Advances in emission control of diesel vehicles in China

Diesel vehicles have caused serious environmental problems in China. Hence, the Chinese government has launched serious actions against air pollution and imposed more stringent regulations on diesel vehicle emissions in the latest China VI standard. To fulfill this stringent legislation, two major technical routes, including the exhaust gas recirculation (EGR) and high-efficiency selective catalytic reduction (SCR) routes, have been developed for diesel engines. Moreover, complicated aftertreatment technologies have also been developed, including use of a diesel oxidation catalyst (DOC) for controlling carbon monoxide (CO) and hydrocarbon (HC) emissions, diesel particulate filter (DPF) for particle mass (PM) emission control, SCR for the control of NOx emission, and an ammonia slip catalyst (ASC) for the control of unreacted NH₃. Due to the stringent requirements of the China VI standard, the aftertreatment system needs to be more deeply integrated with the engine system. In the future, aftertreatment technologies will need further upgrades to fulfill the requirements of the near-zero emission target for diesel vehicles.     

Developing China's roadmap for air quality improvement: A review on technology development and future prospects

Air pollution control policies in China have been experiencing profound changes, highlighting a strategic transformation from total pollutant emission control to air quality improvement, along with the shifting targets starting from acid rain and NO_x emissions to PM_2.5 pollution, and then the emerging O₃ challenges. The marvelous achievements have been made with the dramatic decrease of SO₂ emission and fundamental improvement of PM_2.5 concentration. Despite these achievements, China has proposed Beautiful China target through 2035 and the goal of 2030 carbon peak and 2060 carbon neutrality, which impose stricter requirements on air quality and synergistic mitigation with Greenhouse Gas (GHG) emissions. Against this background, an integrated multi-objective and multi-benefit roadmap is required to provide decision support for China's long-term air quality improvement strategy. This paper systematically reviews the technical system for developing the air quality improvement roadmap, which was integrated from the research output of China's National Key R&D Program for Research on Atmospheric Pollution Factors and Control Technologies (hereafter Special NKP), covering mid- and long-term air quality target setting techniques, quantitative analysis techniques for emission reduction targets corresponding to air quality targets, and pathway optimization techniques for realizing reduction targets. The experience and lessons derived from the reviews have implications for the reformation of China's air quality improvement roadmap in facing challenges of synergistic mitigation of PM_2.5 and O₃, and the coupling with climate change mitigation.     

High NO2/NOx emissions downstream of the catalytic diesel particulate filter: An influencing factor study

Diesel vehicles are responsible for most of the traffic-related nitrogen oxide (NO_x) emissions, including nitric oxide (NO) and nitrogen dioxide (NO₂). The use of after-treatment devices increases the risk of high NO₂/NO_x emissions from diesel engines. In order to investigate the factors influencing NO₂/NO_x emissions, an emission experiment was carried out on a high pressure common-rail, turbocharged diesel engine with a catalytic diesel particulate filter (CDPF). NO₂ was measured by a non-dispersive ultraviolet analyzer with raw exhaust sampling. The experimental results show that the NO₂/NO_x ratios downstream of the CDPF range around 20%–83%, which are significantly higher than those upstream of the CDPF. The exhaust temperature is a decisive factor influencing the NO₂/NO_x emissions. The maximum NO₂/NO_x emission appears at the exhaust temperature of 350°C. The space velocity, engine-out PM/NO_x ratio (mass based) and CO conversion ratio are secondary factors. At a constant exhaust temperature, the NO₂/NO_x emissions decreased with increasing space velocity and engine-out PM/NO_x ratio. When the CO conversion ratios range from 80% to 90%, the NO₂/NO_x emissions remain at a high level.     

