The blowout behavior of non-premixed turbulent coflow jet flames under microgravity environment was studied experimentally by utilizing a 3.6 s drop tower. Variations of flames leading to liftoff as well as blowout were examined by varying the coflow velocity and compared with those obtained under the normal gravity condition. A modeling work was conducted to incorporate the effects of the gravity (buoyancy) and coflow velocity on blowout behavior. Major findings include: (1) the flame length in microgravity was longer than that in normal gravity and decreased with increasing coflow velocity. The flame in microgravity showed more intense yellow luminosity with larger sooting zone; (2) the flame liftoff height increased with increasing coflow velocity in both gravity levels. The flame base was closer to the burner in microgravity as compared with that in normal gravity; (3) the blowout velocity in microgravity was appreciably larger than that obtained in normal gravity; and (4) a physical model based on Damköhler number was developed by using similarity solutions to characterize the differences in the blowout limits considering both the coflow and gravity (buoyancy) effects. The proposed model can successfully predict the experimental data. This work provided new data and basic scaling analysis for blowout limit of non-premixed turbulent jet flames considering both the coflow and gravity (buoyancy) effects.
|Original language||English (US)|
|Number of pages||9|
|Journal||Combustion and Flame|
|State||Published - Sep 13 2019|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported jointly by National Natural Science Foundation of China (NSFC) (51976051, 51636008, 51606057, and U1738117) and Key Research Program of Frontier Sciences, Chinese Academy of Science (CAS) under Grant No. QYZDB-SSW-JSC029. OF was supported by a Grand-in-Aid for Scientific Research (KIBAN(A) No. 18H03755). SHC was supported by King Abdullah University of Science and Technology (KAUST). This work was also supported by Fundamental Research Funds for the Central Universities (JZ2018HGTB0256), China Postdoctoral Science Foundation funded project (2018T110625; 2016M590580), and the Strategic Pioneer Program on Space Science, the Chinese Academy of Sciences under Grant No. XDA15012800.