重型柴油机尾气NO_x的SCR概述

随着车辆数目的日益增多,汽车尾气污染日趋严重,为了降低柴油机尾气中NOx对大气的污染,SCR(Selective Catalytic Reduction)是一种有效的控制方法。文中着重对SCR降低柴油机尾气中NOx的还原剂喷射和混合管道进行了优化设计。一般认为,柴油机仅仅依靠机内优化措施不能满足欧Ⅳ排放限值的要求,达到第Ⅳ阶段排放标准必须采用排气后处理系统技术。在众多的柴油机排气后处理措施中,选择性催化还原技术最有前途,尤其针对柴油机的NOx排放。     

现代柴油机的技术武器(二)废气后处理装置

大量的研究表明，柴油机仅靠机内净化不能完全满足欧Ⅲ以上的排放法规要求，必须同时采取废气后处理技术。而减少NOx和微粒的排放装置则是实现欧Ⅳ和欧Ⅴ标准废气后处理的有力武器。     

欧Ⅳ发动机排气后处理技术

随着人们环保意识的不断增强,汽车排放法规不断升级,对汽车尾气排放的要求越来越严格。国际上某些公司已针对欧Ⅳ排放法规开发了一种整体式发动机和排气后处理系统,文章叙述了针对欧Ⅳ排放要求的某型号发动机排气后处理技术,详细论述了车用选择性催化还原(SCR)排气后处理系统的工作原理、关键结构及其技术要求,从而呈现了欧Ⅳ与欧Ⅲ发动机的主要技术差异,及其发动机尾气处理的研究方向和发展趋势。     

柴油机排气微粒后处理系统的研制

论述了自行开发研制的以过滤体微波再生技术为基础的柴油机排气微粒后处理系统的总体组成、工作原理、设计原理及设计思想。详细分析了微粒过滤器的结构设计及微波再生系统的特点。试验结果表明，微粒后处理系统对柴油机排气微粒具有一定的净化效果，净化率在５０％～７５％。     

柴油机排气微粒控制技术的发展

柴油机排放的大量微粒和NOx对环境的影响较为严重。回顾了柴油机排气微粒控制技术的发展历程，介绍了柴油机排气微粒控制的三种方法，指出虽然采用缸内措施及燃油质量的改善可大幅度降低微粒排放，但面对未来更为严格的排放法规，需要使用微粒后处理装置，对催化转换器和捕集氧化系统的技术发展进行了较为全面的评述。     

Renault柴油机氮氧化物后处理系统的开发

柴油机为达到未来的废气排放标准限值,要求在机内优化的基础上应用排气后处理系统.Renault公司开发的降氮氧化物(NOx)催化器系统使得质量较重的商务车能达到未来的排放标准,并仍保持柴油机二氧化碳排放低的优势,从而降低了Espace dCi 175型轿车的NOx排放,并达到了欧5排放标准,为未来的欧6排放标准作好了准备...     

满足国Ⅴ排放的重型柴油机排气后处理技术

研究了国外重型发动机在欧Ⅳ到欧Ⅴ阶段(或US2007到US2010)的技术路线,并探讨国内重型柴油机达到国Ⅴ排放可采用的排气后处理技术方案。由于柴油机排放物PM与NOx存在折中效应,为达到国Ⅴ排放标准,应采用组合式后处理技术。在各种后处理技术方案中,SCR+DOC+DPF/POC和EGR+DOC+DPF是两种主要的技术措施,而LNT+DOC+DPF技术对排气中的S特别敏感。     

基于Boost的柴油机微粒捕集器(DPF)性能分析

柴油机微粒排放控制技术已成为柴油机技术发展中的核心之一。文中探讨了微粒捕集器的捕集机理、过滤体材料特性以及再生技术。并利用AVL Boost软件建立模型,仿真分析了发动机的排气温度和柴油机微粒捕集器(Diesel Particulate Filter,DPF)的过滤孔密度对DPF的最高温度、排气背压和排气碳烟量的影响,提出了柴油机微粒捕集器设计优化的方法。     

