Burning characteristics of PMMA with varied stretch rates under stagnation-point diffusion flames

Author: Tao, S. Q., Fang, J., Zhao, L. Y., Wang, J. W., Shah, H. R., Yang, L. Z.

Journal: Combustion and Flame

DOI:  10.1016/j.combustflame.2020.06.022

Keywords: Low stretch rate, Stagnation-point diffusion flame, Flame standoff distance, Burning rate, Modified B number, extinction, boundary, model, Thermodynamics

Abstract: 

This study investigated the burning characteristics of PMMA with varied stretch rates under stagnation point diffusion flames both theoretically and experimentally, focusing on the manner in which the surface energy balance and heat losses affected burning rate with varied stretch rates. The burning rate versus stretch rate was firstly investigated by introducing a modified Spalding B number, where the burning rate was proved to equal the buoyancy or forced flow induced stretch rate to the power of 0.5. At lower stretch rate, burning was largely affected by heat losses, associated with a lower B number, and decreased up to the quenching limit, similar to the microgravity results. At higher stretch rate, burning was controlled by flame radiation with a larger B number and increased burning rate. Additionally, ice bath increased the solid in-depth conduction heat loss due to the lower temperature maintained at the upper surface of the sample, and further influenced the energy balance with a larger heat losses fraction, leading to reduced B number and burning rate. This study provided an insightful investigation of the burning behaviors of stagnation-point diffusion flames with low stretch rates, which was used in a terrestrial environment to simulate microgravity flames. (c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.