Md. Durbin et Dr. Ballal, STUDIES OF LEAN BLOWOUT IN A STEP SWIRL COMBUSTOR, Journal of engineering for gas turbines and power, 118(1), 1996, pp. 72-77
The design requirements of a modem gas turbine combustor are increasin
gly dictated by wide stability limits, short flame length, and uniform
mixing. To achieve the best trade-off between these three factors, fl
ame characteristics (length, shape, mixedness), lean blowout (LBO), an
d optimum combustor configuration should be investigated over a wide r
ange of inner and outer air velocities, inner and outer vane angles, a
nd co- versus counterswirl arrangements. Such an investigation was per
formed in a step swirl combustor (SSC) designed to simulate the fuel-a
ir mixing pattern in a gas turbine combustor dome fitted with an airbl
ast atomizer. It was found that an increase in the outer vane angle an
d a decrease in inner air velocity decreased the flame length. LBO was
improved when outer flow swirl intensity was increased. An optimum ha
rdware and velocity configuration for the SSC was found for inner swir
l = 45 deg, outer swirl = 60 deg, coswirl direction, and inner air vel
ocity = outer air velocity = 16 m/s. This optimum SSC configuration yi
elded: (i) low values of LBO, (ii) short flame length, (iii) uniformly
mixed stable flame, and (iv) little or no variation in these characte
ristics over the range of operation of SSC. Finally, the co- versus co
unterswirl an arrangements and the operation of the optimized combusto
r configuration are discussed.