- Author
- Trouve, A. C.
- Title
- Turbulent flame Propagation in Partially Premixed Combustion. BFRL Fire Research Seminar. VHS Video.
- Coporate
- George Washington Univ., Washington, DC
- Report
- Video, May 4, 1999,
- Keywords
- turbulent flames | premixed combustion | flame propagation
- Abstract
- Stratified spark-ignition engines that use direct fuel injection into the combustion chamber feature both small- and large-scale spatial variations in unburnt mixture composition. In these configurations, the spark-ignited turbulent flame propagates into a mixture with variable equivalence ratio. Under lean-rich conditions, the reaction zone can be described as a staged combustion system with a first stage corresponding to a propagating premixed flame front followed by a second stage corresponding to multiple post-diffusion flames that burn the remaining excess fuel and excess oxidizer. Direct numerical simulations (DNS) are used in the present study to bring basic information onto the effects of partial premixing both on the turbulent flame topology and the overall mean reaction rate. DNS results are also used to determine if and how current flamelet combustion models should be modified to account for these effects. It is shown for instance that partial premixing tends to have a net negative impact on the overall mean turbulent reaction rate. It is also shown how this effect may be incorporated into current turbulent combustion models. Based on these findings, a modified version of the now well-established Coherent Flame Model for turbulent flame propagation is proposed and preliminary results from test problems are presented.