A GT-SUITE vehicle-aftertreatment model has been developed to examine the cold-start emissions reduction capabilities of a Vacuum Insulated Catalytic Converter (VICC). This converter features a thermal management system to maintain the catalyst monolith above its light-off temperature between trips so that most of a vehicle’s cold-start exhaust emissions are avoided. The VICC thermal management system uses vacuum insulation around the monoliths. To further boost its heat retention capacity, a metal phase-change material (PCM) is packaged between the monoliths and vacuum insulation. To prevent overheating of the converter during periods of long, heavy engine use, a few grams of metal hydride charged with hydrogen are attached to the hot side of the vacuum insulation.
The GT-SUITE model successfully incorporated the transient heat transfer effects of the PCM using the effective heat capacity method. A variety of conventional, stop-start and hybrid electric vehicles have been simulated over standard drive cycles using this model. For each vehicle, prep-cycle simulations were followed by soak simulations of differing time periods. Model predictions show that the VICC was able to maintain converter temperatures above 300°C for at least 12 hours for all of the simulated vehicles and standard prep-cycles. Furthermore, this heat retention ability directly translated to a proportional reduction in cold-start exhaust emissions. With the introduction of intermediate soak times as part of the EPA emissions test regulations, the benefits of the VICC should be seen in all standard drive cycle emissions tests. The simulation results of the GT-SUITE model demonstrate the contribution of the Vacuum Insulated Catalytic Converter in meeting stringent future emission standards.
