Experimental investigation and comparison of nanoparticle emission characteristics in light-duty vehicles for two different fuels

In recent years, particle number emissions rather than particulate mass emissions in automotive engines have become the subject with controversial discussions. Recent results from studies of health effects imply that it is possible that particulate mass does not properly correlate with the variety of health effects attributed to engine exhaust. The concern is now focusing on nano-sized particles emitted from I. C. engines. In this study, particulate mass and particle number concentration emitted from light-duty vehicles were investigated for a better understanding of the characteristics of the engine PM from different types of fuels, such as gasoline and diesel fuel. Engine nano-particle mass and size distributions of four test vehicles were measured by a condensation particle counter system, which is recommended by the particle measurement program in Europe (PMP), at the end of a dilution tunnel along a NEDC test mode on a chassis dynamometer. We found that particle number concentrations of diesel passenger vehicles with DPF system are lower than gasoline passenger vehicles, but PM mass has some similar values. However, in diesel vehicles with DPF system, PM mass and particle number concentrations were greatly influenced by PM regeneration. Particle emissions in light-duty vehicles emitted about 90% at the ECE15 cycle in NEDC test mode, regardless of vehicle fuel type. Particle emissions at the early cold condition of engine were highly emitted in the test mode.     

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.     

Effects of gasoline, diesel, LPG, and low-carbon fuels and various certification modes on nanoparticle emission characteristics in light-duty vehicles

This study was focused on experimental comparisons of the effects of various vehicle certification modes on particle emission characteristics of light-duty vehicles with gasoline, diesel, LPG, and low-carbon fuels such as bio-diesel, bioethanol, and compressed natural gas, respectively. The particulate matter from various fueled vehicles was analyzed with the golden particle measurement system recommended by the particle measurement programme, which consists of CVS, a particle number counter, and particle number diluters. To verify particle number and size distribution characteristics, various vehicle emission certification modes such as NEDC, FTP-75, and HWFET were compared to evaluate particle formation with both CPC and DMS500. The formation of particles was highly dependent on vehicle speed and load conditions for each mode. In particular, the particle numbers of conventional fuels and low-carbon fuels sharply increased during cold start, fast transient acceleration, and high-load operation phases of the vehicle emission tests. A diesel vehicle fitted with a particulate filter showed substantial reduction of particulate matter with a number concentration equivalent to gasoline and LPG fuel. Moreover, bio-fuels and natural gas have the potential to reduce the particulate emissions with the help of clean combustion and low-carbon fuel quality compared to non-DPF diesel-fueled vehicles.     

Effect of various LPG supply systems on exhaust particle emission in spark-ignited combustion engine

The particle size distribution and particle number (PN) concentration emitted by internal combustion engine are a subject of significant environmental concern because of their adverse health effects and environmental impact. This subject has recently attracted the attention of the Particle Measurement Programme (PMP). In 2007, the UN-ECE GRPE PMP proposed a new method to measure particle emissions in the diluted exhaust of automotive engines and a regulation limit (<6.0×10¹¹ #/km, number of particles). The specific PN regulation of spark-ignited combustion engine will be regulated starting on September 1, 2014 (EURO 6). In this study, three types of LPG supply systems (a mixer system and a multi-point injection system with gas-phase or liquid-phase LPG fuel) were used for a comparison of the particulate emission characteristics, including the nano-sized particle number density. Each of the three LPG vehicles with various LPG injection systems contained a multi-cylinder engine with same displacement volumes of 2,000 cm³ and a three-way catalytic converter. The test fuel that was used in this study for the spark-ignited combustion engine was n-butane basis LPG fuel, which is primarily used for taxi vehicles in Korea. The characteristics of nano-particle size distribution and number concentration of particle sizes ranging from 20 to 1,000 nm (aerodynamic diameter) that were emitted from the three LPG vehicles with various LPG supply systems were investigated by using a condensation particle counter (CPC), which is recommended by the PMP under both the NEDC and FTP-75 test modes on a chassis dynamometer. The experimental results indicate that the PN emission characteristics that were obtained by the CPC system using the PMP procedure are sufficiently reliable compared to other regulated emissions. Additionally, the sources of PN emissions in ascending order of magnitude are as follows: mixer type, gas-phase LPG injection (LPGi) and liquid-phase LPG injection (LPLi) passenger vehicles. The liquid-phase LPG injection system produced relatively large particle sizes and number concentrations compared to the gaseous system, regardless of the vehicle driving cycle. This phenomenon can be explained by unburned micro-fuel droplets that were generated due to a relatively short homogeneous fuel-air mixture duration in the engine intake manifold. Also the particle number emissions from the LPG vehicle were influenced by the vehicle driving cycle.     

