(154g) Analysis and Optimization of the Design Aspects of Electrically Heated Converters for Automotive Emission Control

The next round of automobile emission regulations would mandate a drastic reduction of hydrocarbon (HC) exhaust emissions. In view of the significant cold-start HC emission reduction potential of the electrically heated converter (EHC) technology demonstrated in recent studies, there is considerable interest in better understanding of the behavior and design aspects of an EHC during the cold-start portion of actual vehicle emission tests. Computer simulations show that although decreasing the volume of an electric heater generally improves the emission performance of the EHC system, there is a critical heater volume below which no significant additional emission benefit is obtained. This presentation examines the EHC sizing issue in detail by analyzing a simplified version of the EHC model. The analytical asymptotic solution derived for the regime of small heater volumes explains why the emission benefit of decreasing the electric heater volume eventually disappears and provides a simple relationship that allows one to determine the critical heater volume where this occurs from the system parameters. Implications of these results for EHC application to hybrid vehicles are also briefly discussed.