Audi公司新一代V6涡轮增压直喷式轿车柴油机——热力学、应用和排气后处理

Audi公司开发的新一代V6涡轮增压直喷式(TDI)柴油机系列使柴油动力装置获得进一步发展,其开发目标是在满足欧6排放法规要求的同时降低燃油耗,并进一步提高功率和扭矩。其中,集成模块化近发动机布置的排气后处理装置对达到上述目标起到关键作用,全新设计的链传动机构能为此提供自由的安装空间,因而能在低CO2排放水平下获得最佳的排气后处理效果。详细介绍新型V6-TDI柴油机的热力学、应用和排气后处理系统。     

工程机械用柴油机排放控制标准及措施

介绍了工程机械所用柴油机动力排放的国家标准以及该标准对柴油机尾气排放限值的要求和试验方法，并分别对控制柴油机尾气排放有害物质的几种方法即废气再循环（EGR）、燃料改性、排气微粒后处理系统、使用还原转换装置予以介绍。     

达到欧洲Ⅵ排放法规的新一代车用重载柴油机

概括介绍了2013年将在欧盟实施的车用重载柴油机欧洲Ⅵ排放法规;讨论研发新一代高性能、低燃油消耗、长寿命、达到欧洲Ⅵ排放法规的车用重载柴油机时,在机械开发、燃烧系统、喷油设备、增压和废气再循环系统及排气后处理系统等方面可以采用的先进技术。     

基于模型控制的未来柴油机开发（英文）

Heavy duty diesel vehicles compliant with current Euro VI/EPA13 emission limits employ aftertreatment systems based on DOC/DPF technology for soot and particulate matter reduction and SCR catalysts with urea dosing for NO x reduction. Traditionally, the majority of the control systems used for urea dosing are map based. However, increasing system complexity combined with real-world performance requirements are a strong motivation to switch to a model-based control approach. Firstly, this article describes a model-based design approach for aftertreatment control development. Focus is on urea dosing control for Euro VI level SCR systems. To achieve the legal emissions limits, including in-service conformity over the vehicle lifetime, advanced model-based control strategies enable maximal NO x conversion in combination with minimum ammonia slip, while ensuring robustness against real-life disturbances. Simulation and experimental results of the control system are presented, which demonstrate the performance and robustness properties. Following this model-based approach, a concept study is performed to explore aftertreatment and control technologies to achieve ultra-low NO x emissions as will be imposed by regulatory bodies in the near future. It is shown that aftertreatment concepts with Passive NO x Adsorber and SCR on DPF are most promising. To optimize overall engine-aftertreatment performance, the modelbased control approach is extended towards Integrated Emission Management(IEM). Based on the actual system state, this supervisory controller minimizes operating costs at each instant in time under all operating conditions. This is key for costoptimal and robust performance.     

微粒捕集器再生技术的研究动态和发展趋势

微粒捕集器技术是满足未来车用柴油机严格排放法规的重要措施,再生技术是其中的关键环节。综述了柴油机微粒捕集器再生技术的研究现状,对各种再生技术进行了分析。阐述了这些再生技术存在的问题以及相关措施,并展望了微粒捕集器再生技术的发展趋势。     

Comparison of fuel efficiency and exhaust emissions between the aged and new DPF systems of Euro 5 diesel passenger car

This study was conducted to examine the impact of aged and new DPF systems of the Euro 5 diesel passenger car on fuel efficiency and exhaust emissions. Test diesel vehicle used in this study was equipped with diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) as aftertreatment systems, and satisfied the Euro-5 emissions standard. The displacement volume of engine was 1.6 L and the cumulative mileage was 167,068 km before the test. The FTP-75 test procedure was used, and the time resolved and weight based exhaust emissions of total hydrocarbon (THC), carbon monoxide (CO) and nitrogen oxides (NOx) were measured. The results show that the vehicle with the new DPF system has lower emissions of THC, CO and NOx than the aged one, and fuel efficiency also increased about 5 percent. The aged DPF system had higher backpressure due to the particulate matter (mostly in the form of ash) accumulated in the DPF. As was shown in the analysis using X-CT (X-ray computer tomography), the aged DPF system had particulate matter (PM) accumulated to a length of 46.6 mm. In addition, a component analysis of PM through XRF (X-ray fluorescence) analysis found that 50 % or more of the components consisted of the P, S, Ca, and Zn.     

