Fig xA Evolutions of a the heat of reaction versus
For their work, Bonhomme et al.  expressed a consumption speed with respect to a product species, Scp. They derived Eq. (1) for spherical coordinates  and foundequation(4)Scp=ρb‾ρudRfdt+Rf3ρudρb‾dt,where ρb‾ is the burnt gas density (spatially averaged) and RfRf is identified as a flame radius based on the mass of products. The calculation is done knowing the total mass of products and the spatially averaged product density, see reference  for further details. From Eq. (4), assuming that CEP-18770 the burned gas density is constant and equal to the equilibrium value, the indirect flame speed Sl,iSl,i is recovered. Assuming an isentropic compression for the fresh gases, Bonhomme et al.  also derived Eq. (1) for the fuel, Scf, yieldingequation(5)Scf=dRfdt-R03-Rf33Rf21γupdpdt,where γuγu is the ratio of the heat capacities in the fresh gases, p the pressure and RfRf is the flame radius based on the fuel mass. In Eq. (5), the pressure trace and its derivative are needed during the time before the pressure increase impacts the reaction kinetics. Experimentally, this measurement is quite challenging. Therefore, this formula is not used in the experiments described below.