代用燃料在柴油机中的应用研究

本文对植物油,生物柴油,乳化油,乙醇/柴油等的制备和理化特性进行了研究.通过柴油机台架试验,研究了柴油机燃用生物柴油、乙醇/柴油、微乳燃油的排放特性.对比试验表明:生物柴油CO,碳氢(HC)和颗粒物(PM)的比排放下降幅度分别为34.6％,40.2％和28.9％,但NOx比排放增加了6.63％;柴油机燃用乙醇/柴油时,...     

乙醇柴油添加剂对柴油机颗粒排放及其挥发氧化特性影响

研究了乙醇柴油及燃油添加剂对柴油机颗粒排放及其挥发氧化特性的影响。采用热重分析法分析柴油机燃用不同燃料时排气颗粒物的可溶性有机物挥发性、碳烟样品和颗粒物氧化特性。研究结果表明:含添加剂的乙醇柴油颗粒物排放远低于0#柴油的颗粒物排放,降幅在50%以上。颗粒在热失重过程中经历颗粒失水干燥、可溶性物质氧化和烟煤基元发生氧化反应三个阶段。与0#柴油相比,乙醇柴油及柴油添加剂能降低颗粒物中的可挥发部分质量份额,且乙醇柴油的效果最佳。乙醇及柴油添加剂有助于降低碳烟起燃温度和最大氧化速率对应的温度;与0#柴油相比、N5E10、N5E10XY0.1%和N5E10CN0.3%的碳烟最大氧化速率对应的温度依次降低了39、92、146℃。     

自然吸气直喷压燃式发动机燃用柴油醇的性能和排放

应用助溶剂解决了乙醇和柴油相溶性较差的问题并配制柴油醇燃料,分析了柴油醇的主要理化特性,结果表明,柴油醇的黏度、热值和十六烷值有所下降,但汽化潜热却明显增加。自然吸气直喷压燃式发动机不作任何调整,燃用E10柴油醇,动力性和经济性基本不变,燃用E20柴油醇,动力性下降,小负荷经济性恶化。燃用柴油醇,在中小负荷工况,CO和HC浓度排放增加,NOx浓度排放减少;在大负荷工况,CO浓度排放减少,HC浓度排放变化较小,NOx浓度排放增加,排气烟度降低明显。柴油醇中乙醇含量越多,排放性能变化越大。适当推迟供油提前角对压燃式发动机燃用柴油醇的性能有利。     

增压中冷压燃式发动机燃用柴油醇的燃烧和排放

采用助溶剂解决乙醇和柴油相溶性差的问题并配制出柴油醇燃料,在一台增压中冷压燃式发动机循环供油量未作调整情况下,进行了燃用不同乙醇含量柴油醇的燃烧、性能和排放特性试验研究。结果表明：在供油量一致情况下燃用柴油醇,发动机的燃烧特性发生改变,导致性能和排放变化,且随燃料中乙醇含量的增加,变化趋势加剧,尤其小负荷的燃油消耗率及CO、HC排放增加较大。     

柴油机燃用乙醇-生物柴油的性能试验研究

对乙醇和生物柴油的互溶性和抗水性进行了研究,在ZS195型柴油机上进行了燃用生物柴油、乙醇-生物柴油、含水乙醇-生物柴油与纯柴油的经济性与排放特性对比试验研究。试验结果表明:B90E10和B90A10混合燃料能在20℃环境温度下保持良好的物理稳定性;B90E10,B90A10和生物柴油有效燃油消耗率高于纯柴油;CO排放量,在小负荷时趋于纯柴油的排放水平,大负荷时下降;生物柴油NOx排放量在小负荷时高于纯柴油水平,而B90E10和B90A10较生物柴油依次下降,其中B90A10的NOx排放量低于纯柴油水平,大负荷时3种燃料的NOx排放量接近,均高于纯柴油水平;THC排放量均低于纯柴油水平,其中生物柴油下降幅度最大,B90E10下降幅度最小;碳烟排放较纯柴油大幅度下降,且随着燃料中含氧量的增加依次下降。     

