正丁烷气相着火的骨架反应机理模型

为了研究正丁烷催化着火过程中气相反应与表面反应的相互作用，需要建立一个能够与表面催化反应机理耦合且规模较小的正丁烷着火动力学机理模型。通过反应途径分析和灵敏度分析相结合的方法，构建了包含80个组分和378个基元反应的气相动力学机理。通过与详细机理进行对比，该简化机理在压力1 MPa、计量比1、初始温度700 K条件下燃料和氧气的消耗速率、温度以及主要产物（H2O和CO2）的分布等保持一致。同时，在较宽的压力(0.1、1、2、3 MPa)、计量比（0.5、1、2）和温度（650～1450 K）范围内与详细机理计算的着火延迟时间具有很好的一致性，体现了简化机理的准确性。     

甲烷/乙烷与甲烷/丙烷混合燃料着火特性

利用激波管与CHEMKIN软件研究了不同初始条件下乙烷和丙烷的掺混对甲烷着火延迟时间的影响规律,并从化学动力学角度分析了掺混乙烷和丙烷对甲烷着火延迟时间造成影响的原因。实验与模拟研究表明乙烷和丙烷的掺混会造成甲烷着火延迟时间的大幅度缩短,但随着温度的升高,其对甲烷着火延迟时间的影响逐渐变小。通过敏感性分析发现无论是甲烷/乙烷混合燃料还是甲烷/丙烷混合燃料,对着火促进最大的基元反应都是H+O₂=O+OH（R1）,在甲烷/乙烷和甲烷/丙烷混合燃料的着火反应中对着火抑制最大的两个基元反应是CH₄+H=CH₃+H₂（R128）和CH₄+OH=CH₃+H₂O（R129）。通过路径分析发现在甲烷/乙烷与甲烷/丙烷混合燃料中,随着混合燃料中乙烷与丙烷比例的增加,甲烷的主要反应路径基本不发生变化,主要影响了CH₃的消耗速率。     

基于贵金属催化剂的低浓度甲烷催化燃烧实验研究

本文在自行搭建的催化燃烧实验台上,用贵金属催化剂进行了低浓度甲烷燃烧实验,研究了催化剂活性组分、催化剂载体、甲烷浓度、混合气流速和温度对甲烷转化率的影响。结果表明,钯-铑催化剂起燃温度最低为280℃,铂催化剂均在300℃以上。钯-铑催化剂的甲烷转化率最高可达90%,而铂催化剂最高仅为75%。因此,钯-铑催化剂更适合于甲烷催化燃烧。     

正丁烷气相着火的骨架反应机理模型

为了研究正丁烷催化着火过程中气相反应与表面反应的相互作用,需要建立一个能够与表面催化反应机理耦合且规模较小的正丁烷着火动力学机理模型。通过反应途径分析和灵敏度分析相结合的方法,构建了包含80个组分和378个基元反应的气相动力学机理。通过与详细机理进行对比,该简化机理在压力1 MPa、计量比1、初始温度700 K条件下燃料和氧气的消耗速率、温度以及主要产物（H₂O和CO₂）的分布等保持一致。同时,在较宽的压力（0.1、1、2、3 MPa）、计量比（0.5、1、2）和温度（650～1450 K）范围内与详细机理计算的着火延迟时间具有很好的一致性,体现了简化机理的准确性。     

分解炉用无烟煤的催化燃烧研究

在无烟煤中添加CuO,Fe2O3,MnO2,可以不同程度的改善无烟煤的着火温度;通过燃烧产物的XRD分析,探讨了催化剂催化燃烧的机理:催化剂在煤粉燃烧过程中参与了无烟煤燃烧中的化学反应过程,对无烟煤中难燃的碳发生了催化燃烧反应,使无烟煤着火温度下降.     

