Development of a laminar burning velocity empirical correlation for combustion of iso-octane/ethanol blends in air

This study presents the first demonstration of Marshall and Hinton's empirical correlation for laminar burning velocity (LBV) applied to iso-octane/ethanol blends. The "Oxford"correlation is first validated for neat isooctane and ethanol combustion against the outputs of three different chemical kinetics mechanisms and experimental data from the literature. The effects of three different mixing rules, simple energy fraction, modified Le Chatelier, and modified version of the more complex mixing law of Hirasawa, on the predicted LBVs of iso-octane/ethanol blends are evaluated. The modified Le Chatelier mixing law is used with the Oxford correlation to predict blend LBVs at various temperature and pressure conditions. The results are validated against previously unpublished data for iso-octane/ethanol binary fuels at elevated temperature and pressure (up to 10 bar) both from this group, and from the earlier experimental studies of Varea et al. (CORIA) and Broustail et al. (PRISME). The Oxford correlation is shown to perform well across a wide range of temperature and pressure conditions (respectively 298-640 K and 1-10 bar) for the single component fuels. Used in conjunction with a modified Le Chatelier mixing law, the LBVs predicted by the correlation provide an excellent match to the available experimental data across the full range of ethanol concentrations examined (25, 50, and 75% v/v).