Numerical analysis of rim seal flow in gas turbine secondary air systems with hot gas ingestion and vane cooling

Hot gas ingestion from the main gas path into the wheelspace of gas turbines can lead to severe thermal damage to critical components, reducing operational reliability and lifespan. Hence, predicting and mitigating hot gas ingestion is crucial for improving turbine efficiency and durability. This study conducts a novel and comprehensive 3D numerical analysis to investigate hot gas ingestion and rim seal effectiveness in the first wheelspace of the Frame 9 gas turbine at Shahid Rajaei Power Plant (Qazvin, Iran). Novelty of this work lies in its use of a high-fidelity, 3D computational Fluid Dynamics (CFD) model that includes actual engine operating conditions, first-stage vane and blade geometries, and all relevant cooling paths (vane convection, film cooling, and rim cavity leakage), which allowed for a detailed investigation of the complex fluid dynamics often oversimplified in conventional models. Furthermore, this study introduces an integrated methodology that couples the CFD results with a 0D Secondary Air System (SAS) code to model the system-level thermal effects of ingestion. The analysis revealed several key conclusions. The effectiveness curve of the rim seal, extracted under these realistic conditions, diverges significantly from conventional effectiveness curves under off-design conditions. A significant result of the integrated analysis is the establishment of a fundamental relationship between the dimensionless ingestion and sealing parameters. Results reveal that maintaining the sealing parameter above a certain threshold is crucial for mitigating hot gas ingestion, which offers a direct and actionable guideline for optimizing sealing flows. This research presents a robust methodology and provides important insights into the performance of the F9 turbine’s secondary air system, offering valuable guidance for optimizing sealing flow rates to enhance turbine longevity and efficiency.