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On-board hydrogen generation technology using a fuel reforming catalyst is an effective way to improve the fuel efficiency of automotive internal combustion engines. The main issue to be addressed in developing such a catalyst is to suppress catalyst deterioration caused by carbon deposition on the catalyst surface due to sulfur adsorption. Enhancing the hydrocarbon and water activation capabilities of the catalyst is important in improving catalyst durability. It was found that the use of a rare earth element is effective in improving the water activation capability of the catalyst. Controlling the hydrocarbon activation capability of the catalyst for a good balance with water activation was also found to be effective in improving catalyst durability.

To improve the fuel economy via high EGR, combustion stability is enhanced through the addition of hydrogen, with its high flame-speed in air-fuel mixture. So, in order to realize on-board hydrogen production we developed a fuel reformer which produces hydrogen rich gas. One of the main issues of the reformer engine is the effects of reformate gas components on combustion performance. To clarify the effect of reformate gas contents on combustion stability, chemical kinetic simulations and single-cylinder engine test, in which hydrogen, CO, methane and simulated gas were added to intake air, were executed. And it is confirmed that hydrogen additive rate is dominant on high EGR combustion. The other issue to realize the fuel reformer was the catalyst deterioration. Catalyst reforming and exposure test were carried out to understand the influence of actual exhaust gas on the catalyst performance.

Fuel economy can be improved by reducing engine displacement, thanks to the resulting smaller friction losses and pumping losses. However, smaller engines frequently operate at high-engine speed and high-load, when pressure on the accelerator increases during acceleration and at high speed. To protect exhaust system components from thermal stress, exhaust gas temperature is reduced by fuel enrichment. To improve fuel economy, it is important to increase the frequency of stoichiometric operation at high-engine speed and high-load. Usually, the start timing of fuel enrichment is based upon temperature requirements to protect the catalyst. In the high-engine speed and high-load zone, the threshold temperature of catalyst protection is attained after some time because of the heat mass. Therefore, stoichiometric operation can be maintained until the catalyst temperature reaches the threshold temperature.

In 2006, Nissan began limited leasing of the X-TRAIL FCV equipped with their in-house developed Fuel Cell (FC) stack. Since then, the FC stack has been improved in durability, cold start-up capability, cost and size with the aim of promoting full-scale commercialization of FCVs. However, reduction of cost and size has remained a significant challenge because limited mass transport through the membrane electrode assembly (MEA) has made it difficult to increase the rated current density of the FC. Furthermore, it has been difficult to reduce the variety of FC stack components due to the complex stack configuration. In this study, improvements have been achieved mainly by adopting an advanced MEA to overcome these difficulties. First, the adoption of a new MEA and separators has improved mass transport through the MEA for increased rated current density. Second, an integrated molded frame (IMF) has been adopted as the MEA support.

In 2006, Nissan began limited leasing of the X-TRAIL FCV equipped with their in-house developed Fuel Cell (FC) stack. Since then, the FC stack has been improved in cost, size, durability and cold start-up capability with the aim of promoting full-scale commercialization of FCVs. However, reduction of cost and size has remained a significant challenge because limited mass transport through the membrane electrode assembly (MEA) has made it difficult to increase the rated current density of the FC. Furthermore, it has been difficult to reduce the variety of FC stack components due to the complex stack configuration. In this study, improvements have been achieved mainly by adopting an advanced MEA to overcome these difficulties. First, the adoption of a new MEA and separators has improved mass transport through the MEA for increased rated current density. Second, an integrated molded frame (IMF) has been adopted as the MEA support.

In recent years, the study of volumetric ignition using high-speed (nanosecond) pulsed low temperature plasma for gasoline engines was reported by authors [ 1 ]. However, the fundamental analysis of ignition characteristics of the low temperature plasma ignition and the analysis of combustion initiation mechanism of the low temperature plasma ignition was not enough in the previous paper. In this study, a low temperature plasma igniter of a barrier discharge (silent discharge) model was developed for trial purpose. A fundamental analysis of ignition characteristics was carried out when the low temperature plasma ignition was applied as the ignition system for gasoline engine using single-cylinder. The difference between the ignition characteristics of the low temperature plasma and the thermal plasma of a conventional spark plug was investigated by comparing a combustion characteristic of both in various driving conditions.

Simultaneous crank-angle-resolved measurements of gasoline vapor concentration, gas temperature, and liquid fuel droplet scattering were made with three-color infrared absorption in a direct-injection spark-ignition engine with premium gasoline. The infrared light was coupled into and out of the cylinder using fiber optics incorporated into a modified spark plug, allowing measurement at a location adjacent to the spark plug electrode. Two mid-infrared (mid-IR) laser wavelengths were simultaneously produced by difference-frequency-generation in periodically poled lithium niobate (PPLN) using one signal and two pump lasers operating in the near-infrared (near-IR). A portion of the near-IR signal laser residual provided a simultaneous third, non-resonant, wavelength for liquid droplet detection. This non-resonant signal was used to subtract the influence of droplet scattering from the resonant mid-IR signals to obtain vapor absorption signals in the presence of droplet extinction.

