Interaction of Hydrogen Jets with Hot Surfaces of Various Sizes and Temperatures

The formation of hydrogen jets from pressurized sources and ignition has been studied by many projects, also when hitting hot devices. In the paper presented at the conference 2 years ago, the ignition was caused by glow plug a “point like source” at various temperatures, distances of igniter and source and source pressures. In continuation of that work, ignition now occurred by 1 or 3 platelets of size 45 x 18 mm at a temperatures of 1223 K. When hitting these hot platelets, the resulting flame explosions and flame jets show interesting characteristics, in contrast to the point like ignition, where the explosions drifts downstream with the jet. Parameters of the experiments vary in initial pressure of the tubular source (10, 20 and 40 MPa), distance between the nozzle and the hot surface (3, 5 and 7 m) and temperature of the hot surface (1223 K). The initial explosions stabilize already at the stagnation point or the wake of the hot platelets. Furthermore, flames propagate upstream and downstream, depending on the pressure of the hydrogen reservoir and the distance. The achieved flame velocities vary strongly from 30 to 240 m/s. With all investigated hydrogen pressures strong reactions v > 40 m/s occur at platelet distances of 3 and 5 m. The higher values are mainly achieved with jets with 40 MPa pressure at 3 m distance. In these cases the initial explosion contours show irregular shapes. Various effects are found like explosion separation, further independently initiated explosions and two parallel flame jets upstream as well as downstream.