正丁醚/柴油混合燃料在单缸柴油机中的燃烧与排放特性研究

基于一台单缸压燃式发动机,研究了正丁醚（di-n-butyl ether, DnBE）/柴油混合燃料的燃烧与排放特性,并与纯柴油的试验结果进行了对比。分别采用平均指示有效压力（indicated mean effective pressure, IMEP）即发动机负荷0.55 MPa、0.65 MPa、0.75 MPa,废气再循环（exhaust gas recirculation, EGR）率0%、15%、30%,喷油正时上止点后-15°、-10°、-5°、0°及正丁醚掺混体积比20%、40%,综合评估了正丁醚/柴油混合燃料在不同发动机运行工况下的特性。台架试验结果表明：相比于纯柴油,正丁醚的添加使得缸内压力上升相位及放热开始时刻提前,并且在30% EGR率工况下更加明显。在所有测试工况下,正丁醚/柴油混合燃料的预混燃烧比例均小于纯柴油,且第一阶段放热率峰值更低。由于十六烷值的差异,40%正丁醚/柴油混合燃料的着火延迟时间与燃烧持续期更短且燃烧重心更早,表明其具有更快的燃烧速率。试验发现大比例正丁醚/柴油混合燃料的燃烧等容度更高,指示热效率高于纯柴油。此外,添加正丁醚后尾气中的NO_x与碳烟排放都会降低,而提高EGR率或推迟喷油均能有效减少NO_x的生成。综合而言,添加正丁醚可以有效缓解柴油机中NO_x排放、碳烟排放与指示热效率之间的权衡关系。     

径向密封泄漏作用下喷射策略对柴油转子发动机燃烧过程的影响

为进一步提升柴油转子发动机的性能,对柴油转子发动机缸内燃烧过程进行了研究。此外,考虑到转子发动机在实际工作过程中难以避免的径向泄漏,建立了一种考虑径向密封泄漏的周边进气转子发动机三维动态计算模型,并对模型进行了验证。结合该计算模型,研究了柴油喷射时刻和喷射持续期对燃料分布及燃烧过程的影响。结果表明：当喷射时刻为上止点前80°曲轴转角且喷射持续期为50°曲轴转角时可获得较好的燃烧和排放特性。与原方案相比,缸内峰值压力提升了11.38%,碳烟和CO生成量分别降低了78.71%和92.72%,NO_x和CO₂生成量有所增加。     

掺氢天然气充量均质压燃发动机燃烧和排放特性的数值模拟研究

为研究掺氢对天然气充量均质压燃（homogeneous charge compression ignition, HCCI）发动机的燃烧及排放特性的影响,基于化学反应动力学软件包CHEMKIN中的零维模型模拟天然气HCCI发动机在掺氢比为0%~40%时的燃烧过程及排放,并对其进行数值分析。结果表明：掺入氢气后缸内温度和放热率先略下降后上升而缸内压力变化不明显,着火时刻随掺氢比增加不断提前,CO和CO₂的生成浓度降低而NO的生成浓度上升。掺入氢气为体系提供大量H,使链分支和链传递反应加快,HO₂和OH生成速度加快,造成着火时刻提前。NO的总生成速率随掺氢比增加而加快。     

氢气直喷对发动机燃烧及排放性能的影响

基于一台高压直喷汽油机,将汽油直喷喷射器替换为氢气直喷喷射器,试验研究了发动机燃用氢气与汽油时的燃烧和排放特性差异。采用空气稀释,进一步分析了氢气发动机稀薄燃烧模式下热效率提升潜力及氮氧化物排放特性,明确了氢气燃料对发动机燃烧及污染物排放的影响规律。结果表明,当量燃烧模式下,相比汽油发动机,氢气发动机的燃烧持续期明显缩短,有效热效率降低,NO_x排放升高,CO及总碳氢（total hydrocarbon, THC）排放显著降低。提高氢气发动机的过量空气系数有助于改善有效热效率。在中等负荷工况下,过量空气系数为2.7时有效热效率可达43.5%。增大过量空气系数,氢气发动机能够在保持较高燃烧稳定性的情况下显著降低NO_x排放。在低负荷工况下,当过量空气系数大于2.3时NO_x排放最低可降低至44×10^-6。     

聚甲氧基二甲醚和汽油双燃料火花辅助压燃燃烧及排放试验研究

试验平台基于汽油缸内直喷（gasoline direct injection, GDI）发动机改造,缸内直喷聚甲氧基二甲醚（polyoxymethylene dimethyl ether, PODE）,进气道喷射汽油,并将压缩比从10提升至15以利于压燃,以点火和直喷策略作为控制参数,获取双燃料火花辅助压燃（dual-fuel spark-assisted compression ignition, DF-SACI）发动机的运行特征。试验结果表明：DF-SACI呈现多阶段放热,直喷正时提前可提高混合气均匀性,减小不同燃烧阶段的界限,放热率明显提高;直喷比例可以更为有效地调节CA50和等容燃烧的比例,对热效率影响明显;同时放热率受点火正时提前的影响最小。试验中有效热效率最高可达37.5%。排放方面,DF-SACI模式在合适的点火和喷射策略下,可在一定程度上降低HC和CO的排放,HC体积分数可降低至3 00010^-6以下,CO体积分数可降低至1 50010^-6以下,同时将NO_x排放控制在较低水平。通过对燃烧策略的合理调整,PODE/汽油双燃料发动机借助火花辅助压燃可实现高效清洁燃烧。     

