LAMINAR AND TURBULENT FLAME SPEEDS FOR NATURAL GAS/HYDROGEN BLENDS
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Hydrogen-based fuels have become a primary interest in the gas turbine market. To better predict the reactivity of mixtures containing different levels of hydrogen, laminar and turbulent flame speed experiments have been conducted. The laminar flame speed measurements were performed for various methane and natural gas surrogate blends with significant amounts of hydrogen at elevated pressures (up to 5 atm) and temperatures (up to 450 K) using a heated, high-pressure, cylindrical, constant-volume vessel. The hydrogen content ranged from 50% to 90% by volume. All measurements were compared to a chemical kinetic model, and good agreement within experimental measurement uncertainty was observed over most conditions. Turbulent combustion experiments were also performed for pure H2 and 50:50 H2:CH4 mixtures using a fan-stirred flame speed vessel. All tests were made with a fixed integral length scale of 27 mm and with a turbulent intensity level of 1.5 m/s at 1 atm initial pressure. Most of the turbulent flame speed results were in either the corrugated or thin reaction zones when plotted on a Borghi diagram, with Damkhler numbers up to 100 and turbulent Reynolds numbers between about 100 and 450. Flame speeds for a 50:50 blend of H2:CH4 for both laminar and turbulent cases were about a factor of 1.8 higher than for pure methane.
