Improved Correlations for the Unstretched Laminar Flame Properties of Mixtures of Air with Iso-octane and Gasoline Surrogates TRF86 and TRF70

Abstract

<div>Laminar flame properties embody the fundamental information in flame chemistry and are key parameters to understanding flame propagation. The current study focuses on two parameters: the unstretched laminar flame speed (LFS) and <i>ϕ_m </i> (the equivalence ratio at which the LFS reaches its maximum). Most existing correlations for LFS are either only applicable within a narrow range of conditions or built on a large number of coefficients. Few correlations are available for <i>ϕ_m </i>. Thus, the objectives of the current study are to provide accurate, while concise, correlations for both properties for a wide range of working conditions in internal combustion (IC) engines, including dilution effects. The original results were obtained for iso-octane and gasoline surrogates from one-dimensional (1D) simulations for a range of 300–950 K for unburned temperature, 1–120 bar for system pressure, 0.6–1.4 for equivalence ratio, and 0–0.5 for diluent mass fraction, and then were correlated using an improved power law method and an improved Arrhenius form method. Comparisons with the literature show that the predicted LFSs from both methods and <i>ϕ_m </i>s are close to the experimental measurements for a wide range of conditions. The predicted dilution factor has a similar trend with others, but fewer coefficients are needed. Overall, the improved Arrhenius form is recommended to calculate the LFS for future use, considering its lower standard errors. The experimental measurements at very high temperatures and pressures are limited, and thus the predictions under these conditions need further validation.</div>