Optimization of new annular combustion chamber design for micro gas turbine

Micro gas turbine (MGT) is a good candidate for distributed generation power systems. This study aims at optimizing MGT combustion chamber geometry to be fueled by low-grade liquid biofuels without the need for any fuel blending with diesel or external fuel preheating process. The chamber utilizes internal exhaust gas recycling to evaporate the fuel (palm oil) in a fuel evaporation chamber. Design of Experiment (DOE) was performed in three stages to optimize chamber geometry while combustion performance for each geometry was performed using CFD simulation. The geometry consists of three annular tubes containing three layers (air, combustion and recycle) which were interchangeably tested Two final geometries were further optimized for number of holes in each zone to control air-fuel mixing and equivalence ratio (ER) to prevent thermal NOx formation. The findings reflected the negative effect of counter-flow air supply on flame stability where flames tended to leak towards the air jacket. The other major finding is the effect of gradual reduction of ER inside flame tube on emissions. The optimum geometry controls ER beyond flammability boundaries from 8.5 at premix zone to 0.5 at dilution zone which resulted in low NOx emission of 23 ppm and 347 ppm for CO.