2024 Volume 24 Issue 1 Pages 17-22
This paper discusses the effects of gravity on the combustion-wave propagation through a dust cloud. Two models, continuum and point-source models, are developed by extending the models of Goroshin et al. to consider gravity effects. The continuum model treats a particle cloud as a continuum phase, while the point-source model considers heat generation from individual particles; hence, the latter model better represents the actual phenomenon. Both the models have three dimensionless parameters: dimensionless reaction time, 𝜏c, dimensionless ignition temperature, 𝜃ign, and dimensionless terminal velocity of particles, 𝑈g. It is first confirmed that the continuum model is a good approximation of the point-source model when 𝜏c ≳1, whereas their differences are apparent when 𝜏c ≲1. Evaluating the values of 𝜏c for the propagation through a cloud of aluminum particles shows that 𝜏c is less than unity in conditions of interest. The point-source model is therefore applied to assessing the gravity effect, revealing that the extinction condition (minimum explosive concentration, MEC) is significantly influenced by gravity even for particles as small as 10 μm.
