The effect of wall heat loss on the flame behavior in a sudden-expansion channel

摘要

The flame behaviors in a mesoscale one-stepped sudden-expansion channel are numerically investigated by a two-dimensional model without symmetric assumption at the centerline. The channel expansion ratio β is set equal to 2. The complete Navier-Stokes equations and one-step chemical reaction are used. The wall heat loss adjusted by varying the external heat convection coefficient (h ≥ 50 W/m~2 · K). Three types of flame behaviors are found: steady slant-shaped flame, unsteady vibrating flame and periodically oscillating flame. The steady slant flame exists if the heat loss is low (50 W/m~2 K). As the wall heat loss increases, the flame becomes unsteady and vibrating (h = 60 ～ 93 W/m~2 · K). In addition, if the wall heat loss further increases, the periodically oscillating flame is observed (h > 96 W/m~2 · K).