Flame Transfer Function Measurements In A Multi-Element Combustor With Blends of Natural Gas And Hydrogen

Abstract Hydrogen is a key pathway for gas turbine decarbonization and optionality in sectors where energy demand is rising rapidly. Several demonstrations have shown that hydrogen blending is successful in currently operating gas turbines. However, due to significant differences in key flame properties like flame speed and ignition delay time between hydrogen and natural gas, the use of hydrogen can affect operability in gas turbine combustors. Issues related to flameholding have been addressed through the development of multi-nozzle arrays where many smaller flames allow for better flashback resistance than traditional combustor designs. However, issues related to thermoacoustic instability may still arise in these multi-nozzle array configurations. The goal of this work is to understand fundamental flame response behaviors in several multi-nozzle configurations with blends of natural gas and hydrogen ranging from 100% natural gas to 100% hydrogen. To achieve this goal, flame transfer functions have been measured over a range of operating conditions and fuel blends. Global OH* chemiluminescence is used as a marker of heat release rate oscillations and a two-microphone method is used to measure the input velocity oscillation amplitude over a range of frequencies. Results show marked differences in the flame response as the fuel composition is varied, including variations in both the peak response Strouhal numbers as well as the gain of the FTF. High-speed OH* chemiluminescence imaging is used to explain some of the differences in the flame response with different fuel compositions and multi-nozzle injector configurations.