Experimental Observation of the Instability Mode in the Combustion Wave by the Differential Chronoscopy Method

The paper represents the results of observing the spin instability mode during the propagation of a combustion wave in a mixture of Ni and Al powders, obtained using a special television micropyrometer ( 1200 pixels ×800 pixels) with high spatial ( 5.85 μm/pixel) and resolution time (1 ms/frame). High accuracy of temperature measurement was ensured using the new method of spectral light pyrometry (Patent RUS 2616937) from 800 to 2000°C with an error of less than 1%. To process the experimental video data, we used the differential chronoscopy method (DCS-map), which allows us to represent the trajectory of the isotherm in the combustion front as a set of periodic and continuous isoclinic lines. Visualization of the DCS-map using the trace transform demonstrates the presence of nodal points where the spin instability of the combustion wave is observed. The appearance of new nodal points is a sign of a transition from the mode of thermal instability to the mode of diffusion instability of the combustion wave, which is explained by the phenomenon of thermal hysteresis of the speed of the combustion wave from the synthesis temperature.