Use of an Electrically Heated Catalyst to Reduce Cold-Start Emissions in a Bi-Fuel Spark Ignited Engine

Abstract

Reduction of cold-start emissions using electrically-heated catalyst (EHC) technology was the focus of this work. Comprehensive emission measurements of CO, CO2,NOx, and total hydrocarbons (THC) are reported for a spark-ignited engine operated on baseline gasoline and compressed natural gas (CNG). Electric heating times of 0, 20, and 40 s with and without secondary air injection were investigated. The 40-second electric catalyst heating with secondary air injection scenario yielded the greatest catalyst system (EHC+OEM three-way catalyst) conversion efficiencies for THC, CO, and NOx for gasoline and natural gas fueling. Electric catalyst heating coupled with secondary air injection significantly improved THC and CO emissions for gasoline fueling. THC oxidation was difficult for CNG fueling due to the high content of nonreactive methane in the fuel. The independence of NOx emissions on heating time was demonstrated for all fueling cases.