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Technical Paper

Degradation of DeNOx Performance of a Urea-SCR System in In-Use Heavy-Duty Vehicles Complying with the New Long-Term Regulation in Japan and Estimation of its Mechanism

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.
Technical Paper

Real-time Analysis of Benzene in Exhaust Gas from Driving Automobiles Using Jet-REMPI Method

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.
Technical Paper

Combustion Characteristics and Performance Increase of an LPG-SI Engine with Liquid Fuel Injection System

Compared with petroleum fuel, liquefied petroleum gas (LPG) demonstrates advantages in low CO2 emission because of propane and butane, which are the main components of LPG, making H/C ratio higher. In addition, LPG is suitable for high efficient operation of a spark ignition (SI) engine due to its higher research octane number (RON). Because of these advantages, that is, diversity of energy source and reduction of CO2, in the past several years, LPG vehicles have widely used as the alternate to gasoline vehicles all over the world. Consequently, it is absolutely essential for the performance increase of LPG vehicles to comprehend the combustion characteristics of LPG and to obtain the guideline for engine design and calibration. In this study, an LPG-SI engine was built up by converting fuel supply system of an in-line 4-cylinder gasoline engine, which has 1997 cm3 displacement with MPI system, to LPG liquid fuel injection system [1].
Technical Paper

Effective NOx Reduction in High Boost, Wide Range and High EGR Rate in a Heavy Duty Diesel Engine

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).
Technical Paper

Diesel Emissions Improvement by RME in a High Boost and EGR Single Cylinder Engine

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.
Technical Paper

Effect of Exhaust Gas Recirculation on Exhaust Emissions from Diesel Engines Fuelled with Biodiesel

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.
Technical Paper

Detection of Deteriorated Catalyst on Vehicle under Actual Operation Conditions: Application of FFT Analysis to Signal Wave by the Dual Oxygen Sensors Method

The object of this study is to investigate an on-board diagnostic method to detect the deterioration of a three-way catalyst (TWC) under actual vehicle operating conditions, including the acceleration state. The signal data of two oxygen sensors were processed by the fast Fourier transformation (FFT) method. As a result, we found that the power spectrum of the signal waves can be the index of catalyst deterioration degree. Furthermore, it was confirmed that the difference between the power spectrum of the upstream oxygen sensor signal and one of the downstream oxygen sensor signal named ΔPower is effective index for detection of deteriorated catalyst under acceleration conditions.
Technical Paper

Optimization of Engine System for Application of Biodiesel Fuel

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.
Technical Paper

Development of DME Engine for Heavy-duty Truck

In recent years, attention has focused on smokeless, sulfur-free dimethyl ethyl (DME) as a clean fuel for heavy-duty diesel vehicles [1]. In this development, the DME engine applied for 20-ton GVW truck was developed under the auspices of the Ministry of Land, Infrastructure and Transport of Japan, the first known instance worldwide. With careful design of the fuel system considering DME's unique fuel characteristics and suitable combustion improvement, higher torque was obtained with DME, compared to diesel fueling. and also use of the proper EGR and catalyst, exhaust emissions levels were generally less than one-fourth of new long-term regulation value promulgated in 2005 Japan.
Technical Paper

Emission Characteristics of a Urea SCR System under Catalysts Activated and De-Activated Conditions

Urea SCR (Selective Catalytic Reduction) system has high potential of reducing NOx. But such as system durability and safety under deteriorated catalysts conditions have not been well enough clarified because it is new technology for vehicles. In this paper, current NOx emission level of an engine equipped with urea SCR system is discussed and then exhaust emission characteristics were analyzed when the SCR catalyst and/or oxidation catalyst lose their functions. When both SCR and oxidation catalyst were de-activated, not only NOx but also PM increased remarkably, which were much more than the engine-out emissions. Oxidation catalyst downstream of SCR catalyst was effective to suppress such deteriorations.
Technical Paper

Comparative Measurement of Nano-Particulates in Diesel Engine Exhaust Gas by Laser-Induced Incandescence (LII) and Scanning Mobility Particle Sizer (SMPS)

Particulate Matter (PM) from diesel engines is thought to be seriously hazardous for human health. Generally, it is said that the hazard depends on the total number and surface area of particles rather than total mass of PM. In the conventional gravimetric method, only the total mass of PM is measured. Therefore, it is very important to measure not only the mass of PM but also size and number density of particulates. Laser-Induced Incandescence (LII) is a useful diagnostic for transient measurement of soot particulate volume fraction and primary particle size. On the other hand, Scanning Mobility Particle Sizer (SMPS) is also used to measure the size distribution of soot aggregate particulates at a steady state condition. However, the measurement processes and the phenomena used to acquire the information on soot particulate are quite different between the LII and SMPS methods. Therefore, it is necessary to understand the detailed characteristics of both LII and SMPS.
Technical Paper

N2O Emissions from Vehicles Equipped with Three-Way Catalysts in a Cold Climate

Nitrous oxide (N2O) is a strong green house effect gas and three-way catalyst is one of the major sources. N2O is mostly emitted at temperatures during the process of light off in the catalyst and the frequency of this temperature range over total temperature range distribution affects strongly on N2O emission. The effect of cold ambient on N2O emission was analyzed based on N2O-catalyst temperature characteristics and catalyst temperature data gained by road driving test at north part of Japan in winter. As results, N2O emission may drastically increase in colder cities and winter city traffic conditions.