Calibration of thermopile heat flux gauges using a physically-based equation

Pountney, Oliver J.; Patinios, Marios; Tang, Hongxiao; Luberti, Dario; Sangan, Carl M.; Scobie, James A.; Owen, J. Michael; Lock, Gary

doi:10.1177/0957650920982103

Cited by 8 publications

(3 citation statements)

References 22 publications

(25 reference statements)

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“…An additional thin-foil thermocouple was used to set the temperature on the outside surface of the shroud. The shroud heat transfer was measured using an RdF 27160-C-L-A01 thermopile heat flux gauge, calibrated using the method described by Pountney et al [34]. Thermocouples to determine the temperature of the axial throughflow were located on three rakes mounted on the stationary shaft, one upstream of the disc drum and two near the cobs of the test cavity.…”

Section: Experimental Rig Instrumentation and Methodologymentioning

confidence: 99%

Experimental Investigation of Transient Flow Phenomena in Rotating Compressor Cavities

Pernak,

Nicholas,

Williams

et al. 2023

Journal of Turbomachinery

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The clearance of compressor blade tips during aero-engine accelerations is an important design issue for next-generation engine architectures. The transient clearance depends on the radial expansion of the compressor discs, which is directly coupled to conjugate heat transfer in co-rotating discs governed by unsteady and unstable buoyancy-induced flow. This paper discusses an experimental and modelling study using the Bath Compressor Cavity Rig, which simulates a generic axial compressor at fluiddynamically scaled conditions. The rig was specifically designed to generate heat transfer of practical interest to the engine designer and validate computational codes. This work presents the first study of the fundamental fluid dynamic and heat transfer phenomena under transient conditions. The rotating flow structure was seen to be characterised by coherent pairs of cyclonic/anticyclonic vortex pairs; the strength, rotational frequency, stability and number of these unsteady structures changed with changing rotational Reynolds and Grashof numbers during the transients. These structures, measured by unsteady pressure transducers in the rotating frame of reference, were only present when the flow in the rotating cavity was dominated by buoyancy. Experimental correlations of both Nusselt number and radial mass flow rate in the rotating core were correlated against Grashof number. Remarkably, the experiments revealed a consistent correlation for both steady-state and transient conditions over a wide range of Gr. The results have a practical application to thermo-mechanical models for engine design.

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Section: Experimental Rig Instrumentation and Methodologymentioning

confidence: 99%

Experimental Investigation of Transient Flow Phenomena in Rotating Compressor Cavities

Pernak,

Nicholas,

Williams

et al. 2023

Journal of Turbomachinery

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“…Thin foil thermocouples and fluxmeters (see [24]) were attached on the underside surfaces of the shroud. However, no results are presented for heat transfer from the shroud, as this would involve the measurement or calculation of the core temperature, which is beyond the scope of this paper.…”

Section: Bath Compressor-cavity Rigmentioning

confidence: 99%

Measurement of Heat Transfer and Flow Structures in a Closed Rotating Cavity

Jackson

Tang

Scobie

et al. 2022

Journal of Engineering for Gas Turbines and Power

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Buoyancy-induced flow occurs inside the rotating compressor cavities of gas turbines. These cavities are usually open at the inner radius, but in some industrial gas turbines, they are effectively closed. This paper presents measurements of the disc heat transfer and rotating flow structures in a closed cavity over a wide range of engine relevant conditions. These experimentally derived distributions of disc temperature and heat flux are the first of their kind to be published. The radial distribution of the non-dimensional disc temperature virtually collapsed onto a single curve over the full experimental range. There was a small, monotonic departure from this common curve with increasing Reynolds number; this was attributed to compressibility effects where the core temperature increases as the rotational speed increases. These results imply that, if compressibility effects are negligible, all rotating closed cavities should have a disc temperature distribution uniquely related to the geometry and disc material; this is of important practical use to the engine designer. Unsteady pressure sensors detected either three or four vortex pairs across the experimental range. The number of pairs changed with Grashof number, and the structures slipped relative to the rotating discs by less than 1% of the disc speed.

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“…The dimensions of this gauge were 15 mm by 46 mm, spanning the full width along the underside of the downstream disc. The gauge was calibrated using a generic method described by Pountney et al [24] where an equation based on physical properties was derived to establish the theoretical relationship between the measured voltage output of the gauge and the heat flux through it. A bespoke experimental rig was used to calibrate the gauge under steady-state conditions for heat fluxes 0.5 < q < 8 kW/m 2 .…”

Section: Bath Compressor Cavity Rigmentioning

confidence: 99%

Stratified and Buoyancy-Induced Flow in Closed Compressor Rotors

Lock¹,

Jackson

Pernak

et al. 2022

Journal of Turbomachinery

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The radial growth of compressor discs is strongly influenced by conjugate heat transfer between conduction in the co-rotating discs and buoyancy-driven convection in the rotating fluid core between the discs. An accurate prediction of metal temperatures of these discs is an important issue in thermo-mechanical design. This paper presents an experimental study of the fluid dynamics and heat transfer in a closed rotating cavity, comparing results with theoretical models and introducing a new compressibility parameter χ . At large values of χ, where compressibility effects are significant, the air temperature approaches that of the shroud; such conditions suppress buoyancy effects and the flow in the rotating cavity becomes stratified. The experiments reveal that there is a critical value of χ where the convective heat flux to the shroud is zero. The radial distribution of disc temperature was that expected from pure conduction in a cylinder. A new heat transfer correlation based on measured shroud heat flux and the theoretical core temperature is presented. The unsteady flow characteristics in the cavity were also investigated, identifying coherent rotating structures across a range of experimental conditions. These cyclonic / anti-cyclonic vortex pairs generate the non-dimensional circumferential pressure difference necessary for the radial outflow (of cold fluid) and inflow (of hot fluid) through the rotating core. The experiments show the magnitude of these pressure variations can be correlated against Grashof number and that at high values of χ the structures do not exist.

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Calibration of thermopile heat flux gauges using a physically-based equation

Cited by 8 publications

References 22 publications

Experimental Investigation of Transient Flow Phenomena in Rotating Compressor Cavities

Experimental Investigation of Transient Flow Phenomena in Rotating Compressor Cavities

Measurement of Heat Transfer and Flow Structures in a Closed Rotating Cavity

Stratified and Buoyancy-Induced Flow in Closed Compressor Rotors

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