基于交通事故深度调查数据的行人头部损伤特征研究

基于未来出行交通事故场景研究 （Future Mobile Traffic Accident Scenario Study,FASS） 数据库中135例人车碰 撞事故深度调查数据,对造成行人头部损伤的来源及车速对头部损伤来源的影响进行了统计分析。采用Spearman相关系 数检验法,建立了车辆速度区间与头部平均 MAIS 的回归模型。结果表明,行人头部致伤物主要来源于车辆,占比约 58%,其次为地面,占比约40%。行人事故中,碰撞车速对行人头部损伤来源的分布情况有一定的影响,当车速低于30 km/h时,行人头部损伤主要来源为地面,当车速为 ［30,50］ km/h时,车辆和地面对行人头部造成的损伤风险相近,当 车速高于 50 km/h时,行人头部损伤主要致伤物来源为车辆。因此,在进行交通损伤流行病学研究、交通损伤事故数据 库构建时,特别是在中低速碰撞中,应重视地面对头部造成损伤的风险。     

汽油车和天然气汽车颗粒物排放特性研究

利用颗粒物数量测试仪器ELPI对瞬态循环下的汽油车和天然气汽车的颗粒物排放进行了测量研究,研究结果表明:汽油车排放的颗粒物明显多于天然气汽车,两种燃料车辆排放的颗粒物中粒径小于70nm的颗粒物均占绝对优势,占总排放量的80%～90%;大于200nm的颗粒物在总排放颗粒物中占的比例非常小;颗粒物数量排放浓度与车辆速度基本成正比例关系,颗粒物数量排放随速度的增加而增加;在车辆速度大于70km/h后,颗粒物数量排放随车速急剧增加.     

深圳市柴油车排放现状研究

通过深圳市车流量信息摄录及数据核实,获得深圳市柴油车的基本结构组成,货运车辆在柴油车中所占比例达到了81．5％,是深圳市PM与NOx污染物的主要排放源。通过使用OBS2200与ELPI进行实际道路情况下的车载测试,得到了深圳市主要类型柴油车PM的排放因子：其中轻型货车1．4691g/km、货柜车4．1756g/km、重型货车2．3818g/km、客运车辆1．6954g／km;以及NOx排放因子：轻型货车4．44581g/km、货柜车8．4848g/km、重型货车10．7517g/km、客运车辆8．5656g/km。并由此计算出PM的年排放总量为39171．20t;NOx的年排放总量为120614．01t。统计结果表明,占柴油车总数6％的国Ⅰ货柜车产生了27％的PM排放。深圳市20％的高污染柴油车的PM与NOx排放量超过所有柴油车的PM与NOx排放量的70％。     

CNG/柴油双燃料车用发动机排放特性研究

通过用YZA102Q柴油机改装的CNG／柴油双燃料发动机进行燃用双燃料和纯柴油两种情况下的对比试验。对CNG／柴油双燃料发动机THC、CO、NOx和烟度的排放特性，以及空燃比、引燃油量、喷油提前角对双燃料发动机排放的影响进行了研究和分析。     

Development of quantitative measuring technique to find critical flow conditions for preventing soot deposit accumulated in the diesel exhaust system using main muffler composed of three chambers

If a vehicle that meets emission regulations operates sufficiently for a long time under low speed and low load conditions, soot contained in the exhaust gas is accumulated on the inner surface of the exhaust system. This soot deposition problem occurs frequently in all diesel cars. However, when a vehicle is placed under the conditions of sudden start and sudden acceleration after city mode driving for a long time, the deposited soot is abruptly blown up with the soot produced during fuel combustion. In the present study, the main cause of the abrupt outburst of deposited soot is investigated to overcome this adverse phenomenon. First, we developed a method to quantify the amount of the exhausted soot particles (or the accumulated soot particles) by measuring the opacity that represents the contamination level of the exhaust gas due to soot particles. Using this measuring scheme for deposited soot, we found the critical conditions for engine speeds and load conditions at which soot particles are emitted into the air without accumulation in the exhaust system using main muffler composed of three chambers. In order to meet these critical conditions and thus to drastically reduce soot accumulation, the exhaust system using the main muffler applied in this study must be designed to ensure that the flow velocity of the exhaust gas is higher than 62 m/s when the back pressure at the exit of the turbocharger is under 0.08 bars.     