甲烷催化燃烧的实验研究

在含铂的Ｍｏｎｏｌｉｔｈ催化剂上进行了甲烷的催化燃烧反应。实验表明，室温下必须先用氢气来点火，甲烷才能催化燃烧。甲烷催化燃烧的允许工作温度为９００～１１００℃，过低的温度导至熄火，过高则会使铂催化剂失活。在实验的反应条件下，甲烷进料浓度范围很窄为４％—６％（体积）。为实现甲烷的稳定燃烧必须对反应条件提出较高的自动化要求     

甲烷催化燃烧反应工艺研究进展

甲烷催化燃烧是一种清洁高效的甲烷燃烧技术,在节能减排中具有重要的应用价值。从催化剂、反应工艺和过程强化等方面对近年来甲烷催化燃烧技术进行综述,重点介绍颗粒催化剂固定床反应工艺、整体式催化剂反应工艺、流化床反应工艺和吸放热耦合反应工艺研究进展。用于固定床反应器的颗粒催化剂主要为负载型贵金属催化剂和非贵金属氧化物催化剂。贵金属催化剂活性好,起燃温度低,适合低浓度甲烷的催化燃烧。非贵金属氧化物催化剂耐高温性好,适合较高浓度甲烷燃烧体系。整体式催化剂的甲烷催化燃烧反应工艺中,最常用的是蜂窝陶瓷和金属合金等整体式催化剂的多段式催化燃烧反应器的设计。设计直接采用多段式整体催化剂,催化剂的位置不同,发挥的催化作用也不同。流化床催化燃烧装置具有燃烧过程接触面积广、热容量大和换热效率高等特点,可有效避免传统的固定床催化燃烧反应工艺存在的问题,非常适合应用于低浓度甲烷的催化燃烧过程。利用甲烷催化燃烧强放热的特点,将催化燃烧产生的热量进行时间或空间的耦合,可以开发出吸-放热耦合反应工艺。其中,固定床催化反应器中的流向变换强制周期操作作为一种高效的过程强化技术,在节约反应器成本的同时,可以提高反应热量的利用率。     

催化剂对兖州煤泥燃烧特性的影响

为充分利用煤泥资源 ,在其中添加助燃催化剂 ,以期提高它的燃烧热效率 .对比研究了硝酸钾催化剂及 TF配方助燃催化剂对兖州煤泥着火温度、燃尽温度和放热面积的影响 .研究结果表明 ,添加催化剂后 ,煤泥着火温度降低 ,燃尽温度提前 ,且燃烧放热量增加 ;TF配方催化剂对煤泥催化燃烧的效果优于硝酸钾催化剂 .探讨了助燃催化剂对煤催化燃烧的作用机理 .     

二氧化硫在钒催化剂上氧化动力学的研究——Ⅰ.永利钒催化剂的动力学方程式

<正>二氧化硫在钒催化剂上的氧化动力学问题,已经有很多人进行过研究。不过异相催化过程一般是比较复杂的,影响催化速度的因素除了催化剂本身的化学及表面性质,反应的温度,反应物与生成物的浓度之外,还有反应物或生成物在催化剂表面上的吸附或解吸速度,到达或离开催化剂表面上的物质传递过程的速度等复杂性。     

甲烷/乙烷与甲烷/丙烷混合燃料着火特性

利用激波管与CHEMKIN软件研究了不同初始条件下乙烷和丙烷的掺混对甲烷着火延迟时间的影响规律,并从化学动力学角度分析了掺混乙烷和丙烷对甲烷着火延迟时间造成影响的原因。实验与模拟研究表明乙烷和丙烷的掺混会造成甲烷着火延迟时间的大幅度缩短,但随着温度的升高,其对甲烷着火延迟时间的影响逐渐变小。通过敏感性分析发现无论是甲烷/乙烷混合燃料还是甲烷/丙烷混合燃料,对着火促进最大的基元反应都是H+O_2=O+OH(R1),在甲烷/乙烷和甲烷/丙烷混合燃料的着火反应中对着火抑制最大的两个基元反应是CH_4+H=CH_3+H_2(R128)和CH_4+OH=CH_3+H_2O(R129)。通过路径分析发现在甲烷/乙烷与甲烷/丙烷混合燃料中,随着混合燃料中乙烷与丙烷比例的增加,甲烷的主要反应路径基本不发生变化,主要影响了CH_3的消耗速率。     

