Publications

@article{Zhao2019,

title = {Lateral Flame Spread over PMMA Under Forced Air Flow},

author = {Kun Zhao and Michael J Gollner and Qiong Liu and Junhui Gong and Lizhong Yang},

url = {https://doi.org/10.1007/s10694-019-00904-x http://link.springer.com/10.1007/s10694-019-00904-x},

doi = {10.1007/s10694-019-00904-x},

issn = {0015-2684},

year  = {2019},

date = {2019-09-01},

journal = {Fire Technology},

publisher = {Springer US},

abstract = {In wildland and other flame spread scenarios a spreading fire front often forms an elliptical shape, incorporating both forward and lateral spread. While lateral flame spread is much slower than forward rates of spread, it still contributes to the growth of the overall fire front. In this work, a small-scale experiment is performed to investigate the mechanisms causing this lateral spread in a simple, small-scale configuration. PMMA strips with thicknesses ranging from 1 mm to 3.1 mm and widths of 5 cm and 10 cm were ignited under forced flow in a laminar wind tunnel. Unlike traditional concurrent or opposed flame spread experiments, flames were allowed to progress from one side of the sample to the other, perpendicular to the wind direction. An infrared camera was used to track the progression of the pyrolysis front by estimating the surface temperature of the PMMA. The flame spread rate, depth of the burning region, thermal diffusion length, and radiant heat flux were determined and analyzed. Based on a theory of heat and mass transfer for a laminar diffusion flame, a thermal heat transfer model was developed for the preheating region to predict the lateral flame spread rate. Results show that the thermal diffusion length decreases with wind velocity, ranging from 4.5 mm to 3 mm. Convection dominates the flame-spread rate, accounting for more than 80% of the total heat flux. The theoretical flame spread rate agrees well with experimental data from all but the thinnest samples tested, overpredicting the lateral flame spread rate for 1 mm thick samples. The resulting model for lateral flame spread under concurrent flow works for forced-flow dominated flame spread over thermally-thin fuels and helps provide physical insight into the problem, aiding in future development of two-dimensional, elliptical fire spread models.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Zhao2018,

title = {Experimental and theoretical study on downward flame spread over uninhibited PMMA slabs under different pressure environments},

author = {K Zhao and X Zhou and X Liu and W Tang and M Gollner and F Peng and L Yang},

doi = {10.1016/j.applthermaleng.2018.02.059},

issn = {13594311},

year  = {2018},

date = {2018-01-01},

journal = {Applied Thermal Engineering},

volume = {136},

abstract = {textcopyright 2018 Elsevier Ltd This paper presents an experimental and theoretical study of side-edge effects on downward flame spread over two parallel polymethyl methacrylate (PMMA) slabs under different pressure environments. Identical experiments of downward flame spread over thin PMMA slabs with side-edges unrestrained were conducted at different altitudes in Hefei (102 kPa), Geermu (73.2 kPa) and Lhasa (66.3 kPa). Experimental results show that the flame spread rate is controlled by ignition along the side-edge, rather than at the center of the samples, for experiments with both single and two parallel slabs. Based on these results, a thermal model is developed which describes flame spread along the edge and quantitatively agrees with experimental results. In the parallel-slab case, convective heating appears to influence the spread rate only when the separation distance is very small, with radiative heating playing a more important role as separation distance increases. The angle of the pyrolysis front, formed between the faster side-edge spread and slower center-region spread, hardly changes with pressure, but changes significantly with separation distance, due to differing modes of heat transfer between the side-edge and center region. In addition, variations of flame height with pressure and separation distance are reasonably interpreted from diffusion flame theory.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jiang2018,

title = {Flame spread and burning rates through vertical arrays of wooden dowels},

author = {Lin Jiang and Zhao Zhao and Wei Tang and Colin Miller and Jin Hua Sun and Michael J Gollner},

doi = {10.1016/j.proci.2018.09.008},

issn = {15407489},

year  = {2018},

date = {2018-01-01},

journal = {Proceedings of the Combustion Institute},

volume = {000},

pages = {1--8},

publisher = {Elsevier Inc.},

abstract = {Fuel loads in real-world fire scenarios often feature discrete elements, discontinuities, or inhomogeneities; however, most models for flame spread only assume a continuous, homogeneous fuel. Because discrete fuels represent a realistic scenario not yet well-modeled, it is of interest to find simple methods to model fire growth first in simple, laboratory-scale configurations. A detailed experimental and theoretical study was therefore performed to investigate the controlling mechanisms of flame spread through arrays of wooden dowels, with dowel spacings of 0.75, 0.875, and 1.5 cm. Flames were found to spread vertically for all spacings; however, for the 1.5 cm spacing, the gap was too large for horizontal flame spread to occur. A radiation-controlled model for horizontal flame spread was developed that predicted the horizontal flame spread rate through various arrays of dowels. Combined with an existing convection-based model for vertical flame spread, both horizontal and vertical flame spread was modeled to predict the number of burning wooden dowels as a function of time. Using models for the burning rate of wooden dowels and boundary-layer theory, a global burning rate model was developed that provided reasonable agreement with experimental results.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Miller2017,

title = {Investigating coherent streaks in wildfires via heated plates in crosswind},

author = {C Miller and M A Finney and S McAllister and E Sluder and M J Gollner},

doi = {10.1016/j.firesaf.2017.03.035},

issn = {03797112},

year  = {2017},

date = {2017-01-01},

journal = {Fire Safety Journal},

volume = {91},

abstract = {textcopyright 2017 Elsevier Ltd Streaklike coherent structures are consistently observed in boundary layer flames, but their role in modifying heat and mass transfer remains unknown. In the following experiment, a non-reactive thermal plume was employed to study analogous streaks in an environment where the local source of buoyancy could be directly modified. A horizontal hot plate was exposed to crossflow, and infrared thermography was successfully employed to capture thermal traces of streaks on the surface. Post-processing of surface temperature data enabled the quantification of important properties of streaks, such as location, spacing, width, and strength. The distribution of streak spacing was found to have a lognormal distribution. Mean streak spacing and width increased with downstream distance, indicating the amplification and aggregation of coherent structures. Streak spacing decreased when either the hot plate temperature increased from 150 °C to 300 °C or the wind speed increased from 0.5 to 1.2 m/s. Streaks were seen to modify the spanwise distribution of heat transfer to the surface, most notably when the hot plate temperature was increased from 150 °C to 300 °C.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}