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Exhaust gas from the diesel engine contains particulate matter (PM) of soot that affects human health and the environment. For the reduction of the emission of the PM, the diesel particulate filter (DPF) is placed in the exhaust system. The pressure drops increases with the PM deposit quantity in the DPF, which results in the burden of the engine. Therefore, the PM should be removed regularly by oxidation process called regeneration. Consumption of fuel is improved by optimizing the timing of regeneration. However, it is difficult to visualize the behavior of PM trapping and oxidation. We have proposed a series of models from PM deposition to the oxidation process in the DPF. In this study, the behavior of deposition and oxidation of PM in the DPF with a catalyst are calculated. The numerical calculations are performed to estimate PM deposition-oxidation process within the DPF. The results are obtained using the simplified model constructed in this study.

The objective of this study was to develop a test method for heavy-duty HEVs using a hardware-in-the-loop simulator (HILS) to enhance the type-approval-test method. To achieve our objective, HILS systems for series and parallel HEVs were actually constructed to verify calculation accuracy. Comparison of calculated and measured data (vehicle speed, motor/generator power, rechargeable energy storage system power/voltage/current/state of charge, and fuel economy) revealed them to be in good agreement. Calculation error for fuel economy was less than 2%.

Soot accumulation in diesel engine crankcase is the dominant factor which governs engine oil drain interval. So, efficient soot elimination from crankcase oil can be a practical way to achieve drain interval extension. Combination of high performance oil filter and low soot dispersancy oil results in an effective measure to trap soot efficiently. In this paper, the behavior of newly developed high performance diesel engine oil having low soot dispersancy is reported. Prior to oil development, an evaluation method of soot dispersancy in oil was elaborated. Based on relative viscosity defined as ratio of soot containing oil viscosity to soot eliminated oil viscosity, dispersancy parameter was determined. Oil dispersancy evaluated on this parameter agreed with the results obtained from particle size analyzer. Secondly, a method to obtain oil filter soot trap rate to total soot contaminated into crankcase (trap rate) was established.

In complying with a customer demand for improving low-speed maneuverability of commercial vehicles in narrow streets, a medium-duty truck with a mechanical linkage type four-wheel steering system with a hydraulic assist and a steering lock device is developed. A mode select gearbox allows a driver to select one of three rear-wheel steering modes; 2WS, same-phase 4WS, and opposite-phase 4WS. The steering lock device is locked during 2WS operation for preventing rear-wheel steering. An electronic control system is applied for easier mode selection, synchronization of locking and unlocking the steering lock device with a mode select operation, and vehicle speed limitation during 4WS operation. We made efforts particularly to suppress vehicle yaw motion when the vehicle is running in the same-phase 4WS mode. Several innovative new mechanisms are incorporated on this vehicle. This paper deals with these mechanisms and these functions.

Because of smaller ratios of tread to height of gravitational center, longer wheel-bases, and larger moment of inertia, vehicle roll is the most important characteristics governing truck controllability and stability. And longer wheel-bases result in a reduction in vehicle body torsional stiffness. Hence, the influence of vehicle body torsional stiffness on vehicle roll characteristics is investigated. We carried out a simulation analysis and vehicle test on medium-duty trucks, in studying the vehicle frequency response characteristics by changing vehicle design parameters. The results show that a reduction in body torsional stiffness increases the steady state gain of the front roll angle without affecting the yaw and lateral characteristics of vehicle motion. Accordingly, even if body torsional stiffness is unavoidably lowered, reducing the front roll angle by increasing the roll stiffness of the front suspension can maintain appropriate vehicle controllability and stability.

Transmission electron microscope (TEM) is a powerful tool for studying catalyst materials at nano-size and/or atomic level. Conventional TEM usually needs to be observed at room temperature in high vacuum conditions. A gaseous atmosphere and high temperature condition may change the properties of catalyst materials. Recently we developed an in situ observation system in TEM for observing the oxidation and reduction under a gas atmosphere at high temperature. Using the new in situ observation system in TEM, the morphological changes of the nano particle and support were observed in the heated gaseous atmosphere at atomic level in real time.

In Biodiesel Fuel Research Working Group(WG) of Japan Auto-Oil Program(JATOP), some impacts of high biodiesel blends have been investigated from the viewpoints of fuel properties, stability, emissions, exhaust aftertreatment systems, cold driveability, mixing in engine oils, durability/reliability and so on. In the impact on exhaust emissions, the impact of high biodiesel blends into diesel fuel on diesel emissions was evaluated. The wide variety of biodiesel blendstock, which included not only some kinds of fatty acid methyl esters(FAME) but also hydrofined biodiesel(HBD) and Fischer-Tropsch diesel fuel(FTD), were selected to evaluate. The main blend level evaluated was 5, 10 and 20% and the higher blend level over 20% was also evaluated in some tests. The main advanced technologies for exhaust aftertreatment systems were diesel particulate filter(DPF), Urea selective catalytic reduction (Urea-SCR) and the combination of DPF and NOx storage reduction catalyst(NSR).

