Flow Instability: Richtmyer-Meshkov and Pulsating Flows

Combustion instabilities in hybrid fuel rockets appear in different modes. Some manifest through flame luminosity or pressure variation, where the spectral intensity of the flame front and pressure throughout the chamber oscillate. These oscillations in flame luminosity or pressure can interfere with the combustion process. Unwanted acoustic resonance may structurally damage the system, extinguish flames, or cause variations in thrust. The experiment conducted attempts to identify dominant instability modes and subsequently determine resulting combustion changes through the pulsation of gaseous oxygen flow. New possible characteristics of the resulting combustion may affect transient lag, regression rate, and flame-front behavior. The experimental setup consists of a rectangular combustion chamber made of 6061 T6 Aluminum, with ceiling and floor mounting points. A long, square channel connected to the chamber front provides gaseous oxygen (GOX) flow at varying rates determined by a flow meter. An exhaust tube is connected at the end of the chamber. The end of the chamber is open to the atmosphere. The square channel has two prongs at it’s connection point to the chamber front, acting as terminals for nichrome wire to heat a paraffin wax slab inserted into the chamber. A pressure transducer is inserted flush with the chamber ceiling to detect dynamic pressure changes in the experiment. The dynamic pressure changes will indicate pressure frequencies associated with instabilities that can sometimes present itself audibly through low to high freqeuncy noise. Chemiluminescence imaging should determine any changes with the flame overlapping the wax through excited chemical species.