LPG喷射形式对发动机性能的影响

针对LPG进气道气态喷射、进气道液态喷射和气缸内液态直接喷射对发动机性能的影响，进行了理论分析和在F170汽油机上的对比试验。试验结果表明：液态LPG缸内直接喷射发动机的最大扭矩比燃用汽油时提高约10％，能有效解决LPG常规供应方式发动机动力性下降的问题。     

LPG摩托车发动机喷射方式的研究

阐述了LPG摩托车的发展及存在的问题。在试验研究的基础上，分析了LPG摩托车进气道气态喷射、进气道液态喷射和缸内液态直接喷射对发动机动力性和排放的影响。提出采用液态喷射可以提高LPG摩托车发动机的动力性，是未来LPG摩托车的发展方向。     

小型发动机燃用汽油、乙醇和LPG燃料的排放对比

对125mL发动机燃用汽油、乙醇和液化石油气(LPG)时的过量空气系数和点火提前角与排放性能之间的关系进行了试验研究．指出了影响这三种燃料发动机排放性能的敏感参数的合理取值范围．通过对比试验，验证了发动机燃烧乙醇可降低NOx排放浓度．发动机燃烧LPG时，低HC排放的空燃比范围比其它两种发动机空燃比范围广．研究结果可为小型汽油、乙醇和LPG发动机参数匹配提供参考。     

汽油发动机燃用LPG的燃烧性能数值模拟及试验研究

应用GT-POWER软件和化学动力学软件CHEMKIN建立了汽油发动机工作过程计算模型,并用试验结果进行了验证。在此基础上对汽油发动机燃烧LPG时的动力性能及经济性能进行了变参数研究。模拟结果表明,在相同工况条件下,随着压缩比的增大,燃用LPG发动机的经济性和动力性能都有所提高,但同时爆震指数也相应增加。随着空燃比的增加,发动机的经济性能和动力性能均先提高后降低,空燃比对缸内层流燃烧速度和绝热火焰温度影响较大。     

摩托车发动机电控喷射LPG/汽油双燃料系统的试验研究

介绍了电控喷射LPG／汽油双燃料系统及控制方法,并进行了系统和原机对比的排放试验及LPG喷射量对发动机性能的影响试验。试验结果表明：LPG／汽油双燃料系统可以大幅降低CO、HC排放;在稳态工况下,较小的LPG喷气量变化,对发动机混合气空燃比和动力性影响不大,而对排放性能影响较大。     

汽油—液化石油气（LPG）两用燃料发动机的研究

介绍了汽油－液化石油气（LPG）两用燃料发动机空燃比的调节和作者研制成功的无混合器式双蒸发器LPG供气系统,该供气系统取消了LPG发动机惯用的混合器,在原机双腔化油器的主、副腔喉管处钻孔,接入LPG主供气系和LPG加浓系,从而取消了混合器,解决了全负荷时动力性与部分负荷时燃料经济性、排放之间的矛盾,取得了良好的效果。用该系统改装的汽油－LPG两用燃料发动机,在燃用汽油时性能无任何变化,燃用LPG时取得了动力性、燃料经济性和排放指标俱佳的效果。     

空燃比对LPG发动机排放特性影响的研究

介绍了与叉车配套的柴油机改装成燃用液化石油气（LPG）发动机的台架试验结果，作者针对叉车发动机的常用运行工况，采用宽域空燃比氧传感器（UEGO）的电控单元来控制发动机的空燃比，得到了在中，高转速下的HC，CO，NOx，排气温度同空燃比的关系，试验结果表明空燃比对LPG发动机排放影响极大，为了得到较好的排放性能，需要随工况的变化精确地控制空燃比。     

LPG／汽油双燃料发动机排放规律的试验研究

介绍LPG／汽油双燃料发动机的排放特性,主要分析燃用LPG时发动机的排放规律,并对比分析了燃用汽油和燃用LPG时发动机的排放规律。     

液态喷射LPG发动机掺氢燃烧的研究

通过对LPG发动机技术与氢发动机及其双燃料发动机的研究现状的分析,结合LPG液态喷射实验特点,提出了液态喷射LPG发动机掺氢燃烧的构想。设计了液态喷射LPG发动机掺氢燃烧的燃料供应系统和控制系统,重点考察了该发动机掺氢燃烧时的性能及排放特点。     

轻便摩托车发动机燃用液化石油气与排气催化净化研究

本文对燃用液化石油气(LPG)加配金属载体的稀土贵金属催化净化装置的幸福XF135QMA-2轻便摩托车发动机的排放特性进行了试验研究，并与燃用汽油的排放特性进行了比较。结果表明：与燃用汽油相比，LPG能使摩托车发动机CO、HC排放有效降低，加配催化净化技术后能进一步降低排放。     

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.