커먼레일 디젤기관의 착화지연기간에 미치는 Pilot 분사의 영향

Recently, high oil prices and the air pollution have become serious social problems, so the world class diesel engine manufacturers make an effort to study the high combustion efficiency as well as low emission of noxious gas. These days, Diesel engine can emit lower exhaust gas than gasoline one because Common Rail system on which electrical control is combined with high pressure injection system, Turbocharger, and DPF(Diesel Particulate Filter) which is an equipment to decrease exhaust gas. Especially, the pilot injection that is one of the combustion improvement method is a small quantity of fuel injected before the main injection. This strategy is effective in the reduction of the combustion noise, vibration and NOx emission which are the biggest characteristic of diesel engine. The object of this paper is to study ignition delay period and combustion process after ignition of diesel fuel with pilot injection by using equipment which can control injection pressure, quantity, and timing regardless of engine rpm. The ignition delay period is defined as the time interval from fuel injection to detection of the first hot flame by photo sensor. Flame photos were taken' by high speed camera to analyse combustion process after ignition.