In recent years, catalyst systems such as a lean NOx trap (LNT) catalyst system and a urea selective catalytic reduction (SCR) system have been developed to obtain cleaner diesel emissions. At Nissan, we developed an emission control system for meeting Tier 2 Bin 5 requirements in 2003. On the basis of that technology, a new HC-NOx trap catalyst system has now been developed that complies with the SULEV standards without increasing the catalyst volume and precious metal loading. Compliance with the SULEV standards requires a further reduction of HC (NMHC) emissions by 84% and NOx by 60% compared with the emission performance Tier 2 Bin 5 compliant catalyst system. Consequently high conversion performance for both HCs and NOx is needed. An investigation of HC emission behavior under the FTP75 mode showed that a reduction of cold-phase HCs was critical for meeting the standard. Large quantities of HCs above C4 are emitted in the cold state.

To reduce quenching distortion, step gas quenching has been proposed in recent years, which refers to rapid gas cooling of steel from austenitizing temperature to a point above or below Ms temperature, where it is held for a specific period of time, followed by gas cooling. In this study, by using infrared thermography combined with conventional thermocouple, a new temperature monitoring and control system was developed to realize the step gas quenching process of a hypoid ring gear after low pressure carburizing. The test production results indicate that by using the new monitoring and control system, we can control the gas quenching process and the distortion of carburized gear treated by step gas quenching can be reduced significantly compared with standard gas quenching.

A new method for measuring unregulated substances in the exhaust gas is being investigated to clarify the influence of the vehicles' exhaust emissions into the environment. This paper explains our work on developing an analysis method for detecting and quantifying trace substances in the exhaust gas. A new analysis method was examined that uses thermal desorption to analyze trace amounts of polycyclic aromatic hydrocarbons (PAHs) in vehicle exhaust gas. This technique is faster than conventional methods and does not require any preconditioning of the samples before analysis. While lead and chloromethane were detected in the exhaust gas samples, it was made clear that these substances did not originate in the engine system. Accordingly, the results of this study indicate that careful attention must be paid to the test environment and the presence of measurement interfering substances in exhaust samples when measuring trace constituents in the exhaust gas from low-emission vehicles.

This paper presents a new measurement technique for in-cylinder gas temperature and residual gas concentration during the compression stroke of an internal combustion (IC) engine. This technique is based on the infrared absorption of water vapor by a wavelength modulated laser. Wavelength modulation spectroscopy with second harmonic detection (WMS-2f) was adopted to enable the short-path measurements over a wide range of temperatures and pressures corresponding to the late compression stroke in a typical automotive engine. The WMS-2f signal is detected through a bandpass filter at a width of 7.5 kHz, enabling crank angle-resolved measurements. The temperature is determined from the ratio of optical absorption for two overtone transitions of water vapor in the intake gas mixture, and the H2O concentration is determined from this inferred temperature and the absorption for one of the transitions.

In the Japan Clean Air Program II (JCAP II) Diesel WG, effects of fuel properties on the performance of two types of diesel NOx emission aftertreatment devices, a Urea-SCR system and a NOx storage reduction (NSR) catalyst system, were examined. For a Urea-SCR system, the NOx emission reduction performance with and without an oxidation catalyst installed in front of the SCR catalyst at low exhaust gas temperature operation was compared. For an NSR catalyst system, the effect of fuel sulfur on both emissions and fuel economy during 50,000 km driving was examined. Furthermore, effects of other fuel properties such as distillation on exhaust emissions were investigated. The results show that sulfur is the influential factor for both devices. Namely, high NOx emission reduction performance of the Urea-SCR system with the oxidation catalyst at low exhaust gas temperature operation is influenced by sulfur.

Emission regulations for diesel-powered vehicles have been gradually tightening. Installation of after-treatment devices such as diesel particulate filters (DPF), NOx storage reduction (NSR) catalysts, and so on is indispensable to satisfy rigorous limits of particulate matter (PM) and nitrogen oxides (NOx). Japan Clean Air Program II Oil Working Group (JCAPII Oil WG) has been investigating the effect of engine oil on advanced diesel after-treatment devices. First of all, we researched the impact of oil-derived ash on continuous regeneration-type diesel particulate filter (CR-DPF), and already reported that the less sulfated ash in oil gave rise to lower pressure drop across CR-DPF [1]. In this paper, impact of oil-derived sulfur and phosphorus on NSR catalyst was investigated using a 4L direct injection common-rail diesel engine with turbo-intercooler. This engine equipped with NSR catalyst meets the Japanese new short-term emission regulations.

