Mechanism of Oxygen Concentration Effects on Combustion Process and Emissions of Diesel Engine

Abstract

The mechanism of oxygen concentration effects on the combustion process of diesel combustion and the effects of injection pressure and intake pressure on low-temperature combustion are investigated by CFD simulation. The oxygen concentration is modulated by CO 2 . The results indicate: with the decrease of oxygen concentration, the peak of the average in-cylinder pressure decreases and the ignition delay becomes long. Decreasing oxygen concentration is the most effective method to control NO x emissions. With the decrease of oxygen concentration, soot emissions increase first and then decrease. It is the essential reason of low soot emissions at low oxygen concentrations that the low in-cylinder combustion temperature leads to the inhibition of soot formation. With the increase of injection pressure, the flow velocity and turbulent kinetic energy in the cylinder increase, which are beneficial to improving the mixing of fuel and air; soot emissions decrease; and NO x emissions increase. The enhancement of intake pressure improves the condition of oxygen lack at lower oxygen concentration. With the increase of intake pressure, ignition delay becomes long. Soot and NO x emissions decrease.

Numerical Investigation and Multi-Objective Optimization of Internal EGR and Post-Injection Strategies on the Combustion, Emission and Performance of a Single Cylinder, Heavy-Duty Diesel Engine

“…Despite the decrease in O 2 concentration, the ICT shows an increasing trend due to the rise of the high temperature residual gases as α 2IVO increases from 149 • CA to 210 • CA [35]. Since the effect of increased ICT and charge dilution at the beginning of the cycle due to iEGR [36] compensated each other, no significant change in ignition delay is observed for the main injection. In the case where α 2IVO increases, since the main combustion mostly takes place in the form of diffusion combustion and the main combustion duration is prolonged, post-combustion at α post : 22 • CA occurs while the main combustion proceeds, especially for α 2IVO : 210 • CA.…”

Numerical Simulation of PAHs Formation and Effect of Operating Conditions in DI-Diesel Engines Based on a Comprehensive Chemical Mechanism

“…Some researchers [8,9] directly used the EBU model in threedimensional simulations to describe diesel engine combustion. Cordiner et al [10] used a mixed 1D-3D numerical procedure, together with the Shell and characteristic-time combustion models, to analyse combustion and exhaust emission in a dual-fuel diesel/natural gas engine.…”