Spontaneous ignition of high-pressure hydrogen during its sudden release into hydrogen/air mixtures.

Abstract This paper investigates the effects of hydrogen additions on spontaneous ignition of high-pressure hydrogen released into hydrogen-air mixture. Hydrogen and air are premixed with different volume concentrations (0%, 5%, 10%, 15% and 20% H 2) in the tube before high-pressure hydrogen is suddenly released. Pressure transducers are employed to detect the shock waves, estimate the mean shock wave speed and record the shock wave overpressure. Light sensors are used to determine the occurrence of high-pressure hydrogen spontaneous ignition in the tube. A high-speed camera is used to capture the flame propagation behavior outside the tube. It is found that only 5% hydrogen addition could decrease the minimum storage pressure required for spontaneous ignition from 4.37 MPa to 2.78 MPa significantly. When 10% or 15% hydrogen is added to the air, the minimum storage pressure decreases to 2.81 MPa and 1.85 MPa, respectively. When hydrogen addition increases to 20%, the spontaneous ignition even takes place at burst pressure as low as 1.79 MPa inside the straight tube. Highlights • Effect of hydrogen doping to air on the spontaneous ignition occurrence is investigated experimentally. • Minimum storage pressure required for spontaneous ignition decreases with the increasing of hydrogen addition. • 5%, 10% and 15% hydrogen decrease minimum storage pressure from 4.37 MPa to 2.78, 2.81 and 1.85 MPa, respectively. • Spontaneous ignition takes place at storage pressure as low as 1.79 MPa when 20% hydrogen is added. [ABSTRACT FROM AUTHOR]