A gas turbine combustor dilution process is modeled numerically using both 2-D and 3-D approaches, then an experimental set-up was designed and built for validation using standard air ducts. The combustor model is used to test various air cooling strategies with the goal of uniformly diluting combustion gas before it enters the turbine section. The high temperature combustion gas (simulated as hot air) is cooled by introducing a lower temperature secondary air flow through perforated plates. First a 2-D simulation was conducted to compare between introducing the dilution air from smaller but large number of holes or larger but smaller number of holes. It was found that the larger holes are more effective especially when pressure drop is taken into consideration. Then a 3-D simulation was run with larger holes for different configurations and the experimental set up was constructed accordingly. The temperature profile at the exit of the dilution section is considered the criteria for testing the uniformity of temperature after the dilution process, and it will be measured in the experimental work.
This paper presents a brief discussion on the importance of cooling combustion exit gas uniformly before it enters the turbine section. With this in mind, a testing concept is derived in order to gauge methods of improving this cooling. Detailed design specifications and initial conclusions are also outlined. Initial conclusions have yielded a desired primary airflow of 6 m/s (19.7 ft/s) and primary duct diameter of 0.4 m (16 in). With this information it was determined that the flow rate required by the fan is 1.727 m3/s (3660 CFM).