Role of particle diameter in the lower flammability limits of hybrid mixtures containing coal dust and methane gas

摘要

The lower explosion limit of a hybrid mixture is an important parameter for industrial safety, and can be used to design processes such that they are unable to sustain flame propagation within industrial equipment. The objective of this work is to use computational fluid dynamics to explore the role of particle diameter on hybrid mixture flammability limits for freely propagating laminar flames. Specifically, the lower flammability limits of coal dust with 10 and 33 pm particle diameters and of hybrid mixtures with methane gas are explored. Previous work by the author group demonstrated that Le Chatelier's mixing law can approximately delineate flammable mixtures for the smaller particle size when the particles are represented as a continuum. In the current work, both increasing the particle diameter and representing the particles discretely caused a slight widening of the flammability limits towards Bartknecht's curve. Narrowing of the flammability limits has been demonstrated in recent experimental closed-chamber investigations in the literature, but was not found for the freely propagating flames in this work.