基于不同润滑油的内燃机轴承性能研究

对内燃机连杆轴承和主轴承进行动力学分析,得到了轴承最大载荷和最小油膜厚度等可靠性参数,进而评估了轴承润滑油消耗和摩擦损失等性能指标。研究发现,与使用15W-40润滑油相比,使用高黏度20W-50润滑油的轴承,其最小油膜厚度、润滑油消耗量和摩擦损失等参数都有很大的改善。     

基于不同润滑油的内燃机轴承性能研究

对内燃机连杆轴承和主轴承进行动力学分析,得到了轴承最大载荷和最小油膜厚度等可靠性参数,进而评估了轴承润滑油消耗和摩擦损失等性能指标。研究发现,与使用15W-40润滑油相比,使用高黏度20W-50润滑油的轴承,其最小油膜厚度、润滑油消耗量和摩擦损失等参数都有很大的改善。     

润滑油添加剂在发动机上的应用

１概述 这里所说的润滑油添加剂不是通常所说的为提高润滑油的质量指标,在成品润滑油生产过程中在基础油中加上一定比例的诸如粘度指数改善剂、倾点下降剂、抗氧化剂、清净分散剂、磨擦缓和剂、油性剂、极压剂、抗泡沫剂、防腐剂、防锈剂等添加剂所形成的高级润滑油或复合润滑油。而是指,用户为了达到特殊的使用目的,在使用的成品润滑油中所加的各类添加剂。 本文介绍的是发动机出厂试车磨合阶段所用的润滑油促磨剂和发动机正常使用阶段所用的润滑油减磨剂。２润滑油减磨剂 降低摩擦功不但可以提高输出的有效功率,而且可以提高发动机的…     

长寿命柴油机润滑油抗磨损性能测评方法研究

针对中国自主品牌柴油发动机的关键摩擦副测量方法和试验测评工况进行研究,结合润滑油理化分析和关键摩擦副磨损精密测量,形成柴油机润滑油抗磨损性综合评测方法。工况研究显示,延迟喷油正时可在排气温度不超过高温限值的同时实现碳烟的快速生成,加剧摩擦副零件的磨损;提升发动机转矩及降低发动机转速能够有效扩大混合润滑区和边界润滑区占比,利于润滑油抗磨损性的考核。试验结果表明,提出的400 h台架试验后润滑油的老化程度超过了实车100 000 km,具有显著的苛刻性;经过两种不同润滑油的6次试验验证,发动机活塞一环失重、活塞油环磨损、缸套磨损、挺柱磨损、连杆上瓦失重等主要摩擦副评价项目具有较好的重复性和区分性,可以作为润滑油抗磨损性能的评价指标。     

中国重型车用柴油机润滑油评价方法研究

近年来中国重型柴油机已基本实现了技术自主化,润滑油评价标准等同采用美国石油学会(API)规格的模式已经不适合中国国情。与API使用多个发动机台架试验分别评价润滑油不同性能的评价方法不同,首创以单个发动机台架试验来综合评价润滑油性能的自主认证方法。试验以潍柴典型机型WP13发动机为基础,提出了ABC三阶段机油评价试验方法,并对350 h试验过程中机油的理化参数进行分析。三阶段分别以Cu元素增长、烟炱含量(Soot)增长、Fe元素增长等作为标志。结果表明:开发的三阶段机油综合评价试验方法可检测出机油烟炱含量和黏度的增加,以及发动机摩擦副的快速磨损,因此该方法用于柴油机润滑油的综合性能评价是可行的。其中,三阶段机油评价试验中的B阶段为烟炱生成阶段,采用推迟喷油提前角和减少循环喷油量相结合的方法,能达到增加机油烟炱含量和降低排温的目标。     

多缸柴油机摩擦扭矩的建模与仿真

对柴油机摩擦扭矩进行深入分析,将整机摩擦扭矩分为活塞组、轴承、气阀等几个部分,并分别进行建模研究。模型以多缸四冲程机为研究对象,分别得到了各部分单独的摩擦扭矩模型和柴油机整体摩擦扭矩模型,并利用某型四冲程柴油机实测倒拖时的气缸压力和转速等参数对模型进行了仿真。     

微配缸间隙活塞处理技术的开发研究

为满足市场对柴油机动力性、经济性及可靠性的的要求,开发了一种微配缸间隙的活塞处理技术(纳米渗透),并针对柴油机的燃油消耗率、机油消耗率和摩擦功进行发动机台架性能试验。试验结果表明,活塞经纳米处理后,柴油机燃油消耗率降低2.0%～2.6%,机油消耗率降低10.0%～50.0%,摩擦功降低0.5～1.0 kW,可满足柴油机可靠性要求,大幅提高柴油机的燃油经济性。     

活塞环摩擦特性的研究

在往复式内燃机中,需要弄清楚的最重要的课题之一就是活塞环与气缸套之间的摩擦特性,以期达到减小摩擦损失或者是解决最近几年伴随着发动机性能的提高而出现的擦伤和磨损等问题。本文是利用液体静压轴承来支撑气缸套这一改进的浮动气缸套法,用以精确地测量在着火运行试验时活塞组件的摩擦力与曲轴转角的函数关系。利用这一装置所获得的试验结果,探讨了发动机的转速、润滑油的粘度,气缸内气体的压力及活塞环的数目对摩擦特性的影响以及在反拖知着火运行试验时摩擦特性的差别。     

排气制动工况下摇臂轴断裂问题的分析与试验研究

某四缸柴油机在电力测功机台架上采用倒拖方法进行排气制动工况模拟试验时,功率突然下降,拆机检查发现摇臂轴断裂且排气门与活塞有碰撞痕迹。本文借助有限元计算、断口分析和理化检验等手段对故障件进行分析,同时在试验台架上测量活塞与排气门的运动间隙。经分析和试验研究发现在制动工况下排气门出现反跳导致活塞与排气门碰撞是摇臂轴断裂的主要原因。     

大功率发动机磨合规范浅谈

发动机分别按两种磨合规范进行磨合,根据磨合后各摩擦副的表现,结合润滑油光谱分析,得出不同磨合规范对发动机各摩擦副的影响。研究表明:发动机磨合时的载荷、转速应遵循逐级提高的原则;柴油机的磨合规范不尽相同,应针对发动机的强化程度和标定参数来确定磨合的转速、载荷以及磨合时间。     

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.     

Contents in Volume 23,2014

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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.