EGR率对农用单缸柴油机燃用生物柴油的NOx与PM排放特性影响分析

单缸柴油机作为小型农用机械不可或缺的动力源,在使用过程中会产生大量污染物.其中氮氧化合物（NO_x）和颗粒（PM）是气溶胶的主要组成部分,对大气环境造成了严重污染.为有效改善农用单缸柴油机NO_x和PM排放,本研究通过添加生物柴油对柴油进行改质以及采用机内EGR净化技术两种方案,测量了柴油机分别燃用柴油B0,生物柴油调合燃料B20、B50在不同EGR率下的NO_x和PM排放.结果表明,采用EGR技术能够明显改善柴油机的NO_x排放,但同时会引起碳烟排放的增加.通过在柴油中添加生物柴油能够在一定程度上降低碳烟排放,其中高负荷、大EGR率条件下的改善最为明显.在2000 r·min^-1、75%负荷,EGR率为30%时,燃用B50的碳烟排放与燃用B0相比降低了47.3%.总体上柴油中添加生物柴油与EGR技术共同作用能够有效降低柴油机高负荷工况时的颗粒排放总数量.     

Advances in air pollution control for vessels in China

Vessel emissions have contributed a great deal to air quality deterioration in China. Hence,the Chinese government has promulgated a series of stringent emission regulations. It is in this context that vessel emission control technology research is in full swing. In particular,during the 13th Five-Year Plan, the air pollution control technology of vessels has greatly improved. Vessel emission control has followed two main governance routes: source emission reduction and aftertreatment technology...     

City-specific vehicle emission control strategies to achieve stringent emission reduction targets in China's Yangtze River Delta region

The Yangtze River Delta (YRD) region is one of the most prosperous and densely populated regions in China and is facing tremendous pressure to mitigate vehicle emissions and improve air quality. Our assessment has revealed that mitigating vehicle emissions of NOx would be more difficult than reducing the emissions of other major vehicular pollutants (e.g., CO, HC and PM_2.5) in the YRD region. Even in Shanghai, where the emission control implemented are more stringent than in Jiangsu and Zhejiang, we observed little to no reduction in NOx emissions from 2000 to 2010. Emission–reduction targets for HC, NOx and PM_2.5 are determined using a response surface modeling tool for better air quality. We design city-specific emission control strategies for three vehicle-populated cities in the YRD region: Shanghai and Nanjing and Wuxi in Jiangsu. Our results indicate that even if stringent emission control consisting of the Euro 6/VI standards, the limitation of vehicle population and usage, and the scrappage of older vehicles is applied, Nanjing and Wuxi will not be able to meet the NOx emissions target by 2020. Therefore, additional control measures are proposed for Nanjing and Wuxi to further mitigate NOx emissions from heavy-duty diesel vehicles.     

重型柴油车道路循环工况下排放特性的仿真分析

柴油车道路工况下NO_x排放和排温的动态特性对柴油机排气后处理系统的工作以及后处理系统控制策略的确定具有重要的影响.根据6114涡轮增压柴油机的万有特性及NO_x和排温的MAP图,仿真分析了道路循环工况下配有6114柴油机的重型柴油车的NO_x排放和排温的动态变化;研究了道路工况、行驶特征、驾驶行为以及柴油车载荷等对柴油车排放的影响规律.研究结果表明,城市道路循环工况下,柴油车NO_x排放的整体水平不高,但变化频繁、剧烈;高速公路道路循环工况下,柴油车NO_x排放整体水平较高,但变化平缓;加速过程,尤其是在高速区对柴油车排放的影响显著;冲动的驾驶方式会显著提高柴油车的排放水平;满载时,柴油车的高排放区将由半载时的高速高加速区向外扩展至其他工况点,高排放区显著增大.     

