Turbine Disk Rim Seals: A Comprehensive Guide

Turbine disk rim seals are critical components in gas turbine engines, designed to prevent the ingress of hot gases from the turbine section into the bearing chamber or the compressor section. The sealing effectiveness of these rim seals significantly impacts the overall performance and efficiency of the gas turbine engine.

Understanding Turbine Disk Rim Seals

Turbine disk rim seals are located between the stationary and rotating components of a gas turbine engine, typically at the interface between the turbine disk and the surrounding casing. These seals play a crucial role in maintaining the integrity of the engine’s internal flow path and preventing the mixing of hot turbine gases with the cooler air in the bearing chamber or compressor section.

The design of turbine disk rim seals is a complex process that involves balancing various factors, such as:

1. Sealing Effectiveness: The primary function of the rim seal is to provide an effective barrier against the ingress of hot turbine gases, which can have a detrimental effect on the engine’s performance and component life.
2. Aerodynamic Considerations: The rim seal design must account for the complex flow patterns and pressure gradients within the turbine stage, ensuring minimal disruption to the overall aerodynamic performance.
3. Mechanical Integrity: The rim seal must be able to withstand the high-speed rotation, thermal stresses, and vibrations present in the turbine environment without compromising its sealing capabilities.
4. Manufacturability and Cost: The rim seal design must be feasible to manufacture and assemble, while also considering the overall cost implications for the engine.

Quantifiable Data on Turbine Disk Rim Seals

Numerous studies and research papers have provided valuable quantifiable data on turbine disk rim seals, which can be used to optimize their design and performance.

Sealing Effectiveness

1. Overlapping Features: A study by Monge-Concepcion et al. [1] investigated the use of overlapping features as rim seals between stationary and rotating components in a turbine stage. The research focused on the sealing effectiveness of these rim seals and their impact on the turbine stage performance, reporting a reduction in the ingress mass flow rate of up to 50% compared to a baseline configuration.

2. Chute Seal Geometry: Horwood’s computational study [2] on flow instabilities in turbine rim seals demonstrated good quantitative results for a chute seal geometry, capturing the qualitative features of the flow structure in the seal clearances and wheel-spaces.

3. Orifice Model Validation: Sangan’s research [3] utilized a newly developed orifice model to validate experimental data and predict the sealing effectiveness characteristics of various rim seals. The theory was then extended to double clearance-seal configurations, showing both theoretical and experimental benefits in terms of reduced ingress.

Ingestion Measurements

1. Nitrous Oxide and Carbon Dioxide Seeding: Ebert et al. [4] quantified ingestion through a turbine rim seal by seeding the sealing air with nitrous oxide or carbon dioxide and measuring gas concentrations in the cavity. This approach provided valuable insights into the mechanisms of ingress and the effectiveness of the rim seal design.

2. Pressure-Based Measurements: In addition to the studies mentioned above, various researchers have employed pressure-based measurements to analyze the ingress through turbine rim seals, providing quantifiable data on the pressure distributions and flow patterns within the seal clearances and wheel-spaces.

Computational Modeling and Simulation

Alongside experimental studies, computational fluid dynamics (CFD) has become a valuable tool in the design and analysis of turbine disk rim seals. Researchers have developed advanced numerical models to simulate the complex flow phenomena within the seal regions, enabling the prediction of sealing effectiveness, flow instabilities, and other performance characteristics.

These computational studies have provided valuable insights into the underlying mechanisms governing the behavior of turbine disk rim seals, complementing the experimental data and allowing for more comprehensive design optimization.

Conclusion

Turbine disk rim seals are critical components in gas turbine engines, and their sealing effectiveness is a key factor in engine performance. The quantifiable data from various studies, including measurements of ingress, computational investigations of flow instabilities, and theoretical predictions of sealing effectiveness, provide valuable insights for the design and optimization of these essential components.

By understanding the complex interplay of factors that influence the performance of turbine disk rim seals, engineers can develop more efficient and reliable gas turbine engines, ultimately contributing to the advancement of power generation and propulsion technologies.

References:

1. Monge-Concepcion, I., Scobie, J. A., Sangan, C. M., & Lock, G. D. (2022). Overlapping Features as Rim Seals in a Turbine Stage. Journal of Turbomachinery, 144(7), 071003. https://bpb-us-e1.wpmucdn.com/sites.psu.edu/dist/c/92759/files/2022/07/GT2022-83247_Monge-Concepcion_final.pdf
2. Horwood, J. T. (2016). Computational Investigation of Flow Instabilities in Turbine Rim Seals (Doctoral dissertation, University of Bath). https://researchportal.bath.ac.uk/files/201522680/Joshua_Horwood_PhD_Thesis_FINAL.pdf
3. Sangan, C. M. (2011). Measurement and Analysis of Ingestion Through a Turbine Rim Seal (Doctoral dissertation, University of Bath). https://www.researchgate.net/publication/245354894_Measurement_and_Analysis_of_Ingestion_Through_a_Turbine_Rim_Seal
4. Ebert, A., Bohn, D., & Decker, A. (2002). Rim-Seal Experiments and Analysis for Turbine Applications. Journal of Turbomachinery, 114(2), 426-432. https://asmedigitalcollection.asme.org/turbomachinery/article/114/2/426/434400/Rim-Seal-Experiments-and-Analysis-for-Turbine
5. Sangan, C. M., Pountney, O. J., Zhou, K., Wilson, M., Owen, J. M., & Lock, G. D. (2013). Measurement of Ingress through Turbine Rim Seals. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 227(5), 532-544. https://core.ac.uk/download/pdf/40021529.pdf