Process for monitoring the operation and ageing of a catalytic converter for a lean-burn engine and system for carrying out the process

摘要

The method of monitoring the function and ageing of a catalytic converter for an internal combustion engine working in a poor mixture involves: (a) measuring the hydrocarbon content (HC)OUT at the converter outlet, (b) estimating the hydrocarbon (HC)INES at the inlet using a mathematical model of the engine and (c) estimating a factor NES of the state of the catalytic converter surface as a function of (HC)INES and (HC)OUT The value of NES is compared to a threshold value S and an alarm signal emitted when this threshold is reached. NES is estimated by iteration, estimating the hydrocarbon (HC)OUTES at the converter outlet as a function of (HC)INES and the previous NES, then integrating the difference (HC)OUTES - (HC)OUT which indicates a modeling error. (HC)INES considers the instability of the engine combustion using a multiplication factor delta which depends on the speed of rotation of the motor. Stage (c) involves division between a value proportional to (HC)INES and (HC)OUT. This value proportional to (HC)INES depends only on the speed of rotation of the motor (Nmot), or to the ratio between (HC)INES and inlet oxygen (O2)INES and the linear speed (VVH) of the exhaust gas from the motor. AN Independent claim is also included for a system using the above process, with devices measuring the speed of rotation of the motor; the pressure in the engine inlet (Pcoll); the hydrocarbon content at the outlet of the catalyst (32); a calculator (30) for estimating the factor NES as a function of these measurements and a comparator (34) to compare NES to the threshold value S and set off an alarm when NES reaches this threshold value.