Peculiarities of self-ignition of a hydrogen–air mixture in shock tubes of different roughnesses

The induction time in shock tubes with different surface roughnesses and different mixture densities was measured, local features of self-ignition were described, and the results obtained were compared with the results for tubes with other diameters in order to determine the effect of gasdynamic parameters on the formation of ignition kernels and ignition in general. It was discovered that ignition at temperature range of 904–1200 K for \(\rho _{\textrm{5}} = 2.80\,{\hbox {kg/m}}^{\textrm{3}}\) ${\rho }_{\text{5}}=2.80{\text{kg/m}}^{\text{3}}$ and 1020–1120 K for \(\rho _{\textrm{5}} = 1.53\,{\hbox {kg/m}}^{\textrm{3}}\) ${\rho }_{\text{5}}=1.53{\text{kg/m}}^{\text{3}}$ is determined by the ignition kernel that forms near the tube axis and is a consequence of the gasdynamic effect at the tube axis (axial effect), but is not explained by the adiabatic compression of the mixture due to the expansion of gas from the reflected shock wave bifurcation stagnation region. An increase in the size of the bifurcation structure due to an increase in tube surface roughness does not affect ignition at these temperatures, but expands the ignition range at lower temperatures, in which multi-kernels or volumetric ignition is observed.