Distributed combustion response function modeling and measurement

A Velocity-Coupled Distributed Combustion (VCDC) magnetic flowmeter has been developed to measure the velocity-coupled response of aluminum particles above a combusting solid propellant. In order to measure the VCDC response, a transverse velocity oscillation is coupled to an axial acoustic wave, which is generated inside of the chamber by means of a toothed gear rotating above a choked nozzle. The use of a magnetic flowmeter allows the acoustic velocity inside of the chamber to be measured. Combined with simultaneous measurements of the acoustic pressure, the acoustic conditions inside of the chamber can be characterized. The experimental results are analyzed by comparison to a numerical model to obtain a value of the VCDC response. The model incorporates the dynamics of a combusting aluminum particle in a rocket flow environment and an acoustic model to obtain the acoustic conditions inside of the VCDC chamber. The aluminum combustion model is constructed using a burn time expression developed by Beckstead et al. Cold flow testing of the chamber indicates the experimental setup is able to produce the acoustics required to measure the VCDC response.