Passive Combustion Control Device for Noise Reduction and Improved Life in Turbine Engines, Phase II

Reduction of combustion-generated noise is one of the most significant challenges in the development of advanced gas turbine engines. Several processes contribute to the noise, but combustion instabilities pose the most serious threat to engine operation and safety. In Phase I, highly porous open-cell foam structures were employed to modify the combustor flow field and passively suppress unsteady flow fluctuations, thereby reducing noise. Use of structural foam inserts in gas turbine engines offers an effective, simple, and reliable approach for combustion control and noise reduction. Material development and component fabrication were conducted by Ultramet, and design, analysis, and component testing were performed by the University of Alabama. Two approaches were explored. In the first, the foam insert was located downstream of the reaction zone to dissipate the combustion noise and instability generated upstream. In the second, the vortex shedding mechanism of combustion instability was curtailed by placing the foam insert within the recirculation region of the reaction zone. The porous insert media were experimentally demonstrated to reduce combustion noise by up to 15 dB, depending on the operating conditions and test configuration. In Phase II, Ultramet will team with the University of Alabama and Solar Turbines (a subsidiary of Caterpillar Inc.), the world’s largest manufacturer of small- and medium-sized (1 to 5 MW) industrial gas turbines, to perform comprehensive component design and material optimization, ultimately leading to performance demonstration of open-cell foam noise reduction components through hot-fire testing under realistic turbine operating conditions using gaseous methane propellant.