Role of flamefront motion and criterion for global quasi-steadiness in droplet burning

Longting He, Stephen D. Tse, Chung K. Law

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12 Scopus citations


A theoretical study has been conducted on the role of the flamefront motion in droplet burning to determine the range of validity of the classical quasi-steady theory in predicting the flame standoff ratio, as well as its implication on transient fuel vapor accumulation/depletion. Recognizing that flamefront motion can be induced by droplet surface regression, by initial conditions, and by far-field unsteadiness, and that the flamefront standoff ratio is in general large, of the order of 10, it is phenomenologically anticipated that small flamefront velocities can lead to large variations of the mass flow rate. Furthermore, it is demonstrated that the influence of this flamefront motion can be characterized by a quasi-steady parameter Qs, which is the product of the cube of the standoff ratio and the ratio of the gas to liquid densities, such that the influence is large when it is O(1), and small otherwise. By working in the flame coordinate and, hence, naturally allowing for this motion, and by further assuming gas-phase quasi-steadiness (in this coordinate), calculated results show that the standoff ratio continuously increases with time for O(1) values of Qs but approaches a constant, which is close to but exceeds the d2-law prediction, when it is sufficiently small. The present generalized transient formulation also provides a rigorous description of fuel vapor accumulation effects related to the initial condition, demonstrates that these effects can indeed be accounted for on the basis of gas-phase quasi-steadiness, and allows for the simultaneous inclusion of far-field transient diffusion effects.

Original languageEnglish (US)
Pages (from-to)1943-1950
Number of pages8
JournalSymposium (International) on Combustion
Issue number2
StatePublished - 1998
Externally publishedYes
Event27th International Symposium on Combustion - Boulder, CO, United States
Duration: Aug 2 1998Aug 7 1998

All Science Journal Classification (ASJC) codes

  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Mechanical Engineering
  • Physical and Theoretical Chemistry
  • Fluid Flow and Transfer Processes


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