NOx emitted from diesel is one of the main air pollutants for most countries. To reduce the emission of NOx could promote to diffuse diesel vehicles. A NOx storage/reduction (NSR) catalyst has been developed for the diesels. The catalyst for NSR is strongly poisoned by sulfur. We have found good reaction of CaCO3 with sulfur dioxide by using a thermogravimetry. We obtained desulfurization breakthrough characteristic for the sample of the CaCO3 which is washcoated on the monolith. As a result, this sample which has specific surface area, of 100 m2/g, absorbed SO2 about 0.43 ~ 0.45 g−SO2/g−CaCO3. In this experimental condition, The conversion of the sulfate does not depend on the amount of the supported CaCO3. The absorption efficiency of these samples were more than 99.4%. According to this result, it was found that the necessary amount of the absorbent was supposed to be 0.538 kg or 2.1 L for 100,000 km running.

Analysis results of used oils sampled from many engines operating in the field show that the most critical factor governing the limits of oil use is insoluble fraction concentration in oil. Hence, the authors developed a new oil and by-pass oil filter to increase soot trapping efficiency, so as to extend oil change interval. Soot trapping efficiency could be improved from 30% to more than 80% using a bigger oil filter with fine mesh and a newly developed low soot dispersancy oil. Engine lubrication performance of the new oil was compared to that of standard and commercial long-drain oils by conducting 300-hour endurance tests on an 11.7 liter direct injection, turbocharged and aftercooled diesel engine at rated output. Test results proved superior engine lubrication performance of the new oil. THE INTERVAL between lubricating oil changes for diesel engines is twenty to forty thousand kilometers, depending on engine manufacturers' recommendations (1)*.

Several types of oxidation catalyst material are tested in repeated particulate emission measurements over the US HDD transient test procedure. Particulates are effectively reduced in the initial stage of the measurements. However, particulates tend to increase when repeating the measurements. This is believed to be caused by sulfate adsorption on the catalyst surfaces. Hence, oxidation catalysts are tested after stabilizing surface adsorption. Test results show that an oxidation catalyst which forms more sulfates is not effective in reducing particulates because the sulfate increase offsets the SOF reduction effect. An effective catalyst for particulate reduction is developed by suppressing sulfate formation.

Nissan Diesel Motor Co.,LTD have developed a new turbocharged diesel engine with a variable nozzle turbocharger for the purpose of solving the contradictory problems of mobility and fuel economy, while meeting the 1990 Japanese emission standards. The heavy-duty trucks equipped with this new turbocharged engine have been released in the market recently. The variable nozzle turbocharger capable of maintaining sufficient turbine efficiency over the broad range of engine operating band was jointly developed with Allied Signal, Garrett Automotive Group in United States of America.It's control method, a stepless boost pressure feedback control system, was newly developed in order to make the most effective use of the turbocharger.

The characteristics of a new diesel particulate filter material made of SiC were studied through engine tests in varying material properties, such as average pore diameter, and wall thickness. Compared to a conventional cordierite filter of the same size, particulate trapping efficiency is almost the same, and the pressure loss and the deterioration of fuel consumption can be reduced to about half with the optimum material properties. If the same pressure loss is allowed, the filter size can be reduced by 30%. Its good thermal conductivity prevents local temperature increases, which doubles the permissible amount of trapped particulates. As heat crack problems occurred in integral-type filters due to the high thermal expansion of SiC, a split-type filter having 49 filter segments with a square section was developed.

A heavy-duty, naturally aspirated diesel engine was converted into a turbocharged, aftercooled, compressed natural gas engine. Engine test results show that excess air ratio and ignition timing strongly affect NOx and THC emissions. Leaning the air-fuel mixture reduces NOx emission, but it increases THC emission and combustion becomes unstable above a certain excess air ratio. Retarding the ignition timing reduces both the NOx and THC emissions. Dual-plug ignition improves brake thermal efficiency. The NOx emission level can be reduced to meet the Japanese long-term emission regulation limit for heavy-duty gasoline engines with a sufficient safety margin by appropriately selecting the air-fuel ratio and ignition timing so as to keep the THC emission level below the regulation limit without using any after-treatment. The engine full torque characteristics were almost the same as the base engine throughout the engine speed range, while the maximum exhaust gas temperature was lower.

