System for controlling the urea supply to SCR catalysts

Abstract

A reductant dosing control system, for use in a Selective Catalytic Reduction (SCR) system of a motor vehicle includes an input receiving a NOx feedback signal from an NOx sensor provided to the SCR system. A base dosing module calculates a required quantity of reductant to inject in front of a SCR catalyst of the SCR system based on the NOx feedback signal. The SCR catalyst has ammonia storage properties. An output signals a reductant metering mechanism to periodically or continuously inject excess reductant based on the required quantity of reductant.

Description

technical field [0001] The present invention relates generally to engine control systems for internal combustion engines, and more particularly to intermittent or continuous reductant supply to a Selective Catalytic Reduction (SCR) catalyst based on feedback from an engine output NOx sensor. Background technique [0002] The method of Selective Catalytic Reduction (SCR) of NOx using urea as reductant is well established for NOx emission reduction on stationary sources and mobile applications. During SCR, NOx is reacted with a reducing agent such as pure anhydrous ammonia, aqueous ammonia and / or urea, which is injected into the exhaust gas stream ahead of a dedicated SCR catalyst. The SCR method significantly reduces NOx in internal combustion engines. [0003] The SCR process requires precise control of the reductant injection rate. Insufficient injection can result in unacceptably low NOx conversion. Excessively high injection rates can release reducing agents into the a...

AI Technical Summary

Problems solved by technology

However, open-loop controller logic may not result in optimal NOx emission abatement, possibly due to transient operation with low-level emissions

Due in part to the minimal practical setup of the reductant dosing mechanism, it is difficult to accurately dose reductant at these low levels without leakage of reductant into the atmosphere

Images