Diesel engine operation to suppress nitrogen oxides emission

摘要

This novel method offers nitrogen oxide- (NOx) free running of an internal combustion engine, especially a car diesel engine. In a first mode of operation, fuel injection is advanced (6, 10), and an NOx suppressing agent is added (5, 7, 8) to the exhaust flow ahead of the NOx reducing catalyst (4). In a second mode, injection is more retarded. The temperature is measured (18) in the catalyst (4) and on reaching a specific range, at which the catalyst becomes ineffective, the second mode of operation is adopted. The NOx concentration is measured (19, 20) on either side of the catalyst. An alarm is raised, when the outlet concentration exceeds a given fraction of the inlet concentration, given also that the temperature lies in the effective range. In a further, preferred similar method, injection timing is adjusted in the second mode for a set, constant NOx emission. Also claimed is the corresponding system, generally as described.