Generalized pyrolysis model for combustible solids

Abstract

This dissertation presents the derivation, numerical implementation, and verification/validation of a generalized model that can be used to simulate the pyrolysis, gasification, and burning of a wide range of solid fuels encountered in fires. The model can be applied to noncharring and charring solids, composites, intumescent coatings, and smolder in porous media. Care is taken to make the model as general as possible, allowing the user to determine the appropriate level of complexity to include in a simulation. The model considers a user-specified number of gas phase and condensed phase species, each having its own temperature-dependent thermophysical properties.Any number of heterogeneous (gas-solid) or homogeneous (solid-solid or gas-gas) reactions can be specified. Both in-depth radiation transfer through semi-transparent media and radiation transport across pores are considered. Volume change (surface regression or swelling/intumescence) is handled by allowing the size of grid points to change as dictated by mass conservation. All volatiles generated inside the solid escape to the ambient with no resistance to mass transfer unless a pressure solver is invoked; the resultant flow of volatiles is then calculated according to Darcy's law. A gas phase 2 convective-diffusive solver can be invoked to determine the composition of the volatiles.Oxidative pyrolysis is simulated by modeling diffusion of oxygen from the ambient into the pyrolyzing solid where it may participate in reactions. Consequently, the mass flux and composition of volatiles escaping from the solid can be calculated. To aid in determining the required input parameters, the model is coupled to a genetic algorithm that can be used to estimate the required input parameters from bench-scale fire tests or thermogravimetric analysis.

Interactions of Earth's atmospheric oxygen and fuel moisture in smouldering wildfires

“…This 1D model, developed in the open-source code Gpyro, is also used for this study. The details of Gpyro can be found in Lautenberger and Fernandez-Pello (2009). The smouldering model solves transient equations for Eq.…”

“…Gpyro adopts a fully implicit formulation is adopted for the solution of all equations (Lautenberger and Fernandez-Pello, 2009). The sample height during spread is equal to the sum of the heights of each cell, H t = N n=1 ∆z n , which depends on mass conservation and density.…”

Pyrolysis Characterization of a Lineal Low Density Polyethylene

“…A range of empirical formulations based on experimental data obtained from the cone calorimeter or furniture calorimeter tests, to semiempirical models [1][2][3] that consider transient heat conduction, to comprehensive models [4,5] based on advanced descriptions of the in-solid heat and mass transfer processes, have been developed. Comprehensive pyrolysis models adopt a material science perspective, and describe the heat-driven physical-chemical transformation of the virgin solid into solid, liquid and gaseous products.…”

“…This will add to the portfolio of validation exercises already in existence and help improve the use of computer models for predicting behaviour of fires, and thus highlight whether there is a need to further clarify if the real properties are directly usable as inputs for these kind of models [4,5].…”

“…Along with the computational pyrolysis model called 'Gpyro' (version 0.700 for windows) developed by Lautenberger at Berkeley University [5]. In Gpyro, the material is defined through a set of parameters that can be optimized by an evolutionary algorithm implemented within the computational model.…”