METHOD FOR CORRECTING THE INFLUENCE OF WATER ON THE SIGNAL OF A SENSOR TO DETECT THE CONCENTRATION OF REDUCER IN THE EXHAUST GAS OF AN ENGINE

摘要

A method of correcting the influence of water on the signal of a sensor for a reducing agent in IC engine exhaust gas, such as ammonia which has been added to reduce NOx. Exhaust-gas moisture is determined taking into consideration moisture originating from combustion and moisture in induction air, the moisture originating from combustion being determined by one or more sensors which characterise the operating state of the IC engine, such air induction air mass flow, fuel mass flow, air temperature or pressure, or from the oxygen content of the exhaust gas. The moisture in the induction air is determined with a moisture sensor. The sensor signal is then corrected in dependance on the determined exhaust-gas moisture. The ammonia injection system described also determines defects in other components of the system.