柴油轿车颗粒多环芳烃的排放特性

以一辆柴油轿车为研究样车,分别使用纯柴油、生物柴油掺混比例为10%的B10燃油,进行了NEDC整车循环工况试验,测取了该车HC、CO、NOx、颗粒等法规限制的排放,利用气相色谱-质谱法对采集的排气颗粒样品进行了分析,重点研究了颗粒中多环芳烃的排放特性.结果表明,与柴油相比,燃用B10燃油的HC、CO、NOx和颗粒等常规排放均有所降低;两种燃料产生的颗粒多环芳烃排放中均以荧蒽和芘最多,与纯柴油相比,燃用B10燃油产生的低环数PAHs排放略有增加,中高环数的PAHs排放降幅明显.苯并[a]芘等效毒性分析结果显示燃用B10燃油的BEQs值比纯柴油降低了21.6%,表明柴油轿车燃用生物柴油后,排气颗粒的多环芳烃毒性有所下降.     

北京市农业机械排放因子与排放清单

利用车载排放测试技术对典型的联合收割机、拖拉机、农用运输车和农田建设机械实际工况下的尾气进行测试,建立了实际工况下农业机械的排放因子和2017年北京市农用机械排放清单.结果表明,不同的工作状态对农业机械尾气排放有较大的影响,怠速和行走时CO、NO_x、HC和PM排放趋于平稳;而切地和翻地模式下的波动较为明显.根据各类机械的分类和排放标准对排放因子进行细化,建立了较为完整的实际工况下的排放因子.根据农业机械排放因子和燃油消耗量计算出2017年北京市CO、NO_x、HC和PM的排放量分别是2 566.60、 1 239.29、 563.08和538.32 t.拖拉机、运输机械和联合收割机的污染物总量占CO、NO_x、HC和PM这4种污染物总量的98%、 95%、 95%和98%.因此,农用拖拉机、运输机械和联合收割机在农业机械污染减排中应作为重点控制对象.     

成都市非道路施工机械排放清单研究

随着大气污染控制形势的日益严峻,非道路移动源排放日益受到关注.本研究通过软件调研获得了成都市非道路施工机械保有量、功率分布,通过现场及文献调研获得了非道路施工机械活动水平数据.参照《非道路移动污染源排放清单编制技术指南(试行)》中的方法,计算了成都市2018年非道路施工机械排放清单.结果表明,2018年成都市非道路施工机械PM、HC、NO_x和CO的排放量分别为845、2898、16738、11231 t.按机械类型划分,挖掘机4项污染物排放占比最高,PM、HC、NO_x和CO分别占59%、61%、59%和62%;按排放阶段划分,国2机械4项污染物排放占比最高,PM、HC、NO_x和CO分别占55%、66%、68%和65%.排放清单结果的不确定性受到多种因素的影响,其中影响最大的为排放因子.     

Vehicle emissions of primary air pollutants from 2009 to 2019 and projection for the 14th Five-Year Plan period in Beijing, China

Over the past decade, the emission standards and fuel standards in Beijing have been upgraded twice, and the vehicle structure has been improved by accelerating the elimination of 2.95 million old vehicles. Through the formulation and implementation of these policies, the emissions of carbon monoxide (CO), volatile organic compounds (VOCs), nitrogen oxides (NO_x), and fine particulate matter (PM_2.5) in 2019 were 147.9, 25.3, 43.4, and 0.91 kton in Beijing, respectively. The emission factor method was adopted to better understand the emissions characteristics of primary air pollutants from combustion engine vehicles and to improve pollution control. In combination with the air quality improvement goals and the status of social and economic development during the 14th Five-Year Plan period in Beijing, different vehicle pollution control scenarios were established, and emissions reductions were projected. The results show that the emissions of four air pollutants (CO, VOCs, NO_x, and PM_2.5) from vehicles in Beijing decreased by an average of 68% in 2019, compared to their levels in 2009. The contribution of NO_x emissions from diesel vehicles increased from 35% in 2009 to 56% in 2019, which indicated that clean and energy-saving diesel vehicle fleets should be further improved. Electric vehicle adoption could be an important measure to reduce pollutant emissions. With the further upgrading of vehicle structure and the adoption of electric vehicles, it is expected that the total emissions of the four vehicle pollutants can be reduced by 20%-41% by the end of the 14th Five-Year Plan period.     

