Експериментальні дослідження та фізико-математичне моделювання впливу неоднорідності температурного поля по вуглецевій частинці на характеристики її займання, горіння і згасання

Editorial Board PCSS Journal; S.G. Orlovska

doi:10.15330/pcss.27.1.179-187

Authors

S.G. Orlovska Odessa I.I. Mechnikov National University, Odessa, Ukraine

DOI:

https://doi.org/10.15330/pcss.27.1.179-187

Keywords:

carbon particles, ignition, combustion, extinction, temperature gradient, internal thermal conductivity, induction period, burning time

Abstract

This work is devoted to experimental studies and physico-mathematical modeling of high-temperature heat and mass transfer and chemical transformation of carbon particles, accounting for internal thermal conductivity. The relevance of the study is driven by the need to improve the accuracy of predicting the ignition, combustion, and extinction characteristics of solid fuels in thermotechnical processes. Most theoretical approaches utilize an isothermal particle approximation, which can lead to errors in determining the induction period and burnout time, particularly for particles in the submillimeter and millimeter range.

A non-isothermal model is proposed, incorporating internal thermal conductivity within the particle, oxidation reactions, and heat exchange via convection and radiation. Numerical calculations were performed for a diameter range of 100–1000 μm, with an analysis of temperature fields and gradients during the ignition and extinction stages. It is shown that as the particle diameter increases, the temperature differential between the surface and the center grows, while the radial temperature gradient decreases due to the spatial expansion of the temperature field and the increase in transient thermal time. Experimental studies with millimeter-sized particles revealed significant temperature gradients at the ignition stage and identified the moment of ignition by the maximum value of the time derivative of the particle's surface temperature.

A comparison of calculations using isothermal and non-isothermal models demonstrated a systematic overestimation of ignition and burning time when internal thermal conductivity is neglected. It is shown that in the range of small particle sizes, failing to account for internal thermal conductivity leads to a predicted absence of ignition. The results obtained confirm the necessity of a non-isothermal description for the correct prediction of combustion characteristics for carbon particles larger than 200 μm.

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