国六柴油机轨压和喷油正时对柴油机性能的影响

为优化柴油机性能,基于一台配备了完整国Ⅵ后处理系统的高压共轨直列4缸柴油机,开展了柴油机负荷特性研究,在此基础上研究轨压和喷油正时对柴油机性能的影响。研究结果表明：以适当较小的轨压配合较为提前的喷油正时可以达到较为理想的柴油机油耗及排放;轨压和喷油正时对HC排放的影响较小;轨压对柴油机油耗、排温、NO_x排放、CO排放的影响较大,且在中等偏高负荷时更为敏感,随着轨压增加了57 MPa,柴油机油耗、排温分别下降了16.1 g/（kW·h）、63 ℃,NO_x排放上升了663×10^-6,CO排放下降了785×10^-6;喷油正时对烟度及柴油机氧化催化器前端温度T₄、柴油机颗粒捕集器前端温度T₅、选择性催化还原系统前端温度T₆的影响较大,且在低负荷时更为敏感。随着喷油正时提前6.0°,烟度下降了0.43%,T₄、T₅、T₆峰值出现在轨压为76 MPa且喷油正时为上止点前7.5°时,温度分别为315.3、338.4、329.3 ℃。     

工作环境对自然吸气柴油机性能影响仿真

基于CY4102BG四冲程自然吸气柴油机,利用GT-POWER一维仿真计算软件建立柴油机工作过程仿真模型,研究高原和水下工作环境对柴油机性能的影响。仿真结果表明：随着海拔的增高,柴油机有效功率有所下降,NO_x排放上升,排气温度增加;随着水下排气背压的增高,柴油机有效功率下降,NO_x排放显著上升。针对柴油机在非标况环境下NO_x排放性能的恶化,通过调节喷油参数来优化柴油机综合性能。经优化,在不同工作环境下柴油机NO_x排放降低7.3%~21.4%,优化效果较为明显。     

水冷中冷器对非道路移动机械用柴油机性能的影响

为研究进气特性对非道路移动机械用柴油机动力性能及排放的影响,建立某柴油机系统一维仿真模型,结合柴油机试验数据对该模型的污染物排放与动力输出进行分析。通过台架试验验证模型的可靠性,并分析不同进气温度对整机的影响。试验结果显示：进气温度对柴油机性能有显著影响;使用水冷中冷器能够有效提升柴油机性能,并抑制碳烟与NO_x的生成,使非道路移动机械能够满足更严格的排放标准。     

可变进气对船用柴油机性能影响的试验研究

为了探究可变进气系统对船用柴油机性能的影响,在一台配备进气可变配气和进气旁通阀的船用中速柴油机上开展试验研究。分别在可变配气机构处于强米勒正时和弱米勒正时,进气旁通阀处于开启和关闭状态下开展船用柴油机螺旋桨特性试验。试验结果表明：采用弱米勒正时可降低燃油消耗率,但是最高燃烧压力和NO_x比排放增加,燃油消耗率降低幅度随负荷升高而减小,最高燃烧压力和NO_x比排放增加幅度随负荷升高而增加,弱米勒正时对低负荷优化效果更明显。受到最高燃烧压力限制,高负荷必须采用强米勒正时。弱米勒正时角度从20°增加到30°,燃油消耗率基本不变,最高燃烧压力和NO_x比排放进一步增加,对于试验柴油机而言,20° 弱米勒正时配置更优。开启进气旁通阀可以提高中低负荷增压压力,降低燃油消耗率、排温和烟度。在超低负荷及高负荷时开启进气旁通阀效果与中低负荷相反。在25%及50%负荷下应用可变进气技术,燃油消耗率分别降低6.0%和2.9%、烟度分别降低61.6%和59.7%。合理的可变进气系统控制策略可有效优化船用柴油机性能。     

