Numerical Simulation And Analysis Of Combustion Characteristics In Swirl Flow

In the energy and power systems, swirl combustion is widely applied as an aid to promote stabilization of high intensity combustion and the mixing of fuel and air so that to improve combustion efficiency and reduce emissions. Therefore, the study of swirl combustion characteristics is of great significance for basic research and technology development. In this paper, we combined numerical calculation and experiments based on a vehicle heater and a gas turbine combustor to study the effects of the swirl characteristic parameters and the structure of swirl nozzle on the flow structure, droplet evaporation and combustion characteristic.For vehicle heater, we first did experiment to study the effects of atomization pressure on atomization stability, droplet size, spray angle and fuel flow. On this basis, we selected the appropriate atomization pressure to do non-burning and burning experiment to observe droplet motion and flame shape. Then based on the experimental conditions of mist swirl combustion process we did numerical calculation and compared with experimental results. The results showed that the structure of cyclone flow field can be divided into three parts, the central recirculation zone and two kinds of helical vortex, whose structure is influenced by the swirl number. With the increase of swirl number, the inner vortex became stronger, the outer vortex became weaker. Meanwhile, when swirl number was increased, the oil droplets spread further, evaporated more quickly, mixed with air better so that the fuel concentration upstream was promoted and the combustion efficiency was increased. With the increase of Reynolds number, the central recirculation zone stretched gradually and the length of flame became shorter.For gas turbine combustor, we first collate the commissioning data and actual parameters of IGCC combustion chamber, and then did numerical simulation on this basis. By changing the equivalence ratio, the arrangement of swirl blades, the number of mixing holes, the effects of swirl nozzle parameters on pollution emissions was studied and combustion characteristics was identified. The results showed that with the increase of equivalence ratio of the combustion chamber, outlet temperature was increased, the center recirculation zone moved downstream. When the spine direction of swirl blades is different, the central recirculation zone decreased, but the shear stress of airflow was enhanced. Mixing holes are arranged such that synthesis gas can mixes with air in advance, which may cause nozzle erosion. Secondary dilution air and water vapor can effectively reduce the combustion temperature and reduce NOx emissions.This article provide help for further study how swirl effects oil and gas combustion, optimizing burner structure, improve combustion efficiency and reduce emissions.