Numerical Analysis of Diesel Engine oxygen-enriched Combustion Characteristic Based on the Simplified Mechanism of n-heptane Oxidation

Based on the simplified n-heptane oxidation chemical kinetics model and the multi-dimensional Diesel combustion model coupled method, from both the macro and micro perspective of the combustion in cylinder, cylinder pressure, temperature, heat release rate, fuel and NO emissions´ development and changes of different concentrations of oxygen-enriched combustion in engine were analyzed. By comparison with the experimental results verified the correctness of the model used. Also found that: oxygen-enriched combustion can promote the formation of combustible mixture, which making the burn more quickly and fully, also make the premixed combustion and diffusion combustion heat release rates change. In the condition of oxygen-enriched combustion, cylinder peak pressure, pressure rise rate, peak temperature, temperature rise rate, NO generation capacity and its distribution are increasing with the oxygen concentration. In addition, the temperature uniformity increases gradually as the concentration of oxygen in cylinder, while the pressure uniformity declines after reaching a peak point. Finally, this paper proposed some specific technologies to control the diesel engin´s bad combustion and emission performances cased by oxygen-enriched combustion, which can not only give full play to the advantage of the oxygen-enriched combustion technoloy, but also can guarantee the performance of diesel engine´s emission.