Effect of Water Vapor on the Kinetics of Combustion of Hydrogen and Natural Gas: Experimental and Detailed Modeling Study

The dilution of fuels by exhausts gases (mainly CO, CO₂ and H₂O) affects the kinetics of combustion. This dilution is used in gas turbines and flameless combustor. It helps reducing pollutant emissions, particularly NOx. Therefore, it is useful to study the effect of such compounds on the kinetics of oxidation of fuels such as natural gas and hydrogen. The oxidation of hydrogen and that of methane were studied experimentally in a fused silica jet-stirred reactor (JSR) over the temperature range 800–1500 K, from fuel-lean to fuel-rich conditions. The experiments were repeated in presence of 10% in mole of water vapor. A detailed chemical kinetic modeling of the present experiments and of literature data (flame speed, ignition delays) was performed using a previously proposed kinetic reaction mechanism, showing good agreement between the data and this modeling. Sensitivity and reaction paths analyses were used to delineate the important reactions influencing the kinetic of oxidation of the fuels in presence of water vapor. The kinetic reaction scheme proposed helps understanding the inhibiting effect of water vapor on the oxidation of hydrogen and methane. The effect of water vapor on NOx formation under gas turbine conditions was also investigated numerically using the proposed kinetic scheme.