Self-acceleration characteristics of premixed C1-C3 alkanes-air mixtures in a constant-volume chamber.

The effects of initial pressure on the self-acceleration characteristics of C1-C3 alkane flames were studied in a constant-volume chamber at an initial temperature of 400 K. The pressures of 0.25, 0.5, 1.0, and 1.5 MPa and the equivalence ratios of 0.8–1.6 were analyzed. Flame propagation images were recorded using high-speed Schlieren photography techniques. The self-accelerating exponent and fractal dimension of C1-C3 alkane flames were measured using the spherically expanding flame method and the Schlieren photography system. The results show that the self-acceleration exponent and fractal dimension of C1-C3 alkane flames increased with the increase in pressure, and the maximum values appeared when the pressure was 1.5 MPa. Furthermore, the evolution of the cellular structure in the flame front during self-acceleration was studied quantitatively. The wrinkling ratio λ=1.0635 can be used to determine the critical point at which the flame is completely cellular. It was found that under the same conditions, for a higher cellular instability of the flame, more cells split on the front surface of the same sized flame, and the cell density increases accordingly. However, the cell density does not increase indefinitely, and upon reaching a certain value, it does not change with the change in working conditions. • A constant-volume combustion test system and schlieren photography technology were used. • Self-accelerating exponent and fractal dimension of C1–C3 alkane-air premixed flames at elevated pressures were measured. • The wrinkling ratio was used to estimate the critical radius. • Qualitative and quantitative methods are used to analyze flame self-acceleration characteristics. [ABSTRACT FROM AUTHOR]