山路行驶的柴油车污染物排放特性试验

在山路和平路上,进行了不同载荷下国V柴油车的实际道路行驶排放(RDE)试验.采集车速、海拔、氮氧化物(Nox)和颗粒物数量(PN)排放浓度等数据,分析了道路坡度、车辆载荷与输出功率对排放的影响.研究发现:测试柴油车辆,在平均坡度约6％山路行驶时Nox排放因子高于平路20％以上,PN低于平路20％以上.道路坡度自0增大到...     

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.     

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.     

Investigation of particle emission characteristics from a diesel engine with a diesel particulate filter for alternative fuels

Particle number measurement is a new approach to determine emission, which may be more accurate at very low emission levels than when using gravimetric measurements. An experimental study was performed to investigate the effect of fuel properties on the performance, combustion process, regulated gaseous emissions and particle number emissions of a diesel engine with an uncatalyzed diesel particulate filter (DPF). The effect of the filter on the particle size distribution was reported. The DPF number-based filtration efficiency in terms of number efficiency and fractional efficiency for petroleum diesel fuel and two alternative fuels, BTL and GTL, were analyzed. For nearly all test modes, the filter had a higher number efficiency for diesel than for BTL and GTL. The DPF fractional efficiency showed it was highly dependent on fuel type and varied widely at each size range. For diesel, the filter fractional efficiency was sufficiently high and behaved as predicted by filtration theory. For BTL and GTL, the fractional performance of the filter decreased when unexpectedly low efficiencies within the nuclei mode were exhibited. This research will be helpful in understanding DPF number-based filtration performance for alternative fuels and will provide information for the development of particulate emission control technology.     

发展柴油车是汽车行业节能减排的重要选择

伴随着中国经济的高速增长,能源短缺、环境污染等问题已成为中国能否实现可持续发展所面临的重大挑战。在今年初的十一届全国人大代表大会上,温家宝总理在政府工作报告中再次强调了十一五规划大纲中的节能减排目标,即万元GDP能耗降低20％左右和主要污染物排放减少10％,并提出今年是实现目标的关键性的一年。     

基于柴油机排气后处理的排放控制技术应用研究

柴油机排放控制的重点是氮氧化物(NOx)和颗粒物(PM)两种污染物,文章对目前已经实用化的柴油机排气后处理技术的发展现状和趋势进行分析研究,对将柴油机机内净化技术与机后处理技术相结合同时能降低NOx和PM的排综合控制技术进行了分析探讨。     

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.     

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.     

Effects of split injection,oxygen enriched air and heavy EGR on soot emissions in a diesel engine

The effects of split injection, oxygen enriched air, and heavy exhaust gas recirculation (EGR) on soot emissions in a direct injection diesel engine were studied using the KIVA-3V code. When split injection is applied, the second injection of fuel into a cylinder results in two separate stoichiometric zones, which helps soot oxidation. As a result, soot emissions are decreased. When oxygen enriched air is applied together with split injection, a higher concentration of oxygen causes higher temperatures in the cylinder. The increase in temperature promotes the growth reaction of acetylene with soot. However, it does not improve acetylene formation during the second injection of fuel. As more acetylene is consumed in the growth reaction with soot, the concentration of acetylene in the cylinder is decreased, which leads to a decrease in soot formation and thus soot emissions. A combination of split injection, a high concentration of oxygen, and a high EGR ratio shows the best results in terms of diesel emissions. In this paper, the split injection scheme of 75.8.25, in which 75% of total fuel is injected in the first pulse, followed by 8°CA of dwell time, and 25% of fuel is injected in the second pulse, with an oxygen concentration of 23% in volume and an EGR ratio of 30% shows a 45% reduction in soot emissions, with the same NOx emissions as in single injection.     

Influence of turpentine addition in Jatropha biodiesel on CI engine performance,combustion and exhaust emissions

The prospect of using turpentine oil as an additive for Jatropha biodiesel and using it as an alternative fuel for diesel in CI engines has been experimented in this work. Tests were carried out in a single cylinder, air cooled, constant speed, direct injection diesel engine. The results display that the performance of Jatropha-Mineral Turpentine (JMT) and Jatropha- Wood Turpentine (JWT) blends were found close to diesel, emission features were enhanced and combustion parameters were noticed to be comparable with diesel. Brake thermal efficiency of JMT20 blend found closer to diesel at 75 % load. BSFC increases for JMT and JWT blends at part load and maintains at full load. CO, HC and Smoke emissions were reduced with JMT and JWT blends at 75 % load. NOx emissions were on the raise. Furthermore, JMT and JWT blends offered comparable performance and combustion parameters, reduced emissions and both can substitute standard diesel in CI engines.     

Experimental investigation of abrasive flow machining effects on injector nozzle geometries,engine performance,and emissions in a di diesel engine

The effects of the Abrasive Flow Machining (AFM) process on a direct injection (DI) Diesel engine fuel injector nozzle are studied. Geometry characterization techniques were developed to measure the microscopic variations inside the nozzle before and after the process. This paper also provides empirically-based correlations of the nozzle geometry changes due to the AFM process. The resulting impact of the process on the engine performance and emissions are also assessed with a DI Diesel engine test setup. This study shows that properly AFM-processed injectors can enhance engine performance and improve emissions due to the improved quality of the nozzle characteristics. However, an extended process can also cause enlargement of the nozzle hole as a side effect, which can adversely affect emissions. Emission measurements show the trade-off for the minimum levels as the process proceeds. Since the enlargement of the hole during the AFM process is not avoidable and must be minimized, strict control over the process is required. This control can be enforced by either limiting the AFM processing period, or by properly preparing the initial hole diameter so as to accommodate the inevitable changes in the nozzle geometry.     

