Design of an Improved Turbine Rim-Seal

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
James A. Scobie ◽  
Roy Teuber ◽  
Yan Sheng Li ◽  
Carl M. Sangan ◽  
Michael Wilson ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Navier Stokes ◽  
Computational Time ◽  
Gas Concentration ◽  
Engine Design ◽  
Successful Design ◽  
Purge Flow ◽  
Rotor Disk ◽  
Computational Fluid Dynamics Cfd ◽  
Improved Performance

Rim seals are fitted in gas turbines at the periphery of the wheel-space formed between rotor disks and their adjacent casings. These seals, also called platform overlap seals, reduce the ingress of hot gases which can limit the life of highly stressed components in the engine. This paper describes the development of a new, patented rim-seal concept showing improved performance relative to a reference engine design, using unsteady Reynolds-averaged Navier–Stokes (URANS) computations of a turbine stage at engine conditions. The computational fluid dynamics (CFD) study was limited to a small number of purge-flow rates due to computational time and cost, and the computations were validated experimentally at a lower rotational Reynolds number and in conditions under incompressible flow. The new rim seal features a stator-side angel wing and two buffer cavities between outer and inner seals: the angel-wing promotes a counter-rotating vortex to reduce the effect of the ingress on the stator; the two buffer cavities are shown to attenuate the circumferential pressure asymmetries of the fluid ingested from the mainstream annulus. Rotor disk pumping is exploited to reduce the sealing flow rate required to prevent ingress, with the rotor boundary layer also providing protective cooling. Measurements of gas concentration and swirl ratio, determined from static and total pressure, were used to assess the performance of the new seal concept relative to a benchmark generic seal. The radial variation of concentration through the seal was measured in the experiments and these data captured the improvements due to the intermediate buffer cavities predicted by the CFD. This successful design approach is a potent combination of insight provided by computation, and the flexibility and expedience provided by experiment.

Design of an Improved Turbine Rim-Seal

2015 ◽  
Author(s):  
James A. Scobie ◽  
Roy Teuber ◽  
Yan Sheng Li ◽  
Carl M. Sangan ◽  
Michael Wilson ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Computational Time ◽  
Bench Mark ◽  
Swirl Ratio ◽  
Turbine Stage ◽  
Gas Concentration ◽  
Engine Design ◽  
Successful Design ◽  
Purge Flow ◽  
Improved Performance

Rim seals are fitted in gas turbines at the periphery of the wheel-space formed between rotor discs and their adjacent casings. These seals, also called platform overlap seals, reduce the ingress of hot gases which can limit the life of highly-stressed components in the engine. This paper describes the development of a new, patented rim-seal concept showing improved performance relative to a reference engine design, using URANS computations of a turbine stage at engine conditions. The CFD study was limited to a small number of purge-flow rates due to computational time and cost, and the computations were validated experimentally at a lower rotational Reynolds number and in conditions under incompressible flow. The new rim seal features a stator-side angel wing and two buffer cavities between outer and inner seals: the angel-wing promotes a counter-rotating vortex to reduce the effect of the ingress on the stator; the two buffer cavities are shown to attenuate the circumferential pressure asymmetries of the fluid ingested from the mainstream annulus. Rotor disc pumping is exploited to reduce the sealing flow rate required to prevent ingress, with the rotor boundary layer also providing protective cooling. Measurements of gas concentration and swirl ratio, determined from static and total pressure, were used to assess the performance of the new seal concept relative to a bench-mark generic seal. The radial variation of concentration through the seal was measured in the experiments and these data captured the improvements due to the intermediate buffer cavities predicted by the CFD. This successful design approach is a potent combination of insight provided by computation, and the flexibility and expedience provided by experiment.

