Effects of particle fracturing and moisture content on fire behaviour in masticated fuelbeds burned in a laboratory

2011 ◽  
Vol 20 (2) ◽  
pp. 308 ◽  
Author(s):  
Jesse K. Kreye ◽  
J. Morgan Varner ◽  
Eric E. Knapp
Keyword(s):  
Moisture Content ◽  
Bulk Density ◽  
Surface Area ◽  
Field Experiments ◽  
Particle Surface ◽  
Fire Behaviour ◽  
Particle Surface Area ◽  
Fuels Treatment ◽  
Fuel Loads ◽  
Long Duration

Mechanical mastication is a fuels treatment that converts shrubs and small trees into dense fuelbeds composed of fractured woody particles. Although compaction is thought to reduce fireline intensity, the added particle surface area due to fracturing could also influence fire behaviour. We evaluated effects of particle fracturing and moisture content (ranging from 2.5 to 13%) on fire behaviour in fuelbeds composed of masticated Arctostaphylos manzanita Parry and Ceanothus velutinus Dougl. shrubs in the laboratory. Fuelbeds composed of fractured particles did not burn with greater intensity than fuelbeds composed of intact particles, as hypothesised. Flame heights ranged from 54 to 95 cm and fireline intensity from 50 to 140 kJ s–1 m–1, approximating values observed in field experiments. Masticated fuelbeds burned with shorter flame heights and longer flaming duration under higher fuel moistures, but duration of lethal heating (>60°C) above fuelbeds did not differ across the range of fuel moistures, averaging 12 min over a 0.1-m2 area. Our results suggest that expected fire behaviour increases due to particle fracturing may be overwhelmed by fuelbed bulk density. The long-duration heating of burning masticated fuels may require managers to mitigate effects to trees and soils when fuel loads are high.

Influence of particle surface area on the toxicity of insoluble manganese dioxide dusts

1997 ◽  
Vol 71 (12) ◽  
pp. 725-729 ◽  
Author(s):  
Dominique Lison ◽  
Cécile Lardot ◽  
François Huaux ◽  
Giovanna Zanetti ◽  
Bice Fubini
Keyword(s):  
Manganese Dioxide ◽  
Surface Area ◽  
Particle Surface ◽  
Particle Surface Area

scholarly journals Effect of particle surface area on ice active site densities retrieved from droplet freezing spectra

2016 ◽  
Vol 16 (20) ◽  
pp. 13359-13378 ◽  
Author(s):  
Hassan Beydoun ◽  
Michael Polen ◽  
Ryan C. Sullivan
Keyword(s):  
Surface Area ◽  
Active Sites ◽  
Particle Surface ◽  
Active Surface ◽  
Freezing Temperature ◽  
Ice Nucleation ◽  
Critical Surface ◽  
Cold Plate ◽  
Particle Surface Area ◽  
Immersion Freezing

Abstract. Heterogeneous ice nucleation remains one of the outstanding problems in cloud physics and atmospheric science. Experimental challenges in properly simulating particle-induced freezing processes under atmospherically relevant conditions have largely contributed to the absence of a well-established parameterization of immersion freezing properties. Here, we formulate an ice active, surface-site-based stochastic model of heterogeneous freezing with the unique feature of invoking a continuum assumption on the ice nucleating activity (contact angle) of an aerosol particle's surface that requires no assumptions about the size or number of active sites. The result is a particle-specific property g that defines a distribution of local ice nucleation rates. Upon integration, this yields a full freezing probability function for an ice nucleating particle. Current cold plate droplet freezing measurements provide a valuable and inexpensive resource for studying the freezing properties of many atmospheric aerosol systems. We apply our g framework to explain the observed dependence of the freezing temperature of droplets in a cold plate on the concentration of the particle species investigated. Normalizing to the total particle mass or surface area present to derive the commonly used ice nuclei active surface (INAS) density (ns) often cannot account for the effects of particle concentration, yet concentration is typically varied to span a wider measurable freezing temperature range. A method based on determining what is denoted an ice nucleating species' specific critical surface area is presented and explains the concentration dependence as a result of increasing the variability in ice nucleating active sites between droplets. By applying this method to experimental droplet freezing data from four different systems, we demonstrate its ability to interpret immersion freezing temperature spectra of droplets containing variable particle concentrations. It is shown that general active site density functions, such as the popular ns parameterization, cannot be reliably extrapolated below this critical surface area threshold to describe freezing curves for lower particle surface area concentrations. Freezing curves obtained below this threshold translate to higher ns values, while the ns values are essentially the same from curves obtained above the critical area threshold; ns should remain the same for a system as concentration is varied. However, we can successfully predict the lower concentration freezing curves, which are more atmospherically relevant, through a process of random sampling from g distributions obtained from high particle concentration data. Our analysis is applied to cold plate freezing measurements of droplets containing variable concentrations of particles from NX illite minerals, MCC cellulose, and commercial Snomax bacterial particles. Parameterizations that can predict the temporal evolution of the frozen fraction of cloud droplets in larger atmospheric models are also derived from this new framework.

