Emission Characteristics of a Dual-Injector Diesel Fuel Injection System

Environmentally speaking, simultaneous reduction of smoke and NO_x with minimal effects on the fuel economy has been an ideal goal for diesel engine designers. In the past decade several in-cylinder approaches were proposed with various degrees of success in operation. Here, we consider one promissing technique called as double (split) or staged injection. A single-cylinder compression-ignition two-stroke research engine with optically-accessible head, mounted on a high-speed CFR engine crankcase, was used to investigate the combustion and emission characteristics of a dual-injector injection system. The injection system produces two separate independently-controlled sprays with a good degree of adjustability with regard to their fuel quantities and injection timings. Results are presented to show the effects of the varied injection system characteristics on the combustion and exhaust emissions ( NO_x and smoke). The effects of the injection timing and time separation between the first and second injections of the dual injection system are explored. Conditions are identified for which a favorable influence on both smoke and NO_x production is observed. A new injection system and strategy are proposed as a result of the data acquired in this study.