This paper describes a newly developed HC-adsorption three-way catalyst and adsorption system that reduce cold-start HC emissions with high efficiency. This system is the first of its kind anywhere in the world to be implemented on production vehicles. An overview is given of the various improvements made to achieve higher cold-start HC conversion efficiency. Improvement of conversion performance was accomplished by (1) increasing the thermal stability of the HC adsorbent, (2) improving desorbed HC conversion efficiency and durability and (3) optimizing the geometric surface area (GSA) of the substrate. Concretely, the thermal stability of the adsorbent was improved by enhancing the high-temperature durability of zeolite. Improvement of desorbed HC conversion efficiency was accomplished by improving the OSC material so as to match the temperature rise characteristic and usage temperature of the catalyst.

The thinnest wall thickness of automotive catalyst substrates has previously been 30 μm for metal substrates and 50 μm for ceramic substrates. This paper describes a newly developed catalyst substrate that is the world's first to achieve 20-μm-thick cell walls. This catalyst substrate features low thermal capacity and low pressure loss. Generally, a thinner cell wall decreases substrate strength and heat shock resistance. However, the development of a “diffused junction method”, replacing the previous “wax bonding method”, and a small waved foil has overcome these problems. This diffused junction method made it possible to strengthen the contact points between the inner waved foil and the rolled foil compared with previous substrates. It was also found that heat shock resistance at high temperature can be much improved by applying a slight wave to the foil instead of using a plane foil.

A new multidimensional calculation method has been developed to simulate the warm-up characteristics of close-coupled catalytic converter systems. First, a one-dimensional gas exchange simulation and a three-dimensional exhaust gas flow calculation are combined to simulate the pulsation gas flow caused by the gas exchange process. The gas flow calculation and a heat transfer calculation are then combined to simulate heat transfer in the exhaust manifold and the catalyst honeycomb under pulsation flow. The predicted warm-up characteristics of the systems examined agreed well with the experimental data. In this simulation, CPU time was reduced greatly through the use of new calculation methods. Finally, the warm-up process of close-coupled catalysts is analyzed in detail with this simulation method. The design requirements for improving warm-up characteristics have been made clear.

An adsorber system for reducing cold-start hydrocarbon (HC) emissions has been developed combining existing catalyst technologies with a zeolite-based HC adsorber. The series flow in-line concept offers a passive and simplified alternative to other technologies by incorporating one additional adsorber substrate into existing converters without any additional valving, purging lines, secondary air, or special substrates. Major technical issues to be resolved for practical use of this system are 1) the ability to adsorb a wide range of HC molecular sizes in the cold exhaust gas and 2) the temperature difference between HC desorption from the adsorber and activation of the catalyst to convert desorbed HCs. This paper describes the current development status of hydrocarbon adsorber aftertreatment technologies. We report results obtained with a variety of adsorber properties, washcoat structures of adsorber catalyst and start-up and underfloor catalyst system combinations.

This paper describes new technologies for achieving exhaust emission levels much below the SULEV standards in California, which are the most stringent among the currently proposed regulations in the world. Catalyst light-off time, for example, has been significantly reduced through the adoption of a catalyst substrate with an ultra-thin wall thickness of 2 mil and a catalyst coating specifically designed for quicker light-off. A highly-efficient HC trap system has been realized by combining a two-stage HC trap design with an improved HC trap catalyst. The cold-start HC emission level has been greatly reduced by an electronically actuated swirl control valve with a high-speed starter. Further, an improved Air Fuel Ratio (AFR) control method has achieved much higher catalyst HC and NOx conversion efficiency.

It is projected that compliance with Japanese new exhaust emission regulations set to be enforced in 2000 year will be difficult for turbocharged engines with conventional technologies. This is mainly because of the delay in catalyst lightoff at engine start due to the lower exhaust gas temperature of turbocharged engines compared with that of their naturally aspirated counterparts. Compliance will be particularly difficult for V-6 engines on account of the large heat mass of the exhaust system, resulting in a slower temperature rise. Previously, improvement of hydrocarbon (HC) conversion rates following engine start depended solely on the low-temperature characteristic of the catalyst. The catalyst system described here adopts a completely new mechanism that traps HCs before the catalyst lights off and then desorbs them for conversion after the engine warms up.

This paper concerns research on an emission control system aimed at reducing emission levels to well below the ULEV standards. As emission levels are further reduced in the coming years, it is projected that measurement error will increase substantially. Therefore, an analysis was made of the conventional measurement system, which revealed the following major problems. 1. The conventional analyzer, having a minimum full-scale THC range of 10 ppmC, cannot measure lower concentration emissions with high accuracy. 2. Hydrocarbons are produced in various components of the measurement system, increasing measurement error. 3. Even if an analyzer with a minimum full-scale THC range of 1 ppmC is used in an effort to measure low concentrations, the 1 ppmC measurement range cannot be applied when the dilution air contains a high THC concentration. This makes it impossible to obtain highly accurate measurements. 4.