Laminar Flame Speed Measurements of Primary Reference Fuels at Extreme Temperatures

Experimentally measured values of the laminar flame speed (S_L) are reported for the primary reference fuels over a range of unburned-gas temperatures (T_u) spanning from room temperature to above 1,000 K, providing the highest-temperature S_L measurements ever reported for gasoline-relevant fuels. Measurements were performed using expanding flames ignited within a shock tube and recorded using side-wall schlieren imaging. The recently introduced area-averaged linear curvature (AA-LC) model is used to extrapolate stretch-free flame speeds from the aspherical flames. High-temperature S_L measurements are compared to values simulated using different kinetic mechanisms and are used to assess three functional forms of empirical S_L–T_u relationships: the ubiquitous power-law model, an exponential relation, and a non-Arrhenius form. This work demonstrates the significantly enhanced capability of the shock-tube flame speed method to provide engine-relevant S_L measurements with the potential to meaningfully improve accuracy and reduce uncertainty of kinetic mechanisms when used to predict global combustion behaviors most relevant to practical engine applications.