Flame response to acoustic excitation in a rectangular rocket combustor with LOx/H2 propellants

Abstract

Research efforts are currently underway at DLR Lampoldshausen which aim to understand the mechanisms by which self-sustaining oscillations in combustion chamber pressure, known as high frequency combustion instabilities, are driven. Testing has been conducted in the rectangular combustor ‘BKH’, running cryogenic oxygen and hydrogen propellants under pressure and injection conditions which are representative of real rocket engines and with acoustic forcing. Optical access to the combustor allowed the application of high speed OH* chemiluminescence imaging of the flame during periods of forced excitation of acoustic resonance modes of the combustion chamber. This paper reports the investigation of flame response to acoustic excitation. Both fluctuation in OH* emission intensity and deflection of the flame at frequencies corresponding to the excitation frequency have been observed. These responses are then discussed as potential indicators of driving mechanisms for combustion instabilities.