Performance of a Finned Turbine Rim Seal

2014 ◽  
Author(s):  
Carl M. Sangan ◽  
James A. Scobie ◽  
J. Michael Owen ◽  
Gary D. Lock ◽  
Kok Mun Tham ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Turbine Stage ◽  
Research Facility ◽  
Flow Rates ◽  
Co2 Gas ◽  
Gas Concentration ◽  
Solid Body Rotation ◽  
Turbine Disc ◽  
Purge Flow ◽  
Improved Performance

In gas turbines, rim seals are fitted at the periphery of the wheel-space between the turbine disc and its adjacent casing; their purpose is to reduce the ingress of hot mainstream gases. A superposed sealant flow, bled from the compressor, is used to purge the wheel-space or at least dilute the ingress to an acceptable level. The ingress is caused by the circumferential variation of pressure in the turbine annulus radially outward of the seal. Engine designers often use double rim seals where the variation in pressure is attenuated in the outer wheel-space between the two seals. This paper describes experimental results from a research facility which models an axial turbine stage with engine-representative rim seals. The radial variation of CO2 gas concentration, swirl and pressure, in both the inner and outer wheel-space, are presented over a range of purge flow rates. The data are used to assess the performance of two seals: a datum double-rim seal and a derivative with a series of radial fins. The concept behind the finned seal is that the radial fins increase the swirl in the outer wheel-space; measurements of swirl show the captive fluid between the fins rotate with near solid body rotation. The improved attenuation of the pressure asymmetry, which governs the ingress, results in an improved performance of the inner geometry of the seal. The fins also increased the pressure in the outer wheel-space and reduced the ingress though the outer geometry of the seal.

Performance of a Finned Turbine Rim Seal

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Carl M. Sangan ◽  
James A. Scobie ◽  
J. Michael Owen ◽  
Gary D. Lock ◽  
Kok Mun Tham ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Turbine Disk ◽  
Turbine Stage ◽  
Research Facility ◽  
Flow Rates ◽  
Co2 Gas ◽  
Gas Concentration ◽  
Solid Body Rotation ◽  
Purge Flow ◽  
Improved Performance

In gas turbines, rim seals are fitted at the periphery of the wheel-space between the turbine disk and its adjacent casing; their purpose is to reduce the ingress of hot mainstream gases. A superposed sealant flow, bled from the compressor, is used to purge the wheel-space or at least dilute the ingress to an acceptable level. The ingress is caused by the circumferential variation of pressure in the turbine annulus radially outward of the seal. Engine designers often use double-rim seals where the variation in pressure is attenuated in the outer wheel-space between the two seals. This paper describes experimental results from a research facility that models an axial turbine stage with engine-representative rim seals. The radial variation of CO2 gas concentration, swirl, and pressure, in both the inner and outer wheel-space, are presented over a range of purge flow rates. The data are used to assess the performance of two seals: a datum double-rim seal and a derivative with a series of radial fins. The concept behind the finned seal is that the radial fins increase the swirl in the outer wheel-space; measurements of swirl show the captive fluid between the fins rotate with near solid body rotation. The improved attenuation of the pressure asymmetry, which governs the ingress, results in an improved performance of the inner geometry of the seal. The fins also increased the pressure in the outer wheel-space and reduced the ingress though the outer geometry of the seal.

Measurements and Modeling of Ingress in a New 1.5-Stage Turbine Research Facility

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Marios Patinios ◽  
James A. Scobie ◽  
Carl M. Sangan ◽  
J. Michael Owen ◽  
Gary D. Lock
Keyword(s):  
Theoretical Model ◽  
Gas Turbines ◽  
Test Facility ◽  
Radial Clearance ◽  
Operating Life ◽  
The Core ◽  
Wide Range ◽  
Purge Flow ◽  
Rotor Disk ◽  
Engine Components

