Transient heat transfer and temperatures in closed compressor rotors

• Published in: Applied thermal engineering 2023-07, Vol.230, p.120759, Article 120759
• Main Authors: Nicholas, Tom E.W., Pernak, Mikolaj J., Scobie, James A., Lock, Gary D., Tang, Hui
• Format: Article
• Language: English
• Subjects: Buoyancy-induced flow; Closed cavity; High-pressure compressor; Mathematical modelling; Transient cycles
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2023.120759

During transient gas turbine operating cycles, the radial clearance between the rotating blades and the stationary casing is governed by the thermal stresses and radial growth of the compressor discs. Robust and accurate prediction of the temperature and heat transfer inside compressor cavities is critical to controlling these clearances and the design of reliable and efficient engines. This paper presents a fully predictive model to determine disc temperatures and shroud heat fluxes for a closed disc cavity (rotating cylindrical annulus), simulating an engine compressor. This is the first published reduced-order modelling of compressor cavities during engine transients in literature and the most detailed publication of transient experimental data in this context. Due to the conjugate nature of the heat transfer, a conduction model of the compressor disc and a model of the flow and heat transfer in the cavity between the co-rotating discs are included. The conduction was computed using a two-dimensional finite element solver, and the disc heat transfer was calculated assuming conductive laminar Ekman layers on the disc surfaces. Correlations for free convection on flat plates are used to model the heat transfer on the inner and outer radii of the rotating cavity. The transient core temperatures were calculated in a quasi-steady manner, with the heat transfer at every time step predicted assuming zero net heat flow. The model was validated using new transient data collected from the Compressor Cavity Rig at the University of Bath. The model shows consistent agreement with all experimental cases, providing insight into the conjugate relationship between the disc and shroud heat transfer, revealing that disc heat transfer is sustained long after there is no convective heat transfer from the shroud. This approach has direct application to practical thermo-mechanical codes, contributing to the design of next-generation, net-zero aerospace architectures. •A predictive model of transient flow and heat transfer in closed compressor cavities.•First published reduced-order modelling of compressor cavity transients.•Compressor disc temperature and shroud heat flux measurements for nine transient cycles.•Remarkable agreement between theory and experiments for all experimental cases.•Demonstration of the mechanism of flow and heat transfer ‘stratification’ in cavities.