Search Results

Degradation of the deNOx performance has been found in in-use heavy-duty vehicles with a urea-SCR system in Japan. The causes of the degradation were studied, and two major reasons are suggested here: HC poisoning and deactivation of pre-oxidation catalysts. Hydrocarbons that accumulated on the catalysts inhibited the catalysis. Although they were easily removed by a simple heat treatment, the treatment could only partially recover the original catalytic performance for the deNOx reaction. The unrecovered catalytic activity was found to result from the decrease in conversion of NO to NO2 on the pre-oxidation catalyst. The pre-oxidation catalyst was thus studied in detail by various techniques to reveal the causes of the degradation: Exhaust emission tests for in-use vehicles, effect of heat treatment on the urea-SCR systems, structural changes and chemical changes in active components during the deactivation were systematically investigated.

Reduction of exhaust emissions and BSFC has been studied using a high boost, a wide range and high-rate EGR in a Super Clean Diesel, six-cylinder heavy duty engine. In the previous single-turbocharging system, the turbocharger was selected to yield maximum torque and power. The selected turbocharger was designed for high boosting, with maximum pressure of about twice that of the current one, using a titanium compressor. However, an important issue arose in this system: avoidance of high boosting at low engine speed. A sequential and series turbo system was proposed to improve the torque at low engine speeds. This turbo system has two turbochargers of different sizes with variable geometry turbines. At low engine speed, the small turbocharger performs most of the work. At medium engine speed, the small turbocharger and large turbocharger mainly work in series.

The use of biofuel is essential for the reduction of greenhouse gas emission. This paper highlights the use of biodiesel as a means of reducing greenhouse gas emission from the diesel engine of heavy-duty vehicles. Biodiesel is fatty acid methyl ester (FAME) obtained through ester exchange reaction by adding methanol to oil, such as rapeseed oil, soybean oil, palm oil, etc. The CO₂ emission from combustion of biodiesel is defined to be equivalent to the CO₂ volume absorbed by its raw materials or plants in their course of growth. On the other hand, however, biodiesel is known to increase the NOx emission when compared with operating with conventional diesel fuel, then suppressing this increase is regarded as a critical issue. This study is intended to identify the fuel properties of biodiesel free from increase in the NOx emission.

Reduction of exhaust emissions and BSFC was studied for high pressure, wide range, and high EGR rates in a Super-clean Diesel six-cylinder heavy duty engine. The GVW 25-ton vehicle has 10.52 L engine displacement, with maximum power of 300 kW and maximum torque of 1842 Nm. The engine is equipped with high-pressure fuel injection of a 200 MPa level common-rail system. A variable geometry turbocharger (VGT) was newly designed. The maximum pressure ratio of the compressor is about twice that of the previous design: 2.5. Additionally, wide range and a high EGR rate are achieved by high pressure-loop EGR (HP-EGR) and low pressure-loop EGR (LP-EGR) with described VGT and high-pressure fuel injection. The HP-EGR can reduce NOx concentrations in the exhaust pipe, but the high EGR rate worsens smoke. The HP-EGR system layout has an important shortcoming: it has great differences of the intake EGR gas amount into each cylinder, worsens smoke.

The use of biomass fuels for vehicles has been a focus of attention all over the world in terms of prevention of global warming, effective utilization of resources and local revitalization. For the purpose of beneficial use of unused biomass resources, the movement of the use of bioethanol and biodiesel made from them has spread in Japan. In Japan, biodiesel is mainly made from waste cooking oil collected by local communities or governments, and in terms of local production for local consumption, it is used as neat fuel (100% biofuel) or mixed with diesel fuel in high concentration for the vehicles. On the other hand, extremely low emission level must be kept for not only gasoline vehicles but also diesel vehicles in the post new long-term regulation implemented from 2009 in Japan.

The application of biodiesel as an alternative fuel for petroleum diesel fuel is very effective for the reduction of CO₂ emission, because biodiesel is produced from renewable biomass resources. In Japan, neat biodiesel derived from waste cooking oil has often been applied to commercial vehicles. However, it is possible that the difference of fuel properties between conventional diesel fuel and biodiesel causes the problems on exhaust emission characteristics of diesel engine. Therefore, it is necessary to clarify the effect of biodiesel fuelling on exhaust emissions from commercial vehicles. Light-duty garbage trucks and heavy-duty diesel buses which were actually fueled with biodiesel in Kyoto, Japan, were used for test vehicles in this study. The exhaust emissions from these vehicles during JE05 mode tests were compared between biodiesel derived from waste cooking oil and conventional diesel fuel.