In gas turbines, hot mainstream flow can be ingested into the wheel-space formed between stator and rotor disks as a result of the circumferential pressure asymmetry in the annulus; this ingress can significantly affect the operating life, performance, and integrity of highly stressed, vulnerable engine components. Rim seals, fitted at the periphery of the disks, are used to minimize ingress and therefore reduce the amount of purge flow required to seal the wheel-space and cool the disks. This paper presents experimental results from a new 1.5-stage test facility designed to investigate ingress into the wheel-spaces upstream and downstream of a rotor disk. The fluid-dynamically scaled rig operates at incompressible flow conditions, far removed from the harsh environment of the engine which is not conducive to experimental measurements. The test facility features interchangeable rim-seal components, offering significant flexibility and expediency in terms of data collection over a wide range of sealing flow rates. The rig was specifically designed to enable an efficient method of ranking and quantifying the performance of generic and engine-specific seal geometries. The radial variation of CO2 gas concentration, pressure, and swirl is measured to explore, for the first time, the flow structure in both the upstream and downstream wheel-spaces. The measurements show that the concentration in the core is equal to that on the stator walls and that both distributions are virtually invariant with radius. These measurements confirm that mixing between ingress and egress is essentially complete immediately after the ingested fluid enters the wheel-space and that the fluid from the boundary layer on the stator is the source of that in the core. The swirl in the core is shown to determine the radial distribution of pressure in the wheel-space. The performance of a double radial-clearance seal is evaluated in terms of the variation of effectiveness with sealing flow rate for both the upstream and the downstream wheel-spaces and is found to be independent of rotational Reynolds number. A simple theoretical orifice model was fitted to the experimental data showing good agreement between theory and experiment for all cases. This observation is of great significance as it demonstrates that the theoretical model can accurately predict ingress even when it is driven by the complex unsteady pressure field in the annulus upstream and downstream of the rotor. The combination of the theoretical model and the new test rig with its flexibility and capability for detailed measurements provides a powerful tool for the engine rim-seal designer.

Re-Ingestion of Upstream Egress in a 1.5-Stage Gas Turbine Rig

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
James A. Scobie ◽  
Fabian P. Hualca ◽  
Marios Patinios ◽  
Carl M. Sangan ◽  
J. Michael Owen ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Co2 Concentration ◽  
Test Facility ◽  
Operating Life ◽  
Annulus Flow ◽  
Purge Flow ◽  
Rotor Disk ◽  
First Time ◽  
Measured Mass ◽  
Insight Into

In gas turbines, rim seals are fitted at the periphery of stator and rotor discs to minimize the purge flow required to seal the wheel-space between the discs. Ingestion (or ingress) of hot mainstream gases through rim seals is a threat to the operating life and integrity of highly stressed components, particularly in the first-stage turbine. Egress of sealing flow from the first-stage can be re-ingested in downstream stages. This paper presents experimental results using a 1.5-stage test facility designed to investigate ingress into the wheel-spaces upstream and downstream of a rotor disk. Re-ingestion was quantified using measurements of CO2 concentration, with seeding injected into the upstream and downstream sealing flows. Here, a theoretical mixing model has been developed from first principles and validated by the experimental measurements. For the first time, a method to quantify the mass fraction of the fluid carried over from upstream egress into downstream ingress has been presented and measured; it was shown that this fraction increased as the downstream sealing flow rate increased. The upstream purge was shown to not significantly disturb the fluid dynamics but only partially mixes with the annulus flow near the downstream seal, with the ingested fluid emanating from the boundary layer on the blade platform. From the analogy between heat and mass transfer, the measured mass-concentration flux is equivalent to an enthalpy flux, and this re-ingestion could significantly reduce the adverse effect of ingress in the downstream wheel-space. Radial traverses using a concentration probe in and around the rim seal clearances provide insight into the complex interaction between the egress, ingress and mainstream flows.

scholarly journals Improved Modeling Capabilities of the Airflow Within Turbine Case Cooling Systems Using Smart Porous Media

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Yanling Li ◽  
A. Duncan Walker ◽  
John Irving
Keyword(s):  
Porous Media ◽  
Gas Turbines ◽  
Tip Clearance ◽  
Computational Time ◽  
Small Scale ◽  
Design Phase ◽  
Local Flow ◽  
Alternative Approach ◽  
Cooling Hole ◽  
Computational Fluid Dynamics Cfd

