Improving Exhaust Temperature Management At Low-loaded Diesel Engine Operations Via Internal Exhaust Gas Recirculation

Abstract

Modern on-road automotive vehicles mostly utilize exhaust after-treatment (EAT) systems to meet the stringent emission regulations. Although those systems are generally effective to reduce emission rates, they are ineffectual at low loads due to low exhaust temperatures (below 250 o C). This study demonstrates on a diesel engine model that exhaust temperatures can be increased above 250 o C at light loads through internal exhaust gas recirculation (IEGR). Engine system operates at 1700 RPM engine speed and within 2.5-4.5 bar brake mean effective pressure (BMEP) engine load. IEGR increases the amount of in-cylinder hot residual exhaust gases and thus causes a considerable exhaust temperature rise (up to 70 o C). Warmer exhaust system keeps EAT emission conversion efficiency mostly above 90 % and accelerates EAT catalyst bed warm-up through increased (up to 142 %) heat transfer rates. IEGR is not as fuel-consuming as conventional EAT warming techniques and can keep the fuel consumption rise below 5 %.