OPTICAL OBSERVATION OF HYDROGEN JET STRUCTURE AND FLAME PROPAGATION IN TURBULENT HYDROGEN JETS

摘要

Experiments on the structure of high momentum hydrogen jets, their ignition and flame propagation regimes have been carried out as a part of hydrogen safety programs. The structure of a jet released from a bulk vessel at pressures of 5 - 260 bar and nozzle diameters 0.16 - 21 mm was studied in order to measure axial and radial distribution of flow velocity and hydrogen concentration in the jet. The jet structure, hydrogen concentration and flow velocity profiles for horizontal and vertical jets were measured using an ultrasonic anemometer, Background Oriented Schlieren (BOS) technique and sampling probes. The laser PIV technique has been used to evaluate the distribution of the flow velocity and the level of turbulence along and across the jet. Because of the nonuniformity of flow velocity and hydrogen concentration, the flame propagation regimes become very sensitive to the position of the ignition source in the jet. Experiments on flame propagation regimes in a turbulent hydrogen jet have been performed using high-speed photography combined with a Background Oriented Schlieren technique and normal video. It was found that depending on flow velocity, local hydrogen concentration and level of turbulence the flame propagates only downstream or in both directions relatively to the main flow.