Impingement cooling is commonly employed in gas turbines to control the turbine tip clearance. During the design phase, computational fluid dynamics (CFD) is an effective way of evaluating such systems but for most turbine case cooling (TCC) systems resolving the small scale and large number of cooling holes is impractical at the preliminary design phase. This paper presents an alternative approach for predicting aerodynamic performance of TCC systems using a “smart” porous media (PM) to replace regions of cooling holes. Numerically CFD defined correlations have been developed, which account for geometry and local flow field, to define the PM loss coefficient. These are coded as a user-defined function allowing the loss to vary, within the calculation, as a function of the predicted flow and hence produce a spatial variation of mass flow matching that of the cooling holes. The methodology has been tested on various geometrical configurations representative of current TCC systems and compared to full cooling hole models. The method was shown to achieve good overall agreement while significantly reducing both the mesh count and the computational time to a practical level.

The Effect of a Meter-Diffuser Offset on Shaped Film Cooling Hole Adiabatic Effectiveness

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Shane Haydt ◽  
Stephen Lynch ◽  
Scott Lewis
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Electrical Discharge Machining ◽  
Density Ratio ◽  
Navier Stokes ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Adiabatic Effectiveness ◽  
Improved Performance ◽  
Film Cooling Holes

Shaped film cooling holes are used extensively in gas turbines to reduce component temperatures. These holes generally consist of a metering section through the material and a diffuser to spread coolant over the surface. These two hole features are created separately using electrical discharge machining (EDM), and occasionally, an offset can occur between the meter and diffuser due to misalignment. The current study examines the potential impact of this manufacturing defect to the film cooling effectiveness for a well-characterized shaped hole known as the 7-7-7 hole. Five meter-diffuser offset directions and two offset sizes were examined, both computationally and experimentally. Adiabatic effectiveness measurements were obtained at a density ratio of 1.2 and blowing ratios ranging from 0.5 to 3. The detriment in cooling relative to the baseline 7-7-7 hole was worst when the diffuser was shifted upstream (aft meter-diffuser offset), and least when the diffuser was shifted downstream (fore meter-diffuser offset). At some blowing ratios and offset sizes, the fore meter-diffuser offset resulted in slightly higher adiabatic effectiveness than the baseline hole, due to a reduction in the high-momentum region of the coolant jet caused by a separation region created inside the hole by the fore meter-diffuser offset. Steady Reynolds-averaging Navier–Stokes (RANS) predictions did not accurately capture the levels of adiabatic effectiveness or the trend in the offsets, but it did predict the fore offset's improved performance.

Investigations of Flutter and Aero Damping of a Turbine Blade: Part 2 — Numerical Simulations

2016 ◽  
Author(s):  
Wei-Min Ren ◽  
Charles E. Seeley ◽  
Xuefeng Zhang ◽  
Brian E. Mitchell ◽  
Hongbin Ju
Keyword(s):  
Numerical Simulations ◽  
Gas Turbines ◽  
Navier Stokes ◽  
Turbine Cascade ◽  
Aeroelastic Response ◽  
Successful Prediction ◽  
Transonic Flutter ◽  
Flutter Boundary ◽  
Computational Fluid Dynamics Cfd ◽  
Last Stage

There is a demand for Modern Heavy Duty Gas Turbines (HDGT) to provide greater MW power output with higher efficiency. This trend leads to longer and slimmer turbine last stage blades with exposure to higher aerodynamic loadings. As a result, they are more prone to flutter risks. Turbine flutter risks must be addressed during the design phase and this requires the accurate prediction of the flutter boundary and the aero damping ratios with quantified uncertainties. Numerical simulations, based on Computational Fluid Dynamics (CFD), of a two-passage linear turbine cascade were carried out. The results are presented in this paper aimed to study aspects of flutter. A time-linearized Navier–Stokes approach was applied to predict the aeroelastic response. Simulations were carried out for Mach numbers ranging from 0.4 to 1.2. The objective of this study is to quantify the aero damping prediction uncertainty. CFD results showed successful prediction of the transonic flutter boundary. The predicted aero work was compared with the experimental data and good agreements were demonstrated for both the subsonic and supersonic flows. The steady and unsteady surface pressures on the test rig sidewalls, predicted by CFD, were then compared with the test data in great detail. Limitations of the linear approach are also discussed.

