Insulated Catalytic Converter with Phase-Change Material under Real-world Driving Conditions
John Hoard, University of Michigan
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 paper 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 converter (VICC) was improved significantly, and detailed explanations of all theoretical modeling considerations are presented. In 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 (HEVs). New model simulations demonstrated the ability of the VICC to achieve significant emissions reductions following vehicle soaks of up to 24 hours.
To examine the real-world benefits of the converter, driving data was obtained from the National Renewable Energy Laboratory (NREL), and a MATLAB code was developed to statistically analyze 23,156 drive cycles. The VICC was simulated on standard drive cycles to develop a correlation between melt time of the phase-change material (PCM), average drive cycle speed and acceleration. This correlation was used to predict the probability that the PCM will melt in a given real-world driving cycle. The MATLAB code was also used to calculate soak time probability and a conservative re-solidification time probability. Finally, FTP emission results were weighted with the soak time probabilities. This analysis showed that in real-world driving conditions, the VICC is expected reduce cold-start exhaust emissions by large percentages