Investigation of Flow Instabilities Near the Rim Cavity of a 1.5 Stage Gas Turbine

Rabs, M.; Benra, Friedrich-Karl; Dohmen, Hans Josef; Schneider, Oliver

doi:10.1115/gt2009-59965

Cited by 45 publications

(26 citation statements)

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“…For an unconstrained flow with uniform density, the instability will apply to any shear layer. Computations with circumferentially uniform imposed annulus flow indicate that the high shear between purge and annulus flows support the occurrence of such instability [43,49]. Further to this Savov et al [34] associated increased unsteadiness in their seal outer cavity or trough with increased shear between purge and main annulus flows at off design conditions.…”

Section: Instability and Wave Theorymentioning

confidence: 91%

“…Amongst these are investigations by Rabs et al [43], and Zhang and Ma [44]. Rabs et al [43] performed URANS simulation on a 22.5 ∘ sector without vanes and blades.…”

Section: Axial Rim Sealsmentioning

confidence: 99%

“…Amongst these are investigations by Rabs et al [43], and Zhang and Ma [44]. Rabs et al [43] performed URANS simulation on a 22.5 ∘ sector without vanes and blades. They associated predicted unsteady flow modes unrelated to the blade passing with the KelvinHelmholtz shear layer instability in the rim seal gap region, where the main annulus flow interacts with the purge flow.…”

Section: Axial Rim Sealsmentioning

confidence: 99%

See 2 more Smart Citations

Flow mechanisms in axial turbine rim sealing

Chew

Gao

Palermo

2018

Proceedings of the Institution of Mechanical Engineers, Part C:

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This paper presents a review of research on turbine rim sealing with emphasis placed on the underlying flow physics and modelling capability. Rim seal flows play a crucial role in controlling engine disc temperatures but represent a loss from the main engine power cycle and are associated with spoiling losses in the turbine. Elementary models that rely on empirical validation and are currently used in design do not account for some of the known flow mechanisms, and prediction of sealing performance with computational fluid dynamics (CFD) has proved challenging. CFD and experimental studies have indicated important unsteady flow effects that explain some of the differences identified in comparing predicted and measure sealing effectiveness. This review reveals some consistency of investigations across a range of configurations, with inertial waves in the rotating flow apparently interacting with other flow mechanisms which include vane, blade and seal flow interactions, disc pumping and cavity flows, shear layer and other instabilities, and turbulent mixing.

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Section: Instability and Wave Theorymentioning

confidence: 91%

“…Amongst these are investigations by Rabs et al [43], and Zhang and Ma [44]. Rabs et al [43] performed URANS simulation on a 22.5 ∘ sector without vanes and blades.…”

Section: Axial Rim Sealsmentioning

confidence: 99%

Section: Axial Rim Sealsmentioning

confidence: 99%

See 1 more Smart Citation

Flow mechanisms in axial turbine rim sealing

Chew

Gao

Palermo

2018

Proceedings of the Institution of Mechanical Engineers, Part C:

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“…Chilla et al [2013] reported strong unsteady flow interaction between rim seal and main gas path at nominal sealing flow conditions, and periodically vortex shedding from rim seal into the main annulus. Rabs et al [2009] identified similar vertex structures and conjectured that they could be induced by the Kelvin-Helmholtz instabilities. The latest researches have all experimentally confirmed the existence of rim seal cavity modes which are unattributed to blade passing.…”

Section: Introductionmentioning

confidence: 99%

Numerical Studies of Turbine Rim Sealing Flows on a Chute Seal Configuration

Gao

Chew

Beard

et al. 2017

European Conference on Turbomachinery Fluid Dynamics and Hermodynamics

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This paper presents CFD (computational fluid dynamics) modelling of a chute type rim seal that has been previously experimentally investigated. The study focuses on inherent large-scale unsteadiness rather than that imposed by vanes and blades or external flow. A large-eddy simulation (LES) solver is validated for a pipe flow test case and then applied to the chute rim seal rotor/stator cavity. LES, Reynolds-averaged Navier-Stokes (RANS) and unsteady RANS (URANS) models all showed reasonable agreement with steady measurements within the disc cavity, but only the LES shows unsteadiness at a similar distinct peak frequency to that found in the experiment, at 23 times the rotational frequency. However, there are some significant differences between unsteadiness predicted and the measurements, and possible causes of these are discussed.

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“…Rabs et al [32] performed unsteady simulations of a 1.5 stage turbine test rig with and without blades. The authors found that the introduction of a blade pressure field suppresses the Kelvin-Helmholtz type instabilities.…”

Section: Introductionmentioning

confidence: 99%

A Comparison of Single and Double Lip Rim Seal Geometries

Savov

Atkins

Uchida

2017

Journal of Engineering for Gas Turbines and Power

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The effect of the purge flow, engine-like blade pressure field, and mainstream flow coefficient are studied experimentally for a single and double lip rim seal. Compared to the single lip, the double lip seal requires less purge flow for similar levels of cavity seal effectiveness. Unlike the double lip seal, the single lip seal is sensitive to overall Reynolds number, the addition of a simulated blade pressure field, and large-scale nonuniform ingestion. In the case of both seals, unsteady pressure variations attributed to shear layer interaction between the mainstream and rim seal flows appear to be important for ingestion at off-design flow coefficients. The double lip seal has both a weaker vane pressure field in the rim seal cavity and a smaller difference in seal effectiveness across the lower lip than the single lip seal. As a result, the double lip seal is less sensitive in the rotor–stator cavity to changes in shear layer interaction and the effects of large-scale circumferentially nonuniform ingestion. However, the reduced flow rate through the double lip seal means that the outer lip has increased sensitivity to shear layer interactions. Overall, it is shown that seal performance is driven by both the vane/blade pressure field and the gradient in seal effectiveness across the inner lip. This implies that accurate representation of both, the pressure field and the mixing due to shear layer interaction, would be necessary for more reliable modeling.

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Investigation of Flow Instabilities Near the Rim Cavity of a 1.5 Stage Gas Turbine

Cited by 45 publications

References 0 publications

Flow mechanisms in axial turbine rim sealing

Flow mechanisms in axial turbine rim sealing

Numerical Studies of Turbine Rim Sealing Flows on a Chute Seal Configuration

A Comparison of Single and Double Lip Rim Seal Geometries

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