A New Interpretation of Hot Gas Ingress Through Turbine Rim Seals Influenced by Mainstream Annulus Swirl

Graikos, Dimitrios; Tang, Hongxiao; Sangan, Carl M.; Lock, Gary; Scobie, James A.

doi:10.1115/1.4055457

Cited by 10 publications

(6 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The inlet total temperature, the inlet-to-outlet total pressure ratio, and the rotational speeds of the two rotors are also kept constant for all the tests, with an uncertainty of ±0.3 • C, ±0.5%, and ±0.1%, respectively. In terms of main stream quantities, the annulus Mach number is approximately M ≈ 0.5, much higher than the values reported in [7,11]. In addition to the PFR variation, four different HPT vanes clocking positions are investigated.…”

Section: Operating Conditionsmentioning

confidence: 81%

“…This suggests that the mentioned models may not provide the most appropriate description of the ingress phenomenon for the setup under examination, where the presence of upstream and downstream airfoils generates a complex hub flow field, and the annulus Reynolds and Mach are relatively high. In this sense, Graikos et al [11] recently proposed a novel interpretation of ingress, correlated to the swirl ratio difference between annulus and rim seal clearance rather than to Δ𝐶 𝑃,𝑚𝑎𝑥 . Unfortunately, the The marker shapes in Figure 7a symbolize different vane clocking positions, which practically collapse all on the same curves, one for each measurement location.…”

Section: Sealing Performancementioning

confidence: 99%

“…Although the stage total pressure ratio is kept constant during the tests, the secondary air injection causes local boundary layer energization on the TVF hub platform, resulting in a static pressure decrease when the PFR rises. The analytical model, described by Equation (11), has been fitted to all the investigated cases but is here reported only for the extremes PFR = 0 (dotted line) and PFR = 2 (dashed line). The agreement with experimental data is very good, and the adjusted coefficient of determination, averaged across the tested PFRs, is R 2 adj ≈ 0.9.…”

Section: Pressure Measurements-effect Of the Sealing Flow Ratementioning

confidence: 99%

“…They concluded that the upstream injection partially mixes with the annulus air stream close to the downstream seal, reducing the adverse effects of ingress. In any case, many of the experimental works on the subject are performed in facilities operating at low speed, with annulus Mach number ranging approximately from M = 0.2 to 0.4 upstream of the rotor blade [9,10] and M < 0.2 downstream [7,11].…”

mentioning

confidence: 99%

See 3 more Smart Citations

Aerodynamics and Sealing Performance of the Downstream Hub Rim Seal in a High-Pressure Turbine Stage

Merli

Krajnc

Hafizovic

et al. 2023

IJTPP

View full text Add to dashboard Cite

The purpose of the paper is to characterize the aerodynamic behavior of a rotor-downstream hub cavity rim seal in a high-pressure turbine (HPT) stage. The experimental data are acquired in the Transonic Test Turbine Facility at the Graz University of Technology: the test setup includes two engine-representative turbine stages (the last HPT stage and first LPT stage), with the intermediate turbine duct in between. All stator-rotor cavities are supplied with purge flows by a secondary air system, which simulates the bleeding air from the compressor stages of the real engine. The HPT downstream hub cavity is provided with wall taps and pitot tubes at different radial and circumferential locations, which allows the performance of steady pressure and seed gas concentration measurements for different purge mass flows and HPT vanes clocking positions. Moreover, miniaturized pressure transducers are adopted to evaluate the unsteady pressure distribution, and an oil flow visualization is performed to retrieve additional information on the wheel space structures. The annulus pressure asymmetry depends on the HPT vane clocking, but this is shown to have negligible impact on the minimum purge mass flow required to seal the cavity. However, the hub pressure profile drives the distribution of the cavity egress in the turbine channel. The unsteady pressure field is dominated by blade-synchronous oscillations. No non-synchronous components with comparable intensity are detected.

show abstract

Section: Operating Conditionsmentioning

confidence: 81%

Section: Sealing Performancementioning

confidence: 99%

Section: Pressure Measurements-effect Of the Sealing Flow Ratementioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Aerodynamics and Sealing Performance of the Downstream Hub Rim Seal in a High-Pressure Turbine Stage