A novel approach to reduce hydrocarbon emissions from the HCCI engine

A novel approach is proposed and investigated to reduce unburned hydrocarbon emissions from a homogeneous charge compression ignition (HCCI) engine by using in-cylinder catalysts. The combustion and emission characteristics of this HCCI engine are numerically simulated in three cases, i.e., the baseline engine with an uncoated piston crown, the engine with a platinum coating on the top and side surfaces of the piston crown (full coated case) and the engine with a platinum coating only on the side surface of the piston crown (partial coated case). A detailed reaction mechanism of methane oxidation on platinum catalyst is adopted. The results show that the unburned hydrocarbons of the HCCI engine arise primarily from sources near the combustion chamber wall, such as flame quenching at the entrance of crevice volumes and at the combustion chamber wall, and the adsorption and desorption of methane into and from the cylinder wall. The in-cylinder catalyst gives rise to a reduction of exhaust unburned hydrocarbon (UHC) emissions by approximately 15% with the full coating of platinum catalyst on the piston crown, however, with the partial coating, the in-cylinder catalyst can reduce the UHC emissions by approximately 20%.     

Fe2O3催化无烟煤燃烧燃点降低机理的实验研究

利用TG-DTG法和DTA法研究了无烟煤催化燃烧时燃点的变化情况,结果表明Fe2O3可使无烟煤的燃点降低。基于无烟煤燃点的形成原因和催化热解过程,研究了催化热解过程中热解转化率、热解气组成、半焦表面结构的变化情况,结果表明Fe2O3促进了无烟煤的热解,热解转化率、热解气的组成明显变化,热解气热值增加。催化热解产生的半焦表面形貌粗糙,颗粒细碎,比表面积大。由于热解过程直接影响到点燃过程,因此通过催化热解的研究,可知催化燃烧过程中均相燃烧（热解气燃烧）提供给异相燃烧（半焦燃烧）的热量高于非催化燃烧。同时催化热解所得半焦的吸附氧气能力强,在低温时吸附氧气的速率较快,缩短了达到点燃时所需氧气浓度的时间,进而降低了无烟煤的燃点。     

Homogeneous charge compression ignition of LPG and gasoline using variable valve timing in an engine

The combustion characteristics and exhaust emissions in an engine were investigated under homogeneous charge compression ignition (HCCI) operation fueled with liquefied petroleum gas (LPG) and gasoline with regard to variable valve timing (VVT) and the addition of di-methyl ether (DME). LPG is a low carbon, high octane number fuel. These two features lead to lower carbon dioxide (CO₂) emission and later combustion in an LPG HCCI engine as compared to a gasoline HCCI engine. To investigate the advantages and disadvantages of the LPG HCCI engine, experimental results for the LPG HCCI engine are compared with those for the gasoline HCCI engine. LPG was injected at an intake port as the main fuel in a liquid phase using a liquefied injection system, while a small amount of DME was also injected directly into the cylinder during the intake stroke as an ignition promoter. Different intake valve timings and fuel injection amount were tested in order to identify their effects on exhaust emissions and combustion characteristics. Combustion pressure, heat release rate, and indicated mean effective pressure (IMEP) were investigated to characterize the combustion performance. The optimal intake valve open (IVO) timing for the maximum IMEP was retarded as the λ_TOTAL was decreased. The start of combustion was affected by the IVO timing and the mixture strength (λ_TOTAL) due to the volumetric efficiency and latent heat of vaporization. At rich operating conditions, the θ_90-20 of the LPG HCCI engine was longer than that of the gasoline HCCI engine. Hydrocarbon (HC) and carbon monoxide (CO) emissions were increased as the IVO timing was retarded. However, CO₂ was decreased as the IVO timing was retarded. CO₂ emission of the LPG HCCI engine was lower than that of the gasoline HCCI engine. However, CO and HC emissions of the LPG HCCI engine were higher than those of the gasoline HCCI engine.     

