Turbulent flame propagation limits of polymethylmethacrylate particle cloud–ammonia–air co-combustion

Abstract

Ammonia is a highly promising energy carrier for achieving a carbon-neutral society. The co-combustion of solid particle clouds–ammonia, in particular, is considered an efficient and feasible method of reducing carbon dioxide emissions. Understanding turbulent flame stabilization and extinguishment processes during the two-phase hybrid-mixture co-combustion of solid particle clouds–ammonia is essential for the co-combustion technology to be used in combustors. To the best of our knowledge, this is the first study to describe the turbulent flame propagation limits and associated mechanism on the co-combustion of solid particle clouds–ammonia–air. Turbulent flame propagation experiments on silica particle clouds–ammonia–air mixing combustion and polymethylmethacrylate (PMMA) particle cloud–ammonia–air co-combustion were conducted in this work using a novel fan-stirred constant-volume vessel to clarify the turbulent flame propagation limits and associate mechanism of solid particle cloud–ammonia–air co-combustion. Results showed that adding inert silica particles contracted the turbulent flame propagation limits of premixed ammonia–air mixtures. However, adding PMMA particles expanded and then contracted the turbulent flame propagation limits of a premixed ammonia–air mixture as the ammonia equivalence ratio increased from lean to rich. In the solid particle cloud–ammonia–air co-combustion, reactive particles induce two types of effects on the turbulent flame propagation limits of premixed ammonia–air mixtures: The local equivalence ratio increment effect is caused by adding volatile matter from preheated particles in the preheat zone of the flame front, and the heat sink negative effect is induced by the unburned particles.