Methods for Decarbonized Aeroengine Combustor Design

There exists an urgent need to decarbonize the civil transportation sector in order to address global warming concerns and its effects. Alternate and sustainable fuel types for combustion systems must be pursued to mitigate the dependency on fossil fuels for power generation. Possible alternative options for aeroengine combustion and propulsion include batteries or hydrogen fuel for fuel-cells or thermal-powered gas turbines. More specifically, thermal-powered aeroengines with premixed flame regimes can promise ultra-low emissions. Future aeroengine combustors operating in highly swirled premixed mode with hydrogen/air mixtures are central to this paper. Prior to the implementation and design of such systems, premixed combustion conditions must be correlated with gas turbine engine performance parameters. This thesis aims to address the gap by introducing a procedure to calculate relevant combustor operating conditions for the retrofit of aircraft engines in premixed mode with hydrogen/air mixture. The pursued method, a combustor performance map, leads to six key requirements: (1) the thermal power for the engine, (2) the mass conservation into the combustor, (3) the momentum conservation into the combustor, (4) the combustor energy budget, (5) the compressor-combustor-turbine power balance, and (6) a coupling relationship. The six requirements are obtained based on the derivation from fundamental conservation laws which are uniquely applied to pertain to a premixed combustor architecture. Whereas hydrogen fuel is considered, any fuel for premixed combustion system can be determined with the present method. To obtain the performance map, thermodynamics-based turbomachinery performance and chemical kinetics data are utilized to populate the governing conservation equations. As these two data sets provide combustor boundary conditions as well as hydrogen flame characteristics, the overall goal is to identify realistic operating points where all five requirements coincide. The results from the performance map analysis are complemented with computational fluid dynamics for validation purposes. The novel combustor performance map alongside the corresponding fluid dynamics simulations provide baseline methods for the development of future hydrogen premixed combustion systems.