Single Zone, Zero Dimensional Model of Diesel Multiple-Injection

Abstract

A detailed single zone, zero dimensional model of diesel multiple-injection system was developed from first principle, for compression, combustion and expansion processes for direct injection diesel engine. Equilibrium equation of Extended Zeldolvich Mechanism (EZM) for NO x formation was incorporated to predict NO x emission. A different approach was assumed for the equilibrium temperature. An approach of using the average cycle temperature within NO x formation region was used in the EZM equilibrium equation. The model codes were implemented in MATLAB. This model is developed to investigate the effects of both single and multiple-pulse fuel injection strategies on engine performance and NO x emissions. The results obtained from the model were validated with experimental data available in the literature. Results obtained showed that the use of average cycle temperature within the NO x formation temperature region could be useful in predicting NO x formation with reasonable degree of accuracy. Injection timing, mass ratio of injected fuel, and dwell between pulses have significant effects on the NO x emission and engine performance. The results also show that as the number of pulses increases, NO x emission and engine performance decrease. For optimal balance between NO x and engine performance, mass of the pilot injection should be between 10 and 25% of the total mass of fuel used per cycle.