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.
Using cone calorimeter data for the prediction of fire hazard
The Cone Calorimeter is an apparatus capable of providing quantitative data which are relevant to the response of combustible materials to fire conditions. Several fire models have been developed to use such data to predict various aspects of fire behaviour. This paper considers how these data are used to model upward spread of flame on flat vertical surfaces and proposes that a modified test procedure may be more appropriate.
Numerical model of upward flame spread on practical wall materials
Abstract The focus of this paper is the development of a thermal, finite difference numerical model to describe one-dimensional upward flame spread on practical wall materials. Practical materials include composite materials and those that char, in addition to clean burning, homogeneous materials. A set of equations used in the model is developed and the methods for obtaining necessary “fire properties” are discussed. Some of the particular features of the model include the use of a correlation for flame heat feedback and the use of an experimentally measured mass loss rate to incorporate the burning characteristics of practical materials. A comparison of the numerical predictions with the experimental results for flame heights and temperatures are shown for Douglas fir particle board. The model correctly predicts trends but underpredicts the flame heights and pyrolysis height in the cases tested. Two additional cases are shown for materials for which experimentally measured heat release rate data are used in place of the mass loss rate data. The flame and pyrolysis height predictions are in much better agreement for these cases. Further efforts to obtain material property data that is appropriate for flame spread modeling is indicated by this work.