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In the conventional approval test method of fuel consumption for heavy-duty diesel vehicles currently in use in Japan, the fuel consumption under the transient test cycle is calculated by integrating the instantaneous fuel consumption rate referred from a look-up table of fuel consumptions measured under the steady state conditions of the engine. Therefore, the transient engine performance is not considered in this conventional method. In this study, a highly accurate test method for fuel consumption in which the map-based fuel consumption rate is corrected using the transient characteristics of individual engines was developed. The method and its applicability for a heavy-duty diesel engine that complied with the Japanese 2009 emission regulation were validated.

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.

The number of traffic deaths in Japan was 4,863 in 2010. Pedestrians account for the highest number (1,714, 35%), and vehicle occupants the second highest (1,602, 33%). Pedestrian protection is a key countermeasure to reduce casualties in traffic accidents. A striking vehicle's impact velocity could be considered a parameter influencing the severity of injury and possibility of death in pedestrian crashes. A collision damage mitigation braking system (CDMBS) using a sensor to detect pedestrians could be effective for reducing the vehicle/pedestrian impact velocity. Currently in Japan, cars equipped with the CDMBS also have vision sensors such as a stereo camera for pedestrian detection. However, the ability of vision sensors in production cars to properly detect pedestrians has not yet been established. The effect of reducing impact velocity on the pedestrian injury risk has also not been determined.

Study of DME diesel engines was conducted to improve fuel consumption and emissions of its. Additionally, DME trucks were built for the promotion and the road tests of these trucks were executed on EFV21 project. In this paper, results of diesel engine tests and DME truck driving tests are presented. As for DME diesel engines, the performance of a DME turbocharged diesel engine with LPL-EGR was evaluated and the influence of the compression ratio was also explored. As for DME trucks, a 100,000km road test was conducted on a DME light duty truck. After the road test, the engine was disassembled for investigation. Furthermore, two DME medium duty trucks have been developed and are now the undergoing practical road testing in each area of two transportation companies in Japan.

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.

A new ignition-combustion concept named PCC (Plume Ignition Combustion Concept), which ignite rich mixture plume in the middle of injection period or right after injection of hydrogen is completed, is proposed by the authors in order to reduce NOx emissions in high engine load conditions with minimizing trade-offs on thermal efficiency. In this study fundamental requirements of hydrogen jet to optimize PCC are investigated by using single and multi-hole nozzle with a combination of high speed laser shadowgraphy to visualize propagating flame. As a result, it was infered that igniting the mixture plume in the middle of injection period with minimizing jet penetration to chamber wall is effective reducing NOx formation even further.

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].

A development project for a hydrogen internal combustion engine (ICE) system for trucks supporting Japanese freightage has been promoted as a candidate for use in future vehicles that meet ultra-low emission and anti-global warming targets. This project aims to develop a hydrogen ICE truck that can handle the same freight as existing trucks. The core development technologies for this project are a direct-injection (DI) hydrogen ICE system and a liquid hydrogen tank system which has a liquid hydrogen pump built-in. In the first phase of the project, efforts were made to develop the DI hydrogen ICE system. Over the past three years, the following results have been obtained: A high-pressure hydrogen gas direct injector developed for this project was applied to a single-cylinder hydrogen ICE and the indicated mean effective pressure (IMEP) corresponding to a power output of 147 kW in a 6-cylinder hydrogen ICE was confirmed.

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).

Repeatabilities of PM measurements on a heavy-duty diesel engine equipped with a diesel particulate filter (DPF) using a filter weighing method and a number counting method with a full flow dilution system and a partial flow system were evaluated. The filter method with partial flow exhibited the best repeatability. However, a good correlation between the full flow and the partial flow number counting results suggests that the fluctuations observed using the number counting method were caused by changes in the engine exhaust. Applying a strict preconditioning procedure should improve the repeatability of the number counting method because this method is more sensitive than the filter weighing method. In addition, the effects of the specifications for the number counting method were evaluated. The results indicate that the hose length from the tip of the sampling probe to the inlet of the number counting system had a negligible effect.

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.

For fuel cell vehicles, which have attracted attention in recent years, the prevention of hydrogen leakage is an essential safety issue. Large fuel cell buses will require a large space to store the hydrogen system. The behavior of hydrogen that has leaked into such a large space is unknown. In this report, we studied hydrogen concentration distribution by leaking hydrogen into simulated spaces in two cases: (1) when hydrogen gas tanks are installed on the roof of the bus, and (2) when an electricity-generating system, such as fuel cell stacks, etc., is installed at the rear of the bus. The results of the experiments show that hydrogen concentration distribution is kept at a constant level throughout each location in the simulated space, depending on the opening area and hydrogen leakage rate. It was also found that the diffusivity of hydrogen in air is extremely high.

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.

Fuel cell vehicles that use high pressure hydrogen gas as a fuel should be able to immediately release hydrogen gas from the cylinder through pressure relief devices (PRDs) in the event of a vehicle fire. The release through PRDs prevents the cylinder from exploding due to the increased pressure of hydrogen gas, but the method of releasing the gas needs to be specified in order to avoid secondary disaster due to the spread of fire. Since hydrogen cylinders for fuel cell buses are different in terms of installation location and size from those for ordinary vehicles, the location of PRDs and the release direction of hydrogen gas should be separately examined. For example, the improper locations of PRDs would raise the possibility of explosion because of a delay in temperature rise, and the direct release of hydrogen gas from a cylinder installed on the rooftop of the bus may disperse the flame over a wide area.

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.

The chemical mechanism responsible for controlling ignition timing by using additives in HCCI has been investigated. Dimethyl ether (DME) and methanol were used as the main fuel and the additive, respectively. Fuel consumption and intermediate formation in the first stage (cool ignition) were measured with crank angle resolved pulse-valve sampling and exhaust gas analysis, where HCHO, HCOOH, CO, H2O2 and other species were detected as the intermediate. The effect of methanol addition retarding ignition is represented by an analytical model in which the growth rate of the chain reaction is reduced by the methanol addition.

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.

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.

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.

Autoignition in the homogeneous charge compression ignition (HCCI) process typically exhibits heat release in two stages called cool flame and thermal flame. The mechanisms governing these two stages were investigated using a DME-fueled HCCI engine and numerical simulations. Composition analysis after cool flame showed that the cool flame is explained by a chain reaction mechanism in which the chain terminator is the intermediate species formed in cool flame. In the case of thermal flame, although the chain reaction mechanism is complex, the behavior is clearly described by thermal explosion theory in which the rate-determining reaction is H2O2 decomposition.