Effects of buoyancy on lean premixed v-flames. Part 1: Laminar and turbulent flame structures
- Lawrence Berkeley National Lab., CA (United States). Environmental Energy Technologies Div.
- Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Mechanical Engineering
Laser schlieren and planar laser-induced fluorescence techniques have been used to investigate laminar and turbulent v-flames in normal, inverse, and microgravity conditions under flow conditions that span the regimes of momentum domination (Ri < 0.1) and buoyancy domination (Ri > 0.1). Overall flame features shown by schlieren indicate that buoyancy dominates the entire flow field for conditions close to Ri = 1. With decreasing Ri, buoyancy effects are observed only in the far-field regions. Analyses of the mean flame angles demonstrate that laminar and turbulent flames do not have similar responses to buoyancy. Difference in the laminar +g and {minus}g flame angles decrease with Ri (i.e., increasing Re) and converge to the {micro}g flame angle at the momentum limit (Ri = 0). This is consistent with the notion that the effects of buoyancy diminish with increasing flow momentum. The +g and {minus}g turbulent flame angles, however, do not converge at Ri = 0. As shown by OH-PLIF images, the inconsistency in +g and {minus}g turbulent flame angles is associated with the differences in flame wrinkles. Turbulent flame wrinkles evolve more slowly in +g than in {minus}g. The difference in flame wrinkle structures, however, cannot be explained in terms of buoyancy that stretches the turbulent flame brushes in +g and compresses the flame brush in {minus}g. Flame wrinkling offers a mechanism through which the flame responds to the field effects of buoyancy despite increasing flow momentum. These observations point to the need to include both upstream and downstream contributions in theoretical analysis of flame turbulence interactions.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 675663
- Journal Information:
- Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: 3 Vol. 116; ISSN 0010-2180; ISSN CBFMAO
- Country of Publication:
- United States
- Language:
- English
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