碳烟氧化模型的研究及在车用柴油机中的计算应用

提出了一个基于平均反应率的碳烟氧化模型,将其应用于柴油机数值模拟中,并结合试验方法研究了后喷射对碳烟排放的影响。将Hiroyasu碳烟生成模型和文中提出的碳烟氧化模型耦合在CFD源程序中构建多维模型,利用数值解析的手段,根据不同的后喷射方案计算柴油机碳烟的生成和氧化历程,并结合试验数据分析后喷射影响碳烟氧化的各种因素。研究结果表明,采用碳烟氧化模型和试验方法能真实反映柴油机碳烟的生成和氧化历程以及后喷射对碳烟排放的影响规律。     

重型柴油机瞬态工况排放和EGR影响的试验研究

本文中对一重型柴油机瞬态工况下的NOx与碳烟排放和引入EGR技术的影响进行试验研究。结果表明,引入EGR后,NOx的瞬态排放有所改善;但碳烟的瞬态排放恶化;关闭EGR阀可缓解碳烟瞬态排放的恶化。通过直流电机EGR阀关闭阶跃试验,揭示了EGR阀的关闭对发动机各项性能的影响规律,为重型柴油机瞬态排放的EGR控制提供了依据。     

重型柴油机DPF非线性非稳态碳载量估算方法研究

通常可以使用压差传感器估计柴油机微粒捕集器(DPF)中的碳载量，但其在较低排气流量时的非线性和非稳定状态下，准确性会严重下降。为了提高精度，建立了新的碳载量估算方法，以计算DPF中的炭烟累计量，从而提高主动再生触发时间的精度。该模型基于发动机炭烟排放和DPF内的炭烟氧化平衡，由炭烟排放模型、NO₂被动再生模型和炭烟高温氧化模型3个子模型组成。测试验证是基于全球统一瞬态试验循环(WHTC)进行的。试验结果表明，在载碳形成过程中，碳载量计算值与实测值的平均误差为4.6%。随着排气温度和NO₂浓度增加，被动再生加快，主动再生间隔延长。     

基于国六标准工况的重型柴油机PN排放特性研究

搭建柴油机排放测试平台,探究某重型柴油机在国六阶段瞬态循环和稳态循环试验中颗粒数目的排放特性。结果表明:无论是瞬态循环还是稳态循环,柴油机颗粒数排放都与其DPF碳载量密切相关。     

基于碳烟粒径分布预测的柴油燃烧机理构建与氧含量影响研究

为预测柴油机碳烟排放的粒径分布，选用90%摩尔分数的正庚烷和10%摩尔分数的甲苯作为柴油替代物，分别构建气相动力学机理和表面动力学机理，并将二者耦合，构建成柴油替代物机理（简称HTS机理），将HTS机理结合矩量法数值模型进行了机理验证，并通过改变进气发动机进气氧的体积分数，进一步研究了氧浓度对碳烟粒径分布的影响。研究结果表明，在滞燃期、层流火焰速度、预混火焰关键组分、预混火焰碳烟粒径分布、柴油机缸压与放热率以及柴油机排放物生成等方面，应用HTS机理计算的模拟值与试验值基本一致。使用HTS机理研究氧浓度对碳烟粒径分布的影响表明：随着氧浓度的增加，碳烟颗粒平均数密度降低、数密度峰值减小、数密度峰值对应的颗粒物直径增大；且小粒径（直径0～50 nm）碳烟的数密度随之降低。     

柴油机碳烟排放的数值模拟及试验研究

考虑碳烟粒子生成速率同时受控于涡团破碎速率和化学反应速率,提出一种输运控制率与碳烟氧化率混合控制模型进行碳烟计算,并用此模型对一台直喷式柴油机燃烧与排放生成过程进行了多维数值模拟。结果表明,计算模拟结果与试验测量结果吻合较好,且使用该模型能够预测柴油机研究样机的碳烟生成与氧化历程。     

基于卷积神经网络的柴油机DPF状态辨识研究

针对柴油机颗粒捕集器功能失效的问题,应用GT-SUITE软件对柴油机颗粒捕集器进行仿真分析,研究颗粒捕集器温度、压降和碳烟浓度等与其状态的关联关系,并采用一维卷积神经网络对颗粒捕集器状态特征"自学习",提高颗粒捕集器状态辨识的准确度.     

