Wind Effects on Smoldering Behavior of Simulated Wildland Fuels

ABSTRACT

The current study presents a series of experiments investigating the smoldering behavior of woody fuel arrays at various porosities under the influence of wind. Wildland fuels are simulated using wooden cribs burned inside a bench scale wind tunnel. Smoldering behavior was characterized using measurements of both mass loss and emissions. Results showed that the mean burning rate increased with wind speed for all cases. In high porosity cases, increases in burning rate between 18% and 54% were observed as wind speed increased. For low porosity cases an increase of about 170% in burning rate was observed between 0.5 and 0.75 m/s. The ratio of CO/CO₂ emissions decreased with wind speed. Thus, wind likely served to promote smoldering combustion as indicated by the decrease of CO/CO₂ which is a marker of combustion efficiency. A theoretical analysis was conducted to assess the exponential decay behavior in the time-resolved mass loss data. Mass and heat transfer models were applied to assess whether oxygen supply or heat losses can solely explain the observed exponential decay. The analysis showed that neither mass transfer nor heat transfer alone can explain the exponential decay, but likely a combination thereof is needed.

KEYWORDS:

• Wildfires
• smoldering
• cribs
• bench scale

Acknowledgments

The authors would like to thank Priya Garg for her assistance in implementing the emissions measurement protocol. This work was sponsored by the California Energy Commission – Energy Program Investment Charge (EPIC) program under Grant #EPC-18–026. Funding for J. Cobian came from the University of California, Merced School of Engineering.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the California Energy Commission – Energy Program Investment Charge (EPIC) program [#EPC-18–026].