燃烧室形状、废气再循环和喷油策略对柴油机性能及排放的影响

尽管有关柴油机新型燃烧方式,比如HCCI（Homogeneous Charge Compression Ignition,HCCI）,PCCI（Premixed Charge Compression Ignition,PCCI）,LTC（Low Temperature Combustion,LTC）等研究已经取得很大进步,但是新型燃烧方式大量应用于工程实践还存在较多的技术难题.当前以及未来一段时间内,传统燃烧方式还将会是柴油机的主要燃烧方式.随着排放法规的日益严格,在改善燃油经济性的同时需要大幅度降低污染物排放,所以对影响油耗和污染物排放的参数进行优化和匹配是满足未来排放法规的关键.本文叙述了燃烧室形状、废气再循环（Exhaust Gas Recirculation,EGR）以及喷油策略对柴油机性能及排放的影响,重点总结了近年来提高柴油机性能和排放的新思路,可以为柴油机的优化设计和燃烧控制提供一定的理论参考依据.     

基于遗传算法—优化长短期记忆神经网络的柴油机瞬态NOx排放预测模型研究

为实现选择性催化还原系统（selective catalytic reduction,SCR）尿素喷射量的精确控制,构建并评估了一套利用遗传算法（genetic algorithm,GA）优化长短期记忆（long short term memory,LSTM）神经网络的柴油机瞬态NO_x排放预测模型。针对柴油机瞬态运行特点,选择柴油机NO_x排放的主要影响因素进行相关性分析,确定模型的输入变量;为避免人为选取参数对神经网络预测性能的不良影响,采用遗传算法优化LSTM神经网络的参数,建立预测柴油机瞬态NO_x排放的GA-LSTM模型;最后对预测模型进行了性能测试。结果表明,该模型具有较好的预测能力。     

基于BP神经网络与遗传算法的高压共轨柴油机喷油器结构参数优化研究

利用AVL-FIRE软件对TBD234高压共轨柴油机燃烧过程进行数值模拟,采用L16（54）正交试验作为BP神经网络的训练样本,建立喷油器主要结构参数与柴油机的燃油消耗率、NOx排放、SOOT排放之间的非线性映射关系,以燃油消耗率为优化目标,同时保持较低的NOx和SOOT排放水平,结合遗传算法进行寻优计算,获得了喷孔直径、喷孔个数、喷射夹角和喷油提前角4个参数的最优组合。     

基于V2G的配电网负荷优化策略研究

基于电动汽车与电网互动（V2G）系统,提出一种电动汽车参与配电网负荷优化调节的分析模型。设计了V2G参与负荷调节的控制系统框架,以配电网负荷曲线波动方差最小为目标,考虑电动汽车用户的充电需求、动力电池的充电约束和传输线的功率约束构建了优化分析模型,并采用遗传算法（GA）分析计算,获得负荷优化后的负荷曲线和电动汽车的充放电时间。实例仿真验证了该优化控制法的有效性。     

柴油机尿素选择性催化还原系统虚拟标定及NOx转化率优化方法研究

基于尿素选择性催化还原系统物理模型与尿素喷射量控制模型联合仿真的虚拟标定方法,获得了目标NO_x转化率脉谱;采用多目标遗传算法对尿素选择性催化还原系统进行优化,得到最优尿素喷射量目标值,同时优化了NO_x转化率和NH₃泄漏值。分析了原排参数及优化结果对NO_x转化率的影响。仿真结果表明,采用优化后的尿素喷射量可实现较高的NO_x转化率,在排温200～300℃的条件下NO_x转化率平均提高35%左右,同时满足国六排放法规对NH₃泄漏限值的要求。     

基于网格-坐标化遗传算法的风电场布局优化

采用Jensen尾流模型来描述风电机组间尾流的干扰效应。首先基于网格化的改进遗传算法获得风电机组的数量和布局初始位置,再通过坐标化遗传算法对风电机组位置进行进一步调整优化,从而提高单位成本的发电量。根据所提出的方法,在3种不同的风场（定风向定风速、定风速变风向和变风速变风向）下,针对2 km×2 km的标准风场区域进行风电机组布局优化,再将其应用到不规则的实际案例,对比分析表明所提出的方法能有效提高发电量。     

