Measurement and prediction of detonation cell size in binary fuel blends of methane/hydrogen mixtures

• New detonation cell sizes for CH4–H2–O2 are obtained from experimental measurement.
• Cell sizes are predicted from a detailed chemical kinetic model.
• A linear relationship between detonation cell size and the ZND induction zone length is determined.

In this study, detonation cell sizes of binary fuel blends of methane–hydrogen–oxygen mixtures with different compositions (i.e., CH4–2H2–3O2, CH4–H2–2.5O2 and CH4–4H2–4O2) are experimentally measured. Good agreement is found between the experimental data and predictions based on the chemical length scales obtained from a detailed chemical kinetic model. The results show that detonation structure in methane–hydrogen–oxygen mixtures are irregular and detonation cell size (λ) for CH4–H2–2.5O2 mixture is larger than CH4–2H2–3O2 and CH4–4H2–4O2 mixtures. A linear relationship is determined by: λ = 34.62ΔI, through scaling the detonation cell size with the ZND induction zone length (ΔI) for methane–hydrogen–oxygen mixtures, and this scaling function is universal in CH4–H2–O2 mixtures at three compositions.