Li-Ming Yuana

Bio: Li-Ming Yuana is an academic researcher. The author has contributed to research in topics: Mobile genetic elements & Effluent. The author has an hindex of 1, co-authored 1 publications receiving 98 citations.

A unified analysis for fire plumes

Abstract: A unified analysis based on an integral approach is presented for fire plumes involving finite axisymmetric and rectangular sources. The analysis, using Gaussian profiles, obtains the best fits to experimental data found in the literature. Phenomenological constants in the theory are found to give consistent results in that coefficients expected to be numerically similar by theory are found similar among the various data sets. Thorough reviews of the literature data for line and rectangular sources are presented and yield consensus correlations, accordingly. The effect of flame radiation is explicitly included by a radiation fraction that proves to be a significant variable, previously overlooked in experiments. Effective entrainment coefficients for the far-field noncombusting plume are found to be 0.09 to 0.10, and for the flame region about 0.22 for the axisymmetric and rectangle cases as long as D/L>0.1. For D/L

Effects of low air pressure on radiation-controlled rectangular ethanol and n-heptane pool fires

Abstract: Experiments on rectangular ethanol and n -heptane pool fires were conducted at different altitudes in Hefei (99.8 kPa) and Lhasa (66.5 kPa). The burners tested had the same fuel area of 900 cm 2 , but with aspect ratio of long side to short side ( n = l / w ) varied from 1 and 8. The individual and combined influences of low pressure and aspect ratio on burning rate, temperature, puffing frequency, flame height and radiation for the two fuels were interpreted and formulated. First, burning rate was found to be proportional to ambient air pressure under radiation control, the main reason is that radiative heat flux decreased with pressure due to the pressure affecting the soot absorption coefficient. Flame temperature slightly increased, leading to higher flame puffing frequency at low pressure. Flame height was almost insensitive to pressure as H ∝ p 0 . Second, for aspect ratio n , flame temperature was constant and independent of fuel type and burner shape. With increasing n , burner wall temperature increased at the long side, and decreased drastically at the short side, especially n = 8. This was attributed to the change of flame tilt and heating of the burner side, caused by variation of entrainment motion. Flame puffing frequency was found to increase with n as a function of f ∼ ( Δ T / T ∞ ) ( n + 1 ) / 2 n . The flame was observed to split into small clusters by enhanced asymmetric entrainment, and H decreased with increasing n as H ∼ ( 1 / n ) 2 / 5 Q ˙ 4 / 15 . Considering fuel differences, with increasing n , the burning rate of the ethanol pool fire decreased, and n -heptane showed the opposite trend.

Linking surface-fire behavior, stem heating, and tissue necrosis

Abstract: Data from 69 experimental, small-plot fires are used to describe relationships among fire intensity, bark-surface heat flux, and depth of necrosis in stem tissue for red maple (Acer rubrum L.) and chestnut oak (Quercus prinus L.). A tetrazolium staining technique was used to determine the depth of necrosis in tree boles subjected to fires with intensities of 20 to 2000 kW/m. Over a range of bark moistures (28%–83%) and bole diameters (3–20 cm), depth of necrosis appears to be primarily a function of fire intensity, flame residence time at the stem, and the corresponding time-integrated heat flux at the bark surface. Our results, along with known relations between bole diameter and bark thickness, and improved models of fire behavior and heat transfer, may be useful for estimating tree mortality resulting from prescribed fires.

Fire eruption through intensity and spread rate interaction mediated by flow attachment

Abstract: Conditions under which a fire has a stable steady spread rate or under which it is able to spread eruptively up a slope or in confined topography are of considerable interest from a practical and safety point of view. The physical interactions that give rise to either form of behaviour are investigated by way of a mathematical model, in which different expressions for the rate of feedback from intensity into spread-rate are found to identify a threshold between eruptive and stable spread of a line fire. In turn, changes in the fireline intensity in any unsteady evolution are mainly determined by the history of the spread-rate over a burnout time (in effect, by changes in flame depth). Under stable conditions, any initial spread-rate evolves towards the steady spread rate on a time-scale of the order of the burnout time. But above the threshold, eruptive fire-growth sets in; the spread-rate and intensity both grow indefinitely. It is argued that a change in the nature of the flow field around a line fire e...