正丁醇/柴油发动机燃烧排放特性及喷油、燃烧室形状影响

针对某型号直喷柴油机,建立了该柴油机中单缸完整燃烧室及气道三维模型,使用三维计算流体力学(computational fluid dynamics,CFD)分析软件CONVERGE对其进行模拟计算,研究了正丁醇掺混比例对柴油机燃烧排放的影响。结果表明:随着正丁醇掺混比例的提高,峰值缸压、滞燃期和燃烧速度均呈递增趋势,碳烟及CO排放量逐渐减少,NO_x排放量小幅增加。为了进一步改善缸内燃烧情况和降低污染物排放,对正丁醇掺混时喷油策略、燃烧室几何形状的综合影响进行了研究,结果表明:掺混时多次喷油及采用合适的燃烧室模型可以有效改善掺混后缸内油气混合情况,增加缸内湍动能强度,进一步降低碳烟排放量。与纯柴油工况对比,掺混并采用多次喷油策略后碳烟排放明显下降,且通过掺混能够有效简化喷油策略,但弱化了燃烧室形状对碳烟排放量的影响。     

掺混比例和喷射定时对二甲醚-乙醇发动机燃烧和排放的影响

在一台电控共轨发动机上,试验研究了乙醇掺混比例和喷射定时对二甲醚-乙醇混合燃料燃烧及排放的影响。结果表明:随乙醇比例的增加,滞燃期延长,燃烧持续期缩短,最大压力升高率上升。随喷射推迟,滞燃期延长,燃烧相位延后,燃烧持续期在纯二甲醚时延长,而在掺混乙醇时则先延长后缩短,最大压力升高率先下降后上升。掺混乙醇和推迟喷射使预混燃烧比例增加。随喷射推迟,混合燃料的排气温度升高,喷射推迟到上止点后,排气温度随乙醇比例的增加而升高,排气温度高,则废气能量高,增压器增压比大,进气流量大,导致缸内压缩压力升高。在上止点前喷射时,掺混乙醇能使HC和CO排放保持在较低范围的同时,一定程度降低NO_x排放,掺混15%的乙醇较纯二甲醚最大降低约11%NO_x排放。随推迟喷射,NO_x排放降低,最大降幅达52%,在过分推迟燃料喷射时,因热效率低,循环喷射量增加,含15%乙醇混合燃料的NO_x排放会高于纯二甲醚。HC和CO排放随喷射推迟而升高,且升高幅度增大。     

柴油机燃用混合替代燃料的燃烧与排放特性

将生物柴油和F-T柴油(F-T diesel)进行掺混,并将其混合燃料应用于4100QBZL柴油机上.在未对原机做任何改动的情况下,研究了该机燃用不同体积配比混合燃料时的燃烧特性及NOx和碳烟排放性能.研究表明,与0#柴油相比,该机的预混燃烧放热峰值降低、扩散燃烧放热峰值升高、燃烧更柔和;NOx排放随着生物柴油掺混比例的增大而升高;碳烟排放显著下降,较0#柴油的降低幅度高达37%;低比例的混合燃料对NOx排放和碳烟排放的trade-off关系有明显改善.生物柴油与F-T柴油混合燃料宜在较低的生物柴油掺混比例范围内使用.     

生物柴油碳烟特性的可视化研究

在1台光学可视化发动机上,采用高速摄影法,对不同掺混比例的柴油/生物柴油混合燃料进行研究,获取缸内燃烧火焰图像,通过双色法得到表征缸内碳烟总体分布的KL因子,分析了生物柴油对缸内燃烧过程和碳烟生成特性的影响.研究结果表明,随着生物柴油掺入比例的增加,最高燃烧压力逐渐降低,滞燃期相对延长,燃烧持续期缩短,火焰的亮度和分布面积都随之下降.KL因子的最高浓度降低,碳烟较浓的分布区域减小,碳烟的氧化进程加快.     

