Control of reagent addition to NOx emission reducing systems, especially vehicle exhaust systems

摘要

A method and system for determining whether a desired amount of reactant, especially a hydrocarbon reductant, is actually injected into an engine exhaust to react with NOx in such engine exhaust is disclosed. The reaction is facilitated with a catalyst downstream of a hydrocarbon injector. The method and system measure a first temperature difference across the catalyst during the reaction. The first temperature difference is compared with an expected temperature difference across the catalyst during the reaction. The difference in exotherm is used to adjust the injected HC quantity and diagnose injector failures. Also claimed is a method for controlling the injection of a reducing agent into a substance to be reduced thereby by means of a catalyst, where the same procedure of measuring actual and expected heat generated by the reaction.