On the propagation modes of an acetylene self-decomposition wave in shock-heated flows in small-diameter pipes

Experimental data on the dynamics of shock wave propagation in acetylene and acetylene–oxygen mixtures diluted with argon in a square pipe of $27 \times 27$ mm$^2$. It is shown that the energy release during the self-decomposition of acetylene under certain conditions can lead to a pulsating acceleration of the shock wave front, but it does not form a stable detonation. In stoichiometric acetylene–oxygen mixtures, a detonation wave is formed, the parameters of which are in good agreement with the calculated Chapman–Jouguet parameters. Kinetic modeling of the process of self-decomposition of acetylene and growth of condensed particles evidenced the imperfection of existing acetylene pyrolysis mechanisms and the need to take into account additional channels of polymerization of hydrocarbon compounds governed by its unique properties.