外文翻译中文--氮氧化物催化技术在汽车尾气中的应用(编辑修改稿)

外文翻译中文--氮氧化物催化技术在汽车尾气中的应用(编辑修改稿)内容摘要：

s been a tendency to expand the leanburn operating region of engines and higher conversion efficiency is being demanded of catalysts. Tighter standards pose a particularly high hurdle for diesel engines. NOx trap and lean NOx catalyst technologies has been applied to some leanburn and directinjection Figure 1. Current and proposed NOx emission standards for gasoline and diesel passenger cars. gasoline engines [1,2], but no effective NOx control technology has been implemented yet for diesel engines that operate under a full lean condition with higher A/F ratios. The exhaust temperature of a diesel engine is lower, and there are more little HCs remaining in the exhaust pared with a gasoline engine. There are many C3 to C5 nonsaturated HCs which are advantageous for reducing NOx emissions in gasoline engine exhaust. On the other hand, diesel engine exhaust contains heavy HCs which are harder to use as a NOx reducing agent, along with SO2 that causes catalytic deactivation. These conditions have thwarted practical application of HCSCR technology to diesel engines. However, the tendency toward lower exhaust gas temperatures and a lower level of residual HCs will result in the same typical exhaust gas conditions for future gasoline and diesel engines that achieve high fuel bustion efficiency. Therefore, if highperformance lean NOx catalysts are developed which can be applied to such conditions, cleaner exhaust will be obtained, leading to further improvements in fuel economy This paper describes the current development status of our HCSCR technologies and discusses the problems that must be addressed to apply these technologies to production vehicles. 2. Exhaust characteristics Figure 2 shows profiles of the HC and NOx emissions and exhaust temperature of the directinjection diesel engine used in this work under the ECE (Economic Commission for Europe)+EUDC (ExtraUrban Driving Cycle) hot mode. The engine was a inline 4cylinder directinjection turbodiesel. The exhaust temperature was measured at the turbocharger outlet. A high level of NOx was produced during acceleration, although the HC level was not so high. This means that the ambient HC/NOx ratio is low under the conditions where the NOx reduction activity of the catalyst is most needed. The characteristics of diesel exhaust are summarized in table 1. The differences in exhaust characteristics between gasoline and diesel engines are quite striking at present. However, if the fuel bustion efficiency of gasoline e。