Experimental study on burning rate and radiative heat transfer of two rectangular fires with different aspect ratios in open space

• Experiments studied burning rate and radiation of two unequal rectangular fires. • A burning rate increment prediction model was developed. • An optimized multi-point source method was proposed to predict the radiation. Combustible liquid fuels can form unequal multi-pool fires upon leakage or container breach, characterized by intense burning and high heat transfer. Understanding the burning rate and radiative heat transfer mechanisms of such fires and developing predictive models are crucial for enhancing thermal management in the chemical industry. This study used two unequal rectangular pool fires (long-side ratios 1:1 to 1:4) with nearest long-edge spacings of 0–100 cm to mimic related asymmetric scenarios. Results showed that the flame tilt angle exhibited a non-monotonic trend, increasing initially and then decreasing as the pool spacing increased. Compared with the larger scale pool, the smaller scale pool had a weaker air entrainment capacity, leading to more pronounced changes in flame tilt angle under the influence of negative pressure between two fire sources. The burning rate of two pools demonstrated a parabolic trend with respect to the dimensionless spacing ( S / D ), peaking at S / D = 2. By introducing burning rate ratios under different flame merging states, a burning rate increment prediction model was developed. Simultaneously, it was observed that the radiative heat flux presented a rising-then-falling trend along the vertical height. To simplify computational complexity, an optimized multi-point source method was proposed to predict the external radiation. This method modeled the continuous and intermittent flames as a cuboid and a triangular prism, respectively. The total quantity of point sources was determined by discretizing the flame length at intervals of pool width. The point source numbers for continuous and intermittent flames were calculated via volume proportions.