Search Results

With the aim to successively remove particulate matter (PM) from exhaust emissions of diesel engines, non-thermal plasma (NTP) system is now under development for practical use. The model analyzer for generating plasma with unit-cell of the NTP reactor, was designed and developed for the quantitative analysis of discharged plasma. The novel NTP reactors with newly developed porous and wave-foil electrodes show excellent plasma specifics such as low Inception voltage for plasma discharge and strong radiation luminance. A virtual vehicle simulator using an engine dynamometer, aiming at the evaluation of the plasma PM removal properties in various modal driving schedules, was constructed. It is confirmed that the novel NTP reactor shows not only excellent PM removal properties but also minimized pressure loss. Especially, PM removal properties are strongly influenced by the increase in plasma radiation luminance.

Increasingly stringent emissions controls have led to a greater emphasis on strategies designed to minimize emission during cold start. One strategy employed is that of close-coupling the catalyst to the exhaust manifold of the engine in an effort to minimize catalyst light-off time. In this configuration, the catalyst must exhibit a high degree of thermal stability. Further, since the catalyst is situated nearer to the engine, it is more liable to sense cylinder-to-cylinder variations in exhaust gas composition and thus needs to possess a wider operating window than a catalyst positioned further underbody. We have previously reported that Perovskite-Pd catalysts exhibit excellent heat resistance and have three-way catalyst activity comparable with or superior to that of Pt-Rh/ Al2O3 catalysts and Pd/Al2O3 catalysts [1]*. Durability at high temperatures and oxygen storage capacity under large air/fuel (A/F) ratio fluctuation conditions have now been tested.

Three-way catalysts which remove different kinds of pollutants, such as CO, THC(total hydro-carbon) and NOx, simultaneously from the automotive exhaust gas employ Rhodium(Rh) in combination with Platinum(Pt) and Palladium(Pd). Rh is the most effective for reducing NOx to N2, but Rh is the most expensive of these precious metals. The ratio of Rh to Pt applied for automobiles frequently exceeds the natural production. The gap between supply and demand of Rh sometimes causes the big price fluctuation. Accordingly, many attempts to reduce the amount of Rh loaded or to develop non-Rh three-way catalysts have been made. Although Pd catalysts are considered to be promising candidates for non-Rh automotive three-way catalysts, some performance are still inferior to Pt-Rh catalysts. We have found that an excellent three-way catalytic activity appears by compounding new Perovskite-structured oxides with Pd and auxiliary oxides.