Lean NOx trap (LNT) and Urea-SCR system are effective aftertreatment systems as NOx reduction device in diesel engines. On the other hand, DPF has already been developed as PM reduction device and it has been used in various vehicles. LNT can absorb and reduce NOx emission in wide range exhaust temperatures, from 150°C to 400°C, and the size of LNT component can be compact in comparison with Urea-SCR system because LNT uses the diesel fuel as a reducing agent and it is needless to install the reducing agent tank in the vehicle. In this study, authors have shown that the NOx conversion rate of LNT is high in the case of extremely low NOx concentration from the engine. Also, the effects of LNT and DPF were examined using the Super Clean Diesel (SCD) Engine, which has low NOx level before aftertreatment and has been finished as Japanese national project.

For reducing NOx emissions, EGR is effective, but an excessive EGR rate causes the deterioration of smoke emission. Here, we have defined the EGR rate before the smoke emission deterioration while the EGR rate is increasing as the limiting EGR rate. In this study, the high rate of EGR is demonstrated to reduce BSNOx. The adapted methods are a high fuel injection pressure such as 200 MPa, a high boost pressure as 451.3 kPa at 2 MPa BMEP, and the air intake port that maintains a high air flow rate so as to achieve low exhaust emissions. Furthermore, for withstanding 2 MPa BMEP of engine load and high boosting, a ductile cast iron (FCD) piston was used. As the final effect, the installations of the new air intake port increased the limiting EGR rate by 5%, and fuel injection pressure of 200 MPa raised the limiting EGR rate by an additional 5%. By the demonstration of increasing boost pressure to 450 kPa from 400 kPa, the limiting EGR rate was achieved to 50%.

Real-time analysis of benzene in automobile exhaust gas was performed using the Jet-REMPI (supersonic jet / resonance enhanced multi-photon ionization) method. Real-time benzene concentration of two diesel trucks and one gasoline vehicle driving in Japanese driving modes were observed under ppm level at 1 s intervals. As a result, it became obvious that there were many differences in their emission tendencies, because of their car types, driving conditions, and catalyst conditions. In two diesel vehicle, benzene emission tendencies were opposite. And, in a gasoline vehicle, emission pattern were different between hot and cold conditions due to the catalyst conditions.

A simple real-time measurement system for the components of volatile organic compounds (VOCs) and polyaromatic hydrocarbons (PAHs) in automobile exhaust gas using a laser ionization method was developed. This method was used to detect VOCs and PAHs in the exhaust gas of a diesel truck while idling, at 60 km/h, and in the Japanese driving mode JE05. As a result, various VOCs and PAHs, such as xylene and naphthalene, were simultaneously detected, and real-time changes in their concentration were obtained at 1 s intervals.

The emission reduction from diesel engines is one of major issues in heavy duty diesel engines. Super Clean Diesel (SCD) Engine for heavy-duty trucks has also been researched and developed since 2002. The main specifications of the SCD Engine are six cylinders in-line and 10.5 l with a turbo-intercooled and cooled EGR system. The common rail system, of which the maximum injection pressure is 200 MPa, is adopted. The turbocharger is capable of increasing boost pressure up to 501.3 kPa. The EGR system consists of both a high-pressure loop (HP) EGR system and a low-pressure loop (LP) EGR system. The combination of these EGR systems reduces NOx and PM emissions effectively in both steady-state and transient conditions. The emissions of the SCD Engine reach NOx=0.2 g/kWh and PM=0.01 g/kWh with aftertreatment system. The adopted aftertreatment system includes a Lean NOx Trap (LNT) and Diesel Particulate Filter (DPF).

The use of biodiesel fuels as an alternative fuel for petroleum diesel fuel is very effective for the reduction of CO2 emission, because biodiesel is produced from renewable biomass resources. Biodiesel is usually blended to conventional diesel fuel in various proportions. It is possible that this biodiesel blending causes the problems on emission characteristics of modern diesel engine, because it could be confirmed that the application of neat biodiesel to modern diesel engines whose control parameters were optimized for conventional diesel fuel deteriorated the emission performances. It is necessary to clarify the effect of biodiesel blending on exhaust emissions of modern diesel engine. Rapeseed oil methyl ester (RME) was selected as a biodiesel used in this study.

The biomass fuel is expected to solve the global warming due to a carbon neutral. A rapeseed oil methyl ester (RME) as biomass fuel was selected, and also a low sulfur diesel fuel is tested as reference fuel in this study. The experiments were carried out to improve diesel emissions and engine performance using high boost and high rate EGR system and a common rail injection system in a single cylinder engine. The diesel emissions and engine performance have been measured under the experimental conditions such as charging boost pressure from atmospheric pressure to 401.3kPa maximum and changing EGR rate from 0% to 40% maximum. RME contain about 10 mass % oxygen in the fuel molecule. Furthermore, RME does not contain aromatic hydrocarbons in the fuel. Due to these chemical properties, RME can be used at 40% high EGR condition.

