Journal article
Droplet combustion in presence of airstream oscillation: Mechanisms of enhancement and hysteresis of burning rate in microgravity at elevated pressure
Combustion and Flame, Vol.157(1), pp.91-105
2010
Abstract
The enhancement and hysteresis behavior of the burning rate of single droplet combustion in the presence of airstream oscillation observed in previously performed microgravity experiments at elevated pressure up to 1.0 MPa were numerically investigated. Excellent agreement with the experimental results was obtained and the mechanisms of these phenomena were examined based on precise numerical data on instantaneous droplet diameter variations corresponding to the unsteady airstream velocity, flow fields around the droplet, and flame movement during combustion. Results show that, depending on the oscillation Reynolds number, which is a function of pressure, flow amplitude and droplet diameter, there are three mechanisms involved in the enhancement of burning rate. In the cases of low oscillation Reynolds numbers, a diffusion-time-delay has a significant effect on the flame front movement and thus, on heat from the flame to the droplet. In the cases of high oscillation Reynolds numbers, a vortex generated outside the droplet flame promotes the motion of the flame, especially in the wake region, and thus enhancing the droplet burning rate. In addition to these two mechanisms, the forced convection during the acceleration period of the flow oscillation causes overshooting of the droplet burning rate due to instantaneous imbalances of the airflow momentum with the Stefan flow. These three mechanisms explain the predominant role of the highest velocity of the oscillatory airstream in determination of the mean burning rate constant and droplet lifetime. Results also show that the hysteresis behavior of the burning rate is a consequence of the different responses of the flame to the deceleration period compared with the responses to the acceleration period under the existence of those three mechanisms.
Details
- Title
- Droplet combustion in presence of airstream oscillation: Mechanisms of enhancement and hysteresis of burning rate in microgravity at elevated pressure
- Authors/Creators
- M. Jangi (Author/Creator)H. Kobayashi (Author/Creator)
- Publication Details
- Combustion and Flame, Vol.157(1), pp.91-105
- Publisher
- Elsevier Inc
- Identifiers
- 991005540630807891
- Copyright
- © 2009 The Combustion Institute.
- Murdoch Affiliation
- Murdoch University
- Language
- English
- Resource Type
- Journal article
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- Domestic collaboration
- International collaboration
- Citation topics
- 7 Engineering & Materials Science
- 7.177 Combustion
- 7.177.238 Combustion Dynamics
- Web Of Science research areas
- Energy & Fuels
- Engineering, Chemical
- Engineering, Mechanical
- Engineering, Multidisciplinary
- Thermodynamics
- ESI research areas
- Engineering