An on-board method to estimate the light-off temperature of diesel oxidation catalysts

Abstract

Current diesel engine regulations include on-board diagnostic requirements so that after-treatment systems need on-board methods to detect their aging state through the available measurements. In a state-of-the-art diesel exhaust line, two temperature and [Formula: see text] measurements can be found upstream and downstream of the diesel oxidation catalyst. Thus, the strategy presented in this article makes use of these measurements to estimate the light-off temperature, which has been widely studied as a characteristic of diesel oxidation catalyst aging. The light-off temperature estimation potential is evaluated first under dynamic engine operating conditions, in which [Formula: see text] measurements are proved to be precise enough to detect oxidation. However, dynamic conditions make the association of a representative temperature with an oxidation event difficult. Therefore, the method makes use of more controlled conditions at idle, during which the exhaust temperature decreases avoiding dynamics of normal driving conditions. During the idle, post-injection pulses are applied to determine whether oxidation occurs at a representative temperature measured by the upstream temperature sensor. The result of each pulse is used to generate a database. Then, after a long enough time window, the database generated will allow characterizing non-oxidation and oxidation temperatures, with an intermediate interval of indefinition. This article shows how the temperatures of these ranges increase as the light-off temperature increases, thereby validating the proposed method for light-off temperature estimation.

Ammonia injection optimization for selective catalytic reduction aftertreatment systems

“…the temperature at which the catalytic reactions are initiated). 14 Increasing the injection pressure affects the atomization process and produces smaller particles at higher speeds, promoting wider overall spray angles, and that when combined with a high-temperature mass flow can improve the evaporation and mixing process in the SCR system. 15…”

Diesel engine optimization and exhaust thermal management by means of variable valve train strategies

“…Recent studies carried out by Deppenkemper et al 7 found that in an engine with similar specifications, the light-off temperature of the DOC is around 200 °C according to an averaged space velocity of 57,700 L/h during the WLTC. 7 Other authors like Guardiola et al 29 take this temperature as a reference for the DOC light-off temperature. In order to evaluate the temperature downstream the DOC, a catalyst model 25 has been included into the engine model.…”

Development of a Variable Valve Actuation Control to Improve Diesel Oxidation Catalyst Efficiency and Emissions in a Light Duty Diesel Engine

“…The faster the light-off temperature (defined as the temperature at which the conversion efficiency reaches 50%) in the catalyst is reached, the faster the efficient oxidation of CO and HC, and the oxidation of NO to NO 2 , is achieved. This light-off temperature is considered to be around 200 • C according to an averaged space velocity of 57,700 L/h during the WLTC [9,31]. The decrease in DOC-out NO 2 may have a negative effect on downstream NO x abatement, specially at temperatures below 250 • C, such as those at engine start up [32].…”