Spectral characteristics of optical discharge in a high-speed methane–air jet

Results of gasdynamic and spectroscopic investigations of optical discharge in the subsupersonic flow of a homogeneous fuel–air (CH$_4$ + air) mixtures are presented. The combustion was initiated and maintained by optical discharge created using a CO$_2$ laser. The laser radiation propagated across the flow and was focused by a lens on the axis of the supersonic jet (M = 2). Emission-spectroscopy techniques provided data on the composition of radiating combustion products and the intensity of components emitted in the region of optical discharge. Patterns of Toepler’s visualization of the flow structure in the schlieren scheme are presented. The images were monitored by a high-speed video camera operating at an exposure time of 1.5 $\mu$s and a frame frequency of 1000 s$^{-1}$.