Interaction of Shroud Leakage Flow and Main Flow in a Three-Stage LP Turbine

Gier, Jochen; Stubert, Bertram; Brouillet, Bernard; Vito, Laurent de

doi:10.1115/1.2006667

Cited by 44 publications

(18 citation statements)

References 20 publications

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“…4-6 all made more detailed study of rim seal leakage flows in the compressor environment and found that the tangential velocity was a key parameter in the interaction of purge flow and endwall flow. Hunter and Manwaring, 7 Gier et al, 8 and Bohn et al, 9 focused their works on turbines. Mclean et al, 10,11 tested the radial, impingement and root injection cooling configurations.…”

Section: Introductionmentioning

confidence: 98%

Numerical investigation of the interaction between upstream cavity purge flow and main flow in low aspect ratio turbine cascade

Wei¹,

Liu²

2013

Chinese Journal of Aeronautics

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In modern gas turbines, rim seal located between the stator-disc and rotor-disc is used to prevent hot-gas ingestion into the inner stage-gap of high pressure turbine. However, the purge flow supplied to the cavity through the rim seal interacts with the main flow, producing additional aerodynamic loss due to the mixing process which plays a significant role in the formation, development and evolution of downstream secondary flow. In this paper, a set of cascade representative of low aspect ratio turbine is selected to numerically investigate the influence of upstream cavity purge flow on the hub secondary flow structure and aerodynamic loss. Cascade with/without upstream cavity and four different purge mass flow rates are all taken into account in this simulation. Then, a deep insight into the loss mechanism of interaction between purge flow and main flow is gained. The results show that the presence of cavity and purge flow has a significant impact on the main flow which not only changes the vortex structure in both the passage and upstream cavity, but also alters the cascade exit flow angle distribution along the spanwise. Moreover, aerodynamic loss in the cascade rises with the increase of purge flow rate while the sealing effect is also enhanced. Therefore, the effect of upstream cavity purge flow must be considered in the process of turbine aerodynamic design. What is more, it is necessary to minimize the purge flow rate in order to reduce aerodynamic loss on the premise of satisfying cooling requirements.

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Section: Introductionmentioning

confidence: 98%

Numerical investigation of the interaction between upstream cavity purge flow and main flow in low aspect ratio turbine cascade

Wei¹,

Liu²

2013

Chinese Journal of Aeronautics

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“…Abo El Ella, et al [4] also found that losses and flow overturning increased for an endwall with an upstream cavity relative to a smooth wall due to a separation in the cavity that strengthened the passage vortex. A loss breakdown scheme proposed by Gier, et al [5] suggested that steps between turbine components were responsible for 20% of the loss increase between a smooth-flowpath model and a more realistic model with leakage interfaces.…”

Section: Review Of Relevant Literaturementioning

confidence: 99%

Endwall Heat Transfer for a Turbine Blade With an Upstream Cavity and Rim Seal Leakage

Lynch

Thole

Kohli

et al. 2013

Volume 3C: Heat Transfer

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Aerodynamic loss and endwall heat transfer for a turbine blade are influenced by complex vortical flows that are generated at the airfoil-endwall junction. In an engine, those flows interact with clearance gaps between stationary and rotating components, as well as with leakage flow that is designed to exhaust through the gaps. This paper describes experimental measurements of endwall heat transfer for a highpressure turbine blade with an endwall overlap geometry, as well as an upstream leakage feature that supplied swirled or unswirled leakage relative to the blade. For unswirled leakage, increasing its mass flow increased the magnitude and pitchwise uniformity of the heat transfer coefficient upstream of the blades although heat transfer further into the passage was unchanged. Leakage flow with swirl shifted the horseshoe vortex in the direction of swirl and increased heat transfer on the upstream blade endwall, as compared to unswirled leakage. For a nominal leakage mass flow ratio of 0.75%, swirled leakage did not increase area-averaged heat transfer relative to unswirled leakage. At a mass flow ratio of 1.0%, however, swirled leakage increased overall heat transfer by 4% due to an increase in the strength of the vortical flows.

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“…The work focused on the shroud leakage flows has demonstrated that the geometry of exit shroud cavity plays a crucial role in their interaction with the mainstream (e.g., Pfau et al [8] and Gier et al [9]). Schlienger et al [10] compared a rectangular cavity configuration with sharp edge corners and the one modified by placing inserts to allow a shallower injection angle.…”

Section: Introductionmentioning

confidence: 98%

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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Interaction of Shroud Leakage Flow and Main Flow in a Three-Stage LP Turbine

Cited by 44 publications

References 20 publications

Numerical investigation of the interaction between upstream cavity purge flow and main flow in low aspect ratio turbine cascade

Numerical investigation of the interaction between upstream cavity purge flow and main flow in low aspect ratio turbine cascade

Endwall Heat Transfer for a Turbine Blade With an Upstream Cavity and Rim Seal Leakage

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

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