METHOD AND ASSEMBLY FOR CONTROLLING FUEL SUPPLY FOR A SPARK IGNITION INTERNAL COMBUSTION ENGINE, IN PARTICULAR FOR A NATURAL GAS FUELED ENGINE

摘要

A method for controlling fuel supply is provided in an assembly (1), which has a spark ignition internal combustion engine (2), an exhaust after-treatment system (10) with a three-way catalyst (14), and an injection device (2) controlled to supply fuel to the engine (2) according to a set-point (λset), indicative of a desired air/fuel ratio during combustion of a mixture of fuel and air in the engine (2); the set-point (λset) has a wobbling pattern so as to operate the engine (2) with alternating lean combustion phases and rich combustion phases; a model simulates the catalyst (14) by a plurality of cells (Cell1, Cell2, ..., Celln), which correspond to respective areas arranged in series in the catalyst (14) and are associated to respective oxygen levels (Ocell1, Ocell2, ... Ocelln), estimated by the model; a parameter (Ocell1), indicative of at least one of the estimated oxygen levels, is compared with an upper and a lower threshold (S1,S2); the wobbling pattern is set so as to bring the engine (2) to the lean combustion phase when the parameter (Ocell1) becomes lower than the lower threshold (S2) and to the rich combustion phase when the parameter (Ocell1) becomes higher than the upper threshold (S1).