Abstract
This study focuses on improving the temperature uniformity of mixed gases stream within combustor dilution zones. Temperature uniformity enhancement is investigated by using passive cooling via Modifier Nozzle Parts (MNP), and Modifier Diffuser Parts (MDP) that are installed on the dilution holes. Multiple parts diameter-length scenarios are investigated to select the optimum designs for controlling the velocity and pressure of dilution jets. An experimental setup with Reynolds number (Re) ranging between 104,000 and 271,000 is used to simulate dilution gas mixing and to validate Computational Fluid Dynamics (CFD) models. Results show that lower-length MNP designs provide comparable temperature uniformity factor (χ) enhancement without the added pressure drop, which results from higher lengths — reducing the area ratio for the MNP yields lower (χ) enhancement but with a notable increase in pressure drop. The most effective design in terms of benefit to cost is the MNP design with area shrinkage ratio of quarter (1/4) and a length corresponding to half the radius (∼10 mm) of the dilution hole. This design results in χ enhancement of 6% and an added pressure drop of 9%. The MDP designs performed poorly compared to the MNP designs. The k-ε (RNG) model showed good agreement with experimental data and performed well against k-ω (SST) and Reynolds Stress Turbulence (RST) models.
