Experimental Investigation on Burning Velocity of Ammonia/Hydrogen/Air Turbulent Premixed Flames under Elevated Pressure

Premixed flames of ammonia/hydrogen/air mixtures were investigated in a combustor capable of creating an isotropic and homogeneous turbulent field. Based on the propagation characteristics under different hydrogen ratios, turbulence intensities, and pressures with Lewis numbers of about 1, the effects of flame chemistry, turbulent stretch, and pressure on the turbulent burning velocity were analyzed. The results show that turbulence intensity can significantly enhance the flame propagation, while the effect of pressure varies under different turbulence conditions and the hydrogen ratio corresponds to the enhancement of the flame chemistry, which has a great influence on the flame propagation. The increase of pressure and turbulence intensity makes the flame have a larger Karlovitz number and thus susceptible to turbulent stretching. In addition, the turbulent flame shows obvious self-similar accelerated propagation, but there is a deviation in the fitting index when the hydrogen ratio is larger. In addition, considering the effect of pressure on the combustion process, this paper studies the applicability of several correlations for turbulent burning velocity under high pressure and introduces the normalized pressure and turbulence integral length scales into these correlations for in-depth analysis and then further discusses the limitations of the existing correlations.