柴油发电机组整机振动及防振

简要分析了柴油发电机组的振动对外界和电站内部零部件的影响,及外部振动同样会引起电站振动和电站内部零件的损坏,在此基础上提出柴油发电机组的防振措施。叙述了隔振器的性能特点以及选择隔振器的方法和步骤,给出隔振弹性支承的主要参数和计算方法,最后指出隔振弹性支承的布置力求对称以减少独立和耦合振动型式。     

摩托车发动机弹性隔振器的设计研究

利用弹性隔振器隔离发动机高频振动是摩托车减振的一种重要方法。对摩托车发动机的弹性隔振系统进行了研究,提出了摩托车发动机的弹性隔振原理和频率设计准则,建立了发动机弹性系统的动力学模型,确定了系统的动特性参数,分析弹性隔振器对车架动特性的设计要求,结合试验测试,设计了弹性隔振器。研究结果表明,弹性隔振器能有效地隔离发动机系统的高频振动。     

摩托车发动机悬挂的最优设计研究

本文以摩托车发动机弹性系统的动力学模型为基础,以降低整车的振动为目标,针对摩托车发动机传统的刚性悬挂方式的缺点,提出了弹性悬挂的方法以及摩托车发动机弹性隔振原理和频率设计准则,改变了刚性悬挂方法中发动机的不平衡惯性力和力矩直接作用于车架的缺点,确定了系统的动态特性参数,分析弹性隔振器对车架动特性的设计要求,基于ADAMS虚拟样机技术,建立了摩托车虚拟样机模型,在理论计算的基础上,通过虚拟样机技术对弹性隔振器刚度和阻尼进行了优化设计。研究成果应用于实践,解决了某型摩托车的振动问题。     

498柴油机隔振系统设计与试验研究

在内燃机与支架之间加上隔振设备是降低内燃机振动和噪声的有效方法之一。作者介绍了498柴油机隔振系统方案和橡胶隔振器的设计，并讨论了引起498柴油机机体振动的主要原因。试验表明，所设计隔振系统能有效的降低内燃机传递给支架的振动。     

车用直列四缸柴油机隔振系统设计及试验研究

将激励源(发动机)与车身两部分进行隔离是解决汽车振动、噪声问题的主要方法之一。本文介绍了D4114Z_LQB柴油机隔振系统方案和橡胶隔振器的设计,并对柴油机、隔振器系统的振动模态进行了计算。装车振动测试表明,所设计隔振系统能有效地降低发动机传递给车架的振动。     

考虑弹性基础的发动机悬置隔振特性分析

本以Ａｕｄｉ１００轿车为研究对象，应用４端参数技术，分析了弹性基础上发动机悬置的隔振性能，从而解释了高频下发动机悬置振动传工上扬的原因。     

498柴油机试验台架隔振系统设计与试验研究

在内燃机与支架之间安装隔振设备是降低内燃机振动和噪声的有效方法之一。本文介绍了498柴油机试验台架的隔振方案和橡胶隔振器的设计,并讨论了引起498柴油机机体振动的主要原因。试验表明,所设计隔振系统能有效地降低内燃机传递给支架的振动。     

船用柴油发电机组悬置隔振特性及隔振器选型分析

针对船用柴油发电机组悬置隔振特性进行了分析,指出:传统隔振理论用于柴油发电机组有一定的缺陷,由于柴油发电机组悬置支撑的弹性作用等因素使振动传递率曲线在高频段上扬,隔振效果变差。就柴油发电机组的隔振器选型原则、安装布置进行了分析,并辅以实例说明。     

柴油机双层隔振系统刚度优化及试验分析

对必须考虑中间质量柔性效应的双层隔振系统,为解决有限元方法进行隔振器刚度优化工作量巨大、计算周期长的难题,提出了一种使用动力学方法进行隔振器刚度优化,根据优化结果采用有限元模型进行验证的优化方法,并最终结合试验对该方法进行有效性检验.根据双层隔振系统的结构参数,以不同的优化目标,编制双层隔振系统解耦优化程序,获得各隔振器刚度方案下的优化结果;利用优化结果,进行双层隔振系统有限元模型的强迫振动计算,计算机组的振动烈度和二级隔振器位置处的支反力总和,其与动力学方法的计算结果变化趋势一致.根据最优隔振器刚度方案,对柴油发电机组进行了台架运行试验.结果表明:有限元方法计算的机组的振动烈度和支反力之和与试验结果吻合很好,验证了该方法的正确性.     

20 RK270型柴油机隔振器的选型及验证

基于20RK270型柴油机的基本参数以及同类项目的经验,进行了该机隔振器的初步选型,在此基础上计算分析了不同工况下的各弹性单元的位移、速度等参数的变化情况。计算结果表明:该隔振系统的选型合理。后续进行的柴油机振动测试结果验证了计算结果的正确性。     

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.