Experimental and numerical studies on the interaction between two identical slot jet H2/CO diffusion flames

Abstract

Hydrogen offers a unique opportunity in achieving a CO2-neutral future, but great challenges exist for the successful transition from conventional fossil fuels to H2, due to the great component variation and safety issues of H2 energy. The multiple-injection combustor concept effectively addresses these problems, with the merits of flexible nozzle distance satisfying the varying H2 content in the fuel and low flash-back risk comparable to diffusion flames. In such combustors, flame interaction plays an essential role in the performance of multiple-injection combustors. This work focused on the flame interaction behavior of two identical slot jet H2/CO diffusion flames. OH* chemiluminescence was captured by an intensified CCD camera and the flame temperature was measured using a type-B thermocouple. The combustion process was modeled using a Fortran flame code by incorporating the detailed thermal and transport properties as well as the chemical kinetic mechanism. With these experimental and numerical efforts, the effects of burner separating distance, fuel composition, and fuel velocity were parametrically studied. Results showed that flame interaction enables a more uniform temperature distribution. Increasing H2 content in the fuel decreases the flame length for the merged flames, but this effect is less distinguished for the merging and separated flames. In addition, flames with a higher H2 content merge more easily because of the enlarged flame radius, featured with a linear relationship between the merging distance and H2 content. When increasing the fuel flow rate, the twin flames contact and merge at farther separating distances, and this influence of fuel flow rate on flame interaction was observed to be fuel-composition-dependent. Increasing the burner separating distance lowers the flame length, which is attributed to the enhancement of CO oxidization rather than the H2 reactions. Moreover, burner separating distance plays a critical role in NO emissions, with a non-monotonical impact due to the combined effect of flame temperature and O2 concentration.