大型LPG公交车运行工况与排放特性的试验研究

采用车载排放测试技术,对大型LPG公交车辆运行工况和排放特性进行试验研究.结果表明,公交车运行工况与国家排放标准规定的重型车发动机台架测试工况ESC和ETC有较大的差异.试验公交车辆的平均运行车速为16.7km/h,怠速时间占总运行时间的26.6％,加减速时间占61.3％,加减速度主要集中在-0.5～0.5m/s2之间...     

PFI汽油机排气微粒数浓度及粒径分布研究

在不同转速和负荷下,用快速微粒光谱仪(DMS500)对PFI汽油机排气微粒的数浓度和粒径分布进行了测量.结果表明:在中低负荷下,PFI汽油机产生的微粒几乎全部为纳米级核模态粒子,随着负荷的增加,微粒数浓度单调增加,并且峰值粒径向粒径增大方向迁移;微粒的几何平均直径(GMD)和中位直径(CMD)都是随着负荷的增加而逐渐增...     

垂直侧碰电动自行车下的小汽车超速辨识方法

为了更加方便准确地判定在垂直侧碰电动自行车事故中小汽车是否超速,以城市交叉口垂直侧碰事故为例,提出了一种垂直侧碰电动自行车下的小汽车超速辨识方法.以碰撞时刻为分界点,将碰撞事故按照时间顺序分为碰撞前和碰撞后2个阶段,采用逆向还原事故发生的方法,结合抛距与碰撞速度的经验公式提出了小汽车碰撞速度模型,在测得制动痕迹长度的基础上利用动能定理构建了小汽车制动时刻速度模型.运用PC-Crash仿真,结果表明,小汽车制动时刻速度在34~38 km/h时,辨识误差为1.47%;在42~70 km/h时,误差小于1.3%.通过比较可知,辨识精度相对GIDAS最多可提升15.94%,可精确地分析小汽车垂直侧碰电动自行车事故,并辨识小汽车有无超速,但仍需提高在34~38 km/h区间内的辨识精度.      

Experimental study on the characteristics of nano-particle emissions from a heavy-duty diesel engine using a urea-SCR system

Particulate matter in diesel engine exhaust, particularly nano-particles, can cause serious human health problems including diseases such as lung cancer. Because diesel nano-particle issues are of global concern, regulations on particulate matter emissions specify that not only the weight of particulate matter emitted but also the concentration of nanoparticles must be controlled. This study aimed to determine the effects on nano-particle and PM emissions from a diesel engine when applying a urea-SCR system for NO_x reduction. We found that PM weight increases by approximately 90% when urea is injected in ND-13 mode over the emission without urea injection. Additionally, PM weight increases as the NH₃/NO_x mole ratio is increased at 250 °C. In SEM scans of the collected PM, spherical particles were observed during urea injection, with sizes of approximately 200 nm to 1 μm. This study was designed to determine the conditions under which nano-particles and PM are formed in a urea-SCR system and to relate these conditions to particle size and shape via a quantitative analysis in ND-13 mode.     

轻型CNG车颗粒物排放特性研究

对同一台轻型两用燃料（C N G和汽油）车使用同一批次基准天然气和基准汽油,在底盘测功机上进行NEDC ,FTP75和WLTC循环对比试验,使用CVS定容取样系统和ELPI设备分析颗粒物等排放。研究发现：3种循环中,试验车辆燃用CNG和汽油,排放颗粒物在 Dp ＝40 nm和 Dp ＝330 nm附近均出现峰值,Dp ＝40 nm处汽油峰值远高于CNG ,Dp ＝330 nm处CNG峰值略高于汽油;CNG的PN和PM的排放率随车速的升高而增大,在较低的匀速工况下增长幅度较小,高速工况下增长幅度较大;CNG在NEDC循环中排放的核态和聚集态颗粒物各占50％左右,FTP75和WLTC循环中排放的聚集态颗粒物占比高于NEDC ;CNG在NEDC循环中单位里程颗粒数和颗粒总数最多,FTP75和WLTC循环中单位里程颗粒数基本相同;WLTC循环中排放的颗粒物质量总量最多,FTP75和NEDC循环中排放的颗粒物质量总量基本相同;FTP75和WLTC循环中单位里程排放的颗粒物质量基本相同,约为N EDC循环的2倍。     

