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Technical Paper

Mixing Control and Combustion in Gasoline Direct Injection Engines for Reducing Cold-Start Emissions

2001-03-05
2001-01-0550
A two-stage combustion is one of the Mitsubishi GDI™ technologies for a quick catalyst warm-up on a cold-start. However, when the combustion is continued for a long time, an increase in the fuel consumption is a considerable problem. To solve the problem, a stratified slight-lean combustion is newly introduced for utilization of catalysis. The stratified mixture with slightly lean overall air-fuel ratio is prepared by the late stage injection during the compression stroke. By optimizing an interval between the injection and the spark timing, the combustion simultaneously supplies substantial CO and surplus O2 to a catalyst while avoiding the soot generation and the fouling of a spark plug. The CO oxidation on the catalyst is utilized to reduce the cold-start emissions. Immediately after the cold-start, the catalyst is preheated for the minimum time to start the CO oxidation by using the two-stage combustion. Following that, the stratified slight-lean combustion is performed.
Technical Paper

Development of the NOx Adsorber Catalyst for Use with High-Temperature Condition

2001-03-05
2001-01-1298
NOx adsorber has already been used for the after-treatment system of series production vehicle installed with a lean burn or direct injection engine [1,2,3]. In order to improve NOx adsorbability at high temperatures, many researchers have recently been trying an addition of potassium (K) as well as other conventional NOx adsorbents. Potassium, however, reacts easily with the cordierite honeycomb substrate at high temperatures, and not only causes a loss in NOx adsorbability but also damages the substrate. Three new technologies have been proposed in consideration of the above circumstances. First, a new concept of K-capture is applied in washcoat design, mixed with zeolite, to improve thermal stability of K and to keep high NOx conversion efficiency, under high temperatures, of NOx adsorber catalyst. Second, another new technology, pre-coating silica over the boundary of a substrate and washcoat, is proposed to prevent the reaction between potassium and cordierite.
Technical Paper

Optimized Gasoline Direct Injection Engine for the European Market

1998-02-23
980150
GDI (Gasoline Direct Injection) engine adopting new combustion control technologies was developed and introduced into Japanese domestic market in August of 1996. In order to extend its application to the European market, various system modifications have been performed. Injectors are located with a smaller angle to the vertical line in order to improve the combustion stability in the higher speed range. A new combustion control method named “two-stage mixing” is adopted to suppress the knock in the low speed range. As a result of this new method, the compression ratio was increased up to 12.5 to 1 while increasing the low-end torque significantly. Taking the high sulfur gasoline in the European market into account, a selective reduction lean-NOx catalyst with improved NOx conversion efficiency was employed. A warm-up catalyst can not be used because the selective reduction lean NOx catalyst requires HC for the NOx reduction.
Technical Paper

Development of Diesel Particulate Trap Oxidizer System

1986-03-01
860294
A particulate trap oxidizer system to reduce diesel particulate emissions has been developed. This system consists of a ceramic foam filter with an optimum volume, shape, and mesh number in terms of collection efficiency, pressure loss and particulate blow-off; a catalyst with a low activated-temperature for particulate incineration and with no sulfate formation during highway driving; and a regeneration system which prevents particulate overcollection during long-term continuous low-load/low-speed driving where it is difficult to achieve self-burning of particulates with a catalytic reaction. This paper describes the development of the particulate trap oxidizer system with these technologies and presents the results of practicability evaluations and 50,000-mile vehicle durability tests.
Technical Paper

Combustion Modes of Light Duty Diesel Particulates in Ceramic Filters with Fuel Additives

1986-03-01
860292
Auto-regeneration of diesel particulate traps, particularly combustion mode of soot in a wall flow filter with fuel additives, was investigated using a diesel engine of a light duty truck and truck itself. Soot burning in the trap and regeneration were observed under any engine operating condition including prolonged idling and stop-and-go driving at 0.18g metal/1 dosage of a mixture of copper and lead in the fuels. However, trap life was limited by ash clogging due to the metallic compounds. Although the influence of metallic additives on the environment was debatable, test results of the trap durability and calculations of soot burning based on the thermal ignition theory indicated that dosage and kind of fuel additives should be optimized in view of both trap life and reliability of soot burning.
Technical Paper

Development of Advanced Emission-Control Technologies for Gasoline Direct-Injection Engines

2001-03-05
2001-01-0254
An extensive effort has been made, at Mitsubishi Motors, in the technology field of new catalysts and of the catalyst reaction control for the purpose of further improvement of the emission control with the GDI engines [1-2]. A new NOx-trap catalyst has been developed to satisfy the required higher catalyst performance under high-temperature condition. The new catalyst contains potassium (K) of excellent NOx-storage capacity under high-temperature region in the catalytic atmosphere, and to retain K stability zeolite is mixed in the catalyst layer as well as the substrate is coated with silica (SiO2). This new catalyst has been proven of the improved NOx conversion efficiency, and solved the long-pending problems particularly those experienced under high-temperature operation.
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