Experimental and theoretical study of metal combustion in oxygen flows

TL;DR

This study combines experimental and theoretical approaches to understand how oxygen flow speed and pressure influence the combustion of iron and steel, identifying key stages and developing a model for dynamic combustion.

Contribution

It provides a new analytical model for dynamic metal combustion in oxygen flows, linking flow conditions to combustion progression.

Findings

Identified three main stages of metal combustion: induction, static, and dynamic.

Developed a model predicting the metal burn fraction and interface speed based on flow parameters.

Experimental results agree with theoretical predictions, validating the model.

Abstract

The effects of oxygen flow speed and pressure on the iron and mild steel combustion are investigated experimentally and theoretically. The studied specimens are vertical cylindrical rods subjected to an axial oxygen flow and ignited at the upper end by laser irradiation. Three main stages of the combustion process have been identified experimentally: (1) Induction period, during which the rod is heated until an intensive metal oxidation begins at its upper end; (2) Static combustion, during which a laminar liquid "cap" slowly grows on the upper rod end; and, after the liquid cap detachment from the sample, (3) Dynamic combustion, which is characterized by a rapid metal consumption and turbulent liquid motions. An analytical description of these stages is given. In particular, a model of the dynamic combustion is constructed based on the turbulent oxygen transport through the liquid metal-oxide flow. This model yields a simple expression for the fraction of metal burned in the process, and allows one to calculate the normal propagation speed of the solid metal--liquid interface as a function of the oxygen flow speed and pressure. A comparison of the theory with the experimental results is made.