Pressure Gain Combustion
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; such as resonant pulsed combustion, constant volume combustion, and rotating detonation; to create a rise in effective pressure across the combustor while consuming the same amount of fuel as a constant pressure combustor. The methodology resulting in a pressure-gain across the combustor shares similar thermodynamic principles to the Atkinson cycle (constant volume combustion) 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 system level, this efficiency increase would partially mitigate the cost and performance penalty incurred by capturing carbon dioxide. The high reactivity of hydrogen fuels from an IGCC plant with pre-combustion capture (due to the lower costs and efficiency losses compared to post-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 NETL’s 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 an 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, improved operability, and furthering current understanding of combustion fundamentals, such as pressure wave-flame interaction. Ultimately, the goal is to utilize experimental testing to enable demonstration-scale operation of a PGC system integrated with a commercial gas turbine.