乌鲁木齐市城区机动车大气污染物排放特征

对乌鲁木齐市城区车辆信息(包括车流量和车辆构成、车辆控制技术水平、车辆行驶工况、车辆启动分布等)进行调研和测试,并根据IVE模型计算得到机动车污染物排放清单,获得分车型、燃料类型及启动/运行方式的机动车污染物排放分担率.结果表明:2011年乌鲁木齐市机动车CO、NO_x、HC和PM的排放量分别为20.22×104、2.60×104、1.84×104和0.44×10~4t·a~(-1),机动车污染物排放分担率差别显著,乘用车、公交车和重型货车是CO和HC主要排放源;重型货车和乘用车是NO_x的主要排放源;重型货车是PM的主要排放源.汽油车是CO和HC排放的主要来源,柴油车是NO_x和PM排放的主要来源,天然气车各类污染物排放量均较低.控制柴油重型货车是消减机动车污染物排放的重要方式.     

On-board measurements of gaseous pollutant emission characteristics under real driving conditions from light-duty diesel vehicles in Chinese cities

A total of 15 light-duty diesel vehicles(LDDVs) were tested with the goal of understanding the emission factors of real-world vehicles by conducting on-board emission measurements. The emission characteristics of hydrocarbons(HC) and nitrogen oxides(NOx) at different speeds, chemical species profiles and ozone formation potential(OFP) of volatile organic compounds(VOCs) emitted from diesel vehicles with different emission standards were analyzed. The results demonstrated that emission reductions of HC and NOxhad been achieved as the control technology became more rigorous from Stage I to Stage IV. It was also found that the HC and NOxemissions and percentage of O2 dropped with the increase of speed, while the percentage of CO2 increased. The abundance of alkanes was significantly higher in diesel vehicle emissions, approximately accounting for 41.1%–45.2%, followed by aromatics and alkenes. The most abundant species were propene,ethane, n-decane, n-undecane, and n-dodecane. The maximum incremental reactivity(MIR)method was adopted to evaluate the contributions of individual VOCs to OFP. The results indicated that the largest contributors to O3 production were alkenes and aromatics, which accounted for 87.7%–91.5%. Propene, ethene, 1,2,4-trimethylbenzene, 1-butene, and1,2,3-trimethylbenzene were the top five VOC species based on their OFP, and accounted for 54.0%-64.8% of the total OFP. The threshold dilution factor was applied to analyze the possibility of VOC stench pollution. The majority of stench components emitted from vehicle exhaust were aromatics, especially p-diethylbenzene, propylbenzene, m-ethyltoluene, and p-ethyltoluene.     

Exhaust emission inventory of typical construction machinery and its contribution to atmospheric pollutants in Chengdu, China

To study the emission characteristics of typical construction machinery in Chengdu, 12 construction machinery (excavators, bulldozers, loaders, and forklifts) under idling mode, moving mode, and working mode, were tested using a portable emission measurement system (PEMS). Under three operating modes, the typical construction machinery in the working mode was higher in the fuel-based average emission factors of PM_2.5 and NO_x, while the fuel-based average emission factors of HC and CO were higher in idling mode. Integrated the results of investigation on ownership and activity levels of construction machinery, an exhaust emission inventory of typical construction machinery of Chengdu in 2018 was established according to the recommendation method. The annual emission of PM_2.5, NO_x, HC, and CO were 1.67 × 10⁶, 1.61 × 10⁸, 3.83 × 10⁶, and 1.26 × 10⁷ kg, respectively, and the excavator contributed the maximum emissions, accounting for an average proportion of 43.95%. The emission of construction machinery in Chengdu exhibited a clear monthly trend, with the highest from April to October and the lowest from November to March. In addition, the exhaust emissions presented an obvious spot-like characteristics, and the high-value areas were mainly concentrated in the surrounding suburban counties such as Shuangliu Wenjiang etc. To reduce pollution from construction machinery and improve the quality of the atmospheric environment, more effective measures on housing construction and municipal construction should be taken in those districts in Chengdu.     