面向控制的DPF再生效率建模和试验研究

对柴油机颗粒物捕集器(DPF)的再生效率进行实时和准确的在线预估,可为DPF热再生结束的控制提供判断依据,是实现DPF系统化和高效应用的重要功能.本文基于热再生过程中DPF内碳烟颗粒的氧化反应机理探讨并建立了DPF再生效率计算模型,通过发动机台架试验对模型的化学反应动力学参数进行了校核和辨识,从而得到DPF内碳烟颗粒热...     

CDPF被动再生特性及再生平衡条件研究

根据Arrhenius方程建立催化型柴油机颗粒捕集器(CDPF)被动再生化学反应模型。通过在一台重型柴油发动机上进行台架试验,对建立的CDPF被动再生模型进行标定和验证,标定后的CDPF被动再生模型可很好地预测CDPF中碳烟被NO_2氧化的反应速率。结果表明,碳烟氧化速率随CDPF初始碳载量的增大和床温的升高而提高;在初始碳载量为3.8 g/L、NO_x含量为550×10~(-6)的工况下CDPF平衡温度约为283℃;增加NO_x排放可促进CDPF被动再生的进行,降低被动再生平衡点碳载量和平衡温度;再生平衡曲线与预设碳载量有关,随着预设碳载量的增大,再生平衡曲线下移,被动再生区域增大。     

高压共轨柴油机燃烧与排放模型的研究

利用高速闪光摄影技术,对高压喷射喷雾体空间发展规律进行了试验分析,提出了一个计算高压喷射喷雾体发展的数学公式;在正确描述高压燃油喷雾的基础上,建立了一个能预测高压共轨柴油机性能和排放的准维燃烧模型,此模型改进了燃油喷射模型及碳烟的生成与氧化模型,考虑到燃烧区的区间传热和缸内工质的对流辐射传热,对一台高压共轨柴油机进行了仿真计算。计算与试验结果对比分析表明,改进后的燃烧与排放模型能较好地反映缸内各区的燃烧与排放情况。     

Effect of fuel choice on nanoparticle emission factors in LPG-gasoline bi-fuel vehicles

Nanoparticle and gas-phase emission factors are presented for a liquefied petroleum gas (LPG) passenger vehicle and are compared to gasoline operation. A bi-fuel LPG-gasoline vehicle certified for use on either fuel was used as the test vehicle so that a direct comparison of the emissions could be made based on fuel choice. These values were considered along with previous studies to determine the relative change in particulate emissions due to fuel choice over a wide range of vehicles and operating conditions. The vehicle examined in this study was tested on a chassis dynamometer for both steadystate and transient conditions. Transient test cycles included the US FTP72 driving cycle, Japanese driving cycle and modified Indian driving cycle while steady-state tests were done at vehicle speeds ranging from 10–90 km/hr in various transmission gears. Exhaust particle size distributions were measured in real-time using a differential mobility spectrometer (DMS50), and particle number and particle mass emission factors were calculated. For both fuels, the majority of the particles ranged from 5 to 160 nm in terms of particle diameter, with typically more than 85% of the particles in the nucleation mode (between 5–50 nm). In most cases, the vehicle produced a greater fraction of larger (accumulation mode) particles when fuelled on LPG. Using the data in the literature as well as the data in the current study, gasoline fuel produces 4.6 times more particles in terms of number and 2.1 times more particles in terms of mass.     

