Flow mechanisms in axial turbine rim sealing

Chew, John W.; Gao, Feng; Palermo, Donato M.

doi:10.1177/0954406218784612

Cited by 41 publications

(24 citation statements)

References 59 publications

(166 reference statements)

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“…Scobie et al [1] and Chew et al [2] have reviewed the scholarly literature related to ingress. Articles directly related to the effect of ingress on the rotor are discussed below.…”

Section: Brief Review Of Relevant Researchmentioning

confidence: 99%

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Effect of Ingress on Flow and Heat Transfer Upstream and Downstream of a Rotating Turbine Disc

et al. 2019

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Ingress is the penetration of a hot mainstream gas in a turbine annulus through the rim seal into the wheel-space between the rotating turbine disc (the rotor) and the adjacent stationary casing (the stator). Purge flow is used to prevent or reduce ingress, and the sealing effectiveness relates the flow rates of the purge and ingress. In this paper, an adiabatic effectiveness is used to relate the temperatures of a thermally-insulated rotor, the purge flow and the ingress. A non-dimensional buffer parameter, Ψ, is used to relate the sealing effectiveness on the stator and the adiabatic effectiveness on the rotor, respectively. This paper reports the first experimental study of the effect of ingress and purge flow on the adiabatic temperatures of both upstream and downstream surfaces of the rotor. Measurements of concentration and swirl over a range of purge have been obtained in wheel-spaces upstream and downstream of the rotor in a turbine rig. In transient heating tests, fast-response thermocouples were used to measure the temperature of the air in the wheel-space core; simultaneously, the temperatures of the upstream and downstream rotor surfaces were determined from infra-red sensors. The extrapolated steady-state temperatures (obtained using a maximum-likelihood estimation analysis) were used to determine the adiabatic effectiveness as a function of purge flow rate. The buffer effect of the purge flow for both wheel-spaces was quantified via comparisons between the variation of Ψ with purge flow rate. It was shown that the sealing effectiveness for the downstream wheel-space was larger than for the upstream. Consequently, and consistent with the theoretical model, the buffering effect of the purge flow was shown to be smaller downstream.

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“…Scobie et al [1] and Chew et al [2] have reviewed the scholarly literature related to ingress. Articles directly related to the effect of ingress on the rotor are discussed below.…”

Section: Brief Review Of Relevant Researchmentioning

confidence: 99%

“…It was shown in Section 4.1 that the adiabatic rotor effectiveness, ε r , is related to the stator effectiveness, ε s , and the buffer parameter, Ψ , by Equation (2). Ψ can be determined using the transient temperature measurements, as shown in Sections 4.3 and 4.4.…”

Section: Adiabatic Effectiveness Of the Rotormentioning

confidence: 99%

Effect of Ingress on Flow and Heat Transfer Upstream and Downstream of a Rotating Turbine Disc

et al. 2019

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“…Although the first openly published study on the rim seal flow was (Bayley and Owen, 1970), but the evidence of the large scale nonsynchronous cavity modes was discussed in detail by (Cao et al, 2004). Recently, (Chew et al, 2018) carried out an excellent review study of the flow mechanisms on the axial turbine rim sealing with a focus on cavity modes. Schädler et al (2016) performed extensive experimental and full annular computations studying the migration of the cavity modes into the annulus flow under two purge flow rates.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity analysis on the impact of geometrical and operational variations on turbine hub cavity modes and practical methods to control them

Iranidokht

Kalfas

Abhari

et al. 2021

J. Glob. Power Propuls. Soc.

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This paper presents an experimental investigation on the impact of different design and operational variations on the instabilities induced at the hub cavity outlet of a turbine. The experiments were conducted at the “LISA” test facility at ETH Zurich. The axial gap at the 2nd stage hub cavity exit was varied, and also three different flow deflectors were implemented at the cavity exit to control the cavity modes (CMs). Furthermore, the turbine pressure ratio was altered to mimic the off-design condition and study the sensitivity of the CMs to this parameter. Measurements were performed using pneumatic, and Fast Response Aerodynamic Probes (FRAP) at stator and rotor exit. In addition, unsteady pressure transducers were installed at the cavity exit wall to measure the characteristic parameters of the CMs. For the small axial gap, distinct and strong CMs were generated, which actively interacted with stator and rotor hub flow structures. Increasing the gap damped the fluctuations; however, a broader range of frequencies was amplified. The flow deflectors successfully suppressed the CMs by manipulating the shear layer velocity profile and blocking the growing instabilities. Eventually, the increase in the turbine pressure ratio strengthened the CMs and vice versa.

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“…Due to the large impact on the engine performance, the rim seal flow has been extensively studied over the past 50 years. A recent review of the progress made is given by Chew et al (2019). Early studies of rim seal ingestion focused on the steady flow field inside the rotor-stator wheel space and the turbine hub region near the rotor-stator cavity.…”

Section: Introductionmentioning

confidence: 99%

Large-Eddy Simulations of Rim Seal Flow in a One-Stage Axial Turbine

Hösgen

Meinke

Schröder

2020

J. Glob. Power Propuls. Soc.

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The flow field in a one-stage axial flow turbine with 30 stator and 62 rotor blades including the wheel space is investigated by large-eddy simulation (LES). The Navier-Stokes equations are solved using a massively parallel finite-volume solver based on a Cartesian mesh with immersed boundaries. The strict conservation of mass, momentum, and energy is ensured by an efficient cut-cell/level-set ansatz, where a separate level-set solver describes the motion of the rotor. Both solvers use individual subsets of a shared Cartesian mesh, which they can adapt independently. The focus of the analysis is on the flow field inside the rotor stator cavity between the stator and rotor disks. Two cooling gas mass flow rates are investigated for the same rim seal geometry. First, the time averaged flow field for both simulations is compared, followed by a detailed investigation of the unsteady flow field. The results for the cooling effectiveness are compared to experimental data. Both cases show good agreement with experimental data. It is shown that for the lower cooling gas mass flux several of the wheel space’s acoustic waves are excited. This is not observed for the higher cooling gas mass flux. The excited waves lead to stable, i.e., bounded, fluctuations inside the wheel space and result in a significantly higher hot gas ingestion.

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Flow mechanisms in axial turbine rim sealing

Cited by 41 publications

References 59 publications

Effect of Ingress on Flow and Heat Transfer Upstream and Downstream of a Rotating Turbine Disc

Effect of Ingress on Flow and Heat Transfer Upstream and Downstream of a Rotating Turbine Disc

Sensitivity analysis on the impact of geometrical and operational variations on turbine hub cavity modes and practical methods to control them

Large-Eddy Simulations of Rim Seal Flow in a One-Stage Axial Turbine

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