Simulation of Combustion Process and Pollutant Generation in a PCCI Diesel Engine with Adaptable Multiple Injection

Abstract

The combustion process in a single-cylinder turbocharged diesel engine with a pilot-pilot-main injection strategy was simulated using a computational fluid dynamics software. The effect of injection timing on the combustion process as well as the generation of NO and soot was analyzed in detail. It was revealed that the retardation of injection timing causes the pressure in the cylinder to decrease gradually. The main heat release peak also reduces while the premixed combustion fraction increases, and this causes the position of the heat release peak to move away from top dead center. At the moment of 1% heat release (q1) with retarding the injection timing, soot generation decreases as the lean premixed combustion takes the major position while more NO is generated due to rapid heat release of the premixed mixtures. At the moment of 9% heat release (q9), NO emission is decreased due to the low temperature in the cylinder. Soot generation is increased initially and later decreased due to the extended combustion space and higher premixed combustion fraction. Therefore, a favorable trade-off between NOx and PM emissions is well compromised in a diesel engine adopting a low-temperature premixed charge compression ignition (PCCI) mode.