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 modern low emissions combustors.For robust operation, large margins for static and dynamic stability are required, leading to higher than optimal emissions, reductions in fuel flexibility and increases in idle fuel consumption.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 to reduce combustion dynamics 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.Plasmas have already been demonstrated in literature to have positive effects on combustion dynamics and static stability.However, further work is necessary to integrate plasma into a realistic gas turbine combustor as well as to understand the dynamics of premixed flame response to plasma, particularly at relevant conditions.So far in phase I, the proposers have worked together with a major gas turbine manufacture to integrate their technology into a proprietary injector from an industrial gas turbine.The phase I work has so far demonstrated that a low-temperature nanosecond discharge can be integrated into an industrial low emissions combustor and is effective both in increasing the lean blow off limit (static stability) at elevated pressures as well as demonstrating authority over dynamic instabilities even in an open loop configuration.Together with their OEM and research institution partners, the proposers feel that this has demonstrated the feasibility of the proposed concept.The phase I is on schedule and the overall feasibility of the concept has been demonstrated.The rest of the phase I will consist in further work in implementing an active combustion control algorithm, scaling to pressures of up to 4 bar and further study of the two electrode configurations which have been down selected.Phase II will continue to develop this technology by refining the active combustion control system and scaling to test a single nozzle at over almost the full range of engine operating conditions at the engine manufacturer’s facility.Various optical, emissions 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 further develop and demonstrate a plasma-based active combustion control system an industrial dry, low emissions combustor such that emissions are reduced and turndown is improved.If this work is successful, it will significantly de-risk the technology and enable further collaboration 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 has the potential to 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.