大豆生物柴油混合燃料性能试验研究

通过在R4105T柴油机上进行对比试验,分析了0#柴油/生物柴油、乙醇/生物柴油混合燃料以不同比例掺混时对柴油机动力性、经济性及碳烟排放特性的影响.研究结果表明:柴油机使用0#柴油/生物柴油混合燃料时动力性、碳烟排放量均有所下降,油耗率稍有上升;使用乙醇/生物柴油混合燃料时,碳烟排放量低于生物柴油,动力性、经济性随乙醇含量的不同而呈现不同的变化趋势.     

大豆生物柴油混合燃料性能试验研究

通过在R4105T柴油机上进行对比试验,分析了0#柴油／生物柴油、乙醇／生物柴油混合燃料以不同比例掺混时对柴油机动力性、经济性及碳烟排放特性的影响。研究结果表明：柴油机使用0#柴油／生物柴油混合燃料时动力性、碳烟排放量均有所下降,油耗率稍有上升;使用乙醇／生物柴油混合燃料时,碳烟排放量低于生物柴油,动力性、经济性随乙醇含量的不同而呈现不同的变化趋势。     

生物柴油/DMF混合燃料对柴油机低温燃烧的影响

在生物柴油中分别掺入体积分数20%和50%,的2,5-二甲基呋喃(DMF)组成DMF20和DMF50混合燃料,在一台单缸柴油机上对柴油、生物柴油和生物柴油/DMF混合燃料开展低温燃烧试验研究.结果表明,生物柴油和柴油燃烧特性相近,生物柴油含氧特性在一定程度上可以改善低温燃烧的碳烟排放;增大生物柴油中DMF掺混比例,混合燃料十六烷值降低,滞燃期延长,燃烧速率加快,预混放热峰值升高,最大压力升高率增大,DMF50即使在高负荷下也呈现典型的预混单峰放热.在低负荷时,掺混燃料热效率并没有优势,随负荷增大,掺混燃料在热效率方面逐渐表现出优势,特别是DMF50在高负荷时优势明显,指示热效率提高到46.5%(此时柴油和生物柴油分别为43%和43.3%).掺混DMF对碳烟改善明显,在高负荷、低温燃烧、低氧浓度条件下DMF50仍可基本实现无碳烟排放,同时提高DMF掺混比例对改善高负荷低温燃烧的CO和HC排放作用显著.     

EGR率对乙醇/生物柴油混合燃料燃烧及排放特性的影响

在一台经过深度改装的四缸直喷水冷柴油机上,燃用乙醇与生物柴油的混合燃料,研究了EGR率与燃料特性对柴油机燃烧及排放的影响.结果表明:EGR系统的介入以及乙醇的掺混均可减小燃烧过程中缸内压力和放热率峰值.燃用同种掺混比的燃料,随着EGR率的增大,滞燃期和燃烧持续期出现了不同程度的延长,当量燃油消耗率升高,有效热效率降低.EGR率不变时,燃用不同掺混比的混合燃料,随乙醇质量分数的增加,滞燃期与燃烧持续期逐渐延长,当量燃油消耗率逐渐降低,有效热效率逐渐升高.NO_x的排放量在EGR引入后出现了显著下降,HC排放量升高.相同EGR率下,随着乙醇掺混比的提高NO_x排放量略微下降,HC排放量表现出先减小后升高的趋势.相比纯生物柴油,乙醇的掺混可以显著减少大粒径颗粒物的数量.EGR率的变化对核模态粒子的数量影响不明显,但聚集态粒子的数量会随着EGR率的提高出现较为明显的增多.将乙醇、生物柴油和EGR系统三者相耦合可改善柴油机的燃烧及排放特性.     

