Propagation and extinction behavior of CH4/air premixed flame passing through straight and converging-diverging (C-D) microchannels (diameters ranging from 1 to 10 mm) were investigated both experimentally and numerically. The dynamic behavior of flame propagation inside the channels was experimentally studied by using CH* chemiluminescence and direct imaging. Three patterns of flame propagation were observed, i.e., the flame can survive, partially extinguish and then re-ignite downstream, or completely extinguish. Regime diagrams showing these different patterns as functions of channel geometry and equivalence ratio were generated for both the straight and C-D channels. Numerical simulations were carried out to explain the experimentally observed flame dynamics inside the channels using a detailed CH4/air chemistry. In general, flames were easier to extinguish in C-D channels than in straight channels for a fixed channel diameter and equivalence ratio. Additionally, flames were harder to survive in C-D channels with larger exit-to-throat area ratios. Both heat loss and flame stretch were key factors that can generally cause flame extinction in narrow C-D channels.
|Original language||English (US)|
|Title of host publication||AIAA Aerospace Sciences Meeting|
|Publisher||American Institute of Aeronautics and Astronautics Inc, AIAA|
|State||Published - 2018|
|Event||AIAA Aerospace Sciences Meeting, 2018 - Kissimmee, United States|
Duration: Jan 8 2018 → Jan 12 2018
|Name||AIAA Aerospace Sciences Meeting, 2018|
|Other||AIAA Aerospace Sciences Meeting, 2018|
|Period||1/8/18 → 1/12/18|
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation with Dr. Song-Charng Kong as the technical monitor.