SI엔진에서 배기온도 저감을 위한 열교환기의 열해석

Abstract

To meet stringent emissions standards, a considerable amount of development is necessary to ensure the suitable efficiency and durability of catalyst systems in SI engines. The c1ose-coupled catalyst performance should satisfy ULEV emission levels after aging at 1050 °C for 24 hours. However, if some malfunctions occurred at engine operation and the catalyst temperature exceeds the 1050°C, the catalytic converter is deactivated and shows the poor conversion efficiency. In that situation, excess fuel is injected intentionally to lower the exhaust temperature. Hence, it resulted in worse fuel economy. In this work, the exhaust cooling system was proposed to lower the exhaust temperature in an SI engine. The cooling systems in exhaust manifold were developed and cooling efficiencies were compared. The heat flux from the exhaust gas into the coolant in the heat exchanger was calculated using the measured coolant temperatures. Exhaust gas temperatures were calculated analytically as a function of engine speed and load. Surface temperature distribution in exhaust manifold was also calculated analytically to investigate the behaviors of cooling systems.