Equation of the gas oscillation frequencies in a closed-circuit Helmholtz resonator type combustion chamber

A solid fuel combustion chamber of the Helmholtz-resonator-type is investigated. In previous works, the air supply tube and the combustion product outlet tube were open at the outlet. In this paper, we consider a device in which the tubes are connected by a total volume. The linearization of the conservation equations in the combustion chamber and the interference chamber gives four boundary conditions for acoustic disturbances. From these conditions, an equation follows that allows us to calculate the frequencies of gas vibrations in the device of the considered type.