燃油温度对喷雾特性的影响研究

以KIVA-3V为基础,研究了在定容室喷雾条件下,燃油温度对喷雾气液相贯穿距、气相总体积及气相混合气燃空当量比分布的影响。研究结果表明:随着燃油温度的升高,喷雾的液相及气相贯穿距缩短,蒸发喷雾在径向上的扩展明显增强,喷雾蒸发的气相体积几乎呈线性增加;在燃油温度为293K时,喷雾中气相混合气燃空当量比小于1的油气质量占所蒸发总油气质量的90%以上,而燃空当量比大于2的油气质量近乎为零;但当燃油温度达530K时,喷雾中气相混合气燃空当量比大于2的油气质量约占所蒸发油气总质量的70%。     

喷油泵结构参数对喷油特性和柴油机性能的影响

本文介绍了喷油泵柱塞直径与凸轮升程的匹配对喷油特性和柴油机性能的影响。叙述了为了获得直喷式柴油机的高喷油速率,如何选用合适的喷油泵结构参数。     

中国中长期碳减排战略目标初探(Ⅲ)——石油能源产品在交通运输等行业中的应用和碳减排

在我国中长期的终端能源需求中石油将占约15%的份额,其中55%～60%将被用于交通运输行业。逐步减少交通运输领域石油能源产品的使用量,对减少能源消费总量和二氧化碳排放量十分重要。目前国内外研究机构预测的中国2050年货运周转总量(8×104～9×104Gt.km)及公路货运周转量均明显偏高,造成预测的运输燃料消耗量太高,这也反映出调整中国经济产业结构和进出口贸易结构的紧迫性。减少私人乘用车的拥有量和出行量也是节能减排的关键,采用西方发达国家私人乘用车的比例,预测中国2050年将拥有5×108～6×108辆乘用车不符合中国人口众多、城市中心区人口密度的特点,将乘用车数量控制在3.0×108辆的水平比较恰当。目前全球运输领域二氧化碳排放量约占总排放量的20%～25%,中国运输领域的二氧化碳排放量将逐步上升,占总排放量的份额将从目前的7%提高到2050年的30%以上。应努力采取各种措施,使2050年乘用车的二氧化碳排放强度降低到40g/km的水平。除了减少化石能源石油产品使用量、使用生物质燃料、推广纯电动汽车和开发燃料电池汽车外,改变出行方式、发展方便快捷的公共交通显得十分重要。预计我国2050年燃料电池汽车将占到小汽车保有量的20%左右,纯电动汽车占30%左右,各种混合动力汽车将占50%左右。为了使中国2050年二氧化碳排放总量控制在40×108～50×108t的水平,有可能也有必要将石油的使用量控制在6.0×108t,交通运输领域石油能源产品使用量控制在4.0×108t以下。     

1.5kW柴油机喷油系统的研究

通过对１５ｋＷ柴油机喷油泵凸轮运动规律、喷油泵、喷油器和高压油管进行试验与分析,论述了这些参数对整机性能的影响,并揭示了现有１５ｋＷ柴油机喷油系统存在的问题,提出了相应的改进措施,即采用小直径喷孔喷油嘴和减小油泵柱塞直径可获得良好的发动机性能。     

不同散热条件下微燃烧的数值模拟

散热是影响微尺度燃烧器燃烧稳定性的重要因素之一.本实验通过在一个长40 mm、内径2 mm、外径4 mm的石英玻璃直圆管表面施加不同的外部吹风温度,控制其表面散热.研究4、107、756℃外部风温下,微燃烧器的工作性能,其中燃料混合气体流量为0.16、0.28、0.32 L/min.实验测得燃烧器壁面温度,结合数值模拟研究内部燃烧过程.计算结果显示,提高燃料流量或外部风温可以提升反应强度、抑制熄火.如在风温107℃时,燃料气体当量配比下,当流量由0.16 L/min上升到0.32 L/min时,峰值温度由1538 K上升到1620 K;在流量0.28 L/min时,燃料气体当量配比下,当外部风温由4℃上升到756℃时,峰值温度由1592 K上升到1731K.     

