- Author
- Ahmad, T. | Groff, E. G. | Faeth, G. M.
- Title
- Fire Induced Plumes Along a Vertical Wall. Part 2. The Laminar Combustion Region. July 1, 1975-June 30, 1977.
- Coporate
- Pennsylvania State Univ., University Park
- Sponsor
- National Bureau of Standards, Gaithersburg, MD
- Report
- Part 2, July 1977, 69 p.
- Contract
- NBS-GRANT-5-9020
- Keywords
- plumes | walls | laminar flow | natural convection | boundary layers | equations | temperature | velocity | flame shapes | heat flux | flame shapes | flame extinguishment | wicks
- Identifiers
- laminar overfire region; pyrolysis zone; position of the flame; thin flame sheet; free-standing surface; fuel slab; tip of the flame
- Abstract
- This report discusses a portion of the research completed under NBS Grant No. 5-9020, during the period July 1, 1975 to June 30, 1977. The work described here considers the laminar overfire region (the region above the pyrolysis zone) along an upright bruning surface under natural convection conditions. Numerical solutions of the boundary layer equations are presented which extend existing similarity solutions for the pyrolysis zone to the nonsimilar overfire region. Predictions are made of temperatures, velocities, and concentraions within the plume; the position of the flame, asuming an infinitely thin flame sheet; and the heat flux to the nonburning poriton of the wall, above the pyrolysis zone. Results are presented for both fires along a wall and for the plume region above a free-standing surface. In addition to the exact solution of the boundary layer equations, an integral model is also developed to provide a rapid method for determining the overfire characteristics for laminar flow. The overfire region along a wlal and above a free-standing fuel slab was also examined experimentally. The burning poriton of the surface was simulated using wicks soaked with methanol, ethanol, and 1-propanol. For wall fires, the flam shape and the wall heat flux were predicted accurately, for various wll inclination angles, except near the tip of the flame where quenching occurs in the region where the flame is present, but declines quite rapidly beyond the tip of the flame. The position of the onset of turbulence was determined, using a shadowgraph; for transition beyond the tip of the flame, laminar flow was generally observed for [equation]. For free-standing fires, the flame shape was predicted reasonably well in the overfire region, including the tip of the flame, since quenching does not occur in this case. In this case the greatest errors in predicted flame shapes were encountered in the pyrolysis region, where experimental difficulities in properly representing the leading edge, and possible breakdown of the boundary layer equations, are suggested as factors contributing to the discrepancy.