Flow Field and Combustion Characteristics of Natural Gas inside a Gas Turbine Combustor

Abstract

The present work is numerical simulat ion results from the modeling of a non-premixed natural gas flame performedin a combustor model. CFD studies using FLUENT code were carried out for different air swirl numbers and inletthermal load with constant A/F. The isothermal flow field was simulated using (SST) k-ω turbulence model and thereacting flow was simulated by the non-premixed combustion model with the P-1 radiation model available in thecomputational fluid dynamics package Fluent 6.3. The model geometry was created and meshing arrangement wasgenerated using Gambit pre-processing software. The domain of the model was based on the dimension of thecombustor and burners. The case studied is a cylindrical enclosure of 0.1 m radius and 1.0 m length. Two reactantstreams emerge from two separate coaxial jets producing a swirling diffusion flame. The natural gas is issued axiallyinto the combustor from the annulus area between the swirler outer diameter and the burner hub diameter whereas thecombustion air is introduced through an annular swirler having uniform swirl vanes. The results show a reasonableagreement of the measured and the calculated reverse flow zone sizes using the shear stress transport (SST) k -ω model.The boundary of the reverse flow zone for weak air swirl number of 0.5 is formed completely inside the combustor withclosed loop, while for air swirl numbers of 0.87 and 1.5 the boundaries fill the combustor and its size increased as theair swirl number increased. Increasing the air swirl number, the high temperature regions size, the flame length, and theCO2 and CO concentrations decreased while the O2 concentration increased. Increasing the thermal load, the hightemperature regions size, the flame length, CO2 and CO concentrations increased, while the O2 concentration decreased.