１９９７年３月１日至１２日太阳辐射、大气臭氧和气象要素等观测资料进行了详细分析,得到实际天气条件下到达地面的太阳紫外辐射计算公式。计算值与观测值吻合得较好。由北京、广州和漠河地区太阳紫外辐射的计算结果表明,用该方法计算到达地面的太阳紫外辐射是可行的。     

稀疏植被地表分光辐射及其反照率特征研究

利用2015年7~10月份敦煌老金矿稀疏植被下垫面地表分光辐射观测资料,分析该地区地表分光辐射及其地表反照率的变化特征。结果表明,2015年7~10月份,由于季节变化,地表长波辐射及分光辐射均呈下降趋势,地表长波辐射始终大于大气长波辐射。晴天时各波段辐射最强,日变化呈光滑的正弦曲线,阴天辐照度有一定的减弱,日变化曲线呈锯齿型,雨天辐照度明显减弱。近红外、可见光和紫外辐射占总辐射的比例平均分别是0.535、0.420和0.045。各波段地表反照率日变化趋势基本一致,近红外波段反照率最高,依次分别为总辐射和可见光波段,紫外波段反照率最低,平均分别为0.26、0.22、0.19和0.08。地表反照率日变化不对称,早晨高于下午。不同天气的地表反照率也有区别,晴天和阴天的地表反照率变化相对平缓,且阴天大于晴天,雨天时地表反照率明显小于其他天气。     

藏北高原紫外辐射的变化特征

对藏北高原五道梁站及其邻的地区以及一些平均地区站点的太阳此外辐射观测资料进行了分析，并与青藏高原其它地区的观测结果进行对比，讨论了紫外辐射的变化特性及其影响因子。结果表明：１）紫外辐射的基本变化主要受天文因子的影响，其一般变化特征与总辐射有良好的对应关系。２）紫外辐射受大气臭氧含量的影响，其在太阳总辐射中占比例的变化是由大气臭氧含量南北不同的空间分布季节变化造成的。３）紫外辐射受测站海拔高度的影响     

用Lowtran 7进行分光辐射的计算研究(Ⅱ)——UVB测量仪的校准方法及影响UVB的环境因子

太阳的紫外光辐射能量随波长变化极大，与室内紫外标准灯的光谱存在着相当大的差异，如何将室内紫外标准光源标定出的工波段紫外辐射表灵敏度校正到太阳到紫外辐射的灵敏度，是观测和标定工作中必须解决的问题。该文提出了通过太阳紫外光谱测量与模式计算相结合的方法，并利用Lowtran7模式软件所能提供的计算参数，分别计算了3个紫外波段（UV－A，UV－B和UV－C）的辐照度，研究了不同太阳高度角，不同气溶胶，不同海拔高度以及大气中不同水汽和气溶胶含量对3个紫外波辐照度的影响；并以Eppley实验室制造的TUVR宽带紫外辐射表测量的紫外辐照度为例，证明了此类辐射表的测量值，并非就是紫外辐射的总量，而是其中的一部分，其所占比例随大气条件变化而改变。此外通过，证实了在紫外辐射中以散射辐射为主的情况。     

华北平原北部太阳辐射及地表辐射平衡特征——基于河北固城站的试验观测研究

利用位于河北定兴县的中国气象局固城生态与农业试验站2005年7月～2007年2月期间观测的太阳辐射各分量的资料,详细分析了该站太阳辐射及地表反射的基本特征.分别对到达地表的太阳总辐射、地面反射短波辐射、地表反射率、净辐射、光合有效辐射和紫外辐射(UV-B)的日、年变化特征进行了分析,揭示了该地区的辐射平衡特征.同时分析并给出了光合有效辐射和紫外UV-B辐射占太阳总辐射比值的变化规律.     