基于微遗传算法的船用柴油机喷油策略优化及研究

为优化大型船用柴油机的燃油喷射策略,采用微种群遗传算法结合三维数值模拟,在一台大缸径低速船用柴油机上对两个喷油器的主喷时刻、预喷间隔和预喷比例进行了优化,并在优化算例的基础上研究了大型船用柴油机各个喷油器预喷参数和顺序喷射对性能与排放的影响。研究结果表明,在采用顺序喷射的前提下,顺序喷射间隔影响NOx排放和指示燃油消耗率。第一个和第二个喷油器的预喷策略对大型船用柴油机的性能与排放有不同的影响,前者是预喷放热与主喷滞燃期缩短综合作用的结果,而后者主要是预喷放热自身的影响。通过以上研究和优化,柴油机的NOx排放降低了21.27%,表明该方法可以用于优化大型船用柴油机的喷射策略。     

PCCI结合EGR对柴油机燃烧排放的影响

燃烧过程对发动机的整机性能有着重要的影响,通过调整进气门关闭时刻和提前喷油角度可以实现预混压燃,预混压燃(PCCI)能够很好的控制SOOT的排放,但对降低NOx排放不是很明显,PCCI结合外部EGR可以很好地控制NOx的排放。本文运用三维CFD模型对由4102BZLQ柴油机改造的PCCI进行了数值模拟,分析预混压燃对燃烧排放的影响,针对PCCI中NOx高排放问题加入外部EGR,对比不同EGR率时NOx、CO、HC排放的变化,并分析了可能导致NOx、CO、HC变化的机理。     

基于遗传算法优化支持向量机的船用柴油机气门漏气故障智能诊断方法

针对船用柴油机气阀漏气故障的问题,提出一种结合遗传算法（genetic algorithm,GA）与支持向量机（support vector machine,SVM）的船舶柴油机气阀漏气振动诊断方法,称之为遗传算法优化支持向量机（GA-SVM）。通过分析静态与动态工况下的缸盖振动信号,提取训练SVM特征参数,利用GA-SVM的惩罚因子与核函数参数对故障进行识别。试验结果表明,GA-SVM方法完善了SVM参数选取方法,可有效识别柴油机气门漏气故障。优化后的整体故障诊断准确率为99.333%,相比于未优化前的测试集,故障诊断正确率提高了约2%。     

基于信息融合的建模方法及其优化

建立基于神经网络技术的柴油机燃油喷射系统简化模型,然后利用进化编程和遗传算法分别对该模型进行结构和参数的优化。优化结果表明:进化编程算法可以使网络逼近精度足够高;而基于信息基准(AIC)判据的遗传算法可以获得网络逼近精度和结构复杂程度之间的折中。建立的模型结构简单,更适合柴油机这类高速系统的实时控制[1]。     

喷油定时对柴油机超多喷孔预混合燃烧影响研究

柴油机低温预混合燃烧能够同时大幅度降低NOx和碳烟(soot)排放,本研究采用大量废气再循环(EGR)实现低温燃烧来降低NOx排放,采用超多喷孔喷油嘴并结合高压喷射来缩短喷油持续期,实现预混合燃烧从而降低soot排放,主要对喷油定时如何影响柴油机超多喷孔预混合燃烧性能进行了试验研究,选定4个试验工况,通过改变喷油定时来测试柴油机性能,结果显示随着喷油始点从上止点前向后推迟,各工况的NOx和soot排放都有不同程度的同时下降,有别于传统燃烧方式,但HC,CO,比油耗(BSFC)有所升高。     

