Testing of a Hydrogen Diffusion Flame Array Injector at Gas Turbine Conditions

High-hydrogen gas turbines enable integration of carbon sequestration into coal-gasifying power plants, though NOx emissions are often high. This work explores nitrogen dilution of hydrogen diffusion flames to reduce thermal NOx emissions and avoid problems with premixing hydrogen at gas turbine pressures and temperatures. The burner design includes an array of high-velocity coaxial fuel and air injectors, which balances stability and ignition performance, combustor pressure drop, and flame residence time. Testing of this array injector at representative gas turbine conditions (16 atm and 1750 K firing temperature) yields 4.4 ppmv NOx at 15% O2 equivalent. NOx emissions are proportional to flame residence times, though these deviate from expected scaling due to active combustor cooling and merged flame behavior. The results demonstrate that nitrogen dilution in combination with high velocities can provide low NOx hydrogen combustion at gas turbine conditions, with significant potential for further NOx reductions via suggested design changes.