A detailed single zone, zero dimensional model of diesel multiple-injection system\nwas developed from first principle, for compression, combustion and expansion\nprocesses for direct injection diesel engine. Equilibrium equation of Extended Zeldolvich\nMechanism (EZM) for NOx formation was incorporated to predict NOx\nemission. A different approach was assumed for the equilibrium temperature. An\napproach of using the average cycle temperature within NOx formation region was\nused in the EZM equilibrium equation. The model codes were implemented in\nMATLAB. This model is developed to investigate the effects of both single and multiple-\npulse fuel injection strategies on engine performance and NOx emissions. The\nresults obtained from the model were validated with experimental data available in\nthe literature. Results obtained showed that the use of average cycle temperature\nwithin the NOx formation temperature region could be useful in predicting NOx\nformation with reasonable degree of accuracy. Injection timing, mass ratio of injected\nfuel, and dwell between pulses have significant effects on the NOx emission\nand engine performance. The results also show that as the number of pulses increases,\nNOx emission and engine performance decrease. For optimal balance between\nNOx and engine performance, mass of the pilot injection should be between 10 and\n25% of the total mass of fuel used per cycle.
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