Experimental investigation and inverse modeling of the flammability behavior of cartoned plastic commodity

Abstract

This work focuses on developing a complementary experimental and modeling approach to investigate and predict the burning behavior of cartoned unexpanded plastic (CUP) standard commodity. Bench-scale flammability tests were designed for a unit cell of CUP commodity, which is comprised of an unexpanded polystyrene (PS) cup enclosed within a single-wall corrugated cardboard box (of 10.7cmx10.7cmx10.7cm dimensions). Combustion tests were conducted on CUP unit cells at multiple heat fluxes to measure mass loss, heat release rate, and smoke generation rate. The data show two distinct burning regimes: corrugated cardboard combustion with eventual transition to a cardboard-PS co-combustion mode. It was found that the critical transition condition was an important determining factor in the tests. Furthermore, the burning behavior of the CUP unit cell during cardboard-PS co-combustion remained invariant regardless of external heat flux. From these findings, a two-fuel combustion model was developed to effectively simulate the global burning behavior of a CUP unit cell. Model-effective parameters were calculated by optimizing the model to fit the experimental data. These parameters include the effective absorptivity/emissivity, flame heat flux, specific heat capacity, chemical heat of combustion, and the fuel ignition temperature. The present methodology, thus, provides fundamental insights into the burning behavior of CUP commodity, and a global pyrolysis model that can be used for CFD modeling of fires from this important standard commodity.