Search Results

It is a generally accepted fact that the advantage of diesel engines over their gasoline-powered counterparts is superior fuel consumption. However, attempts to use diesel engines as car powerplants have been hampered by the associated increase in toxic emissions. Research was carried out with the objectives of achieving the lowest fuel consumption for a diesel-powered passenger vehicle in the 1,590kg equivalent inertia weight class while also meeting the 2005 European diesel exhaust emissions standards (EURO IV). This paper starts with a description of the experiments on combustion and the results of the simulations and experiments using a visualization apparatus, followed by a description of the fuel consumption, emissions and power performance of the engine when fitted in an actual vehicle. To begin with, the relationship between engine displacement and fuel consumption was investigated.

For global environmental protection and resource conservation, Honda has developed a low precious-metal perovskite catalyst system in response to LEV-II, which achieves both low emissions and a reduction in the amount of precious metal used. The amount of precious metals used in the catalyst, per vehicle, is expected to be 50% less than in conventional systems. This system is comprised of an air-fuel ratio control system based on Honda's unique high-accuracy air-fuel control system, combined with a perovskite catalyst jointly developed with the US Company CSI. This system's performance is expected to reach the levels required by LEV-II regulations. Perovskite is a mix-metal oxide material that is widely used in general applications other than catalysts. However, it has not been widely used in automobile catalysts, because, in comparison with precious-metal catalysts, both the heat resistance and conversion efficiency during the warm-up process is reduced.

A simple theoretical analysis was carried out in order to clarify the general characteristics of pressure loss in exhaust gas flow induced when exhaust gas passes through a catalyst, which is generally used for the purification of exhaust gas emitted from automobile engines. Namely, Darcy's friction factor was applied to an equation, which is well known in the field of fluid dynamics, to determine the pressure drop of fluid flowing in a flow path. Using this friction factor, the air pressure difference between the upstream and downstream of the catalyst was calculated using the hydraulic diameter of the catalyst cell, the Reynolds number based on the hydraulic diameter of the catalyst cell, the length of the catalyst, and the density and velocity of the air flowing in the catalyst cell. Here, the flow of air is a laminar flow, which is assumed to be in the steady state, and the cross-sectional shapes of the catalyst cells examined are square, circle and equilateral triangle.

In order to further reduce exhaust gas emissions, an investigation was carried out with premixed charge compression ignition (PCCI) combustion mode using conventional diesel fuel. Past research was carried out with early injection into shallow-dish piston bowl, combined with a narrow nozzle angle setting. Early injection significantly reduced NOX emissions, but some of the fuel spray adhered to the piston bowl surface creating a fuel wall-film which was a major cause in increasing soot, HC and CO emissions and fuel consumption [1]. As a possible solution to this issue, PCCI combustion mode operation on a direct injection diesel engine was investigated with fuel injection timing set close to top dead center (TDC). As a result, regardless of the fuel injection timing, increasing EGR reduced NOx emissions. In terms of fuel consumption, soot, HC and CO, however, fuel injection timing close to TDC was superior to earlier injection, due to the reduction in the fuel wall-film formation.

In order to further reduce exhaust gas emissions, an investigation was carried out concerning premixed charge compression ignition (PCCI) combustion, which is achieved by the early injection of conventional diesel fuel to the combustion chamber. The engine used for the experiments was a single cylinder version of a modern passenger car type common rail engine with a displacement of 550(cm3). An injector with a narrower corn angle was used to prevent interaction of the spray and the cylinder liner. Also, the compression ratio was decreased in order to avoid an excessively advanced ignition situation. Additionally, a large degree of cooled exhaust gas recirculation (EGR) was applied. These measures led to a significantly reduction in NOX emissions. However, a fuel wall-film, which was formed on the surface of the piston bowl wall, caused increases in soot, HC and CO emissions.

Although air pollution has mitigated since the introduction of exhaust emission regulations, further reduction of it especially in the metropolitan areas is anticipated. An effective way to resolve this issue is to improve the catalyst performance. Of many approaches, improving substrate is one promising way to achieve this goal. Results of applying high cell density and light- weight substrates, coupled with high precious metal content, are discussed theoretically and verified experimentally here. The significant improvements made in the low temperature activity and warmed-up conversions by increasing geometrical surface areas and lowering thermal mass of high cell density substrates are described.

Engines are assigned big subjects such as low emission and low fuel consumption as well as higher output (higher efficiency) in the latest trend of environmental protection. In order to meet these requirements, Air/Fuel ratio of recent high performance engines is being arranged leaner than that of conventional engines. As a result exhaust valve seat inserts used in these engines have problems of their wear resistance because of high exhaust gas temperature. By analyzing wear mechanism under the lean burn conditions, authors developed material for exhaust valve seat inserts which show superior wear resistance under high operating temperature. For the purpose to enhance heat resistance, authors added alloy steel powder for matrix powder and used hard particles which have good diffusion with matrix. The developed material does not include Ni and Co powders for cost saving and has superior machinability.