基于小型柴油机多喷油参数协同优化的试验研究

针对一款1.06 L非道路三阶段排放的卧式柴油机,以非道路四阶段稳态排放循环8个工况为基础,展开油轨压力、喷射正时、预喷—主喷间隔、预喷油量4个参数单因子变化和多因子协同变化对柴油机油耗和排放影响的试验研究。利用参数扫描法进行比油耗和NO_x等排放的多目标优化,使发动机排放达到非道路第四阶段法规的要求。通过分析各喷射参数对油耗和排放的敏感性,获得产品优化提升的指导方案。研究结果表明：喷射正时和轨压对柴油机有效燃油消耗率、NO_x排放及CO排放的影响较大,对碳氢化合物（HC）排放影响较小。预喷—主喷间隔和预喷量对燃烧热效率和CO排放影响较大,对其他排放影响微弱。合理设定轨压和喷射正时的标定组合,可获得最佳的NO_x排放与油耗的折中关系。此外,预喷可以有效降低HC排放。多参数协同优化后的8个工况排放加权结果为：颗粒物（particular matter, PM）排放为0.09 g/（kW·h）,HC+NO_x排放为4.17 g/（kW·h）,CO排放为1.46 g/（kW·h）,实现了产品优化升级并达到了“非四”排放法规的要求。     

满足非道路国四排放标准的大功率柴油机技术

某型大功率柴油机的排放值不满足非道路国四排放法规的要求,为此,对该柴油机燃油喷射系统、燃烧系统、增压系统和后处理系统进行优化设计和匹配。优化喷油策略,使柴油机的PM、CO和HC排放降低到非道路国四限值以下;安装选择性催化还原系统以降低NO_x排放。标定试验结果表明,升级后的柴油机满足非道路国四排放法规要求。     

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%。     

喷射正时和喷油持续期对正丁醇-正辛醇双燃料发动机性能的影响

将正丁醇、正辛醇分别作为预混合直喷燃料应用于双燃料发动机中,并利用KIVA4-CHEMKIN程序研究喷射正时和喷油持续期对正丁醇-正辛醇双燃料发动机燃烧及排放特性的影响。结果表明：喷射正时从5°提前到10°时,可以提高发动机的缸内平均压力、热释放率 （heat release rate,HRR）峰值和平均指示压力 （indicated mean effective pressure,IMEP）,减少CO排放量,但会使最大压力升高率和NO_x排放量增加。当喷射正时进一步提前到15°时,会导致机械损失增加,IMEP下降。延长喷油持续期可以降低缸内平均压力、HRR峰值、最大压力升高率和NO_x排放量,提高IMEP,但会使CO排放量先减少后增加。     

聚甲氧基二甲醚/汽油双燃料火花辅助压燃燃烧和排放特性研究

对一台4缸缸内直喷汽油机的进气歧管和活塞进行改造,搭建了聚甲氧基二甲醚（polyoxymethylene dimethyl ethers, PODE）/汽油双燃料火花辅助压燃（spark assisted compression ignition, SACI）发动机试验平台,以PODE和汽油分别作为直喷和进气道燃料,系统地研究了直喷策略、进气温度和点火正时对双燃料发动机燃烧和排放特性的影响规律。结果表明：在转速为1 600 r/min、负荷为0.4 MPa时,不同直喷正时的试验工况下,双燃料SACI燃烧存在3种不同的燃烧模式。随着直喷正时的提前发动机燃烧趋向于均质压燃,但过于靠前的直喷正时会使得发动机起燃变得困难,不完全燃烧比例增加。在稳定燃烧的前提下发动机在接近均质压燃的燃烧模式下可以获得更高的热效率,同时实现极低的NO_x和颗粒物排放。提高进气温度能够显著降低不完全燃烧比例并促进燃料起燃,使得发动机能在更早的直喷正时稳定运行,同时抑制了总碳氢（total hydrogen carbon, THC）和CO排放,但对低温燃烧模式下的NO_x排放影响较小。进气温度80 ℃下的最佳热效率相比40 ℃下提高了11.3%,对应的直喷正时提前了30°。提前点火能够促进燃烧的完全进行从而提高热效率,并有效降低THC和CO排放。在较短的喷油—点火间隔下,点火正时的变化能够改变燃烧进程从而实现对燃烧相位的控制。随着直喷正时的提前,点火正时对燃烧的影响减弱。基于合适的进气温度和点火正时,发动机使用汽油/PODE双燃料可以在接近均质压燃的燃烧模式下实现高效清洁的燃烧。     

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。     

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.     

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。     

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.     

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     

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%.