Interpretation on heat feedback mechanism and mass burning rate in two unequal pool fires with wind flow

This paper aims to elucidate the heat feedback mechanism and burning characteristics of unequal n-heptane fires with wind flow. A total of 98 experimental cases were performed, involving a single pool and two unequal tandem pools (side length, D: 10 cm and 16 cm) with six pool spacings (S: 10-140 cm), across seven wind speeds (U: 0-5.0 m/s). The flame geometry, fuel mass, heat feedback components (radiation, conduction, and derived convection), and airflow were systematically recorded. The results indicate that the mass burning rate ( (center dot)m) can be categorized into three phases: rapid growth, decay, and slow growth, with increasing U. Due to the blockage effect and constraint air entrainment, the critical wind speed at which m(center dot) of the downstream pool attenuates is larger than that of the upstream pool. Concerning the blockage effect, it is observed that the airflow bypassed the upstream flame, reaching the downstream fire instead of passing through the upstream flame. The intensity of the blockage effect increases with the size of the upstream pool, while it decreases with wind speed (U) or pool spacing (S). With increasing S, the primary mechanisms governing fire interactions shift from constraint air entrainment to enhanced heat feedback, ultimately to blockage effect. The heat feedback fractions of the upstream pool are close to that of a single pool, indicating that the interaction effect on the upstream pool can be ignored at large spacings. The dominant heat feedback of the downstream pool changes from radiation to convection with increasing U. Finally, a model for the mass burning flux is established based on stagnant layer theory.