An Experimental Insight into the Smoldering-Flaming Transition Phenomenon

Poorva Shrivastava,A Vinoth Kumar,Vinayak Malhotra,Herambraj Nalawade,Chakshu Baweja,Vikram Ramanan

doi:10.1155/2017/4062945

Abstract

Transitional phenomena of smoldering combustion over thin solid fuels are investigated. An experimental setup was upraised and implications of both smoldering and flaming external heat sources are estimated. Incense sticks were used as potential fuel and external smoldering heat source along with a fixed candle flame. The role of key controlling parameters, namely, separation distance and number of external heat sources in horizontal and vertical direction, was extensively examined. The surfacing issues of enclosure effect and the external heat sources orientation are addressed. The study primarily aims at understanding the feasibility and spontaneity of transition owing to external heat sources (both flaming and smoldering). Forward heat transfer significantly deviates qualitatively and quantitatively with varying separation distance in both directions. Number of external heat sources intensifies the transition phenomenon in smoldering combustion. With practical considerations, external heat sources arrangement and orientation have substantial effect on the combustion process.

Highlights

Smoldering is flameless form of combustion phenomenon, deriving heat from heterogeneous reactions occurring on the surface of a solid fuel (Figure 1)
In forward propagation, the fresh oxidizer flows through the char and reacts at the ignition zone and the oxidizer-depleted flow goes through the virgin fuel
The fresh oxidizer flows through the virgin fuel and reacts at the smolder zone favoring that both the oxidation and the pyrolysis reactions occur at approximately the same location

Summary

Introduction

Smoldering is flameless form of combustion phenomenon, deriving heat from heterogeneous reactions occurring on the surface of a solid fuel (Figure 1). One of the major lessons learned is that it is impossible to eliminate all ignition sources, so fire inhibition is achieved through use of fire resistant materials and prevention of external resources to eliminate excessive spread It is of interest both as a fundamental combustion problem and as a practical fire hazard. In forward propagation, the fresh oxidizer flows through the char and reacts at the ignition zone and the oxidizer-depleted flow goes through the virgin fuel This configuration favors that the oxidation reactions occur at the rear of the ignition zone and pyrolysis at the front. The fresh oxidizer flows through the virgin fuel and reacts at the smolder zone favoring that both the oxidation and the pyrolysis reactions occur at approximately the same location. Present work focuses on opposed mode of combustion, namely, reverse smoldering and opposed flow flame spreading

Methods

Results

Conclusion