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This paper investigated the mutual interaction between two extra-thin line fires under different wind speeds of 0.4, 0.6, 0.8, 1.0 and 1.2 m/s by using a small-scale wind tunnel. The experiments involved the spacing distances of 5, 10, 15, 20, 25, 30, 35 and 40 cm, and the heat release rates of 19.4, 25.7 and 32.7 kW, respectively. The results show that the flame merging probability increase, as the wind speed or the heat release rate increases. Compared with the two rectangular or square fires, the flame height and flame length will be smaller at the same heat release rate for the extra-thin line fires. Meanwhile, the line fires will decrease the flame merging, making the downstream flame temperature smaller than that of the upstream at the relatively larger wind speed or heat release rate. The interesting finding is that, with the increase of the heat release rate, the flame inclination angle will increase in the fully merging stage, which is opposite to that of square fires. Correspondingly, the flame merging model is built on the influences of the buoyancy force and inertial force of the horizontal wind, which can give the good explanation on this behavior.

The high momentum tail (HMT) of nucleons, as a signature of the short-range correlations in nuclei, has been investigated by the high-energy bremsstrahlung γ rays produced in 86Kr+124Sn at 25 MeV/nucleon. The energetic photons are measured by a CsI(Tl) hodoscope mounted on the spectrometer CSHINE. The energy spectrum ≥35 MeV can be reproduced by the Isospin- and Momentum-Dependent Boltzmann-Uehling-Uhlenbeck model calculations incorporating the photon production channel from np process in which the HMTs of nucleons is considered. A non-zero HMT ratio of about 15% is favored by the data. The effect of the capture channel np→dγ is demonstrated.

Flame merging of line fires is very complex with the interaction of fire dynamics and fluid flow et al., which will often generate different burning behaviors. In this paper, the effects of spacing distance and fuel mass thickness on the combustion and flame merging characteristics of two n-heptane line pool fires were studied. With the dimensionless liquid fuel height H* (Fuel height/Groove depth) increase, the probability of flame merging, and the temperature of the additional air entrainment region gradually increase. The merging flame will change from no hole, with hole, hole increased to hole open stage with spacing distance increase. It is interesting to find that, the mass loss rate of each line fire is less than that of a single line fire burning alone, and the closer the distance is, the smaller the value is. Meanwhile, for a single or double linear fires at H* = 3/4, the mass loss rate is the greatest. By establishing a heat transfer model, it is demonstrated that at H* = 3/4, the ullage of the groove has a stabilizing effect on the flame, which makes the flame height the largest. The results of this study will enhance the understanding of the flame merging of line fires with different fuel masses.

In this paper, three types (typeⅠ, type Ⅱand type III) of polyethylene-insulated wires with copper core diameters of 6 mm, 8 mm and 10 mm and thickness of polyethylene of 2 mm respectively, were used to research the flame spread of double wires with spacing sizes of 0 mm,1 mm,2 mm,3 mm,5 mm,7 mm,10 mm,12 mm, 15 mm and 18 mm. The results showed that with the increase of spacing, the flame changed from “less propagating” to “quasi-intermittent merging” stage, to “continuous merging” stage, then to “intermittent merging” stage, and finally to “non-merging” stage. For type III of the largest Cu core diameter, the flame could not spread when s = 1 mm and 2 mm.After that, the same transition from''continuous merging” stage to “non-merging” stage was found. The flame width showed the similar trend with FSR for typeⅠand type Ⅱ, while for type III the correlation between flame width and FSR was not closely related. The mass loss rate and mass dripping rate showed the similar trends with FSR. The faster FSR, the larger mass loss and dripping rates. The “re-burning” phenomena were found during the process of flame spread with small spacing distances, which made the residual material PE ignite again, and the flame width increase.

Experimental and numerical study on upward, vertical flame spread was carried out on expanded polystyrene (EPS) at two different altitudes of 50 m and 3658 m to understand the effect that altitude has on flame spread of melted material. The experiments show that, with the altitude increase, the flame spread rate would decrease. At low altitude, the flame spread rate accelerated at later time, while at high altitude, the stagnant stage of pyrolysis front was formed. The numerical simulation could well give the trend of pyrolysis front evolution and the different flame spread behaviors with altitudes. It was found that, at low altitude, Raxincreased slowly in the turbulent period with relatively large entrainment air flow rate, mainly due to the increased and then decreased mass loss rate in the wall fire zone. While, at high altitude, the simulated increasing entrainment air flow rate, combined with the larger preheating length δf and the smaller flame heat flux qf'', resulted in the stagnancy of pyrolysis front easily. It was hypothesized that extinction occurred eventually at high altitude due to competition between flame spread rate νf and preheating length δf.

The laboratory polyethylene wire with different core diameters of 3 mm, 5 mm, 6 mm, 7 mm, 8 mm, 10 mm and 12 mm was used to study the flame spread characteristics. The flame spread could be divided into initial oscillation stage, stable oscillation stage and burn-out stage. With the increase of the copper core diameter, the flame width and flame area increased firstly and then decreased. For wires with intermediate copper core diameters of 6 mm, 7 mm, 8 mm and 10 mm, the relationship between flame area and core diameter was established as A~dc, the total mass loss rate k with the copper core diameter dc followed as k~dc, and the combustion mass loss rate and dripping mass loss rate gradually equaled to each other at stable oscillation stage. By analyzing the temperature field during the process of flame spread, the temperature gradient was almost same for diameters from 3 mm to 10 mm, which demonstrated the radiation heat would be influenced by flame height. Combined with the increased flame spread, the dominant conduction heat transfer mechanism was built. When the diameter was 12 mm, the smaller conduction heat transfer, which illustrated the core material Cu played an cool effect on flame, thus the dominant heat transfer of Cu was changed from a heat source to a heat sink.