Gas turbine engines are a highly efficient source of power for a variety of applications, including electricity generation, aircraft propulsion, and oil extraction. Typical power generation gas turbines use natural gas fuel, a growing source of fossil fuel in the US and abroad. According to the US Energy Information Administration, 50% of the new electrical generation capacity in 2013 came from natural-gas-fired gas turbines. Half of these new installations were peaker plants, which provide additional power during high demand, and half were combined-cycle plants, which produce intermediate or baseload power and have thermal efficiencies of over 60%. The growing demand for natural-gas-fueled power generation and the high efficiencies that gas turbine engines can achieve make the gas turbine a key player in the energy market for decades to come. These engines are not only efficient but can also meet strict emissions regulations. New gas turbines can achieve single-digit ppm NOx, and increasing efficiency has reduced greenhouse gas emissions. However, these improvements in emissions and efficiency don’t come without significant technical challenges, the greatest of which is combustion instability. Combustion instability, often referred to as “combustion dynamics,” is a potentially disastrous feedback cycle between combustor acoustics and flame heat release rate fluctuations in the combustor. These processes couple through fluid mechanic pathways in the complex combustor flow field, making suppression of instabilities a very difficult task. While “on-the-fly” instability mitigation techniques have been implemented in gas turbines, industry and researchers alike are working to understand the fundamental physics driving these instabilities so as to incorporate instability suppression into the design of the engine. In this talk, we will discuss the fundamentals of combustion instability and see some examples of the coupling pathways by which combustor acoustics are coupled with the flame. We will also explore how instability suppression mechanisms work, and how new methods for suppressing instability may be incorporated into future engine designs.
Dr. Jacqueline O’Connor
Assistant Professor of Mechanical Engineering at The Pennsylvania State University. There, she directs the Reacting Flow Dynamics Laboratory. Her research focuses on unsteady combustion phenomena in power and propulsion technologies, including power-generation gas turbines, aircraft engines, and diesel engines, using high-speed laser diagnostics. Previously, she was a post-doctoral researcher at Sandia National Laboratories in Livermore, California in the Engine Combustion Department. She received a BS from MIT in Aeronautics in 2006, and a MS and Ph.D. in Aerospace Engineering from Georgia Tech in 2009 and 2012. She is the recipient of the 2016 Irvin Glassman Young Investigator Award from the Eastern States Section of the Combustion Institute and the 2018 Dilip R. Ballal Early Career Award from the ASME International Gas Turbine Institute.