Investigation of the Influence of Different Rim Seal Geometries in a Low-Pressure Turbine

Schuler, Philip; Dullenkopf, Klaus; Bauer, H.-J.

doi:10.1115/gt2011-45682

Cited by 9 publications

(8 citation statements)

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“…Furthermore, the authors presented a systematic variation of the overlap-type rim seal design, highlighting that there might not be an optimum rim seal solution which leads to an improvement in terms of aerodynamic losses and sealing effectiveness for the full rim seal purge mass flow range. Schuler et al (2011) have shown for different rim seal designs in a low-pressure turbine an attenuation of the passage vortex when increasing the distance between seal and blade leading edge.…”

Section: Introductionmentioning

confidence: 99%

Novel high-pressure turbine purge control features for increased stage efficiency

Schädler

Kalfas

Abhari

et al. 2017

J. Glob. Power Propuls. Soc.

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Rim seals throttle flow and have shown to impact the aerodynamic performance of gas turbines. The results of an experimental investigation of a rim seal exit geometry variation and its impact on the high-pressure turbine flow field are presented. A one-and-a-half stage, unshrouded and highly loaded axial turbine configuration with 3-dimensionally shaped blades and non-axisymmetric end wall contouring has been tested in an axial turbine facility. The exit of the rotor upstream rim seal was equipped with novel geometrical features which are termed as purge control features (PCFs) and a baseline rim seal geometry for comparison. The time-averaged and unsteady aerodynamic effects at rotor inlet and exit have been measured with pneumatic probes and the fast-response aerodynamic probe (FRAP) for three rim seal purge flow injection rates. Measurements at rotor inlet and exit reveal the impact of the geometrical features on the rim seal exit and main annulus flow field, highlighting regions of reduced aerodynamic losses induced by the modified rim seal design. Measurements at the rotor exit with the PCFs installed show a benefit in the total-to-total stage efficiency up to 0.4% for nominal and high rim seal purge flow rates. The work shows the potential to improve the aerodynamic efficiency by means of a well-designed rim seal exit geometry without losing the potential to block hot gas ingestion from the main annulus.

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Section: Introductionmentioning

confidence: 99%

Novel high-pressure turbine purge control features for increased stage efficiency

Schädler

Kalfas

Abhari

et al. 2017

J. Glob. Power Propuls. Soc.

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show abstract

“…More recently, Schüler et al [3] confirmed the advantages of overlapping seals in terms of reduced hot gas ingestion and loss generation. In addition, they have also observed attenuation of the passage vortex by increasing the distance between the seal and blade-leading edges.…”

Section: Introductionmentioning

confidence: 86%

“…In each case, the loss coefficient is expressed in terms of -Pi (2) ( 3) where Poi is the mass-averaged inlet total pressure at the mainstream inlet located 2Cx upstream of the blade row, while PO2,MIX and P2 are the mixed-out total pressure and static pressure at the plane located 0.5Cx downstream of the blade-trailing edges, respectively. The total pressure loss coefficient was evaluated by assuming that the exit flow is fully mixed-out in a constant area duct as per Amecke [14].…”

Section: Methodsmentioning

confidence: 99%

The Effects of a Parametric Variation of the Rim Seal Geometry on the Interaction Between Hub Leakage and Mainstream Flows in High Pressure Turbines

Popović¹,

Hodson

2013

Journal of Engineering for Gas Turbines and Power

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The objective ofthis work was to assess and understand the effects of a parametric variation performed on a typical overlapping rim seal geometry. The datum geometry has been the focus of a detailed experimental investigation employing a large-scale linear cascade subjected to a range of the mass flow rates and swirl velocities of the leakage air. The parametric variations described in this paper were examined using validated computational fluid dynamics (CFD). As a part of the parametric studies, both the axial and the radial seal clearance between the rotor fin (angel wing) and stator platform were varied as well as the length of the overlap between stator and rotor platforms. In addition, the effects of forward and backward facing annulus steps were also investigated. It has been found that a backward-facing annulus step was detrimental for all conditions considered, while a forward-facing step offered improvements for smaller step heights and/or lower leakage fractions. Tightening of the seal clearances closer to the annulus line improved the sealing effectiveness but often at the expense of increased losses. On the other hand, increasing the overlap length led to improvements in the sealing effectiveness with very small effects on the overall losses. Moving the rim seal away from the blade-leading edges reduced the pressure asymmetry at the rim seal and increased the flow uniformity of the leakage air. However, this led to an increased cross-passage flow (more negative skew) and higher losses at all but lowest leakage fractions. The results presented in this paper highlight the fact that there may not be an optimum rim seal solution that would offer an improvement for the full range of leakage fractions and that, for different rim sealing flows, there may be a different optimum geometiy. In addition, rotor disk movements in radial and axial directions at various off-design conditions should be considered as a part of the design process. Based on the presented results, it may be of a benefit to the turbine designer to consider rotor disk designs that would be more biased towards the upstream and outward disk movements, which would result in tightening of the seal clearances and avoidance of a backward-facing annulus step.

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“…Three different rim seal geometries were studied during the experiments. A first geometry with an axial clearance (simple gap) and two [16] geometries using simple and double axial overlapping (referred as A, B and D in Fig. 2).…”

Section: Configuration and Numerical Methodsmentioning

confidence: 99%

Delineating Loss Sources Within a Linear Cascade With Upstream Cavity and Purge Flow

Fiore

Gourdain

Boussuge

et al. 2019

Journal of Turbomachinery

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Purge air is injected in cavities at the hub of axial turbines to prevent hot mainstream gas ingestion into interstage gaps. This process induces additional losses for the turbine due to an interaction between the purge and mainstream flow. This paper investigates the flow in a low-speed linear cascade rig with upstream hub cavity at a Reynolds number commonly observed in modern low-pressure turbine stages by the use of numerical simulation. Numerical predictions are validated by comparing against experimental data available. Three different purge mass flow rates are tested using three different rim seal geometries. Numerical simulations are performed using a large-eddy simulation (LES) solver on structured grids. An investigation of the different mechanisms associated with the turbine flow including cavity and purge air is intended through this simplified configuration. The underlying mechanisms of loss are tracked using an entropy formulation. Once described for a baseline case, the influence of purge flow and rim seal geometry on flow mechanisms and loss generation is described with the emphasis to obtain design parameters for losses reduction. The study quantifies loss generation due to the boundary layer on wetted surfaces and secondary vortices developing in the passage. The analysis shows different paths by which the purge flow and rim seal geometry can change loss generation including a modification of the shear layer between purge and mainstream, interaction with secondary vortices, and a modification of the flow behavior close to hub compared with a smooth configuration. The study shows the influence of purge flow rate and swirl on the strengthening of secondary vortices in the passage and the ability of axial overlapping rim seal to delay the development of secondary vortices compared with simple axial gaps.

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Investigation of the Influence of Different Rim Seal Geometries in a Low-Pressure Turbine

Cited by 9 publications

References 0 publications

Novel high-pressure turbine purge control features for increased stage efficiency

Novel high-pressure turbine purge control features for increased stage efficiency

The Effects of a Parametric Variation of the Rim Seal Geometry on the Interaction Between Hub Leakage and Mainstream Flows in High Pressure Turbines

Delineating Loss Sources Within a Linear Cascade With Upstream Cavity and Purge Flow

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