The Combustion System Development Of Two-stage Turbocharged HD Diesel Engine To Meet China Stage Ⅳ Emission Standards

Across the whole world internal combustion engine as the main power plant has been widely used and this promotes the social and economic development and also causes increasing pressure to the energy and environment. Due to gradually decrease of world oil reserve and continuous deterioration of urban air quality caused by vehicle exhaust emissions, many governments have formulated more and more stringent emission legislations to restrict engine exhaust emissions; So clean and efficient combustion of internal combustion engine has always been a hot research issue. Two-stage turbocharging and EGR are considered as one of most important and effective technical routines to meet the US2010 and Euro VI emission standards.This research was carried out on an inter-cooler turbocharged electrical controlled common rail heavy-duty diesel engine. Experimental investigation of single stage turbocharging and two types of two-stage turbochargeing systems was made, and then combustion systems, including combustion chambers and injectors, were optimized. The results showed that compared to single turbocharging, the full-load PM emission of two-stage turbocharging at low engine speed could be reduced and the ability of EGR introduction was obviously raised; The two stage turbocharging system 2TC(2), CR16.8 combustion chamber SF1 and injector S4 were selected through experiments because they could improve BSFC and reduce PM emission under most operating conditions.Based on the selected combustion system and combined with EGR, injection strategies which contained pilot injection parameters, main injection timing and injection pressure were optimized experimentally. Reasonable pilot and main injection parameters could reduce NO_x and PM emission simultaneously. Higher injection pressure could lead to good NO_x-BSFC and NO_x-smoke relationship, but raise PM emission under low speed conditions.The ESC cycle test showed that without after-treatment system the original emissions of the optimized two-stage turbocharged diesel engine coupled with EGR can meet China stage IV emission standards.