Moataz Medhat

This paper discusses the effect of burning syngas in a configuration similar to that of the BERL (Burner Engineering Research Laboratory) 300 KW swirl-stabilized combustor which has previously been used with methane as a fuel. Due to the axisymmetric configuration, only 15° from the burner angle is studied with periodic boundary. The model adopts RANS (Reynolds Averaged Navier–Stokes) technique including a realizable k-ε turbulent scheme. The non-premixed combustion model used is based on applying flamelet concept. The study shows that the structure of the flame is affected with changing the burner quarl angle and the inlet air swirl number. The detailed parametric study of this synthetic fuel in the BERL paradigm relates easily to the accumulated experimental and numerical studies available in this configuration and then acquiring add noval value to the present work. The study also shows the presence of different recirculation zones, one of which is central recirculation zone and an external recirculation zone. When increasing quarl angle, the central recirculation zone is shifted outward and the turbulent interaction between the central fuel jet and the recirculation zone induces small vortices between these two flow patterns. On the other hand, the effect of flue gas recirculation and air staging into the burner on the reduction of NOx formation is discussed. The flue gas data show that FGR reduces NOx emissions significantly while having no influence on flame stability, total combustion efficiency, or CO emissions. Changes in fuel composition are also taken into account. The results reveal that when the hydrogen blending in the fuel increases, the temperature rises.

The objective of this work is to computationally assess the performance of a carbon free ammonia-hydrogen mixture when burnt in a gas turbine like combustor. Recently, utilizing ammonia as an alternative carbon-free fuel for future power, industry applications and achieving clean energy attracted enormous interest. Pure ammonia oxidation is facing many challenges such as high NOx emissions, high ignition energy, slow reactivity and lower laminar flame speeds. Therefore, the use of ammonia/hydrogen mixture provides flame stability and increasing flame speed. In this manuscript a numerical study for a new swirl stabilized combustor for oxidizing ammonia/hydrogen mixture. Numerical two dimensional model simulations of a turbulent flame on Reynolds Averaged Navier Stokes (RANS) including a realizable k-e turbulent scheme with the aid of chemistry mechanism were performed under various conditions. Partially premixed combustion model with flame-let concept was selected and radiation effects are also considered. Validation for the predicted results showed a reasonable agreement when validated with the experimental data. The results discuss the influence of changing inlet pressure and equivalence ratio on the stability and the characteristics of unburnt NH3 and NO emissions. Results show that for constant operating conditions such as constant equivalence ratio of 0.8 that increasing hydrogen content resulted in increasing NO emission. Also, for constant ammonia/hydrogen concentrations, NO emissions increases with equivalence ratio then reduced at rich conditions and NH3 emissions are generally low. Equivalence ratio lower than 1.2 will be preferable to reduce the amount of unburnt NH3 formation.