Microwave attenuation in forest fuel flames

The flames of forest fuels form a weakly ionized gas. Assuming a Maxwellian velocity distribution of flame particle and collision frequencies much higher than plasma frequencies, the propagation of microwaves through forest fuel flames is predicted to have attenuation and phase shift. A controlled fire burner was constructed where various natural vegetation materials could be used as fuel. The burner was equipped with thermocouples and used as a cavity for microwaves with a laboratory quality network analyzer to measure phase and attenuation. The controlled fires had temperatures in the range of 500-1000 K and microwave attenuation of 1.0-4.5 dB m⁻¹ was observed across the 0.5 m diameter cavity. Attenuations of this magnitude could affect active remote sensing systems signals at microwave frequencies in forest fire environments where flame depths of up to 50 m are possible. In the experiment, temperature was not the only controlling parameter for the ionisation; type of fuel burnt also influenced it. Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) analysis of the composition of the fuel confirmed that a higher content of alkali (with low ionization potential) lead to higher electron densities. Electron densities in the range of 0.32-3.21×¹⁰¹⁶ m⁻³ and collision frequencies of 1.1-4.0×¹⁰¹⁰ s⁻¹ were observed for flames with temperature in the range of 730-1000 K.     

Numerical simulation of fuel sprays at high ambient pressure: the influence of real gas effects and gas solubility on droplet vaporisation

This paper deals with the numerical simulation of the vaporisation of an unsteady fuel spray at high ambient temperature and pressure solving the appropriate conservation equations. The extended droplet vaporisation model accounts for the effects of non-ideal droplet evaporation and gas solubility including the diffusion of heat and species within fuel droplets. To account for high-temperature and high-pressure conditions, the fuel properties and the phase boundary conditions are calculated by an equation of state and the liquid/vapour equilibrium is estimated from fugacities. Calculations for an unsteady diesel-like spray were performed for a gas temperature of 800 K and a pressure of 5 MPa and compared to experimental results for droplet velocities and diameter distribution. The spray model is based on an Eulerian/Lagrangian approach. The comparison shows that the differences between the various spray models are pronounced for single droplets. For droplet sprays the droplet diameter distribution is more influenced by secondary break-up and droplet coagulation.     

重型柴油机低温环境喷雾及蒸发特性研究

利用定容燃烧弹结合米散射法、阴影法针对喷孔直径(0.12～0.32mm)和环境温度(550～850K)对重型柴油机低温环境下喷雾特性的影响进行可视化测量。结果表明:不同于轻型柴油机,在各个喷射压力和环境压力下提高环境温度到750K时,表征重型柴油机的0.32mm喷孔下的液相燃油依然持续贯穿,无法达到准稳态或达到准稳态时贯穿距离过长而湿壁。随着环境温度增加,0.32mm喷孔下的液相燃油湿壁量减小。只有环境温度增长到850K时,燃油的蒸发作用足够强烈,液相撞壁喷雾的横向扩展长度和浮起高度才能均达到准稳态。     

Effects of atmospheric aerosol on the performance of environmentally sustainable passive air-breathing PEM fuel cells

The effects of different airborne particulate contaminants (oxalic acid, soot, ammonium sulfate, and sodium chloride) and the gaseous air impurity NO_x on the performance of a passive air-breathing proton exchange membrane fuel cell (AB-PEMFC) were investigated by introducing the pollutants into the oxidant air fed to a small AB-PEMFC module. All contamination data were corrected for variations in air temperature and relative humidity. While 10 ppmv NO_x degraded fuel cell performance by 22% within 4 h and showed partial recovery of 70% within another 11 h, the effects of the aerosol particles were considerably less severe. Only oxalic acid and ammonium sulfate exhibited significant performance degradation with upper limits of 24% 1000 h⁻¹ and 3% 1000 h⁻¹, respectively. Sodium chloride as well as soot particles did not cause any significant performance decline. Because diffusion is the main transport mechanism for aerosol particles into a passive AB-PEMFC, only a minor fraction of the total particle mass can actually deposit inside these fuel cells resulting in rather low effects even under very high aerosol loadings. Therefore, aerosol related effects seem negligible under ambient conditions.     