EGR柴油机瞬态性能优化研究

以降低瞬态过程烟度和NO_x排放为目标,在一台高压共轨电控重型柴油机上进行了EGR对柴油机恒转速增扭矩5s典型瞬态过程燃烧和排放性能影响的优化研究。结果表明:瞬态过程中固定EGR阀开度造成EGR率"超调"、烟度剧增;与"全程轨压"策略相比,"分段轨压"有利于改善小负荷工况的燃烧热氛围,提高瞬态起始负荷并耦合"分段轨压"可以有效降低瞬态过程烟度峰值;EGR阀的开闭对瞬态性能影响最大,瞬态过程1.5s关阀、4s开阀的策略可以实现较好的烟度和NO_x排放折中,消光烟度峰值为9.2%,NO_x峰值稍有增加但增幅不大。     

Experimental evaluation of SOF effects on EGR cooler fouling under various flow conditions

An experiment was conducted to characterize the effects of SOF on EGR cooler fouling. A removable singletube test rig combined with a soot generator was developed to represent an EGR cooler and diesel exhaust gas. The use of a soot generator, which controlled the size and concentration of soot particles, enabled independent variables to be completely controlled. Either n-dodecane or diesel lube oil as substitute SOFs were vaporized and injected into the test rig to evaluate their effects on the growth of PM deposits and the degradation performance of the EGR cooler. Coolant temperature, which seemed to be associated with SOF content, was chosen as an independent variable, and PM deposit mass per unit area and the effectiveness drop versus time increased as the coolant temperature decreased. The PM deposit mass per unit area and effectiveness drop had maximum values at a coolant temperature of 40°C for every n-dodecane injection rate. For substitute SOFs tested in this experiment, the deposit mass increased when either n-dodecane or diesel lube oil was injected, but the effect of lube oil was more significant. Diesel lube oil seemed to have a stronger effect on the reduction of thermal conductivity by filling pores in the deposits. When diesel lube oil was injected, the deposit mass per unit area increased 127% compared to dry soot without injection. The effectiveness drop after 10 hours increased only 12.5%.     

Morphological Change and Number-Size Distributions of Particulate Matter (PM) from a Diesel Generator Operated with Wood Pyrolysis Oil-Butanol Blended Fuel

This report details our experimental study investigating particulate matter (PM) emissions from a diesel generator fueled with wood pyrolysis oil (WPO)–butanol blended fuel for electricity generation. Particle number-size distributions and PM mass concentrations from diesel, n-butanol, and WPO-butanol blended fuels were investigated via aerosol measurements using a fast mobility particle sizer and an aerosol monitor with three generator outputs (0, 3.3, and 6.6 kWe). For the n-butanol and WPO-blended fuels, the total number concentrations of exhaust particles were higher than that of conventional diesel combustion; however, the PM mass was observed to be nearly zero for all the engine operating conditions due to the higher number concentration in the nuclei mode. The morphology of the exhaust particles was investigated by analyzing transmission electron microscopy (TEM) micrographs. The morphology of the particles was drastically changed according to the test fuels and engine loads. Two types of particles were observed, including soot and coke shaped particles. These results were directly related to the immaturity of incipient soot particles due to the different physical properties and chemical compositions of the fuels.     

高原低氧环境下含氧燃料对柴油机工作过程的影响

以高原共轨柴油机为研究机型,根据台架试验和发动机结构参数,运用A V L Fire构建其燃用B100（纯生物柴油）和B70N30（体积70％生物柴油＋30％正丁醇）的三维CFD模型,并进行验证。利用该模型对比研究了不同海拔氧浓度对发动机燃用不同含氧燃料工作过程的影响规律,并在此基础研究了B70N30耦合EGR对发动机的影响机理。计算结果表明：相比D100（纯柴油）,B100和B70N30的缸内局部当量比降低,活性自由基（OH ,O）浓度及其缸内分布区域增大,从而导致NO排放升高,但同时使CO生成量峰值减小,Soot和CO缸内分布区域以及排放终值都随大气氧浓度的降低而显著减少;相比B100,B70N30因汽化潜热增大,其NO排放降低,但原子氧的增加导致Soot和CO同时降低;对于B70N30,随EGR率增大,NO大幅度降低,CO显著升高,而Soot因滞燃期延长变化较小。     

预混合氢气对柴油机燃烧和排放性能的影响

针对预混合氢气的柴油机,在AVL Fire软件上建立了计算模型,并与试验结果进行对比,验证模型的准确性。在此基础上改变了喷射策略,对发动机缸内工作过程及相应的燃烧和排放性能进行数值模拟和分析。研究结果表明：随着预混合氢气质量分数的增加,缸内压力和温度升高,NOx 排放恶化,Soot排放改善;随着预喷射油量和预喷间隔角的增加,NOx 质量分数升高,Soot质量分数降低;随着后喷射喷油量的增加,缸内压力和放热率稍微减小,NOx 和Soot质量分数降低;随着后喷间隔角的增加,缸内压力、放热率、NOx 和Soot排放均未发生明显变化。     

