An experimental investigation of detonation limits in hydrogen–oxygen–argon mixtures

Abstract

The present paper reports the results of an experimental study of detonation limits for H2/O2/Ar mixtures. Two stoichiometric mixtures (2H2 + O2 + 3Ar and 2H2 + O2) in three different diameter round tubes (D = 1.8, 4.6 and 10.9 mm) were tested. The choice of the mixture represents those considered as "stable" with a regular cellular pattern and "unstable" with an irregular cellular pattern. Detonation velocity was measured by ionization probes spaced at regular intervals along the small tubes. Consistent with previous findings, the present results show that well within the limits the detonation wave in hydrogen mixtures propagates at a steady velocity close to the theoretical Chapman-Jouguet (CJ) value. With decreasing initial pressure, the velocity deficit increases. It is found that the detonation velocity decreases with decreasing tube diameter, which is a result of the wall boundary layer effect being more prominent for smaller tubes. At the limiting pressure, the steady velocity deficit for both tested mixtures in three different diameter tubes is about 15−18%. Velocity deficits were also estimated theoretically using the Fay model. For the stable mixture good agreement is found between the theoretical prediction and the experimental result of detonation velocity. For the unstable mixture, however, the theoretical prediction deviates from the experimental measurement. The latter thus suggests that, apart from losses due to the flow divergence caused by the boundary layer effect, instabilities are also significant for the detonation propagation and failure in unstable mixtures. Lastly, at the limits, the value of D/λ is found to agree well with that for the onset of single-headed spin detonation. Thus, it can be concluded that the single-headed spin criterion can also be used for defining the detonation limits for hydrogen mixtures.

Dynamics of hydrogen–oxygen–argon cellular detonations with a constant mean lateral strain rate

“…These non-ideal factors include lateral mass divergence, unsteadiness, and momentum and heat losses [1]. Extensive efforts have been made to quantitatively compare the experimentally measured velocity deficits and propagation limits with the theoretical predictions made by relatively simple models, which build up on the classical one-dimensional (1D) Zeldovich-von Neumann-Doering (ZND) model [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The multi-dimensional transient cellular structures, consisting of an intricate ensemble of interacting triple points, shear layers, and transverse waves, of the real gaseous detonations, however, greatly complicate these attempts.…”

“…This question has also been attempted in the past by investigating detonation propagation in narrow tubes [8,9,[11][12][13][14][15] and tubes with porous walls [18,19]. The mean propagation velocites of detonations under varied initial pressures as well as the propagation limits were experimentally determined for various mixtures.…”

“…Firstly, there exist limitations in the unrealistic assumption of uniform mass divergence, i.e., uniform curvature, for detonations in narrow and porous tubes, as Chinnayya et al [20] and Mazaheri et al [21] have numerically demonstrated that a curved detonation front with mass divergence due to wall boundary layers or permeability is not expected to have a unique curvature. Moreover, Fay-type models [8,[12][13][14][15] require the empirical inputs of a specifically defined value of pressure ratio , and a particular length scale for modelling the flow divergence rate, whose impact on the predictions has not been evaluated. All these factors thus potentially diminish the values of the comparisons in relevant works.…”

Simulation of Hydrogen Fuel Combustion in Neon-oxygen Circulated Compression Ignition Engine

“…However, the ignition delay is too long, and the ignition that occurred after TDC is not stable. The rapid increase in temperature and pressure during ignition indicates that the explosion happens during the expansion stroke which also indicates detonation [23][24] as observed from the in-cylinder pressure increasing rate in Figure 5. The incylinder pressure increasing rate of combustion in the ambient temperature of 310K has exceeded the knock boundary.…”

Estimation of the energy of detonation initiation in a hydrogen-oxygen mixture by a high-velocity projectile

“…Despite 70 years of research, the issues related to the combustion and detonation initiation in supersonic flows or by a high-velocity projectile, as well as the structure, limiting regimes, and critical energy of detonation initiation are still receiving considerable attention. For example, in work [14] the detonation limits of stoichiometric mixtures of H 2 /O 2 /Ar and H 2 /O 2 were experimentally studied. The initiation and stabilization of three-dimensional oblique detonation waves by spheres with velocities higher than the Chapman−Jouguet velocity in stoichiometric mixtures of oxygen with acetylene, ethylene or hydrogen diluted with argon were experimentally studied in [15].…”