Concentration fluctuation and ignition characteristics during atmospheric diffusion of hydrogen spouted from high pressure storage

• Published in: International journal of hydrogen energy Vol. 42; no. 22; pp. 15426 - 15434
• Main Authors: Takeno, Keiji, Okabayashi, Kazuki, Kouchi, Akinori, Misaka, Naoyuki, Hashiguchi, Kazuaki
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2017
• Subjects: Concentration fluctuation; Diffusion; Hydrogen jet; Light-up boundary; Probability of ignition; Light-up boundary; Diffusion; Hydrogen jet; Concentration fluctuation; Probability of ignition
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2017.04.062

An experimental study has been performed on the concentration fluctuation during atmospheric diffusion of hydrogen released horizontally from 20 or 40 MPa pressurized storage. The aperture of nozzle is selected to a pinhole of d = 0.2 or 0.53 mm diameter. The concentration fluctuation with time was measured with needle sampling and fast-response analyzing device, and the probability density function (pdf) of hydrogen concentration was approximated with a normal distribution function and the time-averaged concentration along the axis of jet could be expressed with C = α/(x/θ) where α is proportional constant, x is the distance from nozzle outlet, and θ is the nozzle diameter corrected by the square root of the ratio of atmospheric to stagnation pressure in nozzle. Furthermore, the spectrum of concentration fluctuation was analyzed to decay with −5/3 power of wave number except in the vicinity of nozzle outlet, and the typical characteristic spatial scales of the concentration fluctuation at the beginning of the inertial-convective subrange were about 100 and 200 mm for d = 0.2 and 0.53 mm, respectively. The probability of ignition by using an electric spark and the behavior of flame propagation were examined, and for C < 10%, the flame was once formed and extinguished after a short travel of approximately 100 or 200 mm, which may correspond to the characteristic spatial scale of eddy or inhomogeneous hydrogen distribution. •Discharge experiments of hydrogen pressurized up to 20 or 40 MPa have been conducted.•Fluctuation up to 200 Hz of local hydrogen concentration with time was measured.•Power spectrum of concentration fluctuation decayed with −5/3 power of wave number.•Typical spatial scales of fluctuation were almost proportional to nozzle diameter.•Flame propagation distances were limited within the concentration fluctuation scale.