Numerical simulations of the critical diameter and flame stability for hydrogen flames

This study focuses on development and validation of a CFD model to simulate the critical nozzle diameter and stability limits for hydrogen non-premixed flames. The critical diameter represents the minimum nozzle size through which a flame will remain stable at all driving pressures. Flames will not blow-out at diameters equal to or greater than the critical diameter. Accurate simulation of this parameter is important to assess performance of thermally activated pressure relief devices (TPRD) during blowdown from a storage tank. Flame stability is considered for diameters and overpressures ranging from 0.1 mm to 2 mm and from 0.06 MPa to 20 MPa, respectively. The impact of turbulent Schmidt number Sct, on predicted critical diameter is discussed. The model was applied for lower pressures (0.001-0.005 MPa) to understand the pressure at which the flame becomes attached. Simulations of a safer approach to TPRD design are discussed.