Computational Modeling of the Condensed Phase Aerosol Based Fire Extinguisher

Abstract

The computational modeling of a novel condensed phase aerosol based fire extinguisher is considered in this study to assess its operational details and performance. A solid propellant is present inside the canister which is ignited using piezoelectric actuators producing hot fire extinguishing gases. The cooling of these hot gases is facilitated by a matrix of chemically active cooling pellets placed along the canister which condenses hot gas and discharges solid aerosol particulates. The initial experimental investigation of the extinguisher carried out at the premises of the industrial partner showed that improper cooling of the hot gases by the pellets can lead to high temperature of the effluent gases and sparks at the exit. This provided the basis for exploring computational modeling to develop a better understanding of the physics of the extinguisher performance and to develop improved experimental procedures on the basis of the results from a computational fluid dynamics model. Initial modeling efforts centered on the finite volume solution of the Euler equations modified to incorporate the essential physics of the problem such as mass flow from the pellets and the heat transfer. On the basis of the computed results from this simplified model, a multi-component combustion gas flow inside the extinguisher is computed by solving high fidelity three-dimensional Navier-Stokes equations. While detailed chemical kinetics are not accounted for in the computation, initial experimental estimates of these processes are used in the simulations to account for the effects on dynamics of the process. The computed results show how improper cooling by the pellet region may lead to hot spots in the extinguisher. These results will be used to improve the experimental design.