A one-dimensional model simulating the oxidation of CO, HC, and NO was developed to predict the gaseous emissions downstream of a diesel oxidation catalyst (DOC). The model is based on the conservation of mass, species, and energy inside the DOC and draws on past research literature.
Steady-state experiments covering a wide range of operating conditions (exhaust temperatures, flow rates and gaseous emissions) were performed, and the data were used to calibrate and validate the model. NO conversion efficiencies of 50% or higher were obtained at temperatures between 300°C and 350°C. CO conversion efficiencies of 85% or higher and HC conversion efficiencies of 75% or higher were found at every steady state condition above 200°C. The model agrees well with the experimental results at temperatures from 200°C to 500°C, and volumetric flow rates from 8 to 42 actual m3/min. The estimated activation energies and pre-exponential factors obtained from the model calibration are in good agreement with values reported in the literature.
An analytic pressure drop model was used to estimate the pressure drop across the DOC channels, and agreement within 8 % of the experimental data was obtained. This model can be used to predict the pressure drop across the DOC from various displacement engines.
Cycle weighted emissions were collected with and without the DOC using the ISO-8178 8-mode test. The cycle weighted CO and HC conversion efficiencies were over 90% and 86% respectively. The DOC had minimal effect on the total NOx emissions.