This study establishes the feasibility of improving the motion characteristics of commercial vehicles by applying rear axle steering. A model-matching control algorithm for rear axle steering was used to achieve the desired yaw rate response to steering action. Simulations with a two-degree-of-freedom model evaluated the effectiveness of the control method. Results of vehicle tests on an experimental medium-duty truck with rear axle steering proved that this control method can improve vehicle yaw response. However, the simulation results did not well represent the vehicle test results, because the simulation model was too simple. Adding the roll effect to the model reduced the discrepancy between the simulation and vehicle test results.

The effects of fuel properties on diesel engine exhaust emission characteristics are investigated using eleven kinds of fuel with varying levels of sulfur and aromatic contents. Exhaust emissions from three engines are measured over the new Japanese 13-mode cycle as well as the U.S. transient test procedure. Engine test results show that reducing the fuel sulfur content decreases particulate levels. This effect is more pronounced for engines that emit more SOF. Enriching the aromatic content with dicyclic and other polycyclic compounds increases particulate, NOx, CO, and THC emissions. This particulate increase is due to the increase of SOF. Accordingly, low sulfur fuel should be produced without increasing the aromatic content, otherwise the SOF increase will offset the particulate reduction effect of the low sulfur fuel.

Injection process simulation methods were developed for both the unit injector (UI) system and the pump-line nozzle (PLN) system consisting of an in-line injection pump, fuel line, and nozzle. Simulation results agreed well with measured ones. With regard to the shape of injection rate and the peak injection pressure change at various engine speeds, the injection characteristics of the UI system are better than those of the PLN system. Simulation results showed that similar injection characteristics can also be obtained with the PLN system by using a concave cam with a carefully designed cam profile for a sleeve-controlled in-line injection pump and by changing the prestroke according to the operating conditions. Engine test results demonstrated the possibility of improving the trade-off between NOx and fuel consumption by shaping the injection rate. The shape of injection rate plays an important role in diesel combustion(1,2)*, affecting exhaust emissions and also combustion noise.

Engine manufactures are continuing to develop new engine designs that provide higher power output, lower fuel consumption and lower engine weight. In order to achieve significant engine weight reduction, the light weight cylinder block structure employs dry cylinder liners rather than wet cylinder liners. The cast iron dry liner structure is utilized because of the superior wear and scuff resistance of the cast iron. Thin wall dry cast iron liners are being employed in both gasoline and diesel engines. Dry cylinder liners with wall thickness of 1.5mm are in production for Japanese automotive diesel engines. In the case of the dry thin wall cast iron liners, two(2) design configurations are employed: Loose-fit type having a specified clearance between the outer liner surface and the cylinder bore surface. Press-in type having an interference fit between the outer surface of liner and the cylinder bore surface.

Particulate matter (PM) including soot in diesel exhaust gas is a serious atmospheric pollutant, and stricter exhaust emission standards are being set in many countries. As one of the key technologies, a diesel particulate filter (DPF) for PM trap in the after-treatment of the exhaust gas has been developed. Typically, the inlet size of filter monolith is about 2 mm, and the thickness of the filter wall is only 0.2 mm, where soot particles are removed. It is impossible to observe the small-scale phenomena inside the filter, experimentally. Then, in the present study, we conducted microfluidic simulation with soot oxidation. Here, a real cordierite filter was used in the simulation. The inner structure of the filter was scanned by a 3D X-ray CT Computed Tomography) technique. The advantage is that it is non-intrusive system, and it has a high spatial resolution in the micrometer.

In this study, with the purpose of applying to the metal catalyst substrates, we have examined the feasibility of improving the light-off performance of a catalytic converter by enhancing heat transfer in the cells with heat-transfer promoters. Experimental and CFD analyses have been conducted to estimate heat transfer rates and pressure losses of the model cells with hemispherical protrusions. The analyses show that, by enhancing heat transfer of the cells, the cell density can be reduced keeping the catalytic performance in the steady state at the same level as that of conventional ones. As a result, the thermal mass of the substrate can be also reduced effectively without an increase of the pressure loss, and consequently the light-off performance of the catalytic converter can be improved noticeably.

In Japan there is currently a strong social demand for exhaust emissions reduction from heavy-duty diesel engines. Therefore, new Long-Term Regulation will come into effect in October 2005, setting the NOx standard at 2.0 g/kWh and the PM standard at 0.027 g/kWh. At the same time, customers always demand exceptional fuel economy from heavy-duty commercial vehicles. A urea-based Selective Catalytic Reduction (SCR) system was developed to satisfy both these demands, and will be introduced in the fall of 2004. The operating conditions of vehicles in Japan are different from those in the US and Europe. Basically, average vehicle speeds are significantly lower. To improve the low temperature SCR performance, an oxidation catalyst was located upstream of the SCR, and an additional oxidation catalyst was located downstream of the SCR for emergency NH3 slip. The muffler size with all three catalysts was similar to a conventional muffler.