Regimes of spray vaporization and combustion in counterflow configurations Articles uri icon

publication date

  • December 2014

start page

  • 103

end page

  • 131

issue

  • 1-2

volume

  • 187

international standard serial number (ISSN)

  • 0010-2202

electronic international standard serial number (EISSN)

  • 1563-521X

abstract

  • This article addresses the problem of spray vaporization and combustion in axisymmetric opposed-jet configurations involving a stream of hot air counterflowing against a stream of nitrogen carrying a spray of fuel droplets. The Reynolds numbers of the jets are assumed to be large, so that mixing of the two streams is restricted to a thin mixing layer that separates the counterflowing streams. The evolution of the droplets in their feed stream from the injection location is seen to depend fundamentally on the value of the droplet Stokes number, St, defined as the ratio of the droplet acceleration time to the mixing-layer strain time close to the stagnation point. Two different regimes of spray vaporization and combustion can be identified depending on the value of St. For values of St below a critical value, equal to 1/4 for dilute sprays with small values of the spray liquid mass-loading ratio, the droplets decelerate to approach the gas stagnation plane with a vanishing axial velocity. In this case, the droplets located initially near the axis reach the mixing layer, where they can vaporize due to the heat received from the hot air, producing fuel vapor that can burn with the oxygen in a diffusion flame located on the air side of the mixing layer...

keywords

  • counterflow spray flames; coupling functions; diffusion-controlled reaction; spray mixture fraction