VOC emission caps constrained by air quality targets based on response surface model: A case study in the Pearl River Delta Region, China

Because of the recent growth in ground-level ozone and increased emission of volatile organic compounds (VOCs), VOC emission control has become a major concern in China. In response, emission caps to control VOC have been stipulated in recent policies, but few of them were constrained by the co-control target of PM_2.5 and ozone, and discussed the factor that influence the emission cap formulation. Herein, we proposed a framework for quantification of VOC emission caps constrained by targets for PM_2.5 and ozone via a new response surface modeling (RSM) technique, achieving 50% computational cost savings of the quantification. In the Pearl River Delta (PRD) region, the VOC emission caps constrained by air quality targets varied greatly with the NO_x emission reduction level. If control measures in the surrounding areas of the PRD region were not considered, there could be two feasible strategies for VOC emission caps to meet air quality targets (160 µg/m³ for the maximum 8-hr-average 90th-percentile (MDA8-90%) ozone and 25 µg/m³ for the annual average of PM_2.5): a moderate VOC emission cap with <20% NOx emission reductions or a notable VOC emission cap with >60% NO_x emission reductions. If the ozone concentration target were reduced to 155 µg/m³, deep NO_x emission reductions is the only feasible ozone control measure in PRD. Optimization of seasonal VOC emission caps based on the Monte Carlo simulation could allow us to gain higher ozone benefits or greater VOC emission reductions. If VOC emissions were further reduced in autumn, MDA8-90% ozone could be lowered by 0.3-1.5 µg/m³, equaling the ozone benefits of 10% VOC emission reduction measures. The method for VOC emission cap quantification and optimization proposed in this study could provide scientific guidance for coordinated control of regional PM_2.5 and O₃ pollution in China.     

柴油/甲醇组合燃烧发动机的氮氧化物排放研究

在增压共轨发动机上采用柴油/甲醇组合燃烧(DMCC)方式进行了氮氧化物排放特性研究.对DMCC模式下NO x、NO、NO2等排放与纯柴油模式的对比分析表明:DMCC模式下的NO x排放比原机模式平均下降10%以上,NO平均下降幅度超过40%;采用DMCC模式后,NO2排放量都有明显大幅度的升高,并且NO2/NO比值呈现显著增大,平均高达100%以上.     

BED含氧燃料在不同海拔下对柴油机PM和NOx排放的影响

为研究生物柴油-乙醇-柴油(简称为BED)含氧燃料在不同海拔下对柴油机微粒(PM)和氮氧化物(NO_x)排放的影响,在一台高压共轨柴油机上分别燃用纯柴油和BED含氧燃料,在两种大气压力(81和100 k Pa)下进行了排放试验研究.结果表明,燃用纯柴油和B15E5(15%生物柴油+5%乙醇+80%柴油,体积比)燃料后,在中、低负荷时的PM排放在高气压下基本高于低气压下,最高增幅分别达到26.2%和19.0%;在全负荷时的PM排放在高气压下降低,最高降幅分别达到6.1%和17.0%.燃用B25E5(25%生物柴油+5%乙醇+70%柴油,体积比)燃料后,PM排放在高气压下降低.燃用纯柴油后,柴油机在高气压下的NO_x排放低于低气压下;燃用B15E5和B25E5含氧燃料后,在中、低负荷下的NO_x排放在高气压下降低,在全负荷下的NO_x排放在高气压下升高.在中、低负荷下NO_x排放最高降幅分别达到12.1%和15.3%;在全负荷下,NO_x排放最高增幅分别达到6.5%和5.8%.在不同大气压力下,柴油机燃用纯柴油和BED含氧燃料后,PM与NO_x排放均呈现明显的trade-off关系.相比于在低气压下,随负荷增加引起的PM排放降幅和NO_x排放增幅在高气压下增加.     

