Unsteady, 3-Dimensional Flow Measurement Using a Miniature Virtual 4 Sensor Fast Response Aerodynamic Probe (FRAP)

Pfau, Axel; Schlienger, J.; Kalfas, A. I.; Abhari, Reza S.

doi:10.1115/gt2003-38128

Cited by 32 publications

(12 citation statements)

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“…Values were taken from experimental probe measurements with the LEC in-house manufactured fast response aerodynamic probe (FRAP), performed during the same measurement campaign. More details on the FRAP probe and measurement techniques can be found in (Kupferschmied et al, 2000) and (Pfau et al, 2003).…”

Section: Resultsmentioning

confidence: 99%

Purge flow effects on rotor hub endwall heat transfer with extended endwall contouring into the disk cavity

Hänni

Schädler

Abhari

et al. 2019

J. Glob. Power Propuls. Soc.

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Efficiency improvements for gas turbines are strongly coupled with increasing turbine inlet temperatures. This imposes new challenges for designers for efficient and adequate cooling of turbine components. Modern gas turbines inject bleed air from the compressor into the stator/ rotor rim seal cavity to prevent hot gas ingestion from the main flow, while cooling the rotor disk. The purge flow interacts with the main flow field and static pressure field imposed by the turbine blades. This complex interaction causes non-uniform and jet-like penetration of the purge flow into the main flow field, hence affecting the endwall heat transfer on the rotor.To improve the understanding of purge flow effects on rotor hub endwall heat transfer, an unshrouded, high-pressure representative turbine design with 3D blading and extended endwall contouring of the rotor into the cavity seal was tested. The measurements were conducted in the 1.5-stage axial turbine facility LISA at ETH Zurich, where a state-of-the-art measurement setup with a high-speed infrared camera and thermally managed rotor insert was used to perform high-resolution heat transfer measurements on the rotor. Three different purge flow rates were investigated with regard to hub endwall heat transfer. Additionally, steady-state computational fluid dynamics simulations were performed to complement the experiments.It was found that the local heat transfer rate changes up to ±20% depending on the purge flow rate. The main part of the purged air is ejected at the endwall trough location and swept towards the rotor suction side, which is caused by the interaction of main flow and the cavity extended endwall design. The presence of low momentum purge flow locally reduces the heat transfer rate. Changes in adiabatic wall temperature and heat transfer (depending on purge rate) are observed from the platform start up to the cross passage migration of the secondary flow structures.

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Section: Resultsmentioning

confidence: 99%

Purge flow effects on rotor hub endwall heat transfer with extended endwall contouring into the disk cavity

Hänni

Schädler

Abhari

et al. 2019

J. Glob. Power Propuls. Soc.

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“…The probe technology has been developed in-house at LEC at ETH Zurich. Detailed information concerning the measurement technology are presented by (Kupferschmied et al, 2000) and (Pfau et al, 2003). The FRAP allows to measure total and static pressure as well as flow yaw and pitch angle in a frequency bandwidth up to 48 kHz.…”

Section: Measurement Technology and Measurement Uncertaintymentioning

confidence: 99%

Noise characteristics of a reduced blade count rotor with improved stage efficiency

Schädler

Hänni

Kalfas

et al. 2019

J. Glob. Power Propuls. Soc.

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A reduction in rotor blade count in combination with a gain in aerodynamic performance is a desirable design goal for gas turbines to reduce the overall operational costs. Reducing the number of blades provokes inherently an increase in blade loading which drives the secondary flow strength. In the presented experimental work, the results of inter-stage probe measurements in a highly loaded 1.5-stage axial turbine rig show the potential to improve the stage efficiency for a reduced blade count rotor with respect to a baseline configuration with more blades. Time-resolved probe measurements reveal the detrimental effects on the turbine tonal noise level. It is found that the periodic vorticity fluctuations induced by the interaction of the rotor passage secondary flow structures with the potential field of the downstream stator, leads at specific span positions to a strong increase in the noise level at rotor exit with respect to the baseline. Both, the downstream effect of the convected rotor flow structures as well as the periodic interaction of the second stator originated flow structures are found to drive the acoustic field of the turbine. Overall, the stage efficiency benefit achievement of 0.4% for a 22% reduction in rotor blade count is derogated by an increase in tonal noise by up to 13 dB at the second stator exit.

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“…The probe technology has been developed by the laboratory of energy conversion (LEC) at ETH, and is commercialised by Limmat Scientific AG. The measurement technology is described in more detail in (Kupferschmied et al, 2000) and (Pfau et al, 2003). The two sensor miniature probes (1.8 mm tip diameter) were operated in a virtual four sensor mode, as described by (Pfau et al, 2002), to derive the flow velocities and angles.…”

Section: Turbine Configuration and Operating Conditionsmentioning

confidence: 99%

Variable Blade Tip Geometry Inserts for Combined Aerothermal Measurements for Bladed Disk Rotors

Hänni¹,

Schädler²,

Kalfas³

et al. 2019

Proceedings of Global Power &Amp; Propulsion Society

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Cost effective experimental testing in turbomachinery requires the integration of multiple geometries in one rotor. So-called rainbow designs, combined with fast response aerodynamic and entropy probes, allow for experimentally investigating different designs in a timely and cost effective manner. The investigation of new blade tip geometries is of particular interest, because tip leakage losses account for approximately one third of the total aerodynamic losses in a turbine stage. This work presents the design, integration, and testing of a variable and exchangeable blade tip setup integrated in a bladed disk rotor. The key features of the concept are high flexibility of the geometry, coupled with the possibility of introducing blade tip coolant flows in bladed disk arrangements, and the integration of tip heat transfer measurements. After successful bench tests, an existing rotor has been modified with three tip inserts of the same geometry, and subsequently tested in the axial turbine research facility LISA at ETH Zurich. A custom-made thin film heater for optical highresolution heat transfer measurements was successfully integrated on the insert and tested during operation. Flow field measurements behind the rotor indicated that the aerodynamics of the rotor is not influenced by installing tip inserts. The setup has proven its robustness in more than 80 days of experimental testing, and has provided some encouraging tip heat transfer data.

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Unsteady, 3-Dimensional Flow Measurement Using a Miniature Virtual 4 Sensor Fast Response Aerodynamic Probe (FRAP)

Cited by 32 publications

References 0 publications

Purge flow effects on rotor hub endwall heat transfer with extended endwall contouring into the disk cavity

Purge flow effects on rotor hub endwall heat transfer with extended endwall contouring into the disk cavity

Noise characteristics of a reduced blade count rotor with improved stage efficiency

Variable Blade Tip Geometry Inserts for Combined Aerothermal Measurements for Bladed Disk Rotors

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