燃油喷射系统参数对二甲醚闪急沸腾喷雾的影响

在环境温度293 K、环境压力0.1 MPa条件下,采用数字粒子图像速度场仪(DPIV)研究了喷嘴开启压力、喷孔直径对二甲醚(DME)闪急沸腾喷雾和柴油喷雾的影响。研究结果表明:与柴油喷雾相比,DME闪急沸腾喷雾具有较大的喷雾锥角、喷雾面积和较小的喷雾贯穿距;这3个参数均随喷嘴开启压力的提高而增大;当喷孔直径增大时,喷雾锥角和喷雾面积随之增加,而喷雾贯穿距可能增大也可能减小。     

Comparison study of thermochemical waste-heat recuperation by steam reforming of liquid biofuels

The concept of thermochemical exhaust heat recuperation by steam reforming of biofuels is considered. Thermochemical recuperation can be considered as an on-board hydrogen production technology. A schematic diagram of a fuel-consuming equipment with thermochemical heat recuperation is described. The thermodynamic analysis of the thermochemical recuperation systems was performed to determine the efficiency of using various fuels, in particular, methanol, ethanol, n-butanol, and glycerol. The thermodynamic analysis was performed by Gibbs free energy minimization method and implemented using the Aspen Hysys program. The thermodynamic analysis was performed for a wide temperature range from 400 to 900 K, for steam-to-fuel of 1, and pressures of 1 bar. The maximum fuel conversion reaches for the following temperatures: methanol - 600 K, ethanol - 730 K, n-butanol - 860 K, glycerol - 890 K. The dependence of the reforming enthalpy on temperature is determined. It was shown that the reaction enthalpy determines the heat transformation coefficient, which shows the ratio of the low heat value of synthetic fuel and the low heat value of the initial fuel. For all studied fuels, the maximum value of the transformation coefficient is observed for steam reforming of ethanol and the maximum heat transformation coefficient is 1.187. The temperature range is determined at which the maximum efficiency of the use of thermochemical recuperation occurs due to the reforming of biofuels. For methanol, the effective temperature is about 600 K, for ethanol is about 700 K, for n-butanol is 850 K, for glycerol is more than 900 K. The results obtained make it possible to efficiently select the type of fuel for thermochemical recuperation due to steam reforming.     

Three-phase boundary length in solid-oxide fuel cells: A mathematical model

A mathematical model to calculate the volume specific three-phase boundary length in the porous composite electrodes of solid-oxide fuel cell is presented. The model is exclusively based on geometrical considerations accounting for porosity, particle diameter, particle size distribution, and solids phase distribution. Results are presented for uniform particle size distribution as well as for non-uniform particle size distribution.     

108柴油机活塞改进设计

针对2108柴油机机油耗高这一问题，通过改进设计108活塞裙部型线尺寸，优化活塞与缸套的配合间隙，以达到降低柴油机机油消耗率的目的。     

Numerical modelling of a three-zone combustion for heavy fuel oil in inert porous media reactor

Numerical model for heavy fuel oil and air mixtures combustion is presented to simulate the behavior of the fuel in an inert porous medium reactor for hydrogen production. Three-zone combustion of oil and petroleum cokes separated by temperature ranges starting from ambient temperature to 560 K, from 560 K to 673 K, and above 673 K, is presented. Hydrogen production is achieved using water gas shift equilibrium reaction on the combustion products at different temperatures. Results show a high enthalpy contribution due to coke combustion formed in the low temperature oxidation reaction, being the most important reaction in relation to its zone size. Simulations increasing filtration velocity (from 0.05 to 0.9 m/s) has a favorable effect on the maximum temperature and the combustion front velocity. The effect of the simplified combustion model lowers computational time, with acceptable results for temperature as well as hydrogen production in contrast to laboratory tests and other software simulation such as COMSOL Multiphysics.     

