摩托车催化性能考核台架换热器的设计及试验

催化器性能评价试验中,需要调节、控制催化器的入口温度,本文设计了冷轧翅片管、整体轧制式、U型管壳式换热器和单程管壳式换热器,并对四种换热器进行了比较,选定冷轧翅片管换热器进行试验,试验结果表明设计的冷轧翅片管式换热器能够较好的对催化器入口温度进行控制,实用性较好。     

摩托车催化性能考核台架换热器的设计及试验

催化器性能评价试验中,需要调节、控制催化器的入口温度,本文设计了冷轧翅片管、整体轧制式、U型管壳式换热器和单程管壳式换热器,并对四种换热器进行了比较,选定冷轧翅片管换热器进行试验,试验结果表明设计的冷轧翅片管式换热器能够较好的对催化器入口温度进行控制,实用性较好.     

摩托车催化器性能考核台架试验中换热器的研究

催化器性能评价试验中，起燃特性和温度特性是两个重要性能，这两个特性的研究都需要对催化器入口温度进行稳定连续的调节。本文设计了冷轧翅片管、整体轧制式、U型管壳式换热器和单程管壳式换热器，通过比较，选定冷轧翅片管换热器进行温度特性和起燃特性试验，试验结果表明该换热器能够达到设计要求，对温度的控制也比较稳定。     

摩托车催化转化器性能台架评价装置改进及试验研究

针对原摩托车催化转化器台架性能评价存在控制精度不高及调整不方便的缺点,对评价试验装置进行了改进。采用电控系统控制空燃比,设计了翅片管式换热器调节催化器入口温度。试验表明,改进后空燃比的波动可控制在0.1以内,入口温度波动在±2℃以内。利用该台架对MLKV 102-2催化器的性能进行了研究,试验结果表明该台架可以快速有效地评价催化器的性能。     

摩托车催化转化器性能台架考核装置改进

摩托车催化转化器性能台架考核方法,可以快速有效的评价催化器的性能.在本文中对原有的试验装置进行了改进.设计了电喷系统对空燃比进行调节,设计了换热器对催化器入口温度进行调节.试验结果证明改进后的装置可以提高空燃比和入口温度的控制精度,满足快速准确的评价催化器性能的要求.     

摩托车催化转化器性能台架考核装置改进

摩托车催化转化器性能台架考核方法,可以快速有效的评价催化器的性能。在本文中对原有的试验装置进行了改进。设计了电喷系统对空燃比进行调节,设计了换热器对催化器入口温度进行调节。试验结果证明改进后的装置可以提高空燃比和入口温度的控制精度,满足快速准确的评价催化器性能的要求。     

基于前馈-自抗扰算法的换热器动态试验温度控制研究

为了使换热器试验测控系统满足动态换热试验中对温度控制的要求,分析了试验系统中被控温度对象动态模型,设计了前馈-自抗扰温度控制算法。动态换热试验对象为管壳式换热器,试验过程管程流体为强迫对流换热,壳程流体自然对流换热,同时管程流体循环利用,要求控制管程入口温度稳定。控制算法全面利用模型信息,将壳程温度作为管程温度控制中的干扰,为其设计前馈补偿,同时设计自抗扰控制算法,处理模型偏差问题。利用AMESim软件搭建系统模型,在Simulink中设计控制算法,进行了AMESim/Simulink联合仿真,通过对比多种控制算法,验证了在壳程温度变化干扰的换热过程中,使用前馈-自抗扰控制算法能够使管程入口温度波动更小,更快达到稳定。     

柴油机SCR系统催化器温度场试验解析

本文针对一款国五SCR催化器,采用发动机台架试验的方法研究了SCR样件温度场的关键特征,包括SCR催化剂前后温度、催化器外壳温度、喷嘴处温度等,比较了SCR催化剂温度传感器与发动机台架上催化器进出口排气温度测试结果的差异。研究表明:SCR催化器外壳体温度较高;稳态工况下,该样件的SCR入口温度测量值明显比台架的入口温度测量值偏小,在SCR出口处,二者的偏差很小;瞬态循环中SCR样件的温度传感器与台架温度传感器测量值偏差更为明显,由于动态响应的原因,样件的前温传感器测试结果滞后于台架测试结果;尿素不喷射条件下,尿素喷嘴处可以达到很高的温度,可能出现尿素管接口失效。     

摩托车催化器性能及快速老化台架评价试验研究

根据国内外汽车催化器性能台架评价方法 ,结合摩托车工作特点 ,建立了摩托车催化器性能及快速老化台架评价试验装置。采用该装置可以实现催化器快速老化所需要的高温氧化条件 ,老化中空燃比波动模式和老化时间可变动调整 ,可评价催化器的空燃比特性、起燃温度特性、空速特性和起燃时间特性。试验结果表明 ,上述试验装置可以满足试验要求 ,结果可靠     

基于模型的DPF再生温度控制策略开发及验证

为精确控制柴油机颗粒捕集器(diesel particulate filter, DPF)的再生温度,避免因再生失控引起的DPF失效风险,在柴油机氧化催化器(diesel oxidation catalyst, DOC)和DPF组成的后处理系统上建立基于化学反应动力学原理的DOC温度模型,在温度模型和再生温度控制算法的基础上设计DPF再生温度前馈及反馈控制策略;利用发动机台架测试数据进行控制策略联合仿真,对控制参数进行系统整定及优化;通过发动机台架瞬态及稳态工况测试,验证控制策略的实际应用效果。仿真和台架试验结果表明：DPF再生温度控制策略具有很好的动态性能及稳态性能,最大峰值温度及燃油喷射量均控制在限定范围,可确保DPF实现高效可靠的再生。     

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.     

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.     

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.