Abstract:

A numerical simulation of the thermodynamic cycle and especially the combustion process was performed for a turbocharged vehicle diesel engine using different multiple-injection strategy under high load by means of a 3-dimensional CFD numerical analysis software FIRE. The effects of injection timing of the single-injection, the pilot injection quantity and the interval between the pilot and the main injections of the dual-injection, and the two pilot-injections on the combustion process and the formation of NOx and soot were discussed. The simulated results indicated that better trade-off between the formations of NOx  and soot can be achcived by using the multiple-injection strategy than using the simgle-injection strategy. Under the single-pilot dualinjection strategy, increasing the pilot injection quantity and the interval between the injections leads to decrease of soot formation and increase of NOx  formation. The two pilot-injection strategy seems more effective in reducing the soot formation than the single pilot-injection under the same total pilot-injection quantity without obvious penalty on NOx  formation.

Key words: power machinery and engineering, turbocharged diesel engine, multiple injection, combustion, NOx, Soot