应用MPC-相继增压系统改善船用柴油机低负荷性能的研究

采用ＭＰＣ－相继增压系统来改善船用柴油机低负荷性能,提高其经济性。应用“改进容积法”,建立了ＭＰＣ－相继增压柴油机的计算模型,并编制了计算程序,对ＰＡ６－２８０柴油机采用该系统进行了理论计算,计算结果与法国同机型试验结果基本吻合,并在１２ＶＰＡ－２８０柴油机上进行了试验研究。试验结果表明,采用该系统,ＰＡ６－２８０柴油机在（４００～７００）ｒ／ｍｉｎ时,柴油机功率平均提高到２５０％,烟度降低了６６％,涡轮进口温度降低３０％,取得了较好的效果,改善了船用柴油机低负荷性能。     

可变进排气供油正时涡轮增压柴油机的研究

提出了一种改善车用高速增压中冷柴油机低速大扭矩性能的自动变进排气供油正时（ＡＶＩＥＩＴ）涡轮增压系统,阐述了ＡＶＩＥＩＴ系统的基本原理。     

柴油机涡轮增压系统研究现状与进展

从不同方面分析了柴油机涡轮增压系统的研究现状与发展：在排气管系方面,为了改善８缸柴油机的低工况性能,推出了ＭＩＸＰＣ系统,它具有替代常规增压系统──定压系统、脉冲系统、脉冲转换系统及ＭＰＣ系统的趋势;在涡轮增压器方面,使用可变截面涡轮增压器是未来的发展趋势;在配气及供油正时方面,采用可变正时技术是未来的发展趋势,并且设计可变正时幅度大、结构简单、控制可靠的变正时机构是研究的核心,相应地出现了顾氏系统及ＡＶＩＥＩＴ系统;在专门的控制系统方面,发展了进排气旁通系统及相继增压系统,以改善高增压柴油机的低工况性能．文章指出,柴油机涡轮增压系统的发展须围绕如何改善高增压柴油机低工况性能这一核心问题展开,同时应综合考虑各方面因素,以发展新型有效的涡轮增压系统．     

高增压系统相继增压技术的试验研究

本文报告了在一台ＭＷＭＴＢＤ２３４Ｖ８柴油机上所进行的相继增压试验研究结果．试验结果表明,相继增压系统不但可有效解决高增压后的柴油机低工况性能问题,而且能改善标定点的运行性能,从而可在整个运行范围内改善高速高Ｐｍｅ柴油机的工作性能。本文关于高增压系统相继增压技术的研究成果可用于高速高Ｐｍｅ柴油机增压系统的开发,提高高增压柴油机的性能指标与技术水平．     

柴油机新型螺旋流排气系统的设计和试验

采用数学规划优化方法对Ｎ８１６０ＺＣ柴油机新型螺旋流排气系统结构参数进行了优化设计;同时设计了一套结构参数完全一致的ＭＰＣ排气系统,并对螺旋流和ＭＰＣ排气系统进行了推进特性性对比实验。实验结果表明：在大部分运行工况下,螺旋流排气系统对Ｎ８１６０ＺＣ柴油机的整机性能有一定程度的改善,但在低速低负荷工况下较ＭＰＣ排气系统稍差。     

柴油机涡轮谐振复合增压技术的应用

探讨了四缸柴油机采用谐振复合增压系统的可能性。试验结果表明，设计的国产Ｒ４１００ＺＴ型柴油机的谐振复合压系统，改善了增压柴油机的低速扭矩特性，并使整机性能有一定改善。     

供油系统调整对VNT柴油机低速性能影响

基于PW泵的常规供油系统增压补偿器的存在使得可变喷嘴增压器（VNT）对柴油机性能改善不明显。研究了供油系统参数调整对VNT增压柴油机低速全负荷性能的影响。结果表明：使增压补偿器压力室与大气相通以屏蔽增压补偿器并优化VNT开度后，由于供油量减小，低速全负荷排气烟度比装配GT35增压器的基础柴油机下降56．3％～73．5％，但动力性改善不明显；屏蔽增压补偿器、调整油泵供油特性并优化VNT开度后低速全负荷工况烟度下降53．8％～68．1％，同时1000r／min全负荷转矩增加8．2％。可见，基于电控供油系统的柔性供油特性可以更充分地发挥VNT系统潜能。     

改善车用增压柴油机低速扭矩特性的技术途径

讨论了改善涡轮增压柴油机低速扭矩特性所采取的各种解决方案。着重分析了废气旁通涡轮增压和可变截面涡轮增压对改善发动机低速扭矩性能的效果。     

内燃机增压系统一维非定常流混合模型的研究

建立了用于内燃机增压系统流动模拟的零维与一维相结合的非定常流动混合计算模型。计算实践表明,该模型在各种计算条件下,排气压力波预测精度较高,计算流量误差一般均小于１％ ,而且计算稳定。所编制的内燃机增压系统一维非定常流混合模型计算源程序具有较强的通用性,可适用于组合式ＭＳＥＭ、ＭＰＣ、脉冲、脉冲转换器和ＭＩＸＰＣ涡轮增压系统     

Z6V190—2型柴油机增压匹配的试验研究

本文主要介绍Ｚ６Ｖ１９０－２型柴油的研制过程中，为改善柴油机和各项性能指标所进行的增压匹配的试验研究工作，说明了压气机，涡轮机结构参数的调整及其对柴油机性能的影响和供油提前角的调整对柴油机性能的影响，并指出增压匹配调整试验是增压柴油机研制，过程中的一个十分重要的环节。     

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.