增压直喷汽油机燃油喷射特性对排放影响的试验研究

基于某1.5L涡轮增压直喷汽油机,搭建试验测试系统,采用试验匹配测试方法研究了喷油模式、喷油时刻、喷油比例、喷油压力等决定燃油喷射特性的关键参数对碳烟排放的影响。试验结果表明:单次喷油模式下在部分负荷时,喷油越提前,碳烟排放越多;在全负荷时,喷油越推迟,碳烟排放越多。在多次喷油模式下,随第一次喷油的推迟碳烟排放降低,随第二、三次喷油的推迟碳烟排放增加。提高喷油压力对部分负荷工况燃烧及排放改善不明显,但外特性工况碳烟排放显著下降,碳氢化合物排放总量也大幅度降低,缸内燃烧速度加快,燃烧稳定性提高,有效燃油消耗率降低约2%。     

Homogeneous Charge Compression Ignition (HCCI) combustion: Implementation and effects on pollutants in direct injection diesel engines

Homogeneous Charge Compression Ignition (HCCI) combustion is a combustion concept which offers simultaneous reductions in both NO_x and soot emissions from internal combustion engines. In light of increasingly stringent diesel emissions limits, research efforts have been invested into HCCI combustion as an alternative to conventional diesel combustion. This paper reviews the implementation of HCCI combustion in direct injection diesel engines using early, multiple and late injection strategies. Governing factors in HCCI operations such as injector characteristics, injection pressure, piston bowl geometry, compression ratio, intake charge temperature, exhaust gas recirculation (EGR) and supercharging or turbocharging are discussed in this review. The effects of design and operating parameters on HCCI diesel emissions, particularly NO_x and soot, are also investigated. For each of these parameters, the theories are discussed in conjunction with comparative evaluation of studies reported in the specialised literature.     

甲醇缸内直喷热氛围燃烧的试验研究

在单缸直喷式柴油机上进行了二甲醚(dimethyl ether,DME)气道喷射和甲醇缸内直喷的甲醇热氛围燃烧试验研究．结果表明,该燃烧方式呈现分布式放热规律,燃烧过程可分为DME低温放热、高温放热和甲醇扩散燃烧 3个阶段．随负荷的增加,实现稳定燃烧的最小DME比例减小．随DME比例减小,DME高温放热和甲醇燃烧滞后．在稳定燃烧的情况下,随DME比例的增大,燃烧效率和热效率降低,HC和NOx排放呈上升趋势,而CO排放先升高后降低．综合考虑,采用最小比例DME有利于提高其热效率、降低排放．此时热效率、HC排放与原柴油机相当, NOx降低约50％,但CO排放相对原柴油机有较大幅度的增加．     

某GDI发动机二次喷油策略的试验研究

本文研究了某汽油机缸内直喷(Gasoline Direct Injection,GDI)发动机二次喷油策略对自然吸气直喷发动机燃烧性能、经济性和排放性的影响规律,优化了二次喷射比例和时刻,为该类型发动机相关参数优化提供了数据积累和依据.试验工况下,随着二次喷油比例的增加,燃烧质量变差,缸内爆发压力降低,缸内燃烧温度降低...     

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。     

Effects of hydrogen injection strategy on the hydrogen mixture distribution and combustion of a gasoline/hydrogen SI engine under lean burn condition

Hydrogen is a carbon free energy carrier with high diffusivity and reactivity, it has been proved to be a kind of suitable blending fuel of spark ignition (SI) engine to achieve better efficiency and emissions. Hydrogen injection strategy affects the engine performance obviously. To optimize the combustion and emissions, a comparative study on the effects of the hydrogen injection strategy on the hydrogen mixture distribution, combustion and emission was investigated at a SI engine with gasoline intake port injection and four hydrogen injection strategies, hydrogen direct injection (HDI) with stratified hydrogen mixture distribution (SHMD), hydrogen intake port injection with premixed hydrogen mixture distribution (PHMD), split hydrogen direct injection (SHDI) with partially premixed hydrogen mixture distribution (PPHMD) and no hydrogen addition. Results showed that different hydrogen injection strategy formed different kinds of hydrogen mixture distribution (HMD). The ignition and combustion rate played an important role on engine efficiency. Since the SHDI could use two hydrogen injection to organize the HMD, the ignition and combustion rate with the PPHMD was the fastest. With the PPHMD, the brake thermal efficiency of the engine was the highest and the emissions were slight more than that with the PHMD. PHMD achieve the optimum emission performance by its homogeneous hydrogen. The engine combustion and emission performance can be optimized by adjusting the hydrogen injection strategy.     

