单缸试验柴油机进气压力的自动调节研究

以单缸试验柴油机的模拟增压系统为研究对象,通过对单缸机进气压力调节的模拟分析与应用试验验证,开发了一种由计算机数据采集系统控制的进气压力的自动调设方法,使单缸试验中进气压力调节的时间大为缩短,     

可控脉冲增压系统对D6114柴油机性能影响研究

可控脉冲增压系统可以实现气缸相对排气容积的调节,具有兼顾发动机高低转速工况的优势。本文针对D6114ZLQB型柴油机,建立了该发动机可控脉冲增压系统GT-POWER仿真模型,通过不同排气容积条件下发动机性能试验校核了仿真模型。计算研究了不同转速下可控脉冲增压排气系统排气压力波和进气压力变化规律,探讨了脉冲增压系统和准定压增压系统在不同转速下的适应情况。通过仿真计算研究了可控脉冲增压系统对柴油机性能的影响,确定了可变脉冲增压系统的切换边界。     

对船用6135非增压柴油机进排气系统的改进

本文通过论述,主要阐明以下二点:(1)对原6135船用非增压柴油机(以下简称6135非增压机)采用空气滤清器及进气总管进气,存在进气阻力过大问题,在实船上改用渐缩形的进气导管,降低进气阻力,提高进气终点压力,使柴油机节油率达5％～6％;(2)对原6135非增压机排气系统存在的排气不畅、进气不足,阻力过大等不利节能问题,在实船上采用喷射抽气的排气型式,以船速为动力源,使柴油机在实际中节油4％～6％。     

柴油机涡轮增压匹配方法的研究

本文提出了一种柴油机标定工况增压模拟匹配法。这种方法,对于单缸增压模拟,可以根据求得的柴油机标定工作区,在一系列的压气机特性线上所处的位置,来选择增压器。所谓标定工作区,系指柴油机实现了一定增压度,满足了一定性能要求时,所需要的进气压力、进气流量的数值范围。此方法,对于多缸增压模拟,可以通过对标定工作区的调整,改善、放宽柴油机对增压器的适应性,通过对增压器的调整,考核初选增压器的平衡运行点,能否处于工作区内。本方法能较有效地排除增压器和柴油机之间诸因素的相互干扰,而且在 X6105柴油机增压匹配时予以初步应用。     

单缸机实用惯性增压进气系统的开发

本文从结构设计上探讨了惯性增压进气系统在单缸机上应用的可行性。讨论了空气滤清器对惯性增压效果的影响。台架试验表明,本惯性增压进气系统能明显地改善发动机的性能。     

柴油机燃烧路径及其对热效率和排放的影响

采用试验和数值模拟方法研究了充量密度、温度和氧浓度对柴油机高负荷工况下的热效率和排放的影响.试验是在一改装的单缸柴油机上进行,装有进气增压、废气再循环、进气门晚关和可调节的燃油喷射系统等回路,在该试验台上充量密度、温度和氧浓度可自由调节.三维模拟采用ECFM-3Z燃烧模型.提出并应用了质量-φT-θ燃烧路径分析方法.研...     

排气压力波对柴油机性能影响的分析

利用GT-Power软件建立了100单缸柴油机、6100非增压柴油机及6100涡轮增压柴油机仿真模型。在此基础上计算分析了排气管内的排气压力波动规律及其对柴油机功率、充气效率以及增压比的影响。研究工作对于柴油机排气系统的设计与优化具有一定的指导意义。     

发动机进排气边界条件对性能参数的影响研究

在发动机试验开发过程中,经常发生因环境条件变化导致的进气温度、压力和湿度不同的情况,同时,排气侧背压也会对排气压力有所影响,这些都会改变缸内的实际燃烧过程,从而导致发动机状态偏移。以某大缸径船用柴油机为原型,进行了单缸机试验,研究进气温度、压力、湿度和排气压力对发动机性能参数的影响。试验结果表明:进气温度、湿度和排气压力的降低以及进气压力的增大会导致进气流量增加,有利于优化燃烧过程,使油耗、烟度和排温下降,爆压和NOx比排放增加。借助试验数据,可以为发动机开发过程中的边界条件控制、修正和补偿标定提供依据,提高发动机的可靠性以及对各种进排气边界条件的适应性。     

在螺旋进气道内喷气的柴油机可变涡流进气系统

设计了一种在螺旋进气道内喷射空气的柴油机可变涡流进气系统——喷气式可变涡流进气系统。对该系统的稳流气道试验表明,喷嘴在特定位置上向气道内喷射空气,可以增强或者降低气缸内涡流强度。通过稳流气道试验,确定了最大程度改变缸内涡流强度的最佳喷嘴安装位置及空气喷射方向,选择了喷嘴尺寸及空气喷射压力,并测定了不同喷射压力下,气缸内涡流比与模拟发动机转速的关系。对该系统做了单缸柴油机试验,结果表明,喷气式可变涡流进气系统基本不影响充气系数,但通过该系统对气缸内涡流强度的调节,有效地改变了发动机的排放性能     

进气压力对发动机性能的影响研究

在一台3.8L涡轮增压中冷4缸柴油机上通过试验和仿真研究了进气压力对柴油机燃烧和性能的影响。试验中拆除了原机增压器及中冷器,通过自制压力调节装置直接控制柴油机进、排气压力。试验及仿真结果表明:在排气压力维持不变的条件下,最高燃烧压力与进气压力具有明显的线性关系,进气压力每增加100kPa,最高燃烧压力增加约4.8MPa~7.0MPa;进气压力对最高燃烧压力相位的影响不明显;空气质量流量与进气压力具有明显的线性关系,进气压力每增加10kPa,空气质量流量增加约13~37kg/h;柴油机排气温度与空燃比具有明显的线性关系,空燃比每增加1,柴油机排气温度降低约4.2℃;随进气压力增加,柴油机缸内燃烧滞燃期缩短,燃烧始点提前,但进气压力对燃烧持续期没有明显影响;进气压力每增加10kPa,发动机转矩增加约0.8~2.5N·m。     

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。     

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.     

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.