Excitation of combustion oscillations by canalization lines containing two different fluids

The presence of stratified columns of two different fluids in a canalization line was predicted to significantly change the characteristic frequency of the canalization. The multiple wave reflections at the interface of the two fluids and the equivalent increase in the path length of the wave motion were seen to give rise to lower frequencies. A canalization tube comprising of gaseous helium and oxygen, when applied for liquid oxygen pressure measurement in the feed manifold, led to the excitation of low frequency limit cycle pressure oscillations in the combustion chamber. The results of the experimental measurements are discussed.