Numerical investigation of water injection quantity and water injection timing on the thermodynamics,combustion and emissions in a hydrogen enriched lean-burn natural gas SI engine

Water direct injection into the cylinder is one of effective ways to suppress the combustion rate and knocking combustion in turbocharged SI engine. In this study, a detailed one-dimensional model coupled with the water direct injection was built by using the GT-Power according to the real tested hydrogen-enriched lean-burn natural gas (NG) SI engine, and validated against the experimental data. Then, a series of cases with various water injection quantity and injection timing were comprehensively investigated on the thermodynamics, combustion and emissions characteristics of the NGSI engine. The impact of the thermo-physical of the water were discussed in detailed by sweeping various water injection quantity and water injection timing. The results indicated that peak combustion pressure and peak heat release rate decreased with the increasing the water injection quantity. In addition, the 50% combustion location and peak combustion pressure location were retarded with the increasing the water injection quantity. As for the water injection timing, the peak combustion pressure and peak combustion temperature were slightly decreased with retarding the water injection timing. Apart from that, the indicated thermal efficiency decreased 4.03% and the equivalent fuel consumption increased 3.56% with injecting 60 mg water into the cylinder compared the case without water injection. Furthermore, the indicated thermal efficiency decreased 4.68% and the equivalent fuel consumption increased 4.66% by sweeping the water injection timing from the 150 CA to 50 CA before top dead center. However, the volumetric efficiency slightly ascended with increasing the water injection quantity and retarding the water injection timing. Finally, the NOx emissions declined with increasing the water injection quantity and retarding the water injection timing. However, CO emission and unburned HC emissions increased with increasing the water injection quantity and retarding the water injection timing. The main aim of this paper is expected to provide a comprehensively assessment of the thermo-physical of water on the thermodynamics, combustion, and emissions of the hydrogen enriched NGSI engine.     

喷射参数对二甲醚PPCCI发动机燃烧与排放特性的影响

在一台6缸增压电控共轨二甲醚发动机上进行试验,研究了预喷时刻、预喷燃料量、喷射压力、主喷时刻等喷射参数对二甲醚部分预混合充量压缩燃烧(PPCCI)发动机燃烧与排放特性的影响。试验结果表明:随预喷时刻提前,缸内压力峰值降低,二甲醚发动机缸内燃烧由两阶段放热转变为PPCCI三阶段放热,氮氧化物(NOx)排放显著降低,HC和CO排放升高;随预喷射燃料量增加,缸内压力峰值及预混合燃烧的冷焰反应和热焰反应速率明显增大,NOx排放逐渐降低,HC和CO排放显著升高;随喷射压力降低,预混合燃烧热焰反应速率增加,主喷扩散燃烧始点推迟,扩散燃烧放热率峰值和NOx排放明显降低,HC和CO排放升高;随主喷时刻推迟,预喷预混合燃烧几乎没有变化,主喷扩散燃烧延后,缸内压力峰值和放热率峰值降低,NOx排放显著降低,HC和CO排放升高。     

柴油机部分均质预混燃烧模式下混合与化学控制参数对指示热效率的影响

基于部分均质预混燃烧(PPC)的柴油机研究开发和优化了一种混合燃烧控制策略,在平均指示压力(IMEP)高达1.1,MPa的负荷范围内实现了高的指示热效率以及超低排放.燃烧过程中的混合与化学控制参数包括了喷油定时、喷油模式(如多脉冲喷射)、增压压力、EGR率以及进气气门关闭定时等,通过优化耦合以上控制参数可以优化控制当量比与温度的变化路径,从而避开NOx与碳烟(Soot)生成区.基于热力学第一定律,通过能量平衡的分析方法研究了混合与化学控制参数对热效率的影响.研究表明,相对于排放而言,热效率受控制参数的影响更加敏感.