Aerodynamic Performance of a Transonic Turbine Blade Passage in Presence of Upstream Slot and Mateface Gap With Endwall Contouring

Jain, Sakshi; Roy, Arnab; Ng, Wing; Ekkad, Srinath V.; Lohaus, Andrew S.; Taremi, Farzad

doi:10.1115/gt2014-26475

Cited by 5 publications

(4 citation statements)

References 21 publications

(36 reference statements)

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“…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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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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“…The losses were attributed to mixing within the gap, and were shown to be relatively independent of platform gap net flowrate. Measurements in a transonic cascade by Jain et al [10] led them to conclude that the presence of the platform gap (without net flow) resulted in a 5% increase in overall loss, but introduction of net gap flow had negligible effect. In contrast, Piggush and Simon [3] found a small increase in the loss for increased gap flow, but loss did not change for net flowrates above 1% of the mainstream flow.…”

Section: Relevant Past Studiesmentioning

confidence: 99%

Heat Transfer and Film Cooling on a Contoured Blade Endwall With Platform Gap Leakage

Lynch

Thole

2015

Volume 5B: Heat Transfer

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Turbine blade components in an engine are typically designed with gaps between parts due to manufacturing, assembly, and operational considerations. Coolant is provided to these gaps to limit the ingestion of hot combustion gases. The interaction of the gaps, their leakage flows, and the complex vortical flow at the endwall of a turbine blade can significantly impact endwall heat transfer coefficients and the effectiveness of the leakage flow in providing localized cooling. In particular, a platform gap through the passage, representing the mating interface between adjacent blades in a wheel, has been shown to have a significant effect. Other important turbine blade features present in the engine environment are non-axisymmetric contouring of the endwall, and an upstream rim seal with a gaspath cavity, which can reduce and increase endwall vortical flow, respectively. To understand the platform gap leakage effect in this environment, measurements of endwall heat transfer and film cooling effectiveness were performed in a scaled blade cascade with a non-axisymmetric contour in the passage. A rim seal with a cavity, representing the overlap interface between a stator and rotor, was included upstream of the blades and a nominal purge flowrate of 0.75% of the mainstream was supplied to the rim seal. Results indicated that endwall heat transfer coefficients increased as platform gap net leakage increased from 0% to 0.6% of the mainstream flowrate, but net heat flux to the endwall was reduced due to high cooling effectiveness of the leakage flow.

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“…However, most of these studies focus on the endwall heat transfer and cooling performance. With regard to the aerodynamic performance, Jain et al 19 investigated the aerodynamic performance of a transonic turbine blade passage in the presence of upstream slot and midgap with nonaxisymmetric endwall contouring. In their work, numerous conditions test were conducted but the case of the nonaxisymmetric endwall without midgap was not provided thus the disadvantage of the design without considering the midgap was not clear.…”

Section: Introductionmentioning

confidence: 99%

The aerodynamic optimization design of turbine cascade nonaxisymmetric endwall and the midgap influence assessment

Líu

Shen

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part G:

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The nonaxisymmetric endwall profiling has been proven to be an effective tool to reduce the secondary flow loss in turbomachinery. In the present work, first, without considering the endwall midgap in the real machine, an endwall optimization design procedure for reducing secondary flow losses has been developed, which allowed complete threedimensional parameterization turbine endwall design. The profile of the endwall has been designed using automatic numerical optimization by means of an improved efficient global optimization algorithm based on kriging surrogate model. Next, a large-scale linear cascade with a low-speed wind tunnel has been chosen for the experimental validation of the optimization results. The experimental measurements and numerical simulations both demonstrated that the total pressure loss and secondary flow intensity were reduced with the nonaxisymmetric endwall used in the cascade passage. Then, in order to evaluate the ability of the optimized nonaxisymmetric endwall with the midgap, the midgap was added in for both the baseline flat endwall and the optimized nonaxisymmetric endwall in the numerical simulations analysis. The entropy generation rates analysis were used for the investigation of loss distribution in the passage. For the cascade in the present work, with the midgap added in, the optimized nonaxisymmetric endwall did not perform as well as the situation without the midgap in the loss reduction. In addition, comparing to the baseline flat endwall, the optimized nonaxisymmetric endwall needed more net leakage flow to avoid the ingress of passage flow into the midgap.

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Aerodynamic Performance of a Transonic Turbine Blade Passage in Presence of Upstream Slot and Mateface Gap With Endwall Contouring

Cited by 5 publications

References 21 publications

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

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

Heat Transfer and Film Cooling on a Contoured Blade Endwall With Platform Gap Leakage

The aerodynamic optimization design of turbine cascade nonaxisymmetric endwall and the midgap influence assessment

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