松油掺混燃料的喷雾及燃烧排放特性试验

为探究松油作为柴油机替代燃料的可行性,在定容弹中结合高速摄影技术对松油掺混比例为20%,、40%,和50%,的柴油/松油混合燃料在不同喷射压力及背压下的宏观喷雾特性进行可视化研究;同时基于一台4缸涡轮增压柴油机,研究掺混燃料在不同负荷下的燃烧和排放特性.结果表明:随喷射压力及背压的改变,4种燃料喷雾特性的变化规律一致;相同条件下松油掺混燃料的喷雾锥角、贯穿距及油束面积均比柴油大,且松油掺混比越大,雾化效果越好.在试验负荷范围内,松油掺混燃料的有效燃油消耗率、最大压力升高率比柴油略大;在全负荷工况下50%,掺混燃料的转矩较柴油仅降低2%,表明松油可提供与柴油相当的动力输出.掺混燃料在低负荷时的NO_x、CO和THC排放均高于柴油,中、高负荷时掺混燃料的CO及THC排放低于柴油,NO_x排放与柴油差别不大;通过增加松油掺混比例可以大幅降低碳烟的排放.     

增压柴油机燃用不同掺比菜籽油甲酯的燃烧和排放的试验研究

在D6114ZLQB车用增压柴油机上比较研究了不同比例的菜籽油甲酯和0号柴油的混合燃料对发动机燃烧过程、燃油经济性和排放特性的影响。试验结果表明：燃用体积比低于15%的菜籽油甲酯,发动机的缸内燃烧过程和纯柴油基本一致;增压柴油机燃用菜籽油甲酯和柴油的混合燃料可以有效降低碳烟、HC和CO的排放;NOx排放略有上升;15%以内的菜籽油甲酯对柴油机燃料经济性影响很小。研究认为：增压柴油机相对自然吸气式柴油机具有更好的生物柴油燃料适应性;在不改变发动机参数的条件下,低比例的菜籽油甲酯具有良好的推广应用前景。     

小型锅炉烟尘测试时锅炉出力的计算

锅炉烟尘测试时,必须对锅炉出力进行测试。但监测中,许多小型锅炉往往不具备相关的计量装置和仪表,为解决这一问题,文章提出了用烟气量和空气过剩系数来计算锅炉的出力的公式,在实际使用中,该方法简单易行,其结果和实测值具有很好的一致怀。     

Unerroric of control of mutual compliance of the efficiency of hydrogen engines of unmanned vehicles in the conditions of mass production

The issues related to the reliability of hydrogen engines of unmanned vehicles and increasing the efficiency of using hydrogen as fuel when using the method of its production during the decomposition of hydrogen-containing molecules of liquid-phase organic compounds in a plasma discharge under the action of intense ultrasonic exposure are considered. Experiments have shown that as a result of decomposition in the acoustoplasma discharge of liquid hydrocarbons, solid-phase carbon-containing products are formed, chemical transformations occur in the liquid phase and hydrogen-containing combustible gas is formed. Hydrogen-containing gas can be used as fuel immediately after synthesis, i.e. it does not require separation, since in addition to hydrogen it contains only impurities of CO₂ and water vapor. The purpose of the study is to formalize the basic conditions for tightening the control of mutual compliance with the efficiency of hydrogen engines of the same series in the conditions of their mass production. Methods of mathematical statistics and hardware-software modeling were used in the study. The term “unerroric of quality mutual compliance control” is introduced to describe a set of hardware and software tools for such control. The principle of in-depth testing of the technical condition of such engines of one series is described in a multidimensional formulation of the quality control problem for three of their operating parameters at once. The conditions for increasing the mutual correspondence of the measured values of such parameters in the conditions of serial production of hydrogen engines are formalized.     

中国煤炭地下气化技术的发展

本文综述了煤炭地下汽化技术的国内外发展现状,对我国“长通道、大断面”煤炭地下气化新工艺给予了技术经济评述,并提出了发展煤炭地下汽化技术的政策建议。     

Review of theory of distortion and disintegration of liquid streams

Linear and nonlinear analyses of the instabilities and distortion of liquid streams injected into a gaseous media are discussed. The various fundamental mechanisms and the predictive capabilities for the distortions are emphasized. Round jets, planar sheets, annular sheets, and conical sheets are discussed in detail. The balance between capillary and inertial forces is primarily examined. The method for simplifying the analyses in the case of thin liquid sheets is discussed. The capabilities for representing the droplet size distribution that follows the stream disintegration are outlined.     

