Ignition kinetics and burn rates of Al particles

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

This talk will present recent results describing ignition and combustion of aluminum particles in different environments. Ignition is defined as a process in which external heat sources are required to bring the particle temperature up to the point when the exothermic reaction becomes self-sustaining. As a rule, only a small fraction of metal is consumed during this process. Combustion follows up and comprises a self-sustaining oxidation resulting in the major consumption of metal fuel. To model aluminum ignition, heterogeneous oxidation producing a growing alumina layer on the particle surface needs to be described. The rate of this reaction is controlled by diffusion through the alumina layer. It is of critical importance that its diffusion resistance changes as a result of polymorphic phase transformations occurring in alumina upon its growth and upon temperature increase. Presence of different oxidizers, such as CO2 and H2O affects these transformations and respectively affects the rates of oxidation processes controlling ignition. Ensuing combustion reactions involve a combination of the vapor-phase and heterogeneous oxidation processes. It is found that the purely vapor phase flame becomes unsustainable as the particle size decreases to single microns. While a detailed model of the particle combustion is not available, the rates of combustion are measured for the micron-sized particles in air, N2/CO2 and N2/H2O mixtures. The measured burn times exceed substantially the commonly used "d-power" law predictions used in many practical calculations and based upon experiments with much coarser particles.

Original languageEnglish (US)
Title of host publicationFall Meeting of the Eastern States Section of the Combustion Institute 2009
PublisherCombustion Institute
Pages902-914
Number of pages13
ISBN (Electronic)9781615676682
StatePublished - Jan 1 2009
EventFall Meeting of the Eastern States Section of the Combustion Institute 2009 - College Park, United States
Duration: Oct 18 2009Oct 21 2009

Publication series

NameFall Meeting of the Eastern States Section of the Combustion Institute 2009

Other

OtherFall Meeting of the Eastern States Section of the Combustion Institute 2009
CountryUnited States
CityCollege Park
Period10/18/0910/21/09

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Mechanical Engineering
  • Physical and Theoretical Chemistry

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