环境温度对缸内直喷汽油车颗粒物排放特性的影响

利用电子低压冲击仪(ELPI)对一台满足国Ⅴ排放标准的缸内直喷汽油车进行了颗粒物排放特性研究。试验按照NEDC测试循环在转鼓试验台上进行,分别测量车辆在-15℃,-7℃和25℃下的颗粒物排放。通过对试验结果的研究表明:3个温度下,颗粒物的数量浓度随温度的下降大幅上升,粒径分布范围逐渐变大,均在相同粒径下出现峰值;颗粒物体积浓度随粒径的增大而增大;数量浓度对表面积浓度的影响大于体积浓度,尤其在-15℃下,这种影响更加显著。通过对颗粒物的瞬态排放结果的分析发现:3个温度下,颗粒物的排放主要集中在NEDC循环前200s,数量浓度随车辆的加速而上升,随减速而下降;在-15℃下,在整个NEDC循环的加速工况均出现表面积浓度的排放峰值,且峰值之间较为接近。     

柴油机碳烟颗粒在NO气氛下的催化氧化研究

围绕柴油机碳烟颗粒在NO气氛下的催化氧化问题进行相关的实验研究。通过稀土氧化物氧化铈和氧化镧分别负载硝酸盐制备了实验用催化剂,并在催化剂和碳烟颗粒"松接触"情况下,研究了在NO背景下对碳烟颗粒催化氧化过程,实现了在NO背景下对碳烟颗粒催化氧化;实验结果还显示,采用复合性稀土氧化物更能促进碳烟颗粒催化氧化,更有利于同时解决柴油车排放过程中产生的PM和NOx,从而为了开发高性能柴油机用催化剂提供了重要的实验基础。     

Nano-particle emission characteristics of European and Worldwide Harmonized test cycles for heavy-duty diesel engines

This study was conducted for the experimental comparison of particulate emission characteristics between the European and World-Harmonized test cycles for a heavy-duty diesel engine as part of the UN/ECE PMP ILCE of the Korea Particulate Measurement Program. To verify the particulate mass and particle number concentrations from various operating modes, ETC/ESC and WHTC/WHSC, were evaluated. Both will be enacted in Euro VI emission legislation. The real-time particle emissions from a Mercedes OM501 heavy-duty golden engine with a catalyst based uncoated golden DPF were measured with CPC and DMS during daily test protocol. Real-time particle formation of the transient cycles ETC and WHTC were strongly correlated with engine operating conditions and after-treatment device temperature. The higher particle number concentration during the ESC #7 to #10 mode was ascribed to passive DPF regeneration and the thermal release of low volatile particles at high exhaust temperature conditions. The detailed average particle number concentration equipped for golden DPF reached approximately 4.783E+11 #/kWh (weighted WHTC), 6.087E+10 #/kWh (WHSC), 4.596E+10 #/kWh (ETC), and 3.389E+12 #/kWh (ESC). Particle masses ranged from 0.0011 g/kWh (WHSC) to 0.0031 g/kWh (ESC). The particle number concentration and mass reduction of DPF reached about 99%, except for an ESC with a reduction of 95%.     

加载停滞时间对柴油机瞬态性能的影响

为了改善柴油机瞬态加载过程中燃烧与排放性能恶化的问题,在一台增压中冷柴油机上,利用瞬态测控系统,试验研究了先快后慢的多段加载策略,探索不同的加载停滞时间对柴油机θCA10,θCA50,烟度和CO,NOx等排放物的影响规律。试验结果表明:与匀速加载策略相比,加载停滞时间越长,排放性能越好,烟度和CO峰值最大分别降低20.8%和38.32%,但NOx略有增加;在第二段加载过程中θCA10和θCA50延后程度降低;加载过程后期缸内空燃比下降趋势更加缓和。