배기 열교환기로 인해 증가한 촉매 활성화 시간 감소방안에 관한 연구

Abstract

Close-coupled catalyst (CCC) can reduce the engine cold-start emissions by utilizing the energy in the exhaust gas. However, in case the engine is operated at high engine speed and load condition, the catalytic converter may be damaged and eventually deactivated by thermal aging. Excess fuel is sometimes supplied intentionally to lower the exhaust gas temperature avoiding the thermal aging. This sacrifices the fuel economy and exhaust emissions. The heat exchanger was applied in an SI engine to lower the exhaust gas temperature mainly under high load conditions. The heat exchanger was installed between the exhaust manifold and the inlet of the CCC to avoid thermal aging. The exhaust heat exchanger successfully decreased the exhaust gas temperature, which eliminated the requirement of fuel enrichment under high load conditions. The amount of exhaust emissions (HC, CO, NOx) during the cold start increased due to the increment of the catalyst light-off time. This problem could be resolved by adopting the solenoid valve to cut off the coolant at the inlet of the coolant passage of the heat exchanger. New concept of heat exchanger which is combined with the metal catalyst was tested to investigate the possibility of reducing the light-off time