CFD Simulation of Deflagration to Detonation Transition for Nuclear Safety

The present work aims to develop an efficient methodology for evaluating the Deflagration to Detonation Transition (DDT) in accidental scenarios from inherent hydrogen risk in water-cooled NPPs (Nuclear Power Plants). The physical problem is flame acceleration through a confined geometry congested with periodic obstacles, up to formation of a travelling shock wave. The problem was modeled by the Reynolds-averaged Navier-Stokes equations (RANS) with the standard k-ε turbulence model. There are two main combustion models: EDC (Eddy Dissipation Concept) whose equations are the transport equations for chemical species involved; and BVM (Burning Velocity Model) a transport equation for reaction progress (one scalar), to be used with three available turbulent flame speed correlations (Peters, Mueller and Zimont), and a new formulation based on Piston Action of the expanding burnt gas. The present work compared characteristics of these combustion models regarding flame acceleration in the midsize mc043 experiment, in order to apply the proposed combustion model in large scale DDT simulations. Experiment mc043 is consists of igniting a 12-meter long tube with 70 annular obstacles, filled with lean hydrogen-air mixture. The numerical results revealed that the proposed model is superior to BVM model correlations in predicting shock wave formation, and may provide a computationally more efficient option to the EDC model.