天然气发动机最高转速准均质压燃特性的研究

就国产6110增压中冷发动机燃烧天然气的一些性能进行了研究。在压缩终了被少量柴油引燃的均匀天然气混合气的燃烧接近均质压燃燃烧过程。采用了发动机缸内分析以及相应工况的排放测试对比分析方式，对发动机的燃烧特性进行了试验研究。     

CNG汽车的试验研究

对58辆改装后的CNG／汽油两用燃料汽车，在相同试验条件下，分别燃用汽油，CNG时的动力性，燃料消一及排放等进行对比试验，可以看出，改装后的CNG汽车其燃用CNG时加速性能与燃用汽油相比下降较大，但燃料消耗量有所下降且怠速排放明显下降，同时，就在试验中存在的问题进行了讨论。     

二甲醚／柴油混合燃料在压燃式发动机上的应用

为探索二甲醚/柴油混合燃料作为柴油机替代燃料的应用性能,对D20二甲醚/柴油混合燃料的喷雾特性进行了试验研究;同时,开展了直喷式柴油机燃用二甲醚/柴油混合燃料动力性能、经济性能及排放性能研究。结果表明:在同样的环境背压下,D20混合燃料的油束与柴油相比较,贯穿度有所缩短,喷雾锥角有所增大;柴油机燃用二甲醚/柴油混合燃料时,通过适当调整循环油量,发动机的动力性可以超过原柴油机,最低当量比油耗下降4.5%,烟度指标下降70%以上,NOx排放降低30%~50%;二甲醚/柴油混合燃料是一种能实现高比功率、低排放的石油替代燃料。     

进气节流对柴油机低负荷性能影响的试验研究

在柴油机上加装节流阀是提升小负荷工况排温、改善排放的途径之一,但会对柴油机的其他性能造成影响。本研究通过给柴油机加装节流阀,研究了进气节流对柴油机小负荷工况性能的影响。试验结果表明:进气节流对柴油机的排温和NOx排放提升明显;柴油机进气节流后缸内压力下降,缸内平均燃烧温度、机械效率升高,滞燃期延长,燃烧始点后移;中低转速小负荷工况,随着节流程度的增加,燃油消耗率和烟度增加;高转速小负荷工况,一定范围内通过进气节流可以实现燃油消耗率和烟度的降低。2 500r/min,29N·m工况,保持EGR阀全开,随着节流程度的增加,NOx和烟度出现同时下降趋势,当空气流量由191.4kg/h降至140.6kg/h时,燃油消耗率、NOx、烟度分别下降了7.9%,58.1%,27.3%,排温提升了42.5%。     

混凝土公路斜桥的动反应研究

随着车辆质量、速度的逐渐增大和桥梁结构的逐渐轻柔化，车桥相互作用问题越来越受到关注。分别应用拉格朗日方程和模态叠加法建立三维非线性车辆模型和桥梁的振动方程，车轮与桥梁在接触点满足接触力和位移协调条件，利用迭代技术求解二者的相互作用问题。并以公路斜桥为分析对象，研究了不同斜交角、不同车辆行驶状态下以及不同行车速度情况下，横向不同梁的动挠度和动态增量。结果显示，斜交角、车辆行驶状态以及车速均是影响桥梁动反应的重要因素；当车辆行驶速度在30、40km／h左右时，梁的动态增量达到最大；而且随着斜交角的增大，离车辆行驶位置越远的梁的动态增量也越大。     

Effect of UWS injection at low exhaust gas temperature on NO<Subscript>x</Subscript> removal efficiency of diesel engine

Urea-SCR systems have been widely used in diesel vehicles according to the strengthened NO_x (Nitrogen Oxides) emission standard. The NO_x removal efficiencies of the latest well optimized urea-SCR system are above 90 % at moderate exhaust gas temperature of 250 ~ 450 °C. However, a large amount of NO_x is emitted from diesel vehicles at cold start or urban driving conditions, when the exhaust gas temperature is not high enough for SCR catalyst activation. Although many researchs have been stuied to improve NO_x conversion efficiency at these low temperature conditions, it is still one of important technical issues. In this study, the effect of UWS injection at low exhaust gas temperature conditions is studied. This study uses a 3.4 L diesel engine equipped with a commertial urea SCR system. As a result, it is found that about 5 % of NO_x removal efficiency is improved in the NRTC test when UWS injection starts at the SCR inlet temperature of 150 °C compared to 200 °C. It is also found that urea deposits can be formed on the wall of exhaust pipe, when the local wall temperature is lower than temperature of urea decomposition.