Design and Aerothermal Assessment of Two- and Three-stage Sequential Combustors for Hydrogen and Multifuel Gas Turbines

Achieving global net-zero targets requires low-emission, fuel-flexible combustor architectures capable of operating with hydrogen and hydrogen-based fuel blends. Sequential and staged combustion has emerged as a promising approach for controlling heat release and reducing NOₓ formation. This study evaluates the aerothermal performance of two- and three-stage annular combustor configurations representative of high-pressure gas turbine systems for power generation.
Parametric simulations were conducted to examine the influence of fuel staging on temperature distribution, pressure loss, and NOₓ formation under hydrogen and multi-fuel operating conditions. For hydrogen operation, the two-stage configuration with a 10% pilot fuel split produced the most uniform exit temperature profile and achieved approximately a 10% reduction in predicted thermal NOₓ compared to a single-stage baseline. While three-stage operation enabled more distributed axial heat release, it provided limited additional emission reduction and showed increased sensitivity to fuel distribution.
Multi-fuel operation demonstrated that ammonia-containing cases increased NOₓ due to fuel-bound nitrogen chemistry; however, ternary hydrogen–ammonia–natural gas mixtures mitigated this effect by moderating flame temperature and reactivity.
The results indicate that optimized two-stage combustor architectures provide the best balance between NOₓ reduction, operational robustness, and system complexity, while three-stage configurations primarily enhance fuel flexibility rather than minimum-emission performance. These findings support staged combustion as a practical pathway for low-NOₓ, fuel-flexible gas turbines enabling the transition toward hydrogen-compatible energy systems.