甲醇/柴油双燃料发动机的性能

在一台柴油机基础上，采用气道口电控喷射甲醇，缸内柴油引燃甲醇的方式，开发了电控甲醇／柴油双燃料样机，并通过发动机台架实验，研究了柴油／甲醇双燃料燃烧模式在燃烧特性、燃油经济性及排放性能方面的特点．与原发动机相比，双燃料模式的最高爆发压力下降，压力升高率上升，排烟和NOx大幅度下降，但THC和CO排放均升高．该方法能使甲醇喷射量得到精确控制以便燃烧达到最佳状态，是甲醇／柴油双燃料发动机可行的技术方案．     

甲醇／柴油双燃料发动机工作区域的试验研究

在TY1100单缸柴油机的进气管上安装了电控甲醇喷射装置,采用柴油引燃甲醇双燃料工作模式,开展了甲醇/柴油双燃料发动机工作区域的试验研究.结果表明:双燃料发动机存在由熄火界限、工作粗暴界限和碳烟排放界限三者组成的工作区域.在此区域内,甲醇/柴油双燃料发动机的万有特性曲线中最经济区域位于发动机中高转速和中高负荷区,且随着引燃柴油量的增加向发动机高转速区域移动.随着甲醇质量分数的增加,发动机Nox和碳烟排放可以同步降低.     

LPG/柴油双燃料发动机的试验研究

LPG/柴油双燃料发动机以其高效率,低污染成为最有前景的发动机之一.本文以485柴油机为样机,在LPG/柴油双燃料方式下对发动机的动力特性以及排放特性进行了台架试验研究.试验结果表明,LPG/柴油双燃料发动机可以在保持原机高功率的前提下,降低原机的排放量,尤其是烟度和NOx的排放.     

LPG／柴油双燃料发动机的试验研究

LPG／柴油双燃料发动机以其高效率，低污染成为最有前景的发动机之一，本文以485柴油机为样机，在LPG／柴油双燃料方式下对发动机的动力特性以及排放特性进行了台架试验研究，试验结果表明，LPG／柴油双燃料发动机可以在保持原机高功能的前提下，降低原机的排放量，尤其是烟度和NOx的排放。     

柴油/天然气双燃料发动机控制系统设计

利用自主设计的双燃料发动机的控制系统,将高压共轨柴油机改装成双燃料发动机。该系统包括天然气供给系统、控制单元(ECU)及其配套传感器等。发动机起动和怠速时在纯柴油模式下运行,当负荷达到某一设定值时,柴油ECU减少引燃柴油的喷射,同时天然气ECU增加天然气量的喷射,发动机在双燃料模式下运行。台架试验结果表明:在不同工况下,天然气平均替代率达到75%,最高替代率达到90%。     

甲醇替代率对柴油/甲醇反应活性控制压燃发动机性能的影响

对某4缸高压共轨柴油机进气歧管进行改造,搭建了柴油/甲醇双燃料反应活性控制压燃(reactivity controlled compression ignition,RCCI)发动机专用试验台架,系统地研究了甲醇替代率对发动机经济性和污染物排放的影响规律.结果表明:最大转矩转速1600 r/min下,负荷率25％～50...     

液化气／柴油双燃料发动机试验系统研制

对液化气作为柴油机的代用燃料进行了研究,讨论了立式１９５Ｔ液化气／柴油双燃料发动机的改装、运转及控制原理等问题,介绍了双燃料试验系统采用的方案,主要零件的结构和功能以及台架性能试验结果。     

8240ZCDF型柴油-天然气双燃料发动机开发试验

在8240ZC型柴油机的成熟技术基础之上设计开发了8240ZCDF型柴油-天然气双燃料发动机。本文介绍了8240ZCDF型双燃料发动机的主要技术参数、试验系统以及性能开发试验等内容。试验结果表明,发动机各项性能指标满足设计要求。8240ZCDF型双燃料发动机已完成了中国船级社型式认可试验。     

双燃料控制系统在船用发动机上的应用研究

为进一步提高C8190型发动机的性能,使双燃料控制系统在船用发动机上得到应用,在C8190型发动机上配装双燃料控制系统。该控制系统具有纯柴油模式和双燃料模式自动切换功能,满足中国船级社(China Classification Society,简称CCS)要求。通过纯柴油模式和双燃料模式下的推进特性试验,测试该控制系统的性能以及发动机的运行情况。试验结果表明,在双燃料控制系统的控制下,C8190型船用发动机运行平稳,各项性能指标均满足设计要求,可推广应用于船用发动机及其他机型。     

一种新型双燃料发动机控制系统的应用研究

在一款六缸多点喷射船用双燃料发动机上进行新型双燃料发动机控制系统的应用研究。为测试该控制系统的性能,在纯柴油和双燃料模式进行了发动机推进特性试验。试验结果表明:在控制系统的作用下,该船用双燃料发动机运行平稳,各项性能指标均达到设计要求。标定工况下:燃气替代率大于70%;纯柴油模式下烟度为1.90 FSN,双燃料模式下烟度为0.13 FSN。节能减排效果明显。     

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%.     

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.     

Contents in Volume 23,2014

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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.