This approach made it possible to generate a full 3-D model with reasonable grid cell resolution for both the small fuel nozzle passages and the main combustor. The computational models consisted of an average of 300,000 computational cells in as many as 19 blocks. Mass airflow boundary conditions for the combustor came from a one-dimensional external flow code used by AlliedSignal to calculate mass airflow splits through the combustor. To accurately model the mixing jets formed by flow through the dilution holes in the combustor liner, the computational model included the dilution orifices and the liner external flow. The effusion cooling and cooling slot flows were modeled as prescribed mass flow boundaries.
Water is introduced at the injector center through a pressure atomizer.
The CFD analysis revealed that the gas remains highly concentrated in the combustor primary zone center without significant mixing or burning. Slow mixing and burning of the fuel causes the high-temperature region to be located as far downstream as the dilution zone. Outboard of the secondary fuel injector are an annular water airblast injector and a helical air swirler co-rotating with the main air swirler surrounding the fuel nozzle. The liquid fuel spray distribution results in rapid mixing and a much more even fuel-air mixture distribution across the combustor primary zone than in the case of natural gas. The overall flow pattern remained essentially unchanged for both the natural gas and DF-2 fuel when water was injected.