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Unstable detonation and cell structure in hydrogen-oxygen mixtures at temperatures of 77-300 K
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DOI：10.1016/j.combustflame.2026.115018.png)
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Abstract
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The detonation behavior of hydrogen and oxygen mixtures under different initial temperatures (77–300 K), initial pressures (0.2–2.0 atm) and equivalent ratios (1.0–2.6) was studied. The flame propagation trajectory and overpressure curve were recorded by optical fibers and PCB pressure sensors, respectively, and the detonation mode, flame acceleration mechanism, velocity deficit and physical laws of cell structure were discussed. First, three detonation modes were observed experimentally: galloping mode, stuttering mode, and steady detonation mode. Among them, low temperature conditions (such as 77 K) significantly promote the occurrence of galloping mode, indicating that the detonation instability in the near-limit mixture is enhanced. Secondly, Flame Acceleration (FA) is a key factor affecting detonation transformation. Strong FA leads to the formation of supersonic flames and even detonation, while weak FA produces subsonic slow flames; The critical conditions can be quantitatively defined by the acceleration factor model. At low temperatures, the large expansion ratio and temperature gradient enhance the FA. Third, the heat loss effect is particularly prominent at low temperatures, resulting in a significant increase in detonation velocity deficit. The Fay model predicts well at ambient temperature without considering heat loss, but has a large deviation at low temperature, highlighting the importance energy loss. In addition, the cell width (λ) is regulated by the initial conditions: when the initial pressure is higher, the temperature is lower, or the equivalent ratio is close to 1.0, the cell width decreases, and its change is strongly correlated with the detonation velocity. The prediction model was in good agreement with the experimental results, which confirmed the association between the length of the induction zone and the width of the cell. Finally, the regularity of the cellular structure can be characterized by the von Neumann state specific heat ratio ( γVN) and dimensionless effective activation energy ( εi). When εi is high or γVN is low, the irregularity of cellular structure is enhanced.
Keywords:
detonation behavior
flame acceleration
cell structure
hydrogen-oxygen mixtures
temperature effects
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