Laminar burning velocity and cellular instability of 2-butanone-air flames at elevated pressures

2-butanone has been exploited as a promising next-generation biofuel candidate for its impressive knock resistant properties. However, its combustion characteristics and intrinsic instabilities have not been well explored. In this study, an experimental and theoretical investigation on laminar burning velocity (LBV) and onset of flame instability in spherically expanding flames of 2-butanone-air mixtures was conducted in a constant-volume chamber at temperature of 423 K, pressure of 1–8 bar, and equivalence ratio (ϕ) of 0.7–1.5. The measured LBVs and Markstein lengths of 2-butanone were observed to decrease noticeably as the pressure increased. Four recently established kinetic models were applied to predict the experimental data. Stability analysis was performed to investigate the effect of pressure and ϕ on the onset of the cellular instability of 2-butanone flames. Results showed that the hydrodynamic instability monotonically increased as pressure increased and non-monotonically varied with increasing ϕ. Thermal-diffusive instability increased dramatically as ϕ increased while showed less sensitivity to the variation in pressure. The critical conditions at which the flame status turn stable into unstable were also evaluated. The critical Peclet number decreased monotonically as ϕ increased, illustrating that fuel-rich flames suffer more severe cellular instability than fuel-lean flames. The critical flame radius decreased as pressure increased in both experimental measurements and theoretical calculations, reflecting that the onset of cellular instabilities of 2-butanone-air mixtures advanced to smaller radius at higher initial pressures.