Validation of Computational Models for Isobaric Combustion Engines 2020-01-0806
This study aims to contribute to the development of the isobaric combustion engines by exploring multiple injection strategies, employing computational simulations using a commercial CFD code Converge. As a first attempt to achieve isobaric combustion, a multiple injection strategy using a single injector was explored with up to four consecutive injections. Considering that the computational simulations were unable to reproduce the experimental data due to several uncertainties, the present study attempted to identify the leading causes of the discrepancies through a sensitivity analysis. First, different liquid fuel properties were examined, and it was found that, while the physical properties of the fuels have a notable effect in terms of evaporation and atomization, such variations were not sufficient to reproduce the experimentally observed heat release rate. Next, the effects of the uncertainties in the kinetic mechanisms were assessed by the reaction multiplier, an artificial adjustment of the rate constants, and it was found that the reaction multiplier affected the ignition of the first injection, but not the subsequent injection events. As such, the use of reaction multipliers to reproduce the experimental data was found to be unsuccessful. The effect of thermodynamics properties was also examined by employing real-gas equations of state, such as Redlich-Kwong and Peng-Robinson, and the results showed little difference in the conditions under consideration. Finally, advancing the start of injection was found to have the most significant effect on pressure trace and heat release rate to lead to a substantial improvement in the numerical prediction. It was found that the key uncertainties in the modeling of the isobaric combustion are likely the accurate start of injection combined with the exact injection rate shape profile.
Hammam H. Aljabri, Rafig Babayev, Xinlei Liu, Jihad Badra, Bengt Johansson, Hong G. Im
King Abdullah University of Science & Technology, Saudi Aramco