乙醇-柴油混合燃料的理化特性的研究

为了有助于开展乙醇柴油混合燃料在发动机上的应用研究，本文开展了不同乙醇掺混比例柴油乙醇混合燃料的主要理化特性的研究。采用数值计算的方法研究了不同乙醇掺混比例对混合燃料的低热值、十六烷值的影响；开展燃料的蒸馏特性试验、粘温特性试验，研究了不同乙醇掺混比例(EO，E10，E20，E30)对混合燃料的蒸馏特性、粘温特性的影响，并对混合燃料的粘温特性试验结果进行数值回归；采用相溶特性试验研究了不同乙醇掺混比例的混合燃料(EO—E100)的相溶特性，以及助溶剂对混合燃料相溶特性曲线的影响。研究结果表明：随着乙醇掺混比例的增加，混合燃料的低热值、十六烷值、粘度逐渐降低，混合燃料的低温蒸馏特性较强，助溶剂可有效解决乙醇柴油的相溶问题。     

不同海拔下直喷式柴油机燃用生物柴油时的性能研究

在大气模拟试验台架上进行了不同大气压下直喷式柴油机燃用0~#柴油(B0)和纯生物柴油(B100)的动力性、经济性、烟度和噪声声压级测量对比试验.结果表明:随着海拔高度的增加,发动机动力性和经济性下降,噪声升高,但海拔对燃用B100发动机的影响小于B0;同一海拔下二者相比,燃用B100发动机实测油耗增加,动力性降低,全负荷时烟度减小.低负荷时二者有效热效率和噪声相差不大,但随着负荷的增加,特别是全负荷时,燃用B100发动机有效热效率明显提高,噪声小于B0.     

乙醇柴油混合燃料发动机的经济性和排放特性的试验研究

在一YC6J170-21车用六缸发动机上进行了添加助溶剂（正丁醇）情况下,无水乙醇与市售0#柴油的混合燃料对柴油机经济性和排放特性影响的研究。试验结果表明：柴油机燃用乙醇柴油混合燃料的油耗率比纯柴油高,并且随乙醇比例的增大油耗率增大,但混合燃料的等热值当量油耗率与纯柴油相差不大,混合燃料的有效热效率比纯柴油高。柴油机燃用乙醇柴油混合燃料后,NOx和碳烟排放大幅度降低,且随着混合燃料中乙醇比例的增加,下降效果明显。柴油机燃用乙醇柴油混合燃料对CO的排放改善不明显,CO排放与原机相当。柴油机燃用乙醇柴油混合燃料后,HC排放比原机增大,且HC排放与混合燃料中乙醇比例及发动机工况有关,乙醇比例越高,HC排放也基本越大。     

高原环境下生物柴油对压燃式发动机性能与排放特性的影响

在高原发动机大气模拟试验台架上,深入研究生物柴油和大气压力对不同型式压燃式发动机性能与排放特性的影响规律与作用机理。研究结果表明:随着大气压力下降,自然吸气柴油机的最大扭矩和有效热效率下降幅度逐渐加剧,其最大扭矩输出随生物柴油掺混比增大先升后降;而涡轮增压柴油机最大扭矩随生物柴油掺混比的增加一直呈线性下降。对于自然吸气柴油机,随大气压力降低,与纯柴油(B0)相比,纯生物柴油(B100)在中高转速全负荷工况时的烟度显著降低。对于涡轮增压柴油机,B100外特性的不透光度相对B0降低幅度随转速增加逐渐减弱,表现出与自然吸气柴油机相反的变化趋势;对于高压共轨柴油机,在低转速全负荷时,B100与B0的功率输出与实测油耗基本相当,B100的有效热效率高于B0。随着发动机转速增加,与纯柴油(B0)相比,B100外特性功率输出逐渐降低,实测油耗升高,有效热效率与B0逐渐接近;不同生物柴油的理化特性对共轨柴油机性能的综合影响差异较小。在相同功率(或扭矩)时,不同生物柴油的燃烧特性和NOx排放特性基本相当;对于碳烟排放,地沟油最高,橡胶籽次之,小桐子最低。     

着火改进剂对乙醇--柴油燃料排放特性的影响

随着乙醇含量的增加，乙醇柴油混合燃料的含氧量增大，但热值、十六烷值和粘度下降。助溶剂可以提高混合燃料的稳定性，着火改进剂能提高它的十六烷值。在发动机上的研究结果表明：柴油机的排放与负荷、掺醇量、助溶剂及着火改进剂有关。大负荷时，随着混合燃料中乙醇含量的增加，烟度明显改善，NOx排放有所降低，但使用乙醇柴油混合燃料时，未燃乙醇和乙醛排放增加，而且CO和总碳氢(THC)排放高于柴油，但助溶剂与着火改进剂能降低CO和THC排放，THC排放甚至低于柴油。     

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.