Performance of aft-ramp cavities for flame stabilization in supersonic flows

A comparative study was made to evaluate the effect of decrease in ramp angle on the stability of the internal flowfield and fluid entrainment into the cavity for different aspect ratios, by unsteady and steady pressure measurements inside the cavity. The sensitivity of the transducer used for unsteady measurements was 100 mV/psi and the sampling frequency employed for data acquisition is 100 KHz based on the estimated frequency of the cavity tones. The results show that dominant peak amplitude of 560 Pa at the second harmonic frequency of 4728 Hz is obtained for the low-aspect-ratio rectangular cavity. The low-aspect-ratio cavity becomes more stable for a lower ramp angle than that of the high-aspect-ratio cavity. The results also show that for a given cavity dimensions, a shallower ramp angle could entrain more fluid from the main stream, which reduces the cavity-residence time.