Multi-scale Modeling of Ignition Damkohler Number Effect on Cool Flame Propagation at Elevated Temperature and Pressure Using n-Heptane/Air Mixture*

Laminar cool flame propagation speed at elevated temperature and pressure is fundamentally important in many research areas such as knocking control in advanced engines, and it provides one of the most important reference numbers to characterize and model combustion process. However, the laminar cool flame speed especially at high ignition Damkohler number is a challenging task since it is no more the classical eigenvalue problem and need to be reconsidered. The current study proposed a new numerical method to measure cool flame speed at elevated temperature and pressure with a wide range of ignition Damkohler number. The primary focus of the current study is on the effects of pressure, temperature, equivalence ratio and ignition Damkohler number. The results show that  the laminar cool flame speed increases with temperature before and after the negative temperature coefficient(NTC) region. While inside NTC region, the laminar cool flame speeds decreases with higher temperature due to the inhibited low temperature chemistry. In addition, the peak laminar cool flame speed increases with the pressure due to the cross-over temperature change.