Pressure-dependent combustion dynamics of corrugated cartons in aircraft cargo compartments: numerical modeling, HRR validation, and detector-layout optimization

Fires in aircraft cargo compartments develop under reduced ambient pressure and oxygen partial pressure, yet pressure-dependent correlations and independent verification routes for corrugated-carton fires remain limited. A full-scale Fire Dynamics Simulator (FDS) model of the Boeing 707 forward cargo compartment was first assessed against FAA full-scale data and Hughes Center simulations at atmospheric pressure and was then applied to 16 predictive carton-fire cases combining four pressures (61–101 kPa) and four fuel loads. Reducing pressure decreased the peak burning rate and prolonged combustion. The normalized peak burning rate followed a de Ris-type power law, with the fitted exponent increasing from 0.12 to 0.57 as the fuel load increased. At comparable burning rates, the relative flame temperature increased as pressure decreased, although the pressure-dependent stratification weakened for larger fuel loads. The effective heat of combustion increased slightly from 10.96 to 11.32 kJ/g over 61–101 kPa. An oxygen-consumption-based post-processing estimator yielded integrated total heat release values within 5% of the FDS results, supporting the consistency of the predicted energy-release trends across the investigated pressure conditions. Under the fixed-yield species framework, the calculated fractional effective dose increased approximately linearly with pressure, providing a quantitative basis for comparing smoke-toxicity trends among the investigated cases. Among four candidate detector layouts, the linear ceiling layout along the ventilation openings provided the earliest and most spatially uniform response. These results provide scenario-specific scaling evidence and design insight for low-pressure cargo-fire assessment.