Laminar flame speeds of supercritical CO2 diluted oxy-syngas and oxy-methane flames under direct-fired power cycle relevant conditions

Abstract

The propagation of laminar oxy-syngas and oxy-methane flames diluted by supercritical carbon dioxide was numerically simulated for the planar flame configuration under the conditions related to the operation of oxy-combustor in the direct-fired power cycle. Because of the extremely high pressure typically used for such an application, real fluid models were considered for the equation of state, thermodynamic functions, transport properties, as well as the mass action law. Numerical results show that the relative uncertainty on the flame speed caused by real gas effects and by different chemical mechanisms can be on the same order of magnitude for oxy-syngas combustion. For oxy-methane combustion, the deviation of the flame speed between the predictions of different mechanisms is much more significant than that caused by real gas effects. The effects of various non-ideal effects were explored progressively. Including the real gas equation of state and thermodynamic functions reduces the adiabatic flame temperature, and thus the flame speed is decreased. Adopting transport properties of real gas and including revisions on the mass action law and equilibrium constant would both increase the flame speed. Inhibition and promotion of flame propagation resulting from the effects of inter-molecular attraction and finite molecular volume were also identified and analyzed.Novelty and Significance Statement1. Supercritical laminar flame speed was systematically simulated with complete real gas model to quantify the non-ideal effects under direct-fired power cycle relevant conditions.2. The individual impact of components in the real gas model on the flame speed were determined and represented with key parameters.3. The uncertainties on laminar flame speed caused by reaction mechanism and real gas effects were compared and found to be on the same order of magnitude under certain conditions.