Thermal Analysis and Testing of a Vacuum Insulated Catalytic Converter

Abstract

Based on a recent U.S. Environmental Protection Agency (EPA) study, about 95% of all trips start after a cold-soak period of 16 hours or less. By preserving the heat in the catalyst between trips, exhaust gases could be processed without warm-up delay and without the usual cold-start emissions.Vacuum insulation and phase change thermal storage have been incorporated into a catalytic converter design to enhance its heat-retention time.Laboratory testing of a bench-scale prototype showed that a "light off' temperature (above 350°C) could be maintained during a 1 0-hour cold soak.Design improvements currently being tested should increase this heat-retention time··to more than 16 hours. The thermal conductance of the vacuum insulation will be made continuously variable to prevent overheating and excessive thermal cycling. This approach to thermal management may be more durable and less costly than quick-heat methods using electric or fuel-fired preheat catalysts. BACKGROUND

Development and characterization of cerium oxide catalyst supported on ceramic honeycomb substrate to reduce emissions of spark ignition engine

“…This method requires an energy input of about 2kW and 30 seconds to produce the operating temperature. However, this method does not eliminate cold emissions completely, it only reduces the cold start emissions level [24]. The cold start emissions can also be reduced by fitting the catalytic converter closer to the engine.…”

“…It helps the converter to reach its operating temperature quickly. However, there is a danger of overheating of the converter [24]. A combination of vacuum insulation and phase change material helps to eliminate cold start emissions.…”

“…It takes a few minutes for the engine to warm up. During this warm up period, at least 60% to 80% of toxic emissions occur [24]. The toxic emissions that escaped unfiltered during warm up period of the engine are called cold start emissions.…”

“…Many approaches have been proposed to reduce the cold start emissions [24][25][26]. The electrically quick heating method was also tried to reduce cold start emissions.…”

“…Vacuum insulation prevents the transfer of radiant heat from the exhaust to the surroundings, preserving heat between the trips. Phase change material acts as a heat storage system and releases heat to the converter during cold start condition [24]. One of the researchers has made an attempt to improve the effectiveness of catalytic converters via reduction of cold start emissions [25][26][27].…”