Direct drive valve model used as an acoustic source in a network model

Acoustic network models are a popular tool for the analysis of low frequency sound propagation in duct systems (e.g. ventilation or exhaust systems), due to their flexibility and low computational cost. In such models, acoustic sources are often implemented as simple velocity or mass flow boundary conditions. For active control of combustion instabilities in industrial gas turbines, as well as active stall control in turbo machinery, direct drive valves can provide on the one hand the required acoustic excitation with high mechanical and thermal robustness, and on the other hand allow regulation of average flow rates. This paper models a direct drive valve as a combination of a time-varying hydrodynamic resistance in combination with a lumped inertia. The valve model has been implemented in a network modelling package and compared to experimental data. The model captures the basic behaviour of the valve, but is limited to situations where the Mach number remains low though the constriction in the valve.