Search Results

The modern Diesel engine is one of the most versatile power sources available for mobile applications. The high fuel economy and power of the Diesel engine has long made it the choice for heavy-duty applications worldwide. Over the coming years, global emissions legislation applied to heavy-duty Diesel (HDD) engines will become more and more stringent, necessitating the use of advanced emissions control technologies. In particular, the coming exhaust gas emissions legislation focuses on particulate matter (PM) emissions and emissions of nitrogen oxides (NOx). A filtration device can control PM emissions, and a possible technology for the abatement of NOx emissions involves NOx absorber catalysts. This paper describes investigations into the activity and system behaviour of a prototype HDD exhaust system based on NOx absorber technology. The system consists of a “single leg” containing NOx absorber catalyst that is bypassed during rich regeneration of the NOx absorbers.

In a consortium of European industrial partners and research institutes, a combination of industrial development and scientific research was organised. The objective was to improve the catalytic NOx conversion for lean burn cars and heavy-duty trucks, taking into account boundary conditions for the fuel consumption. The project lasted for three years. During this period parallel research was conducted in research areas ranging from basic research based on a theoretical approach to full scale emission system development. NOx storage catalysts became a central part of the project. Catalysts were evaluated with respect to resistance towards sulphur poisoning. It was concluded that very low sulphur fuel is a necessity for efficient use of NOx trap technology. Additionally, attempts were made to develop methods for reactivating poisoned catalysts. Methods for short distance mixing were developed for the addition of reducing agent.

Prototypes of gas sensitive Schottky diodes with a platinum gate electrode have been fabricated on monocrystalline 6H-SiC substrates and tested on petrol engines. The sensors are mounted in the housing and on the heater of HEGO sensors. The air/fuel ratio of each cylinder is individually controlled by UHEGO sensors. Three gas sensitive SiC diodes together with another UHEGO sensor, serving as the reference sensor, are mounted into the exhaust pipe. At the operating temperature used, around 600-800°C, the SiC sensors show a large variation of the output signal for small variations of the air/fuel ratio around the stoichiometric ratio. The response time of the sensor is small enough to detect the air/fuel ratio of individual cylinders. We show how the sensor can be used to detect misfire and/or individual cylinders that deviate from stoichiometry. The SiC sensor thus shows promising potential for cylinder selective and more effective combustion control.