Heat Transfer Performance of a Transonic Turbine Blade Passage in the Presence of Leakage Flow Through Upstream Slot and Mateface Gap With Endwall Contouring

Roy, Arnab; Jain, Sakshi; Ekkad, Srinath V.; Ng, Wing; Lohaus, Andrew S.; Crawford, Michael E.; Abraham, Santosh

doi:10.1115/1.4037909

Cited by 19 publications

(5 citation statements)

References 21 publications

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“…(Thrift et al, 2012) showed that a slot angle of 45°increases cooling effectiveness (compared to 90°) due to a different formation of the horseshoe vortex. An overall averaged reduction in Nusselt number for the endwall, both with and without purge flow, was reported by (Roy et al, 2017) for a contoured endwall due to secondary flow control. Further, (Lynch et al, 2010) reported a 3.1% reduction of averaged heat transfer for endwall contouring.…”

Section: Introductionmentioning

confidence: 85%

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: Introductionmentioning

confidence: 85%

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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“…It is important to understand where the models provide reasonable estimates of Nu, since that information is important to a designer considering cooling schemes for the endwall. Both Lynch and Thole [19] and Roy et al [21] indicate that gap leakage increases local heat transfer coefficients relative to no flow, but also provides significant cool air to the aft suction side region and generally results in lower heat flux.…”

Section: Effect Of Midpassage Gap Leakage For Aligned Endwallsmentioning

confidence: 99%

“…Although this ejected fluid can locally increase heat transfer significantly (>200% relative to the upstream endwall), it is also a source of cooling air. A series of studies with realistic endwall conditions and endwall contouring in a transonic facility by Jain et al [20] and Roy et al [21] also concluded that a majority of the gap leakage flow was located near the throat, and that a contoured endwall improved coolant distribution relative to a flat endwall.…”

Section: Relevant Past Studiesmentioning

confidence: 99%

Computational and Experimental Studies of Midpassage Gap Leakage and Misalignment for a Non-Axisymmetric Contoured Turbine Blade Endwall

Lange

Lynch

Lewis

2016

Volume 5A: Heat Transfer

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Turbine vanes and blades are generally manufactured as single or double airfoil sections that must each be installed onto a turbine disk. Between each section, a gap at the endwalls through the blade passage is present, through which high pressure coolant is leaked. Furthermore, sections can become misaligned due to thermal expansion or centrifugal forces. Flow and heat transfer around the gap is complicated due to the interaction of the mainstream and the leakage flow. An experimental and computational study was undertaken to determine the physics of the leakage flow interaction for a realistic turbine blade endwall, and assess whether steady RANS CFD, commonly used for non-axisymmetric endwall design, can be used to accurately model this interaction. Computational models were compared against experimental observations of endwall heat transfer on a contoured endwall with a midpassage gap. Endwall heat transfer coefficients were determined experimentally by using infrared thermography to capture spatially-resolved surface temperatures on a uniform heat flux surface (heater) attached to the endwall. Predictions and measurements both indicated an increase in endwall heat transfer with increasing gap leakage flow, although the distribution of heat transfer coefficients along the gap was not well captured by CFD. A misalignment of the blade endwall causing a forward-facing step for the near-endwall flow resulted in a large highly turbulent recirculation region downstream of the step and high local heat transfer that was overpredicted by CFD. Conversely, a backward-facing step reduced turbulence and local heat transfer. The misprediction of local heat transfer around the gap is thought to be caused by unsteady interaction of the passage secondary flow and gap leakage flow, which cannot be well-captured by a steady RANS approach.

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“…(Thrift et al, 2012) showed that a slot angle of 45 deg increases cooling effectiveness compared to 90 deg due to a different formation of the horse shoe vortex. An overall averaged reduction in Nusselt number for the endwall with and without purge flow is reported by (Roy et al, 2017) for a contoured endwall due to secondary flow control. Also (Lynch et al, 2010) reported a reduction by 3.1% of averaged heat transfer for endwall contouring.…”

Section: Introductionmentioning

confidence: 98%

Purge Flow Effects on Rotor Hub Endwall Heat Transfer with Extended EndwallContouring into the Disk Cavity

Hänni¹,

Abhari²,

Schädler³

et al. 2019

GPPS Zurich19

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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 use bleed air from the compressor to inject into the stator/rotor rim seal cavity to prevent hot gas ingestion from the main flow, while cooling the rotor disk. This purge flow interacts with the main flow field and static pressure field imposed by the turbine blades. The complex interaction causes nonuniform and jet-like penetration of the purge flow into the main flow field and therefore affects the endwall heat transfer on the rotor. In order to improve the understanding of purge flow effects on rotor hub endwall heat transfer, measurements in the 1.5-stage axial turbine facility LISA at ETH Zurich have been performed. An unshrouded, high-pressure representative turbine design with 3D blading and extended endwall contouring of the rotor into the cavity seal has been tested. A state-of-the-art measurement setup with a high-speed infrared camera and thermally managed rotor insert has been 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 CFD 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 caused by the interaction of main flow and the cavity extended endwall design. The presence of low momentum purge flow is locally reducing 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.

show abstract

Heat Transfer Performance of a Transonic Turbine Blade Passage in the Presence of Leakage Flow Through Upstream Slot and Mateface Gap With Endwall Contouring

Cited by 19 publications

References 21 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

Computational and Experimental Studies of Midpassage Gap Leakage and Misalignment for a Non-Axisymmetric Contoured Turbine Blade Endwall

Purge Flow Effects on Rotor Hub Endwall Heat Transfer with Extended EndwallContouring into the Disk Cavity

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