Back to the Future: Revisiting Nonpremixed Designs for Fuel Flexible (H2/NH3/CH4), Low NOx Combustion

The future of the energy sector requires highly flexible gas turbines that can adapt to a dynamic energy environment. These gas turbines must accommodate a wide range of fuels across a large operating envelope, including natural gas, hydrogen, and ammonia. State-of-the-art gas turbines for power generation have all adopted lean premixed (LPM) combustion strategies as the de facto method to reduce NOx emissions. However, their premixed nature inherently limits their fuel- and operational flexibility. Reverting to non-premixed combustion, the dominant legacy technology before the advent of LPM, would regain much of this flexibility. However, this must be done without sacrificing the low-NOx benefits of modern LPM engines. This paper explores the NOx emissions of a novel Non-premixed Rich Relaxation Lean (NRRL) combustor across various fuels: CH4, NH3, and H2. We demonstrate emissions and performance characteristics via chemical reactor network modeling and compare them to LPM ones at equivalent operating conditions. All these fuels achieve similarly low NOx levels with this concept. H2 decreases the residence time requirements, without a significant impact on exit NOx. NRRL NOx levels are as low as or lower than comparable LPM systems and have dramatically lower sensitivities to pressure or temperature.