Effect of the number of fuel injector holes on characteristics of combustion and emissions in a diesel engine

The diesel combustion process is highly dependent on fuel injection parameters, and understanding fuel spray development is essential for proper control of the process. One of the critical factors for controlling the rate of mixing of fuel and air is the number of injector holes in a diesel engine. This study was intended to explore the behavior of the formation of spray mixtures, combustion, and emissions as a function of the number of injector hole changes; from this work, we propose an optimal number of holes for superior emissions and engine performance in diesel engine applications. The results show that increasing the number of holes significantly influences evaporation, atomization, and combustion. However, when the number of holes exceeds a certain threshold, there is an adverse effect on combustion and emissions due to a lack of the air entrainment required for the achievement of a stoichiometric mixture.     

Physical-chemical properties of ethanol-diesel blend fuel and its effect on the performance and emissions of a turbocharged diesel engine

This paper deals with the main physical-chemical properties of ethanol-diesel blend and the effects of ethanoldiesel blends (up to 15% volume) on engine performance (full load torque vs. engine speed, BSEC vs. torque at 1400 r/min and 2300 r/min, and effect of start of injection angle) and emissions in ECE R49 tests (steady 13 points) using a 6.6 L inline 6-cylinder turbocharged direct injection diesel engine. The results show that an increase in ethanol fraction results in decreased viscosity of the blend fuel and very high distillation characteristics in the low temperature range. Solvents can improve the solubility of ethanol-diesel blends. The engine power was degraded proportional to the ethanol content (10% and 15%) due to the LHV (low heating value) of the blends. The higher latent heat of vaporization and lower CN (cetane number) of ethanol, which results from the steady state emissions of CO, HC, and SOF (soluble organic fraction), were much higher in the ECE R49 tests at low loads. Soot (solid mass) emissions were improved. The particulate matter emissions were significantly increased with higher blend volumes, and NOx emissions slightly increased with higher ethanol volumes. By increasing the injection angle properly, the performance parameters of the diesel engine were improved, but NOx emissions were deteriorated slightly.     

Evaluation of natural and tracer fluorescent emission methods for droplet size measurements in a diesel spray

Spray sizing that records fluorescent emission and scattered light has been widely applied to spray diagnostics over the last two decades. Different experimental strategies have been developed, but comparing the different solutions offered has remained of interest to experimentalists. In this work, a comparison of two fluorescence strategies for measuring droplet size in the liquid phase of a last-generation DI diesel spray is conducted. The natural fluorescent emission of a commercial diesel fuel and the fluorescence emitted by a tracer (Rhodamine B) are compared using theoretical and experimental approaches. The LIF/Mie ratio commonly called Planar Droplet Sizing (PDS) technique is applied in two different ways to elucidate the possible advantages of using a fluorescent dopant. The sprays were injected under non-evaporative conditions into a constant pressure vessel that simulates densities present at the moment of injection in currently used passenger car diesel engines. Characterization of the signal properties was performed by measuring the absorption coefficient, fluorescence emission spectrum, quantum yield and lifetime of both configurations. The scattered light and fluorescence intensities were calculated to verify the dependencies of the droplet surface and volume. When applying the two techniques to quantify droplet size in dense diesel sprays, the results show that signal weakness and lack of control over the properties of natural fluorescence produce distortion in the shape of the spray and cause measurements to be unreliable.     

Characteristics of operating mode distributions of light duty vehicles by road type,average speed,and driver type for estimating on-road emissions: Case study of Beijing

Abstract

Researchers have collected extensive vehicle activity data in Beijing using GPS and attempted to develop a comprehensive database of facility- and speed-specific operating mode (OpMode) distributions of various vehicle types for estimating on-road vehicle emissions. This study developed the specific OpMode distributions of light duty vehicles (LDVs) for both restricted access and unrestricted access road types at various average speeds for characteristic analysis. (1) Strong patterns are found in the variations in OpMode distributions with the increase in the average speed: the time fraction of Decelerating/Braking remains less than 7%. The fraction of Idling decreases dramatically from 95% to 0%, while the fraction of Cruising/Accelerating increases from 2% to 94%. The fraction of Coasting increases to 28% and then decreases. (2) The time fractions for restricted access and unrestricted access are significantly different at the same average speeds, especially in Operating Modes #0, #1, #11, #12, #13, #14, #21, and #22, possibly causing an error of 20% in the emissions estimations. (3) Taxis show different OpMode distributions than those for private cars in the operating modes of Decelerating/Braking, Idling, and high-VSP modes, especially at low average speeds. The differences are derived from the more skillful driving behaviors of taxi drivers and may cause an estimation error of over 10%. Thus, the activities of taxis and private cars should be modeled separately for on-road emissions estimations.