Advanced

Numerical Studies of the Pilot Flame Effect on a Piloted Jet Flame

Yu, S. LU ; Bai, X. S. LU ; Zhou, B. LU ; Wang, Z. LU ; Li, Z. S. LU and Aldén, M. LU (2019) In Combustion Science and Technology
Abstract

In a piloted jet flame, the pilot flame has an effect of stabilizing the main flame. Detailed mechanisms of pilot flame/main flame interaction are however not well studied. It is expected that the pilot flame affects the main flame through the following mechanisms: (a) the pilot flame provides the heat and radicals to the reaction zone of the main flame, (b) the pilot flame prevents the cold ambient air from being entrained into the main flame, and (c) the pilot flame modifies the stretch rate of the main flame. In this paper, detailed numerical simulations of piloted laminar methane/air jet flames are carried out to elucidate the effect of pilot flame on the structure and burning velocity of the main jet flame. One-dimensional (1D)... (More)

In a piloted jet flame, the pilot flame has an effect of stabilizing the main flame. Detailed mechanisms of pilot flame/main flame interaction are however not well studied. It is expected that the pilot flame affects the main flame through the following mechanisms: (a) the pilot flame provides the heat and radicals to the reaction zone of the main flame, (b) the pilot flame prevents the cold ambient air from being entrained into the main flame, and (c) the pilot flame modifies the stretch rate of the main flame. In this paper, detailed numerical simulations of piloted laminar methane/air jet flames are carried out to elucidate the effect of pilot flame on the structure and burning velocity of the main jet flame. One-dimensional (1D) freely propagating flame is also simulated to investigate the effect of hot gas mixing with the unburned fuel/air mixture, and 1D counter-flow flame is simulated to study the diffusion of the hot gas from the pilot flame to the reaction zone of the main flame and the effect of flame stretch. The results showed that heat transfer from the pilot flame to the main flame has a more significant effect on the structures and propagation of the main flame than the mass transfer from the pilot flame to the main flame. The heat and mass transfer from the pilot flame affects the local equivalence ratio and temperature of the unburned mixture, which gives rise to a significant enhancement of burning velocity. When the hot gas from the pilot flame is at sufficiently high temperatures, an ultra-lean fuel/air mixture can burn at equivalence ratio below the flammability limit. The reaction rate and burning velocity of ultra fuel-lean flames are enhanced by the strain rate, whereas for a main flame with the equivalence ratio closer to that of pilot flame, the reactivity and burning velocity of the main flame decrease with increasing strain rate.

(Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
epub
subject
keywords
burning velocity, flame stabilization, pilot, reaction rate, strain rate
in
Combustion Science and Technology
publisher
Taylor & Francis
external identifiers
  • scopus:85074493029
ISSN
0010-2202
DOI
10.1080/00102202.2019.1679550
language
English
LU publication?
yes
id
9652b6a7-e99b-406c-a2dc-6f0cee31851e
date added to LUP
2019-11-22 08:43:30
date last changed
2020-01-13 02:32:31
@article{9652b6a7-e99b-406c-a2dc-6f0cee31851e,
  abstract     = {<p>In a piloted jet flame, the pilot flame has an effect of stabilizing the main flame. Detailed mechanisms of pilot flame/main flame interaction are however not well studied. It is expected that the pilot flame affects the main flame through the following mechanisms: (a) the pilot flame provides the heat and radicals to the reaction zone of the main flame, (b) the pilot flame prevents the cold ambient air from being entrained into the main flame, and (c) the pilot flame modifies the stretch rate of the main flame. In this paper, detailed numerical simulations of piloted laminar methane/air jet flames are carried out to elucidate the effect of pilot flame on the structure and burning velocity of the main jet flame. One-dimensional (1D) freely propagating flame is also simulated to investigate the effect of hot gas mixing with the unburned fuel/air mixture, and 1D counter-flow flame is simulated to study the diffusion of the hot gas from the pilot flame to the reaction zone of the main flame and the effect of flame stretch. The results showed that heat transfer from the pilot flame to the main flame has a more significant effect on the structures and propagation of the main flame than the mass transfer from the pilot flame to the main flame. The heat and mass transfer from the pilot flame affects the local equivalence ratio and temperature of the unburned mixture, which gives rise to a significant enhancement of burning velocity. When the hot gas from the pilot flame is at sufficiently high temperatures, an ultra-lean fuel/air mixture can burn at equivalence ratio below the flammability limit. The reaction rate and burning velocity of ultra fuel-lean flames are enhanced by the strain rate, whereas for a main flame with the equivalence ratio closer to that of pilot flame, the reactivity and burning velocity of the main flame decrease with increasing strain rate.</p>},
  author       = {Yu, S. and Bai, X. S. and Zhou, B. and Wang, Z. and Li, Z. S. and Aldén, M.},
  issn         = {0010-2202},
  language     = {eng},
  month        = {10},
  publisher    = {Taylor & Francis},
  series       = {Combustion Science and Technology},
  title        = {Numerical Studies of the Pilot Flame Effect on a Piloted Jet Flame},
  url          = {http://dx.doi.org/10.1080/00102202.2019.1679550},
  doi          = {10.1080/00102202.2019.1679550},
  year         = {2019},
}