Scaling analysis of regime transitions during transient gasification of a non-charring solid fuel

This study introduces a novel scaling analysis to investigate the transient solid-phase gasification of horizontal clear poly(methyl methacrylate) (PMMA) slabs under both ambient and oxygen-depleted conditions. Small samples were exposed to controlled external radiant heating in normal and nitrogen-diluted atmospheres to simulate low-oxygen fire environments. The energy-based scaling framework removes variability in characteristic timescales and response amplitudes, standardising the results and enabling consistent comparisons across oxygen levels and heat fluxes. It reveals new relationships between governing parameters, clarifies the role of competing mechanisms, and facilitates identification of transitions between heat-transfer–limited and kinetically controlled regimes. Scaling metrics provide predictive tools to discriminate between regimes, quantify energy use, and assess the role of boundary layer dynamics in mass transfer efficiency. Results highlight critical mechanisms: oxygen acts as both a reactant and a catalyst at the onset of gasification, reducing the energy required for decomposition, while external heat flux dominates regime control, with a threshold near 20 kW·m -2 separating flux-dependent from flux-independent behaviour. This framework simplifies modelling and improves CFD predictive capability by describing gasification through energy thresholds rather than time scales.