Experimental and chemical kinetic studies of the effect of H2 enrichment on the laminar burning velocity and flame stability of various multicomponent natural gas blends

Abstract

The effect of the addition of hydrogen to various multicomponent natural gas (NG) blends is experimentally and numerically investigated. All the experiments are performed at a pressure of 0.1 MPa, a temperature of 300 ± 3 K, and a range of equivalence ratios (Φ = 0.6 to 1.4), using a constant pressure freely propagating spherical flame method. Numerical simulations are performed using the CHEMKIN-PRO® simulation software, with three different chemical kinetic mechanisms. Laminar burning velocity (LBV) and burned gas Markstein length (Lb) of the various NG-H2 blends at three different levels of hydrogen in the fuel, viz., 25%, 50%, and 75%, are experimentally evaluated to assess the effect of the simultaneous presence of H2 and higher hydrocarbons (HC) in various NG blends. The addition of H2 enhances the combustion chemistry of all the NG blends, and hence, increases the LBV. However, the effect is more prominent for the NG6-H2 blend, which has a higher mole fraction of CH4. The NG5-H2 blend, which has a higher mole fraction of C3H8 maintains a positive Lb for a wider range of equivalence ratios (0.7–1.4). The LBV prediction using the GRI-MECH 3.0 mechanism is within the range of experimental uncertainty, for the blends with up to 50% H2 in the fuel. The prediction of LBV using GRI-MECH 3.0 is the closest to the experimental results for the blends with 75% H2 in the fuel when compared with those using San Diego and USC-MECH 2.0 mechanisms.