柴油/聚甲氧基二甲醚混合燃料匹配催化型颗粒捕集器的排放特性研究

使用柴油和聚甲氧基二甲醚（polymethoxy dimethyl ether, PODE）混合燃料进行了柴油机催化型颗粒物捕集器（catalytic diesel particulate filter, CDPF）的排放特性试验,研究分析了添加PODE对CDPF的过滤效率及CDPF前后端NO_x、CO₂和颗粒物排放变化的影响。结果表明：加入PODE提高了CDPF对颗粒物的过滤效率,使用90%体积分数的柴油与10%体积分数的PODE掺混（D90P10）可使CDPF的平均过滤效率提高3.6%。CDPF对核态颗粒物的过滤效率低于86.39%,CDPF对聚集态颗粒物的过滤效率高于91.32%,CDPF对核态的过滤效率低于聚集态。CDPF对不同粒径颗粒物的过滤效率不同,且随颗粒物粒径的增加而增加。两种燃料下,通过CDPF后的颗粒物的几何平均直径（geometric mean diameter, GMD）均减小,NO_x排放降低,CO₂排放增加。     

船用直喷式天然气发动机喷射策略的优化

利用CONVERGE软件基于L23/30DF型船用天然气发动机建立了双天然气喷嘴、双引燃柴油喷嘴的直喷天然气发动机的缸内燃烧过程的CFD计算模型,计算了不同的柴油和天然气喷射时刻和间隔下发动机缸内燃烧和排放过程.结果 表明:引燃柴油的喷射时刻及其与天然气喷射时刻的间隔,对直喷式天然气发动机燃烧和排放性能有重要影响.当喷...     

基于废气再循环的防爆柴油机清洁燃烧技术

针对某型煤矿用防爆柴油机NO_x排放物污染严重、危害大的问题,分析防爆柴油机的燃烧过程,建立燃烧数学模型。通过流体仿真分析软件对基于废气再循环系统的防爆柴油机的清洁燃烧过程模拟仿真并进行台架试验。试验结果表明：在8种工况下加装废气再循环的系统在优化后的废气再循环开度下防爆柴油机CO排放加权平均值为0.004 5%,与未加装废气再循环的系统相比体积分数增加0.004 5%;加装废气再循环的系统在优化后的废气再循环开度下防爆柴油机NO_x排放加权平均值为93.35×10^-6,与未加装废气再循环的系统相比降低56.17%,采用废气再循环的系统对降低防爆柴油机的NO_x排放效果明显。     

国六重型柴油–液化天然气车实际道路排放特性研究

利用便携式排放测试系统（portable emission testing system, PEMS）分别对4辆典型重型柴油车和4辆典型重型液化天然气（liquefied natural gas, LNG）车开展实际道路排放测试,并利用功基窗口法与行程平均法分析其实际道路NO_x、CO、CO₂和颗粒数量（particulate number, PN）排放特性。结果表明：排放后处理技术路线能够有效控制国六重型柴油车在实际道路工况下的NO_x、CO和PN排放;但LNG车的CO排放存在超排放限值的风险,部分LNG车存在NO_x排放超过限值的现象,而PN排放则存在较大不确定性,部分LNG车的PN排放较高。在碳排放方面,LNG车实际道路CO₂比排放较柴油车降低6%~18%,有较为明显的减碳优势。     

燃烧系统参数对商用车发动机燃烧和排放特性的影响研究

为改善商用车发动机性能,采用计算流体力学（computational fluid dynamics, CFD）模拟、正交设计等方法,针对某商用车的燃烧室结构参数设计了4种新方案,并选取油束夹角、喷雾锥角、主喷正时等3个喷油参数开展多因素影响研究。结果表明：燃烧室形状曲线向内收缩且最大半径增大的方案1燃烧室可提升缸内湍流特性,改善燃油浓度分布,使燃烧速度加快,油气混合更好,为最优方案。在喷油参数研究方案中,以碳烟（soot）排放为优化指标时,油束夹角对排放特性影响最大,最优匹配方案是油束夹角147°、喷雾锥角15°、主喷正时-1°,其缸内碳烟排放较原机下降13.91%,且NO_x排放减少13.98%;以氮氧化物（nitrogen oxides, NO_x）排放为优化指标时,主喷正时对排放特性影响最大,最优匹配方案是油束夹角160°、喷雾锥角25°、主喷正时-1°,其缸内NO_x排放较原机降低37.79%。     

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