Merli

Krajnc

Hafizovic

et al. 2023

IJTPP

View full text Add to dashboard Cite

show abstract

“…It is worth noting that the experimental measurements of sealing effectiveness also show some strong sensitivities. Graikos et al's [40] plots of effectiveness against main annulus flow swirl ratio show some collapse of data for different configurations but with regions of rapid change in effectiveness with annulus flow velocity. These complex, unstable flows may be susceptible to switching between flow structures and sensitivity to modelling assumptions and experimental condition is certainly plausible.…”

Section: Pressure (Pa)mentioning

confidence: 99%

Effect of Rim Seal Geometry on Rotationally-Driven Ingestion

Burden,

Chew,

Gao

et al. 2024

Journal of Engineering for Gas Turbines and Power

View full text Add to dashboard Cite

This study investigates turbine rim seal geometry effects within the rotationally-driven ingestion regime. Computations were performed with a wall-resolved unsteady Reynolds-averaged Navier-Stokes (URANS) model and a large-eddy simulation (LES) model including near-wall boundary layer modelling, that is wall-modelled LES (WMLES). Use of simplified rim sealing models is proposed as an efficient method of ranking seal designs and investigating sensitivity to seal geometry. Four rim seal configurations, two chute seals, an axial seal and a radial seal which are representative of those used in gas turbines and in previous research were investigated. Furthermore, hybrid seals combining geometric characteristics from both the chute and radial seal were considered. Significant sensitivities of sealing performance to turbulence modelling are identified, but URANS and WMLES show similar trends in ranking of seal performance, and these are consistent with previous experimental work. The addition of an outer radial clearance section to a chute seal is effective in reducing ingestion levels.

show abstract

Influence of swirl and ingress on windage losses in a low-pressure turbine stator-well cavity

Jackson,

Christodoulou,

et al. 2023

Exp Fluids

View full text Add to dashboard Cite

As part of the drive towards achieving net-zero flight by 2050, the development of ultra-high bypass ratio engines will place greater importance on the efficiency of the low-pressure turbine. Stator-well cavities can be a significant source of loss within this system, primarily due to the ingestion of annulus air, which can rotate at a speed less than that of the disc. This paper presents the results of a joint experimental/numerical campaign to relate windage torque to the flow physics in a scaled, engine-realistic stator-well geometry with superposed flows. The primary variables were the pressure ratio across the stator row and the swirl ratio at inlet to the cavity. This is the first paper to relate simultaneous torque and swirl measurements in a stator-well cavity. The numerical simulations have also provided insight into the fluid dynamic behaviour. A reduction in cavity windage torque with superposed flow rate was shown, consistent with the increase in swirl measured by experiments and predicted by computations. The pre-swirled superposed flows reduce the ingestion of negatively swirling fluid from the annulus, effectively increasing the swirl ratio of the flow in the cavity towards that of the rotor. This reduces windage losses; at the design condition with superposed flow, the cavity windage torque reduced by 60% of that of the reference case. Sealing effectiveness increased with superposed flow rate. This was demonstrated through gas concentration measurement/simulations, a reduced radial flow velocity into the cavity and a reduced mass flow rate across the interstage seal. The application of a turbulent transport model showed that ingestion could be explained by shear-driven diffusion. Ingestion increased as inlet swirl ratio reduced, while the pressure ratio was found to have a negligible influence on windage moment coefficient, swirl ratio and sealing effectiveness. In addition to providing fluid dynamic insight, the gas concentration results can be used for validating thermomechanical models. The results in this paper will be of practical interest to the engine designer who wishes to scale information to engine-operating conditions.

show abstract

A New Interpretation of Hot Gas Ingress Through Turbine Rim Seals Influenced by Mainstream Annulus Swirl

Cited by 10 publications

References 20 publications

Aerodynamics and Sealing Performance of the Downstream Hub Rim Seal in a High-Pressure Turbine Stage

Aerodynamics and Sealing Performance of the Downstream Hub Rim Seal in a High-Pressure Turbine Stage

Effect of Rim Seal Geometry on Rotationally-Driven Ingestion

Influence of swirl and ingress on windage losses in a low-pressure turbine stator-well cavity

Contact Info

Product

Resources

About