Influence of an Axial and Radial Rim Seal Geometry on Hot Gas Ingestion Into the Upstream Cavity of a 1.5-Stage Turbine

2006 ◽  
Author(s):  
Dieter E. Bohn ◽  
Achim Decker ◽  
Nils Ohlendorf ◽  
Ralf Jakoby
Keyword(s):  
Carbon Dioxide ◽  
Gas Turbines ◽  
Static Pressure ◽  
Turbine Rotor ◽  
Gas Concentration ◽  
Hot Gas ◽  
Carbon Dioxide Gas ◽  
Flow Parameters ◽  
Pressure Distributions ◽  
Rotor Disk

In gas turbines hot gas ingestion into the cavities between rotor and stator disks has to be avoided almost completely in order to ensure that the guaranteed lifetime of the turbine rotor disk will be reached. The influence of an axial and radial rim seal configuration geometry on the phenomenon of hot gas ingestion into the rim seal section and inside the front cavity of a 1.5-stage axial turbine is experimentally investigated. The results obtained for the reference axial configuration are compared to those for the radial configuration in the upstream cavity of the turbine. The hot gas ingestion phenomenon is examined for different flow parameters such as non-dimensional seal flow rate, Reynolds number in the main annulus and rotational speed. The sealing efficiency is determined by measurements of the carbon dioxide gas concentration in the cavity. Static pressure distributions are measured using pressure taps at the stator disk and rim seal lip. It will be shown for the axial rim seal geometry that the guide vanes mainly influence the flow field in the rim seal gap and inside the cavity whereas for the radial rim seal geometry such an influence is limited almost exclusively to the rim seal gap. For the radial rim seal a higher sealing efficiency was detected, mainly due to the different type of the rim seal.

An OpenFOAM-Based Extension of Low-Re k–ε Model to the Partially Averaged Navier–Stokes Methodology for Simulating Separated Flows With Heat Transfer

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Krishnendu Chakraborty ◽  
Sagar Saroha ◽  
Sawan S. Sinha
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Computational Cost ◽  
Separated Flow ◽  
Classical Case ◽  
Separated Flows ◽  
Navier Stokes ◽  
Computational Time ◽  
Square Cylinder ◽  
Improved Performance

Abstract The partially averaged Navier–Stokes (PANS) methodology is known to give improved performance over the traditional Reynolds-averaged Navier–Stokes (RANS) formulation at an affordable computational cost. Over the years, PANS has gained popularity in both industry and academia. In this work, we strive to improve the performance of the k–ε-based PANS methodology by formulating a low-Reynolds-number (LRN) k–ε model-based PANS closure. We have compared the PANS closure based on Launder-Sharma k–ε model (LSKE) with PANS closure based on the conventional two-layer k–ε model (TLKE) in the classical case of separated flow past a heated square cylinder at Reynolds number (Re) of 21,400. The PANS methodologies are compared on the basis of flow hydrodynamics, heat transfer rate, and computational time. These methodologies are compared with the benchmark experimental and direct numerical simulation (DNS) results. The PANS + LSKE methodology clearly outperforms the conventional PANS + TLKE methodology in predicting the flow hydrodynamics and is computationally much faster as well. Moreover, the performance of the LSKE model in conjunction with the PANS methodology is found to be comparable to the more recent models like the shear stress transport (SST)–k–ω and the k–ε–ζ–f model. In heat transfer aspects, the performance of LSKE (with Yap correction)-based closure is the best on the stagnation surface, while the LSKE (without Yap correction)-based closure performs comparably better on the lateral and rear surfaces.

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