David Louis Burrus

Combustor Diffuser Modeling Part IV: Effect of Cowling Geometry, Mixer Size and Nozzle Blockage

A full-scale single-passage combustor diffusion system has been analyzed with FLUENT code using its grid generation package, the standard k-e model and the nonequilibrium wall function. Inlet conditions were calculated using through the rig inlet. 3-D model predictions were compared with data from a full-scale annular diffuser rig fitted with a center-peak profiler that documented back-to-back performance between: 1) Dome fitted with a baseline cowling, Run 3 and without cowling, Run 6, 2) Reduced cowling inlet area, Run 3 compared with Run 7, 3) a slightly modified cowling geometry along with increased nozzle tip diameter, Run 11 versus Run 3, and 4) with 20% increased blockage caused by the fuel nozzle stem, Run 12 versus Run 3. In general, CFD gave good agreement with data considering the complexity of the flow field.

Combustor Diffuser Modeling Part III: Validation w/ Typical Separating Single Passage Diffusers Combustor Diffuser Modeling

A full-scale single-passage combustor diffusion system has been analyzed with FLUENT code using its grid generation package, the standard k-e model and the nonequilibrium wall function. Inlet conditions were calculated using through the rig inlet. 3-D model predictions were compared with data from a full-scale annular diffuser rig fitted with a center-peak profiler that documented back-to-back performance between: 1) Diffuser with bow-tie and opposed-ring profilers, Runs 3, 7 and 8; 2) Increased area diffuser compared with the baseline design, Run 3 compared with Run 9. In general, CFD gave good agreement with data considering the complexity of the flow field.

Combustor Diffuser Modeling Part I: Inlet Profiles & 2-D Calculations

2-D axisymmetric simulation of a typical gas turbine diffusion system is conducted with two turbulence models, the standard k-e, Shear Stress Turbulence, SST k-ω including its low-Reynolds number formulation. Effect of diffuser inlet profile, center-, innerand outerpeaked on pressure recovery and loss coefficient is modeled with two approaches for specifying the inlet conditions: 1) Measured inlet mean axial velocity with reasonable assumptions for turbulence quantities; 2) Through-the-rig inlet, profiler, duct, prediffuser and dump region 3-D CFD simulation to calculate the prediffuser inlet profiles. Best agreement with data is obtained with the standard k-e model starting with the calculated diffuser inlet conditions.