车用柴油机排放控制的研究现状及前景分析

随着柴油机排放标准的日益严格,柴油机排气污染治理措施愈来愈受到重视,针对目前国内外的研究状况,从机前处理、机内净化和机外处理三方面叙述了国内外柴油机排放控制的最新技术及其应用现状,并就柴油机排放控制的发展前景进行了展望。     

车用柴油机排放控制技术的探讨

简要介绍了车用柴油机排放污染的成分与形成机理,针对目前国内外的研究状况,从燃料品质、柴油机机内净化和排气后处理3方面概述了控制柴油机排放的技术措施,并总结了车用柴油机达到排放标准所需采取的技术对策。     

车用柴油机排放控制现状与技术进展

本文简要介绍了车用柴油机排气污染的特点，分析了我国车用柴油机排放控制现状和存在的主要问题。针对目前国内外的研究状况，从燃料、燃烧和排气后处理三方面概述了控制柴油机排放的技术措施，并总结了车用柴油机达到欧一Ⅲ排放标准所需采取的技术对策。     

车用柴油机排放控制技术进展

简要介绍了车用柴油机排气污染的特点。针对目前国内外的研究状况,从燃料、燃烧和排气后处理三方面概述了控制柴油机排放的技术进展。     

YC6L-40欧Ⅳ柴油机燃烧开发

在欧Ⅲ柴油机基础上,研制出满足欧Ⅳ排放的YC6L-40柴油机,该机采用SCR机后处理技术降低NO_x排放,采用机内净化措施控制颗粒排放。燃烧开发采用提高喷射压力,调整喷油提前角,优化燃烧室,减小喷孔直径等措施,使颗粒排放降低70%,并且改善了经济性,与欧Ⅲ柴油机相比,实际使用燃油耗降低6%。     

降低柴油机NOX排放的机外措施

NOx是柴油机排气中的主要有害排放物，机外措施是控制柴油机NOx排放的有效措施，是柴油机排放控制的关键技术之一。本文介绍的降低柴油机NOx排放的机外措施有：稀NOx技术，等离子体技术，NOx的吸附一催化技术，选择性催化还原技术。     

柴油机废气排放控制技术新进展

首先论述了柴油机的主要排放污染物,概述了目前公认的排放物生成机理。在此基础上,分析了控制柴油机排放的机内和机外净化措施,特别是采用电控技术优化燃烧过程、用还原法降低NO X的SCR法、用微粒过滤器降低PM。最后,展望了柴油机废气排放控制技术的发展趋势,并讨论了在我国为降低柴油机排放所采取的技术路线。     

减少柴油机暖机阶段HC排放的控制策略研究

柴油机在起动后的暖机过程中排出大量含有未燃碳氢(HC)的蓝烟，给人类健康和社会环境都带来极大的危害。本研究提出降低柴油机暖机阶段未燃HC排放的控制策略，并在试验基础上对不同转速与负荷时柴油机的HC排放浓度和HC排放总量进行了比较与分析，找到一种HC排放浓度和HC排放总量都较小的工况作为柴油机的暖机工况，证实了优化控制的可行性。     

减少柴油机NO_x排放的机外措施

控制柴油机有害气体排放不外乎采用机内措施和机外措施．本文着重介绍了降低柴油机ＮＯＸ排放的 ＳＮＣＲ、ＳＣＲ、ＮＳＣＲ、ＮＳＲ、ＳＮＲ等机外措施．     

内河船舶柴油机排放法规及应对措施试验研究

介绍了我国内河船舶柴油机气态污染物排放控制法规。选取某型内河船用主推进柴油机开展原机排放台架测试试验。基于法规限值要求,制定了降低该柴油机排放措施,即加装选择性催化还原系统。试验结果表明:该型柴油机在加装了SCR后处理系统后,排气污染物中CO、HC+NO_x比排放满足法规限值要求,且对柴油机油耗率、压降等性能影响较小。最后,对柴油机颗粒物排放处理措施进行了探讨,可为内河船舶柴油机排放治理技术路线的选择提供参考。     

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.