A NOVEL APPROACH TO DIRT MITIGATION FOR COMBUSTOR WALLS

Ingestion of particulate within a gas turbine engine leads to undesirable consequences such as erosion, hot spots, and cooling hole blockages. These concerns are prevalent in the combustor wall region that commonly employs a double wall design made up of impingement and effusion liners. Numerous studies on double wall liners have demonstrated the negative impacts dirt deposition has on cooling performance; however, to this point, little has been reported to have found an effective means to mitigate dirt deposition. In the current study, a novel design was investigated that added an upstream impingement plate to the common double wall design, resulting in a triple wall liner. The purpose of the additional impingement plate is that it allows for a sacrificial middle impingement plate to capture the dirt prior to the flow impacting the effusion plate where heat transfer is most critical. Several parameters such as impingement hole diameter, dirt injection mass, and plate-to-plate spacing were evaluated for different configurations. Using the triple wall design, the data indicates that dirt deposition on the effusion plate is reduced by as much as 87% compared to the effusion plate of a double wall design. Performance comparisons were made whereby the triple wall design maintained the same pressure ratio across all three layers as that of the double wall. Flow blockages of the cooling holes were shown to diminish for a triple wall compared to a double wall design. Additionally, cooling features were integrated on the surface of the middle impingement plate, which further reduced deposition on the effusion plate by 25% compared to a triple wall design without features. Overall, the results in this study show that a triple wall design significantly reduces dirt deposition on the effusion plate surface leading to less flow blockage as compared to a double wall, making them desirable for improved liner durability.