Numerical Investigation of an Annular Combustor Fuelled with Hydrogen for Next Generation Emission Free Gas Turbines

The motive for this investigation stems from recent initiative by the gas turbine industry towards hydrogen combustion and to provide zero carbon emissions. Mixing hydrogen with natural gas has the potential to reduce net CO2 emissions. The present work focuses on a numerical investigation of an annular combustor fuelled with natural gas and hydrogen blends to provide emission assessment. The influence of the varying natural gas and hydrogen content, air mass flow rate, equivalence ratio on the emission instabilities is investigated using ANSYS. It is found that pure natural gas and natural gas-hydrogen mixture with low hydrogen contents result in stable combustion and reduced CO2 emission. However, when the hydrogen content increases the combustion instability, high combustor pressure and higher flame temperature leads to NOX production. The efficient combustion can be achieved with narrow equivalence ratios using both natural gas and hydrogen blends. Moreover, low concentrations of OH radicals are observed with high hydrogen content. For the right optimal blend of natural gas and hydrogen along with the operating modes of an annular combustor without the formation of flashback, the emissions of NO and CO do not exceed the modern environmental requirements for emissions by gas turbine engines.