Injection Strategy Study of Compression Ignition Engine Fueled with Naphtha

摘要

This study investigates the performance of a diesel engine fueled with naphtha under different load by varying injection parameters and exhaust gas recirculation (EGR) rate. The experiments were conducted on a 1.9-liter common rail diesel engine with a compression ratio of 17.5. Naphtha with a research octane number of 60.5 was tested. Three multi-injection strategies were designed. Each injection strategy, aided with EGR, conducts a characteristic combustion mode. Multi-injection strategies and single-injection strategy were tested and compared at one operating point under different main injection timing and EGR conditions. Results indicate that the well-designed multi-injection strategy has advantages over the single injection strategy in lowering noise, emissions and improving combustion efficiency. Among the three strategies, the strategy with 15-degree pilot timing and 2mg/cycle pilot injection could achieve both low NO_x and PM emissions without sacrificing much fuel efficiency. For example, one of the operating points reached with 49% EGR rate has mean IMEP of 5.68 bar, NO_x emission of 20ppm, PM emission of 1.8×10~6/mm~3, HC emission of 45 ppm and the rate of pressure rise of 1.9 bar/°CA. Meanwhile 51.57% indicated thermal efficiency is achieved.