Slot film cooling performance in combustor with flame holders

This experimental study was conducted to investigate the effect of a flame holder on multi-slot film cooling in a ramjet combustor. A prediffuser-type ramjet combustor equipped with a flame holder was utilized in this study. The change in adiabatic film cooling effectiveness on the downstream wall was measured using thermochromic liquid crystals. Experiments were conducted using five different blowing ratios, ranging from 0.5 to 1.5. The effect of the flame holder on heat transfer shows different characteristics between the first and second slots. In the first slot, the accelerated flows by blockage effect suppress the ejected secondary flows resulting in better cooling performance in case with the flame holder. However, the second slot represents the low cooling performance over all the regions by the disturbed flows with the flame holder compared to that without the flame holder. And the difference in cooling performance is enlarged with the increase of blowing ratio. The results reveal that it is essential to consider the effect of a wake behind the flame holder. Therefore, it should be considered in the design of film cooling systems for a practical application in ramjet combustors.