Insulated catalyst with heat storage for real-world vehicle emissions reduction

Abstract

In previous publications, the model development and simulation of a vacuum-insulated catalytic converter was presented. GT-Suite model simulations demonstrated the heat retention capacity of the converter and corresponding emissions reductions. This article provides an update of the converter model development and analysis of real-world benefits of the converter. The vehicle-aftertreatment model of the vacuum-insulated catalytic converter was improved significantly, and detailed explanations of all theoretical modeling considerations are presented. In the absence of experimental data, a flow test experiment was conducted to measure the flow rate in exhaust tailpipe during vehicle soak due to thermosiphon. These results were used as inputs in the GT-Suite model simulations of conventional and hybrid electric vehicles. New model simulations demonstrated the ability of the vacuum-insulated catalytic converter to achieve significant emissions reductions following vehicle soaks of up to 18 h. To examine the real-world benefits of the converter, driving data were obtained from the National Renewable Energy Laboratory, and a MATLAB code was developed to statistically analyze 23,156 drive cycles. The vacuum-insulated catalytic converter was simulated on standard drive cycles to develop a correlation between melt time of the phase-change material and average drive cycle speed and acceleration. This correlation was used to predict the probability that the phase-change material will melt in a given real-world driving cycle. The MATLAB code was also used to calculate the soak time and re-solidification time probability. Finally, Federal Test Procedure emission results were weighted with the soak time probabilities. This analysis showed that in real-world driving conditions, the vacuum-insulated catalytic converter is expected to reduce cold-start CO and hydrocarbon emissions by 26% and 48%, respectively.