A physical approach of calculating the laminar flame speed in homogeneous medium takes into consideration the preservation of Mass, Energy and Momentum, and using the Ideal Gases relations – yields a system of 4 equations with 5 unknowns, which can be simplified into the graphic intersection of Rankine Lines (denoted from the Rayleigh equation) and the Hugoniot Curve. Chapman-Jouguet suggested that the tangent points will determine the flame speed in both regimes, and while this thesis correctly estimates the Detonation speed, the Deflagration velocity predicted is 2 magnitudes of order higher than expected. A lot of different approaches were suggested over the years to correctly forecast the Deflagration velocity, the leading one (up until today) is the Thermal Theory that predicts a good approximation of the laminar speed but does not conform to the Momentum equation.
Lately, a new approach relying on thermodynamic stability, transition phenomena (mass and heat) and the principal of Entropy increase has been suggested. The work was based on introduction of the principals of irreversible thermodynamics, as formulated by Lars Onsager in the 1930s, into the Thermal Theory. Validations for Methane-Air lean mixtures showed good results.
The present study is the first one to apply the new theory and keeps developing it. The main achievements:
- cancelation of calibration parameters
- Full calculation of the flame front width (using one-step models for the Reaction Rates)
- First application in analytical theories – temperature dependant model for thermodynamic characteristics
- Completion of proof for the Applicability of the new theory