Experiment and Numerical Study of the Combustion Behavior of Hydrogen-blended Natural Gas in Swirl Burners

Hydrogen production from renewable energy is gaining increasing attention to enhance energy consumption structure and foster a more eco-friendly and sustainable society. At the same time, mixing hydrogen with natural gas and supplying it to civilians is one of the best ways to reduce carbon emissions and increase the reliability of technology while reducing the costs of storing and transporting hydrogen. Even though numerous researchers have conducted experimental and simulation studies on hydrogen-doped natural gas, most of these studies have focused on the effects of hydrogen-doped ratio, equivalence ratio, and fuel combustion mode. The impact of burner structure on hydrogen-enriched natural gas has not received much attention. Compared with conventional direct-flow combustion, swirl combustion can improve the mixing effect of the fuel mixture during combustion, and the use of regions of reversed flow due to swirl can make the fuel burn more fully to achieve the reduction of pollutant emissions. Swirling flames are widely used in gas turbines and industrial furnaces because of their high stability. However, the application of swirl combustion in domestic equipment is still in its infancy, which deserves more researchers to explore and enhance the working conditions of domestic combustion equipment. In this paper, a three-dimensional swirl burner model is utilized to examine the effect of swirl angle θ and swirl length L of the swirler on the combustion behavior of hydrogen-enriched natural gas in a swirl burner. The results indicate that the swirl angle θ and swirl length L play an essential role in the combustion of natural gas containing hydrogen. As the swirl angle θ increases, the flame temperature decreases more slowly, the combustion becomes more stable, and the length of the flame is slightly increased. Simultaneously, CO and NO emissions will gradually decrease, and the combustion effect is enhanced when the swirl angle is 45◦. With increased swirl length L, the flame length grows, the high-temperature region expands, and CO and NO emissions decrease. Meanwhile, the change in swirl length has little effect on the increase of flame peak temperature when the fuel is thoroughly mixed. When the swirl length is 12 mm, CO and NO emissions are lower, and NO emissions are reduced by 36.11% compared to a swirl length of 6 mm. This work is a reference point for applying hydrogen-mixed natural gas in the swirl burner, but it must be studied and optimized further in future research.