Analysis of the explosion behaviour of wheat starch/pyrolysis gases hybrid mixtures through experimentation and CFD-DPM simulations

Abstract

As a result of their intrinsic compl5exity and their severe consequences, the study of hybrid mixture explosions requires the consideration of several additional factors and parameters than the study of gas-only and dust-only explosions. The main objective of this work is to perform an exhaustive analysis of the explosion severity of wheat starch/pyrolysis gases hybrid mixtures in the context of the 20-L Sphere Test and to determine how severe hybrid mixture explosions can be when compared to one phase explosions. Several experimental tests were performed at different concentrations of both phases and at fixed operating conditions of ignition delay time (tv) and nozzle geometry. CFD simulations from a previously-validated model were run alongside in order to complement the experimental findings and expand the understanding of the hybrid system as a whole, especially in terms of the development and interaction of the phases’ chemical reactions. The experimental and CFD data were analysed using severity maps and adapted stoichiometric parameters proposed in the literature. It was found that the explosion regimes proposed in the literature are not universally-applicable to all types of hybrid mixtures, given that, for wheat starch/pyrolysis gases hybrid mixtures, each regime could not be uniquely characterized and differences in the explosion behaviour were observed within the same regime. In contrast, it was found that analysing the data in terms of parameters that take into account the nature of the chemical reactions of the phases is a superior methodology given that it provides a more rigorous comparative basis for assessing the explosion severity of different types of combustible materials, including hybrid mixtures.