scholarly journals Salt enhanced solvent relaxation and particle surface area determination via rapid spin-lattice NMR

2018 ◽  
Vol 333 ◽  
pp. 458-467 ◽  
Author(s):  
Laura N. Elliott ◽  
Richard A. Bourne ◽  
Ali Hassanpour ◽  
John L. Edwards ◽  
Stephen Sutcliffe ◽  
...  
Keyword(s):  
Surface Area ◽  
Particle Surface ◽  
Solvent Relaxation ◽  
Particle Surface Area ◽  
Spin Lattice ◽  
Surface Area Determination ◽  
Area Determination

scholarly journals Biomass char particle surface area and porosity dynamics during gasification

Fuel ◽  
2020 ◽  
Vol 264 ◽  
pp. 116833 ◽  
Author(s):  
Ruochen Wu ◽  
Jacob Beutler ◽  
Cameron Price ◽  
Larry L. Baxter
Keyword(s):  
Surface Area ◽  
Particle Surface ◽  
Particle Surface Area ◽  
Char Particle ◽  
Biomass Char

scholarly journals Fire Behaviour Observation in Shrublands in Nova Scotia, Canada and Assessment of Aids to Operational Fire Behaviour Prediction

Fire ◽  
2020 ◽  
Vol 3 (3) ◽  
pp. 34
Author(s):  
Anne-Claude Pepin ◽  
Mike Wotton
Keyword(s):  
Nova Scotia ◽  
Moisture Content ◽  
Bulk Density ◽  
Prediction Models ◽  
Seasonal Effect ◽  
Fuel Type ◽  
Fire Behaviour ◽  
Fire Weather Index ◽  
Rate Of Spread ◽  
Wide Range

Parks Canada, in collaboration with Nova Scotia Lands and Forests and Natural Resources Canada, documented shrub fire behaviour in multiple plots burned over two periods: a spring period in June 2014 and a summer period in July 2017. The study area, located within Cape Breton Highlands National Park, comprised fifteen burn units (20 m by 20 m in size). Each unit was ignited by line ignition and burned under a wide range of conditions. Pre-burn fuel characteristics were measured across the site and used to estimate pre-fire fuel load and post-fire fuel consumption. This fuel complex was similar to many flammable shrub types around the world, results show that this shrub fuel type had high elevated fuel loads (3.17 ± 0.84 kg/m2) composed of exposed live and dead stunted black spruce as well as ericaceous shrubs, mainly Kalmia angustifolia (evergreen) and Rhodora canadensis (deciduous). Data show that the dead moisture content in this fuel complex is systematically lower than expected from the traditional relationship between FFMC and moisture content in the Canadian Fire Weather Index System but was statistically correlated with Equilibrium Moisture Content. A significant inverse relationship between bulk density and fire rate of spread was observed as well as a clear seasonal effect between the spring burns and the summer burns, which is likely attributable to the increase in bulk density in the summer. Unlike most shrub research, wind and dead moisture content did not have a statistically significant association with fire spread rates. However, we believe this to be due to noise in wind data and small dataset. Rate of spread as high as 14 m/min and flame lengths over 4 m were recorded under Initial Spread Index values of 6.4 and relative humidity of 54%. A comparison with a number of well-known shrubland spread rate prediction models was made. An aid to operational fire prediction behaviour is proposed, using a fuel type from the Canadian Fire Prediction System (O-1b) and a modified estimate of fuel moisture of the elevated fuel in the fuel complex.

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