Technologies for the Suppression of Combustion Instability or Screech

This Phase I project will demonstrate how control of fuel and/or air distribution can be used to mitigate combustion oscillations. The project will be done with the perspective that the mechanism of controlling the oscillastions can eventually be implemented into a retrofittable, closed loop approach. It has been well established that the relationship between the location and timing of local heat release can couple with acoustic modes in the augmentor. Examples of exploiting this by pulsing fuel at the correct phase to mitigate can be found, but the requirements for the fast pulsing preclude practical implementation. In the proposed project, spatial movement of the heat release rather than temporal will be demonstrated through a combination of fuel and air placement. The effort will utilize an existing test rig with two-stream mixing to mimic the fan and core air streams. This offers the ability to explore manipulation of the oxidizer stream in addition to fuel placement as a migigating strategy. Complimenting the tests will be the development of analytical flame response transfer functions which will help interpret the reasons the control measures work.