Deflagration velocity analysis by image velocimetry using brightness subtraction and pressure evaluation of blast wave in Hydrogen-Air mixtures

Detailed observations of hydrogen-air spherical deflagrations in open space were obtained using a combination of an image velocimetry and blast pressure measurements. Latex balloons of 0.15 and 1.4 m³ vapor clouds were ruptured and ignited at the center of the clouds. An image velocimetry using brightness subtraction was employed to obtain accurate time evolution records of flame propagation velocity. The maximum flame propagation velocity of about 100 m/s was observed in the 0.15 m³ of equivalence ratio 2.0 and in the 1.4 m³ cloud of equivalence ratio 3.0. The turbulent burning velocities were estimated to be several fold of the laminar burning velocities. It is observed that the propagating flame with the maximum velocity generates the signal of the maximum peak pressure of blast wave propagating with the sound velocity.