Numerical Investigation Into Maximum Pressure Capability of Intershaft Hydraulic Seals

Warusevitane, Achinie; Johnson, Kathy; Ambrose, Stephen

Abstract

Hydraulic seals are used as intershaft seals in aero-engines and consist of an oil filled trough on the higher speed shaft and a fin on the lower speed shaft that dips into the oil forming the seal. Rotation is imparted to the sealing fluid within the trough and, similar to a manometer in operation the liquid either side of the fin can be at different heights allowing the seal to withstand differential pressure. In normal operation hydraulic seals do not leak air but if the differential pressure becomes too high the seal will break down and leakage will occur. There is limited published research relating to hydraulic seals and the accuracy and reliability of the existing design approaches based on analytical derivations is not fully known. This acknowledged need to improve the ability to develop accurate computational models of hydraulic seals provides context for the current study. An approach to evaluate the maximum pressure capacity of a hydraulic seal is therefore introduced in this work. Building on previously published studies, this paper presents results of a 2D numerical study into the performance of a simplified hydraulic seal geometry. This paper reports a numerical CFD methodology based on an axisymmetric Volume-of-Fluid (VOF) method. In this study there is no oil feed into the trough. Results are presented for a range of shaft speeds of 2000–8000 rpm for the high speed shaft and 1000–4000 rpm for the low speed shaft. Fin position within the trough was varied. A criteria for broken seal was developed. The CFD data shows that the seal can withstand higher pressure at higher shaft speed with the characteristic following the expected linear relationship between differential pressure and shaft speed squared. The seal could withstand a higher differential pressure if the fin was closer to the housing on the high pressure side with this being attributed to the secondary air flow in the cavity. The average core velocity was compared to values obtained using different analytical approaches and it was found that one where core angular velocity is proportional to the area averaged rotational velocities of the housing and fin was the best match to CFD data.

Citation

Warusevitane, A., Johnson, K., & Ambrose, S. (2022). Numerical Investigation Into Maximum Pressure Capability of Intershaft Hydraulic Seals. In Proceedings of ASME Turbo Expo 2022 Turbomachinery Technical Conference and Exposition GT2022 June 13-17, 2022, Rotterdam, The Netherlands. https://doi.org/10.1115/GT2022-82196

• Conference Name: ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition
• Conference Location: Rotterdam, Netherlands
• Start Date: Jun 13, 2022
• End Date: Jun 17, 2022
• Acceptance Date: Mar 15, 2022
• Online Publication Date: Oct 28, 2022
• Publication Date: Jun 13, 2022
• Deposit Date: Apr 9, 2022
• Publisher: American Society of Mechanical Engineers
• Volume: 10-C
• Book Title: Proceedings of ASME Turbo Expo 2022 Turbomachinery Technical Conference and Exposition GT2022 June 13-17, 2022, Rotterdam, The Netherlands
• ISBN: 9780791886113
• DOI: https://doi.org/10.1115/GT2022-82196
• Keywords: hydraulic seal; CFD; VOF
• Public URL: https://nottingham-repository.worktribe.com/output/7733967
• Publisher URL: https://asmedigitalcollection.asme.org/GT/proceedings-abstract/GT2022/86113/V10CT32A025/1149383
• Related Public URLs: https://asme-turboexpo.secure-platform.com/a
• Additional Information: This work has been carried out as a part of the CORNERSTONE research programme. The Authors thank Rolls-Royce plc and the EPSRC for the support under the Prosperity Partnership Grant/ Cornerstone: Mechanical Engineering Science to Enable Aero Propulsion Futures, Grant Ref: EP/R004951/1. The calculations were performed using the University of Nottingham High Performance Computing Facility and Athena at HPC Midlands+, which was funded by the EPSRC on grant EP/P020232/1.