High pressure visualisation of liquid oxygen and cryogenic hydrogen combustion under an imposed acoustic field

Abstract

Experimental investigations into combustion instability were undertaken using a rectangular subscale combustion chamber. High speed optical diagnostics were used to observe flame-acoustic interactions. A sector wheel was used to produce an acoustic field with time varying amplitude. The acoustic field under investigation is the first transverse mode with a velocity anti node located in the central combustion zone under observation by high speed optical diagnostics. Increased combustion product emission was observed near to the face plate for periods of high amplitude excitation. Combustion zones with high emission were convected downstream as excitation amplitudes decreased. During phases of increasing amplitude an increase in emission intensity at the mixing border between dense oxygen and cryogenic hydrogen was observed. This provides visual confirmation of increased mixing efficiency due to high amplitude transverse velocities in the vicinity of the injection plane.