Characteristics of Premixed Ammonia/Hydrogen/Methane Blends as an Alternative Fuel in a Swirl Stabilized Gas Turbine Combustor with Sustained Pilot

Ammonia (NH3) and hydrogen (H2) are both being researched as alternative fuel sources for turbine combustion engines. While hydrogen has a high burn velocity, which can improve the response of a combustion engine, it can be difficult to store it in large quantities. Alternatively, ammonia is much easier to store in large quantities but suffers from a low burn speed and low flammability. This research focuses on how NH3/H2/CH4 blends will burn in an air breathing turbine system at high Reynolds numbers. In the present work, a swirl stabilized gas turbine combustor along with a pilot injector (methane (CH4) only) was the computational domain that closely resembled the experimental rig where the Reynolds number based on the swirler diameter was set at 50000 and the swirl number was close to 0.8. The simulation work was done in Converge CFD 3.0 by employing the RNG k-ε technique for modeling turbulence and SAGE detailed chemical kinetic solver to model the premixed combustion phenomena with a mechanism file from the literature that has been demonstrated to work well with NH3/H2/CH4 blends. Two main cases were explored: Case 1: 80% NH3, 5% H2, and 15% CH4 (% by volume), and Case 2: 75% NH3, 5% H2, and 20% CH4. These cases were used at seven different equivalence ratio cases ranging from 0.6 to 1.2. The combustion characteristics of these blends were then compared to a baseline case containing 80% NH3 and 20% CH4 to ascertain the role played by the 5% H2 in the original fuel blend Case 1) on NOX emissions and to determine what happens when NH3 was reduced by 5% (Case 2). The system was adiabatic and the modeling was conducted at standard atmospheric pressure. Data taken from these simulations have shown that, for these initial conditions, a stable flame is possible in both lean and fuel-rich cases.