反照率参数化改进对裸土地表能量和热过程模拟的影响

在陆面过程模式BATS中引入考虑太阳天顶角变化的裸土反照率参数化以改善沙漠、戈壁地表的辐射和热状况模拟,并与观测资料进行了对比。结果表明,各方案不同程度地改善了BATS反照率模拟过高和缺乏日变化等偏差,其中Wang等改进的BRDF和B方案分别使BATS在戈壁地表由-67.75 W·m-2的负偏差缩减到-0.59和0.22W·m-2,感热通量的负偏差缩小了一半,地表温度较大的负偏差控制在1K之内。研究结果肯定了太阳天顶角对裸土反照率计算的重要作用,认为上述方案适用于裸土地表。     

从辐射强度变化分析深圳太阳辐射气象条件

计算太阳辐射典型年,对与到达地面太阳辐射强度变化密切相关的气象和环境因素进行分析研究,总结出深圳太阳辐射气象条件,运用典型天气进行验证。结果发现:1)温度、相对湿度、降水量、云量、最大风速的风向、沿海站的极大风速和大气气溶胶均与到达地面太阳辐射强度有不同程度的关联,云量与直接辐射呈显著的负相关;2)一天中深圳太阳总辐射最大值出现在11:00～12:00,太阳有效辐射时间为05:00～18:00;月总辐射和直接辐射最大值均出现在每年中的6～7月份;3)辐射强度与空气质量指数(AQI)相关性明显,大气污染物对直接辐射起到较明显的削弱作用,其中O3与辐射关联度较大,其次PM2.5、PM10等在傍晚时对辐射具有一定的削弱作用;4)前汛期云量和水汽、降雨等对辐射的影响作用大。     

利用我国气象卫星遥感资料估算黄河源区净辐射辐照度的研究

以黄河源区为研究区域,利用我国静止气象卫星(FY-2D)及极轨气象卫星(FY-3A)资料,估算黄河源区一天中不同时刻的净辐射辐照度的空间分布。在晴天条件下,利用计算的向下太阳辐射照度,结合卫星遥感资料估算的地表反照率,得出地表太阳辐射收支。利用卫星遥感估算地表发射率和地表温度资料,结合地面观测站的气象观测资料,得到大气向下的长波辐射和地面向上的长波辐射值。在阴天条件下,借助FY-2D云顶的反照率资料,根据太阳辐射在大气中的衰减过程,推求透射比系数,进而得出阴天条件下地表净短波辐射照度。     

太阳辐射在理想大气中的衰减

根据世界气象组织仪器和观测方法委员会最近建议采用的太阳常数和太阳光谱辐照度,以及最新的臭氧和分子散射的光谱透明度资料,对理想大气中的太阳辐射重新进行了计算。以表格形式给出了理想大气中大气光学质量1—10情况下各波段的以及全波段的太阳直接辐射值。     

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.     

Contents in Volume 23,2014

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Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

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%.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

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.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

Controls on the Karaha–Telaga Bodas geothermal reservoir,Indonesia

Karaha–Telaga Bodas is a partially vapor-dominated, fracture-controlled geothermal system located adjacent to Galunggung Volcano in western Java, Indonesia. The geothermal system consists of: (1) a caprock, ranging from several hundred to 1600 m in thickness, and characterized by a steep, conductive temperature gradient and low permeability; (2) an underlying vapor-dominated zone that extends below sea level; and (3) a deep liquid-dominated zone with measured temperatures up to 353 °C. Heat is provided by a tabular granodiorite stock encountered at about 3 km depth. A structural analysis of the geothermal system shows that the effective base of the reservoir is controlled either by the boundary between brittle and ductile deformational regimes or by the closure and collapse of fractures within volcanic rocks located above the brittle/ductile transition. The base of the caprock is determined by the distribution of initially low-permeability lithologies above the reservoir; the extent of pervasive clay alteration that has significantly reduced primary rock permeabilities; the distribution of secondary minerals deposited by descending waters; and, locally, by a downward change from a strike-slip to an extensional stress regime. Fluid-producing zones are controlled by both matrix and fracture permeabilities. High matrix permeabilities are associated with lacustrine, pyroclastic, and epiclastic deposits. Productive fractures are those showing the greatest tendency to slip and dilate under the present-day stress conditions. Although the reservoir appears to be in pressure communication across its length, fluid, and gas chemistries vary laterally, suggesting the presence of isolated convection cells.     

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.