一个柴油喷雾与壁面碰撞的数学模型

提出一个柴油喷雾与壁面碰撞的数学模型，可以计算垂直碰壁和倾斜碰壁时壁面射流的性能，适合于在准维燃烧模型中使用。建立了新的壁面射流贯穿距离计算公式，直观地反映了影响壁面射流传播的主要因素。与试验数据对比证实了这个模型的精度是令人满意的。在参数研究中，预测了喷孔直径、从喷孔至壁面的距离和喷射压力对壁面射流贯穿距离和区域空燃比的影响。     

喷油器长径比变化对柴油机性能的影响

探讨了喷油器长径比变化对ZH1105型柴油机性能的影响。结果表明，长径比变化对柴油机大负荷工况的燃油消耗率和烟度有明显影响。通过对燃油喷雾特性的分析，揭示了喷孔长径比变化影响柴油机性能的原因。     

Analysis of design parameters in anodic recirculation system based on ejector technology for PEM fuel cells: A new approach in designing

In this study, the anodic recirculation system (ARS) based on ejector technology in polymer electrolyte membrane PEM fuel cell is studied with employing a theoretical model. A practical method is presented for selecting or designing the ejector in an ARS, that offers the best selection or design. A comprehensive parametric study is performed on the design parameters of a PEM fuel cell stack and an ARS ejector. Four geometrical parameters consist of cell active area, cell number, nozzle throat diameter, and mixing chamber diameter in the design of ARS are intended. The effect of each contributes to the overall system performance parameters is studied. In this parametric study, the correlation between stack design parameters and ejector design parameters are studied. Eventually, based on the results, two dimensionless parameters are useful in the design process are proposed.     

低回油高压共轨喷油器方案优化

通过改变控制柱塞结构,提出一种低回油量高压共轨喷油器方案,以减小与回油节流孔相连的控制腔压力,减小回油量。利用一维仿真工具AMESim对新方案的关键结构参数进行优化,结果表明:随密封环直径减小,针阀关闭延时减小,但密封环直径过小会使针阀发生连续跳动,导致喷油速率脉动且削弱减小回油量的作用;引流节流孔直径减小,回油量减小,但过小的孔径会使关闭响应恶化。在不同共轨压力下对新方案进行仿真,新方案回油量与原高压共轨喷油器相比明显减小,最多可减小41%以上,且响应性不受影响,证明所提出的方案有效。     

Analysis of reformer furnace tubes for hydrogen production using radiative zonal model

Reformer tubes are commonly used in furnaces to produce hydrogen and synthesis gas in the refining, petrochemical and fertilizer industries. An optimum arrangement and dimensions of the reformer tubes could be obtained from a mathematical modeling. In the present study, a comparison of different tube sizes is presented based on the well-established radiation zonal analysis in the furnace beside mass, momentum, and energy balance in the reactor tubes. For the practical case studies, three Cr–Ni alloy stainless steel tubes were selected to analyze different tube dimensions including diameter, thickness and tube spacing with the same inlet process feed, fuel consumption and catalyst weight. It is shown that for three industrial tube materials a 20% increase in the tube diameter causes a 20% increase in the tube thickness, 10–20% decrease in furnace length (according to the design procedure) and 3–6% decrease in methane conversion. The results of another analysis show that a 5–9% decrease in the fuel consumption is followed by a 20% decrease in the tube diameter for the same amount of hydrogen production for three cases. Moreover, the three tube materials were compared in accordance to the fuel consumption. In all cases minimum tube thickness is desirable.     

Energy utilization and efficiency analysis for hydrogen fuel cell vehicles

This paper presents the results of an energy analysis for load-following versus battery-hybrid direct-hydrogen fuel cell vehicles. The analysis utilizes dynamic fuel cell vehicle simulation tools previously presented [R.M. Moore, K.H. Hauer, J. Cunningham, S. Ramaswamy, A dynamic simulation tool for the battery-hybrid hydrogen fuel cell vehicle, Fuel Cells, submitted for publication; R.M. Moore, K.H. Hauer, D.J. Friedman, J.M. Cunningham, P. Badrinarayanan, S.X. Ramaswamy, A. Eggert, A dynamic simulation tool for hydrogen fuel cell vehicles, J. Power Sources, 141 (2005) 272–285], and evaluates energy utilization and efficiency for standardized drive cycles used in the US, Europe and Japan.