A fundamental study on the control of the HCCI combustion and emissions by fuel design concept combined with controllable EGR. Part 2. Effect of operating conditions and EGR on HCCI combustion

In Part 1, the effects of octane number of primary reference fuels and equivalence ration on combustion characteristics of a single-cylinder HCCI engine were studied. In this part, the influence of exhaust gas recirculation (EGR) rate, intake charge temperature, coolant temperature, and engine speed on the HCCI combustion characteristics and its emissions were evaluated. The experimental results indicate that the ignition timing of the first-stage combustion and second-stage combustion retard, and the combustion duration prolongs with the introduction of cooled EGR. At the same time, the HCCI combustion using high cetane number fuels can tolerate with a higher EGR rate, but only 45% EGR rate for RON75 at 1800 rpm. Furthermore, there is a moderate effect of EGR rate on CO and UHC emissions for HCCI combustion engines fueled with n-heptane and RON25, but a distinct effect on emissions for higher octane number fuels. Moreover, the combustion phase advances, and the combustion duration shorten with the increase of intake charge temperature and the coolant out temperature, and the decrease of the engine speed. At last, it can be found that the intake charge temperature gives the most sensitive influence on the HCCI combustion characteristics.     

Effect of a narrow fuel spray angle and a dual injection configuration on the improvement of exhaust emissions in a HCCI diesel engine

The aim of this work was to investigate the effect of narrow fuel spray angle injection and dual injection strategy on the exhaust emissions of a common-rail diesel engine. To achieve successful homogeneous charge compression ignition by an early timing injection, a narrowed spray cone angle injector and a reduced compression ratio were employed. The combination of homogeneous charge compression ignition (HCCI) combustion and conventional diesel combustion was studied to examine the exhaust emission and combustion characteristics of the engine under various fuel injection parameters, such as injection timings of the first and second spray.The results showed that a dual injection strategy consisting of an early timing for the first injection for HCCI combustion and a late timing for the second injection was effective to reduce the NO_x emissions while it suppress the deterioration of the combustion efficiency caused by the HCCI combustion.     

Ignition control of homogeneous-charge compression ignition (HCCI) combustion through adaptation of the fuel molecular structure by reaction with ozone

The present paper describes a method of controlling the time of ignition in homogeneous-charge compression ignition (HCCI) combustion. In the described experiments some control of ignition timing in HCCI combustion is achieved through alteration of the fuel molecular structure using a chemical reaction of the fuel with ozone, prior to introduction of the fuel into the combustion chamber. Controlling ignition timing is essential, in achieving high thermal efficiency and low pollutant emission in HCCI engine operation. To this end, ignition should occur in the vicinity of piston top-dead-centre (TDC), the point of maximum compression of the fuel-air charge. The present paper proposes a method of controlling the time of ignition of the fuel-air charge by adapting the ignitability of the fuel through prior chemical reaction of the fuel with ozone. Ozone can be readily produced using air in conjunction with a corona discharge ozoniser and may be brought into contact with the fuel in a reaction chamber before its injection into the engine. It was shown through experiments that an acetal fuel which has undergone treatment with ozone, ignites earlier during the engine cycle in HCCI combustion, than fuel which has not undergone treatment with ozone, as a result of changes in its molecular structure prior to combustion. The observed changes in molecular structure consisted primarily in the formation of peroxides within the fuel. This method can be used to operate an engine in HCCI combustion mode with some control over the point of ignition of the fuel-air charge by varying the proportions of fuel previously treated with ozone and fuel not treated with ozone. The experiments showed that the time of ignition could be controlled, whilst keeping other parameters such as the load and speed of the engine, and pressure and temperature of the intake air and fuel, constant.     

Ignition control of methane fueled homogeneous charge compression ignition engines using additives