MgO膨胀剂细度对MgO水化和水泥浆体膨胀的影响

基于《水工混凝土掺用氧化镁技术规范》中的Ⅰ型氧化镁（MgO）,研究了该型MgO膨胀剂（MEA）细度对掺粉煤灰水泥浆体膨胀性能的影响。即采用X射线衍射分析(XRD)及同步热分析（TG DSC）分析了掺MEA水泥浆体中MgO的水化性。结果表明,养护温度相同时,MEA的细度对水泥浆体内MEA中MgO的水化和水泥浆体的膨胀无显著影响,产生的膨胀均能补偿水泥浆体的收缩;MEA的细度可从试验设计采用的45 μm筛筛余15%左右增加到30%左右,这将有利于MEA生产企业的节能降耗。     

机车车轮多轴疲劳强度安全评定的研究

使用ANSYS8.0软件对高速列车车轮进行了三维有限元分析,计算出车轮在直线、曲线和道岔条件下牵引、制动共6种工况时孔边薄弱部位的应力,分别通过Mises等效平均应力方法、Sines平均主应力方法和应力分量中考虑平均应力方法计算出应力在极值位置时的等效应力幅、等效平均应力,从而进一步算出车轮的安全系数,对其疲劳强度进行评定,并对3种方法进行了比较研究。     

Constructal optimization of the geometry of an array of micro-channels

This paper documents the geometric optimization of an array of circular and non-circular ducts. The optimization was carried out numerically using finite volume method. As optimal dimensions were independent of the array configuration, the numerical simulation was performed on a unit cell. Numerical optimization for circular, square and isosceles right triangle cross-sections of channels was performed. Based on the results of this investigation, some correlations were proposed to predict the optimal hydraulic diameter and dimensionless heat transfer per unit volume. In addition to examining the effect of pressure drop on these parameters, it was showed that among the different geometries of this study, square cross-section has the most efficiency for a given volume. The numerical results of the present study were compared with approximate results reported in the literature which a good agreement was observed.     

固体热辐射Yong性能分析

本文对漫灰均温物体在常物性条件下对外辐射传热的Ｙｏｎｇ值计算建立了数学模型。通过与物体内能Ｙｏｎｇ公式的数值计算比较,得出了辐射能量的Ｙｏｎｇ值不大于内能Ｙｏｎｇ值的结论。从初步的热射Ｙｏｎｇ值计算公式发现。Ｙｏｎｇ与物体表面辐射率有关。     

Measurements of concentration distribution of hydrogen jet using deflection of center of the laser spot

The main purpose of this work is to propose a new method to evaluate the concentration distribution of the hydrogen jet by using a He–Ne laser through the jet. This research attempts to apply the expression of concentration Gaussian distribution, the refraction formula of inhomogeneous refractive index medium, and the concentration inversion function to disclose the displacement of the center of the laser spot at different heights in the gas jet. The spot images of the laser beam passing through the gas jet at three vertical heights z = 10d, 20d, 30d, and different radial positions are obtained. The radial spatial asymmetry of the gas jet is also found in the experiment. Finally, the calculated concentration distribution curve and the fluent simulation curve, it is found that the two results are very similar. Our findings show that the error between the concentration distribution of this method and the simulated concentration distribution reaches 2.43%.     

Heat of vaporization of mixtures

General expressions for the heat of vaporization of mixtures at constant pressure; at constant temperature; and at constant pressure, temperature, and composition are proposed. The last one is related to the liquid-vapor interface where steady vaporization or condensation is taking place. Numerical examples by the proposed expressions are shown for binary mixtures of HCFC22(R22) and (HCFC123(R123) © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(1): 12–24, 1996