Validation of Computational Models for Isobaric Combustion Engines

The focus of this study is to aid the development of the isobaric combustion engine by investigating multiple injection strategies at moderately high pressures. A three-dimensional (3D) commercial computational fluid dynamics (CFD) code, CONVERGE, was used to conduct simulations. The validation of the isobaric combustion case was carried out through the use of a single injector with multiple injections. The computational simulations were matched to the experimental data using methods outlined in this paper for different multiple injection cases. A sensitivity analysis to understand the effects of different modeling components on the quantitative prediction was carried out. First, the effects of the kinetic mechanisms were assessed by employing different chemical mechanisms, and the results showed no significant difference in the conditions under consideration. Next, different liquid fuel properties were examined, and it was found that the physical properties of the fuels have a notable effect in terms of evaporation and atomization, which lead to a variation in the considered numerical case. The effect of thermodynamics properties was also investigated by testing different equations of state (EOS) such as ideal gas, Redlich-Kwong, and Peng-Robinson. While the ideal gas model underpredicted the results, the other two EOS yielded similar and good predictions of the experimental data. The effects of different heat transfer models and the number of spray parcels were also found to be insignificant. Based on the sensitivity study, general guidance on different parameters to be used for isobaric combustion simulation was achieved.