CFD Predictions of Isothermal Fuel-Air Mixing in a Radial Swirl Low NOx Combustor Using Various RANS Turbulence Models

A radial swirl DLE combustion system was investigated for its gaseous fuel-air mixing performance using various different RANS turbulence models. Two different configurations were investigated; vane passage fuel injection and fuel injection from the wall of an outlet throat directly into the shear layer. The results showed that for vane passage fuel injection, only the standard k-e and standard Spalart-Allmaras models were able to provide a reasonable prediction for the combustor fuel-air distribution, out of all the RANS models and their variants available in Fluent v6.3, although both models predicted that the fuel and air were better mixed than in the measurements. For outlet throat wall fuel injection no models were able to provide a reasonable prediction. This same issue is also reported by several other researchers and represents a serious problem area in combustion modeling for low NOx applications. Improved fuel jet penetration was achieved by using an extremely low value of 0.1 for the turbulent Schmidt number, therefore future work will concentrate on using a localized value of Sc in the vicinity of the fuel injection hole.Copyright © 2012 by ASME