Proposal for Active Control of Static and Dynamic Stability in Lean Combustion via Plasma Actuation in a Novel Fuel Injector Design

Controlling combustion dynamics in gas turbines continues to be a major challenge especially in advanced engine designs where, due to leaner flames, less cooling air and more turbulent injectors, there is a higher potential for damaging combustion dynamics. Therefore, for robust operation, large margins for static and dynamic stability are required. This can lead to higher than optimal emissions. It can be considered in this regard, that control of combustion dynamics can effectively set the NOx floor for a given turbine. Various active combustion control methods have been proposed and demonstrated, at least for gas turbine engines but they have not found wide-spread commercial use. Plasma has been shown to be a promising tool for flame stabilization with nanosecond-repetitively-pulsed-discharges (NSPD) in particular have gained popularity for their ability to create high electric fields and thus produce sufficient concentrations of excited species to enhance combustion. In addition, their rapid actuation time and efficiency make plasma an attractive actuator for active combustion control which can both improve both static stability via kinetic enhancement of reaction pathways and dynamic stability, especially if configured in a closed-loop configuration. Plasmas have already been demonstrated in literature to have positive effects on combustion dynamics. However, further work is necessary to understand the dynamics of flame response to plasma’s, particularly at realistic conditions. To this end, this proposal will use explore a novel method of using plasma as an active control actuator in order to control combustion dynamics, thereby broadening operability and reducing emissions for industrial gas turbines. This combustor and its control system will be characterized both at atmospheric pressure as well as at high pressure and high temperature conditions representative of operation in a gas turbine engine. Various optical and acoustic diagnostics will be used to quantify the effectiveness of the plasma-assisted control system. At a high level, the goal of this work will be to a) develop and demonstrate an active combustion control system using nanosecond-pulsed plasmas as an actuator integrated into a realistic, lean-premixed injector and b) to reduce low-power CO emissions and lean blow off characteristics of the combustor by at least 20% with the aid of the proposed plasma system. If this work is successful, it will significantly de-risk the technology and enable partnerships with major engine manufacturers to bring this technology to market where this technology will provide a single point solution to a wide variety of combustion problems. This technology can therefore enable reduced emissions, lower fuel consumption and greater reliability from gas turbines for stationary power generation. This technology also has dual-use applications in jet engines for civil and military aviation.