高低压废气再循环系统(EGR)对进气道喷醇式柴油甲醇双燃料发动机的影响

以一台加装了进气道喷醇系统（MIIA）、高低压废气再循环系统（EGR）的2.8 L增压中冷高压共轨直喷柴油机为平台,在不同负荷下开展不同外部EGR循环方式对进气道喷醇式柴油甲醇双燃料发动机性能影响的试验研究.结果表明,柴油甲醇组合燃烧（DMCC）技术对EGR技术具有良好兼容性.在采用国VI排放法规标准规定的稳态试验循环（WHSC）测试条件下,借助EGR技术的DMCC发动机氮氧化物（NO_x）排放会显著降低且颗粒物（PM）保持在较低水平,打破了NO_x-PM的trade-off关系.此外,不同EGR方式对排放特性、进排气参数、燃烧特性和经济性能的影响存在显著差异,耦合排气背压阀（BPV）后的低压EGR策略可实现更高的EGR率,将NO_x排放降至国VI限值附近.但同等EGR率下发动机采用高压EGR更具优势,利于均质混合气的形成,增加预混燃烧占比,获得更高的燃烧效率和热效率.然而受限于高EGR率需求,采用单一型式EGR策略实现DMCC发动机满足国VI限值仍存在困难.     

Impacts of continuously regenerating trap and particle oxidation catalyst on the NO2 and particulate matter emissions emitted from diesel engine

Two continuously regenerating diesel particulate filter (CRDPF) with different configurations and one particles oxidation catalyst (POC) were employed to perform experiments in a controlled laboratory setting to evaluate their effects on NO₂, smoke and particle number emissions. The results showed that the application of the after-treatments increased the emission ratios of NO₂/NO_x significantly. The results of smoke emissions and particle number (PN) emissions indicated that both CRDPFs had sufficient capacity to remove more than 90% of total particulate matter (PM) and more than 97% of solid particles. However, the POC was able to remove the organic components of total PM, and only partially to remove the carbonaceous particles with size less than 30 nm. The negligible effects of POC on larger particles were observed due to its honeycomb structure leads to an inadequate residence time to oxidize the solid particles or trap them. The particles removal efficiencies of CRDPFs had high degree of correlations with the emission ratio of NO₂/NO_x. The PN emission results from two CRDPFs indicated that more NO₂ generating in diesel oxidation catalyst section could obtain the higher removal efficiency of solid particles. However this also increased the risk of NO₂ exposure in atmosphere.     

辽宁省港口邻近区域海运废气排放测算

为准确测算沿海地区船舶废气排放量,基于试验数据确定了NO_x、CO、HC和CO₂排放因子;结合文献资料和海事局进出港船舶签证数据,采用基于船舶活动过程的方法测算了2014年辽宁省港口邻近区域〔距港口减速区外边界25 n mile(1 n mile=1 852 m)以外的边界线与港口陆地岸线所围成的区域〕海运废气排放清单. 结果表明:2014年辽宁省港口邻近区域海运NO_x、CO、HC、CO₂、SO₂和PM(颗粒物)的排放量分别为11 827.1、971.4、399.6、1 097 426.5、11 654.1和959.2 t;散货船、集装箱船和油船3种主要类型船舶的NO_x、CO、HC、CO₂、SO₂和PM的分担率之和分别为74.7%、77.8%、70.8%、68.0%、70.9%和70.6%;主机NO_x、CO、HC、CO₂、SO₂和PM的分担率最大,分别为63.7%、63.0%、46.0%、40.4%、46.4%和45.3%;停泊工况下的NO_x、CO、HC、CO₂、SO₂和PM排放量分别为3 318.3、281.7、168.3、520 194.9、4 894.0和411.5 t. 船舶降速运行、减少停港时间、燃用低硫油和向船舶供应岸电等措施能降低港口邻近区域海运废气排放. 基础数据缺乏或数据代表性不足给废气排放清单带来了一定的不确定性.