The aim of the present work is to investigate auto-ignition characteristics of compositionally homogeneous reactant mixtures in the presence of thermal non-uniformities and turbulent velocity fluctuations. First, an auto-ignition regime diagram and the associated theoretical scaling analysis are briefly elucidated, that provide the framework to predict expected ignition behavior based on the thermo-chemical properties of the reactant mixture and flow/scalar field conditions. In the regime diagram, ignition regimes are mainly classified into three categories: weak (deflagration dominant), reaction-controlled strong and mixing-controlled strong (volumetric ignition/spontaneous propagation dominant) regimes. Subsequently, two-dimensional (2D) direct numerical simulations (DNS) of autoignition in a lean thermally-stratified syngas/air turbulent mixture at high pressure and low temperatures are performed to assess the validity of the regime diagram. Various test cases are simulated that correspond to different locations on the regime diagram, by way of varying the characteristic turbulent Damkohler number and Reynolds number. The temporal evolution of heat release rate is analyzed to determine the characteristics of auto-ignition phenomena in each case. It is found that the observed ignition behaviors match quite well with the corresponding expected regimes as predicted by the regime diagram. This shows that the regime diagram provides a comprehensive understanding of the physical and chemical mechanisms controlling the auto-ignition phenomena.
|Original language||English (US)|
|Title of host publication||10th Asia-Pacific Conference on Combustion, ASPACC 2015|
|State||Published - Jan 1 2015|