Pressure gain combustion (PGC) has the potential to significantly improve combined cycle performance when integrated with combustion gas turbines. While conventional gas turbine engines undergo steady, subsonic combustion, resulting in a total pressure loss, PGC utilizes multiple physical phenomena, including resonant pulsed combustion, constant volume combustion, or detonation, to affect a rise in effective pressure across the combustor, while consuming the same amount of fuel as the constant pressure combustor. The methodology resulting in a pressure-gain across the combustor relies on the Humphrey (or Atkinson) cycle and is seen to have great potential as a means of achieving higher efficiency in gas turbine power systems, potentially reaching 4-6% for simple cycle systems and 2-4% in combined cycle systems. At the power system level this efficiency increase would reduce the cost and performance penalty incurred by capturing carbon. The high reactivity of hydrogen fuels from an IGCC with pre-combustion capture is particularly attractive to certain PGC concepts.
Pursuing PGC as a method for realizing a step-change in efficiency provides another approach to the 65 percent combustion turbine combined cycle efficiency goal. Historically, efficiency gains in combustion turbines have been realized by demonstrating higher and higher turbine inlet temperatures. Pressure gain combustion provides alternative pathway to the ultrahigh efficiency target that bypasses the material limitations currently faced by technology developers. Additionally, advanced materials and cooling schemes can still be pursued along with PGC providing the potential for ultrahigh efficiency combustion turbines for IGCC. Potential technical challenges include fuel injection, fuel and air mixing, backflow prevention, detonation initiation, wave directionality, maintaining a pressure gain, controlling emissions of NOx and CO, as well as unsteady heat transfer and cooling flow challenges resulting from integration with the turbine hot gas path expansion components.
The goal of this key technology is to develop PGC systems designed for potential integration with combustion gas turbines in combined cycle applications. The research is focused on combustion control strategies and fundamental understanding of pressure wave-flame interaction that will lead to lab-scale testing and component prototyping for turbine integration with PGC.