NUMERICAL SIMULATION OF FIRE SPREAD ON POLYURETHANE FOAM SLABS | NIST
Computational Fluid Dynamics (CFD) models are used extensively by fire protection engineers for performance based design and forensic analysis. The equations of motion describing the gas phase are relatively well known and the approximations in the various gas phase sub-models have been extensively studied. However, coupling of the gas phase and the condensed phase to describe flame spread over a burning solid, has proven to be difficult to model. This is due to a lack of understanding of the underlying physical phenomena that take place during the decomposition of the solid as well as poor characterization of the fundamental material properties that control the burning process. The overall goal of this project is to improve the capability of the fire models to predict flame spread over materials that typically burn in a compartment fire. In this paper, we attempt to simulate fire growth and spread on 10 cm thick slabs of polyurethane foam. A multi-layered, multi-material model was developed to simulate flame spread, and material properties were obtained from various small scale experiments. Model predictions were compared with large scale experiments on polyurethane foam slabs, ignited on one edge. Results indicate that the model is capable of qualitatively predicting the observed trends in heat release rate, flame spread rate and heat fluxes measured in the experiments. This report will describe the progress that has been made to date on modeling fire growth and spread on polyurethane foam slabs and the comparison of these results with experimental data.
Application of genetic algorithms and thermogravimetry to determine the kinetics of polyurethane foam in smoldering combustion
In this work, the kinetic parameters governing the thermal and oxidative degradation of flexible polyurethane foam are determined using thermogravimetric data and a genetic algorithm. These kinetic parameters are needed in the theoretical modeling of the foam's smoldering behavior. Experimental thermogravimetric mass-loss data are used to explore the kinetics of polyurethane foam and to propose a mechanism consisting of five reactions. A lumped model of solid mass loss based on Arrhenius-type reaction rates and the five-step mechanism is developed to predict the polyurethane thermal degradation. The predictions are compared to the thermogravimetric measurements, and using a genetic algorithm, the method finds the kinetic and stoichiometric parameters that provide the best agreement between the lumped model and the experiments. To date, no study has attempted to describe both forward and opposed smolder-propagation with the same kinetic mechanism. Thus, in order to verify that the polyurethane kinetics determined from thermogravimetric experiments can be used to describe the reactions involved in polyurethane smoldering combustion, the five-step mechanism and its kinetic parameters are incorporated into a simple species model of smoldering combustion. It is shown that the species model agrees with experimental observations and that it captures phenomenologically the spatial distribution of the different species and the reactions in the vicinity of the front, for both forward and opposed propagation. The results indicate that the kinetic scheme proposed here is the first one to describe smoldering combustion of polyurethane in both propagation modes.
Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 ? 1 Rib Cotton Knitted Fabrics
This study investigates the impact of yarn count and stitch length of 100% cotton knitted fabrics. 1 × 1 ribs structured fabrics were used in this research work. The stitch length 2.50 mm, 2.52 mm, 2.60 mm, 2.70 mm, 2.80 mm and 2.96 mm were used of the yarn count of 26Ne, 28Ne and 36Ne. The areal densities of the grey fabrics were in various amounts. The impacts of yarn count and stitch length were measured concerning pilling resistance, abrasion resistance, and shrinkage and tightness factor. The result showed that the fabric pilling grade decreased while number of cycle increased. Abrasion resistance decreased but length wise shrinkage increased despite the fact that the stitch length increased. The results also exposed that the tightness factor of the fabric increased with the increase of the stitch length in both dyeing and washing state and finished state compared to grey state for the yarn count 26Ne and homogeneous result not found for yarn count 28Ne and 36 Ne. Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 × 1 Rib Cotton Knitted Fabrics