Laminar premixed flames in mixed-convection thermal plumes

✍ Scribed by M.-M. Yan; G.M. Faeth

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 847 KB
• Volume: 60
• Category: Article
• ISSN: 0010-2180
• DOI: 10.1016/0010-2180(85)90117-8

✦ Synopsis

A theoretical investigation of laminar premixed flames stabilized downstream of a line heat source for mixedconvection conditions is described. The analysis involves solution of the nonsimilar boundary layer equations for an ideal gas with a one-step reaction while neglecting radiation. A deflagration wave is always stabilized at some point downstream of the source for these assumptions, but its position often shifts rapidly from near to far from the source over a limited range of reaction parameters. Conditions at this shift can provide a practical estimate of necessary conditions for ignition (a wake/plume-ignition criterion) if it is assumed that flames far from the source are not observed due to transition to turbulence and quenching by surfaces. Increased free stream velocities have the following effects on the limit: the magnitude of flame position shifts is reduced, source strengths are increased, the flame moves closer to the source, and the rate of lateral spread of the flame is increased. Similar to other ignition and flame stability processes, large shifts, which are representative of well-defined limits, tend to disappear as the activation energy of reaction is reduced.