In order to discuss future technical issues for urea SCR (selective catalytic reduction) system, it is necessary to assess various technical possibilities that would be applied to urea SCR systems which is capable of complying with future emission level requirements, for example Japanese 2009 emission regulation. In this paper, three measures (enhanced insulation on a DOC (diesel oxidation catalyst), aggressive urea solution injection and idling stop) are installed on a urea SCR system of a commercial engine system in order to achieve further NOx (nitrogen oxide) reductions. With combination of these three measures, NOx is drastically reduced to the levels lower than 0.7 g/kWh, which is a NOx limit value of the Japanese 2009 emission regulation. NH3 (ammonia) and HCN (hydro cyanide) are also measured as unregulated harmful components.

Application of biodiesel fuel (BDF) to diesel engine is very effective to reduce CO2 emission, because bio-diesel is carbon neutral in principle. However, when biodiesel was applied to conventional diesel engines without modification for biodiesel, NOx emission was increased by the change in fuel characteristics. It is necessary to introduce some strategies into diesel engines fuelled with biodiesel for lower NOx emission than conventional diesel fuel case. The purpose of this study is to reveal that exhaust gas recirculation (EGR) is one of the solutions for the reduction of NOx emission and meeting the future emission regulations when using biodiesel. Neat Rapeseed oil methyl ester (RME) as a biodiesel (B100) was applied to diesel engines equipped with high pressure loop (HPL) EGR system and low pressure loop (LPL) EGR system. Cooled HPL EGR was increased during steady-state operations and JE05 transient mode tests.

Application of biodiesel fuel (BDF) to diesel engine is very effective to reduce CO2 emission, because biodiesel is carbon neutral in principle. However, biodiesels yield an increase in NOx emission from conventional diesel engine, compared with diesel fuel case. Therefore, some strategies are needed for meeting the future emission regulations when using biodiesel. In this study, rapeseed oil methyl ester (RME) was applied to diesel engine equipped with exhaust gas recirculation (EGR) system and NOx storage reduction (NSR) catalyst. NOx reduction rate of NSR catalyst was drastically decreased by using RME, even if injection quantity of RME for rich spike was enhanced. However, an increase in EGR rate could reduce NOx emission without the deterioration in smoke and PM emissions.

The engine in the research is a single cylinder DI diesel using the emission reduction techniques such as high boost, high injection pressure and broad range and high quantity of exhaust gas recirculation (EGR). The study especially focuses on the reduction of particulate matter (PM) under the engine operating conditions. In the experiment the authors measured engine performance, exhaust gases and mass of PM by low sulfur fuel such as 3 ppm and low sulfur lubricant oil such as 0.26%. Then the PM components were divided into soluble organic fraction (SOF) and insoluble organic fraction (ISOF) and they were measured at each engine condition. The mass of SOF was measured from the fuel fraction and lubricant oil fraction by gas chromatography. Also each mass of soot fraction and sulfate fraction was measured as components of ISOF. The experiment was conducted at BMEP = 2.0 MPa as full load condition of the engine and changing EGR rate from 0% to 40 %.

A prototype CNG engine for heavy-duty trucks has been developed. The engine had sufficient output in practical use, and the green-house gas emission rate was below that of the base diesel engine. Furthermore, the NOx emission rate was reduced to 0.16 g/kWh in the JE05 mode as results of having fully adjusted air fuel ratio control. The measured emission characteristics of particles from the prototype CNG engine demonstrated that oil consumption was related to the number of particles. Moreover, when oil consumption is at an appropriate level, the accumulation mode particles are significantly reduced, and the nuclei mode particles are fewer than those of diesel-fueled engines.

For reducing exhaust emissions of heavy-duty diesel engines, the authors made an experimental study of diesel combustion using a single cylinder engine. The engine performance and exhaust emissions have been measured using a wide range and high EGR rate under the conditions of high boost intake pressure. The engine test cell has been equipped the external supercharger that is able to raise the boost pressure to 500 kPa, and also equipped the EGR system to increase the EGR rate until 50% under the 500 kPa boost condition. In various test conditions of load and engine speeds the authors have obtained the results, that is, NOx has been reduced drastically without increasing Particulate Matter (PM).

The 1997 Kyoto protocol came into effect in February, 2005 to reduce greenhouse gases within the period 2008-2012 by at least 5 % with respect to 1990 levels. Application of biodiesel fuel (BDF) to diesel engine is very effective to reduce CO2 emission, because BDF is carbon neutral in principle. The purpose of this project is to produce a light-duty biodiesel truck which can be suitable for emission regulation in next generation. The effect of BDF on the performance and emissions of modern diesel engine which was equipped with the aftertreatment for PM and NOx emissions was investigated without modifications of engine components and parameters, as a first step for research and development of biodiesel engine. Rapeseed oil methyl ester (RME) was selected in behalf of BDF, and combustion characteristics, engine performance and exhaust emissions were made a comparison between RME and petroleum diesel fuel by steady operation and Japan transient mode (JE05) tests.