Experimental and numerical study of polyoxymethylene (Aldrich) combustion in counterflow

The burning behavior of polyoxymethylene in the counterflow of oxidizing air has been studied experimentally and numerically. Measurements have been performed using a specially designed burner. The temperature profiles were measured in gas phases by a microthermocouple technique. The burning surface temperature and the mass burning rates of solid fuel were determined. The chemical structure of counterflow flame was investigated using the mass spectrometric sampling by microprobe. The composition of the gas sample was analyzed on-line with a mass spectrometric complex (Hiden HPR 60), based on a quadrupole mass spectrometer. The species CH2O, CO, CO2, H2O, O-2, N-2 were identified and their concentration profiles were measured. The composition of products and kinetic parameters of POM thermal degradation have been determined by mass spectrometry and thermogravimetric analysis. Quasi one-dimensionality of considered diffusion flame has been established experimentally, which allows analysis of flame parameters in relation to the only coordinate normal to the solid fuel's burning surface and substantially simplifies the theoretical description. Predictions have been performed by a coupled model describing feedback heat and mass transfer between gas-phase flame and polymeric solid fuel. A two-dimensional elliptic equation in axisymmetric formulation has been employed to simulate heat transfer in solid fuel, and a set of one-dimensional hyperbolic equations has been used to determine the solid-togas conversion degree of the pyrolysis reaction. Gas-phase formulation is presented by one-dimensional conservation equations for multi-component flow with a detailed kinetic mechanism of combustion. Numerical results showed good agreement with the measurements for temperature and species concentration profiles, as well as for the mass burning rate and the surface temperature of solid fuel. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.