Radiation effects in confined spherically expanding flames: Application to C5[sbnd]C10 flames at engine-relevant conditions

Abstract

Radiation heat loss introduces one of the main uncertainties associated with the determination of laminar flame speeds from experiments using the spherically expanding flame constant volume method. In this study, a radiation model was developed to solve for the volumetric radiative power in spherical geometry using discrete transfer method accounting for spectrally dependent emission and absorption. The model was validated against the results obtained from the discrete ordinate method. Subsequently, the newly developed radiation model was integrated into a hybrid thermodynamic-radiation model used to derive laminar flame speeds from experimental pressure-time history data. Laminar flame speeds were measured for flames of C5C10n-alkanes and isooctane for pressure and unburned mixture temperature ranges of 13–25 atm and 540 – 670 K respectively, and the data are reported with properly derived uncertainties. Additionally, the data are free from measurable instability-induced effects and to assure that a systematic analysis of cell formation was undertaken. Comparison of the experimental data with predicted laminar flame speeds showed consistency and reasonable agreement with two kinetic models. The development of new modeling tools over the last few years, allows for the derivation of accurate laminar flame speeds using the spherically expanding flame constant volume method for engine-relevant fuels and thermodynamic conditions, which other methods cannot accommodate.