Computational study on the effects of volume ratio of DOC/DPF and catalyst loading on the PM and NOx emission control for heavy-duty diesel engines

The use of a diesel particulate filter (DPF) in a diesel aftertreatment system has proven to be an effective and efficient method for removing particulate matter (PM) in order to meet more stringent emission regulations without hurting engine performance. One of the favorable PM regeneration technologies is the NO₂-assisted regeneration method due to the capability of continuous regeneration of PM under a much lower temperature than that of thermal regeneration. In the present study, the thermal behavior of the monolith during regeneration and the conversion efficiency of NO₂ from NO with an integrated exhaust system of a diesel oxidation catalyst (DOC) and DPF have been predicted by one-channel numerical simulation. The simulation results of the DOC, DPF, and integrated DOC-DPF models are compared with experimental data to verify the accuracy of the present model for the integrated DOC and DPF modeling. The effects of catalyst loading inside the DOC and the volume ratio between the DOC and DPF on the pressure drop, the conversion efficiency, and the oxidation rate of PM, have been numerically investigated. The results indicate that the case of the volume ratio of ‘DOC/DPF=1.5’ within the same diameter of both monoliths produced close to the maximum conversion efficiency and oxidation rate of PM. Under the engine operating condition of 175 kW at 2200 rpm, 100% load with a displacement of 8.1, approximately 55 g/ft³ of catalyst (Pt) loading inside the DOC with the active Pt surface of 5.3 m²/g_pt was enough to maximize the conversion efficiency and oxidation rate of PM.     

欧Ⅳ及之后中重型柴油机排放控制两大主要技术路线对比评介

介绍了欧Ⅳ及之后中重型柴油机排放控制“优化燃烧＋SCR”与“EGR＋”两大主要技术路线的优缺点及其在欧洲和北美的应用情况,详细分析了SCR和EGR技术的工作原理、系统构成、应用面临的主要问题和挑战等,同时描述了PM后处理器DOC、DPF、POC的发展应用现状。     

浅谈柴油机满足国IV两条技术路线

近年来,随着人们对环境保护的日趋重视,世界各国对内燃机废气排放的要求变得越来越严格,轻型柴油车开始实施国Iv标准。目前由于机内排放控制并不能完全起到净化效果,因此对已排出燃烧室但尚未排到大气中的废气进行处理,采取机外控制技术显得很有必要。PM和NOx是柴油机主要排放污染物,如何同时降低这两种尾气组成,达到国Ⅳ排放水平,是当今世界柴油机技术的难点和研究热点。本文介绍目前国内满足柴油机国IV排放标准的SCR和EGRDPF／DOC两种主流技术路线。通过对比分析两种系统的原理和优缺点得出适合国内发展的路线,并浅谈未来柴油机排放控制的发展方向。     

变海拔下米勒循环对柴油机及DPF性能的影响

基于某高压共轨柴油机建立了一维热力学仿真模型,对DPF选型进行了优化,并分析了不同海拔下米勒循环对柴油机及DPF性能的影响。结果表明,选择非对称结构以及适当增加载体目数都有利于降低DPF压降,同时可降低DPF对柴油机动力性、经济性及原始排放的影响。进气门早关可以降低柴油机有效燃油消耗率,提高热效率,降低NOx排放,但会导致颗粒物排放增加;同时可降低DPF压降,提高DPF捕集效率,且随海拔升高,进气门早关的时刻越小,作用越明显。在低海拔条件下,进气门晚关策略对柴油机动力性、经济性及排放特性均影响不大;在高海拔条件下,适当增加进气门晚关时刻可以改善柴油机性能。     

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%.