Numerical study of horizontal flame spread over PMMA surface in still air

Flame spread over the horizontal surface of polymethyl methacrylate (PMMA) has been studied numerically by a coupled model of heat and mass transfer describing the feedback between gas-phase flame and solid fuel. Mathematical formulation has been defined by non-stationary two-dimensional elliptic equations applied both for gas phase and solid fuel. The computational procedure is based on modification of the OpenFOAM open-source code. Results of predictions have been compared with the data of comprehensive experimental investigation of the thermal and chemical structure of PMMA flame. Good agreement has been obtained for the detailed gas-phase and the solid fuel temperature and species concentrations profiles, as well as for the macroscopic parameters: the flame spread rate, the total mass regression rate and the length of the pyrolysis zone. Based on the analysis of thermal degradation of methylmethacrylate in inert surrounding, the concept of reduced molar weight for gaseous products of PMMA pyrolysis has been proposed, which provided better agreement for fuel distribution in the gas phase.