Numerical analysis of the hydrogen combustion in a double cavity Trapped Vortex Combustor

Abstract

In the present study numerical simulations are performed to characterize the hydrogen combustion in a double cavity Trapped-Vortex Combustor (TVC). This combustor utilizes two trapped vortices in two cavities to improve flame stability and to provide low pressure drop. Good performances characteristics are obtained injecting a sufficient amount of fuel and air directly into the first cavity. The two cavities are obtained mounting three axisymmetric disks on a tube passing through their centrelines. The geometry and the configuration of this TVC are very similar to that studied by Hsu et al. 1995 and refer to a facility in the Casaccia (Rome) research center of the Italian National Agency for New Technologies, Energy and the Environment (ENEA). The numerical studies were made using a commercial 3-D CFD code. A turbulent steady-state model with finite rate chemistry and second-order accuracy is used to simulate the TVC flowfields. The turbulence-chemistry interaction is provided by the Eddy Dissipation Concept (EDC). This model allows the inclusion of detailed chemical mechanisms in turbulent flows. In the present analysis of reacting flow the chemical kinetic model needed to simulate the hydrogen combustion consists of 37 reactions involving 14 species. In order to evaluate the thermo fluid dynamics in the TVC a parametric study has been conducted. Variable parameters include the length of the first cavity, the power, the equivalence ratio, the humidity of the air and the inlet air composition and temperature. Results from the analysis provide valuable information on the flow and flame structure and on the combustion process demonstrating the versatility and efficiency of burning hydrogen in a double cavity TVC.