Study of the control mechanism on combustion instabilities using perforated injector mounting surface

This study analyzes the key factors affecting the control of combustion instabilities on the basis of getting insight into the intrinsic physical mechanisms, focusing on the application of the perforated injector mounting surface and the outside perforated liner. The interactions between multiple injectors and the perforated screens are modeled using equivalent monopole sources, facilitating an analysis of perforated screens on thermoacoustic instabilities. Results show that lowering the mean temperature in the cooling cavities increases the phase difference of acoustic pressure across perforated screens, enhancing acoustic dissipation and stabilizing azimuthal modes. Additionally, the perforated screens and the flame modify thermoacoustic frequencies, necessitating adjustments of the perforated parameters to suppress unstable modes at various time delays. Changes in thermoacoustic frequency affect both the acoustic energy gained from the flame and the acoustic energy dissipated on the perforated screens, with both factors playing distinct roles in controlling combustion instability at different perforation ratios. Moreover, while maintaining the mass flow entering the combustion chamber primarily through the injectors, the perforated injector mounting surface effectively suppresses combustion instability within the limits of constrained flow adjustment. This work provides a theoretical framework for understanding the control mechanisms associated with perforated screens.