Homogeneous charge compression ignition is a new combustion technology that may develop as an alternative to diesel engines with high efficiency and low NO_x and particulate matter emissions. In this paper, the effect of additives such as dimethyl ether (DME), formaldehyde (CH₂O) and hydrogen peroxide (H₂O₂) for the control of ignition in natural-gas HCCI engines have been investigated numerically by adopting a single-zone zero-dimensional model. The chemical kinetic mechanism incorporated the GRI-3.0 mechanism that considers 53 species and 325 reactions together with the DME reaction scheme consisting of 79 species and 351 reactions. To simulate HCCI engine cycles, a variable volume computation has been performed by including a piston motion into the SENKIN code at a fixed equivalence ratio of 0.3 and initial mixture pressure of 1.5 bar. It was found that an additive-free mixture did not ignite for the intake temperature of 400 K. A mixture containing a small quantity of additives at the same temperature was ignited. For a fixed quantity of additive, it was found that H₂O₂ addition was effective in advancing the ignition timing as compared to the other two additives. It was found that the percentage of additives required to achieve a near TDC ignition timing increases linearly with the increase in the engine speed while decreases with the increase in the equivalence ratio with the superiority of H₂O₂. Furthermore, the addition of even 7% by volume of H₂O₂ could ignite a mixture at an intake temperature of 350 K, while at least the fractions of 12.5% and 35% by volume were needed for DME and CH₂O, respectively. It was also found that the mass fraction of NO with CH₂O addition was less than that with H₂O₂ addition. At the same time, however, a near TDC ignition timing resulted in a similar amount of NO for both additives. Overall, the enhanced reactivity of CH₄ in the presence of small amounts of additives could be used in HCCI engines fueled with methane to alleviate the high intake temperature requirements.     

Sn催化剂对柴油车排气颗粒去除效果

制备了以Sn为活性组分,以Cu、K、V为助催化剂,以TiO₂/γ-Al₂O₃/堇青石为载体的催化剂,催化剂在700℃下于空气中在马弗炉活化3h.采用DSC/TG测试方法确定催化剂的活性.研究发现,以Sn为活性组分的催化剂能显著降低颗粒的起燃温度和扩大燃烧温度范围,Cu、 K、V的添加能进一步降低起燃温度,而燃烧温度范围却稍有所变窄.活化会降低催化活性,活化导致活性下降的原因不是由催化剂的烧结引起的,而是由活性组分的挥发流失造成的.     

Effect of composite aftertreatment catalyst on alkane, alkene and monocyclic aromatic emissions from an HCCI/SI gasoline engine

Designing automotive catalysts for effective control of NO_x, HC and CO emissions under both lean and stoichiometric engine operation is a challenging task. The present work assesses the performance efficiency of a three-zone prototype catalytic convertor in reducing exhaust emissions from a gasoline engine, operating in Homogeneous Charge Compression Ignition (HCCI) and Spark Ignition (SI) mode under lean and stoichiometric conditions. The performance of the convertor for HC oxidation follows the order: lean HCCI > stoichiometric SI > stoichiometric HCCI. The study mainly focused on the quantitative analysis of C1-C7 hydrocarbon compounds before and after the catalytic convertor. The results show that monocyclic aromatic hydrocarbons such as toluene are present at higher concentrations in the exhaust under HCCI operation than in the SI case. On the other hand, benzene concentrations are higher in the SI exhaust. The most common exhaust products of the two engine operating modes are methane, ethylene, propylene, benzene, and toluene. The prototype catalytic convertor eliminates most of the hydrocarbon species in the exhaust under both combustion modes, especially with a lean mixture. Conversion efficiencies for the different hydrocarbon species over the catalyst were in the order of alkenes > alkanes > aromatics. Hydrogen was added upstream of the catalyst primarily to assess its ability to promote NO_x reduction, however it was also found to influence the oxidation characteristics of the catalyst. During H₂ addition, the methane concentration was higher downstream of the catalyst.     

A chemical kinetics model of iso-octane oxidation for HCCI engines

The necessity of developing a practical iso-octane mechanism for homogeneous charge compression ignition (HCCI) engines is presented after various different experiments and currently available mechanisms for iso-octane oxidation being reviewed and the performance of these mechanisms applied to experiments relevant to HCCI engines being analyzed. A skeletal mechanism including 38 species and 69 reactions is developed, which could predict satisfactorily ignition timing, burn rate and the emissions of HC, CO and NO_x for HCCI multi-dimensional modeling. Comparisons with various experiment data including shock tube, rapid compression machine, jet stirred reactor and HCCI engine indicate good performance of this mechanism over wide ranges of temperature, pressure and equivalence ratio, especially at high pressure and lean equivalence ratio conditions. By applying the skeletal mechanism to a single-zone model of HCCI engine, we found out that the results were substantially identical with those from the detailed mechanism developed by Curran et al. but the computing time was reduced greatly.