Thermoacoustics of a T-burner: How to better estimate the combustion response function from a T-burner experiment

The combustion response function, representing the coupling between the pressure oscillation and the combustion rate of a solid propellant, is a key indicator of combustion instability (large unwanted pressure oscillations in a combustion chamber) of a solid rocket motor. To obtain the response function experimentally, a T-burner is often used, in which the lowest longitudinal acoustic resonance of the cylindrical enclosure is excited by the combustion of propellant samples (acting like speakers) at both ends. The existing formula used to derive the combustion response function from a T-burner experiment is based on a series of rather crude assumptions. For example, acoustically rigid boundaries are assumed at both ends, whereas impedance boundary conditions may be more appropriate to reflect the introduction of combustion products from the propellant. In this talk, we propose a few modifications to the current T-burner analysis regime, which could improve the accuracy of the measured response function. T...