Prediction of thermal radiation received by vertical targets based on two-dimensional flame shape from rectangular n-heptane pool fires with different aspect ratios

Abstract

Regarded as a cause of energy dissipation, thermal radiation plays an important role in combustion systems. This work aims to study the flame radiation property of rectangular energy sources. Total nine n-heptane pools with the same width of 8 cm but different aspect ratios of length to width (n = l/w) from 1 to 14 were used as fire sources in open space. The mass loss rate (MLR), flame shape and radiant fluxes received by external vertical targets were analyzed. The MLR per unit length (m˙l) and flame height show three trends of decreasing slopes with increasing n, the boundary are 3 and 10 and the fuel shape becomes linear when n ≥ 10. A new method of two-dimensional description is introduced to determine the mean flame height distribution along the pool length, a piecewise function consisting of three stages is proposed. Assuming the radiative fraction of heptane is 0.3, the radiant fluxes to external targets are calculated by applying a modified weighted multi-point source (WMP) model, which extends the weight to a two-dimensional flame plane. The proposed model is validated by comparing with the other models and using the experimental data in this work.