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The burning of two rectangular fires is a typical phenomenon that occurs in thermal disaster scenes (including industrial fires and forest fires). To realize rapid safety monitoring, controlling, and cooling and even prevent thermal disaster propagation, the corresponding analysis of the burning behaviors of two rectangular fires is necessary. This work experimentally investigates the flame interaction (flame merging and flame height), gas temperature distribution, and radiative heat flux from two rectangular propane burners by varying total heat release rate (80-360 kW) and burner spacing (0-1.28 m). The results show that the dominant mechanism of air entrainment rate changes from spacing to heat release rate with increasing spacing, making two flames from fully merging to non-merging. A method for predicting the flame height is proposed in terms of air entrainment mechanism, which is proportional to the 2/3 power of the group dimensionless parameter (). With the decrease of spacing, gas temperature in the additional region is distributed in an inverted U-shaped manner in the horizontal direction, reaching its extreme value at the center of the two burners. The vertical gas temperature can be employed to estimate the critical flame merging, which depends on the dimensionless parameters of and S/W. When S/W< 51 , two flames are merged; otherwise, the two flames are separated. For two rectangular fires with different burner spacings, the radiative heat flux received by the external targets is accurately predicted using the Richardson Number (Rix, ). The proposed models are verified with the literature-based data and correlations.
Li et al. (2024) studied this question.