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.

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.

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.

Experimental Investigation of Purge Flow Effects on a High Pressure Turbine Stage

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
K. Regina ◽  
A. I. Kalfas ◽  
R. S. Abhari
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Gas Turbines ◽  
Radial Displacement ◽  
Secondary Flows ◽  
Turbine Stage ◽  
Flow Factor ◽  
Purge Flow ◽  
The Impact ◽  
Stage Efficiency

In the present paper, an experimental investigation of the effects of rim seal purge flow on the performance of a highly loaded axial turbine stage is presented. The test configuration consists of a one-and-a-half stage, unshrouded, turbine, with a blading representative of high pressure (HP) gas turbines. Efficiency measurements for various purge flow injection levels have been carried out with pneumatic probes at the exit of the rotor and show a reduction of isentropic total-to-total efficiency of 0.8% per percent of injected mass flow. For three purge flow conditions, the unsteady aerodynamic flow field at rotor inlet and rotor exit has been measured with the in-house developed fast response aerodynamic probe (FRAP). The time-resolved data show the unsteady interaction of the purge flow with the secondary flows of the main flow and the impact on the radial displacement of the rotor hub passage vortex (HPV). Steady measurements at off-design conditions show the impact of the rotor incidence and of the stage flow factor on the resulting stage efficiency and the radial displacement of the rotor HPV. A comparison of the effect of purge flow and of the off-design conditions on the rotor incidence and stage flow factor shows that the detrimental effect of the purge flow on the stage efficiency caused by the radial displacement of the rotor HPV is dominated by the increase of stage flow factor in the hub region rather than by the increase of negative rotor incidence.

VORTEX TRACKING OF PURGE-MAINSTREAM INTERACTIONS IN A ROTATING TURBINE STAGE

2021 ◽  
pp. 1-22
Author(s):  
Alex Mesny ◽  
Mark Glozier ◽  
Oliver J Pountney ◽  
James Scobie ◽  
Yansheng Li ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Gas Turbines ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Turbine Stage ◽  
Baseline Case ◽  
Flow Features ◽  
Purge Flow ◽  
Cycle Efficiency

Abstract The use of purge flow in gas turbines allows for high turbine entry temperatures, which are essential to produce high cycle efficiency. Purge air is bled from the compressor and reintroduced in the turbine to cool vulnerable components. Wheel-spaces are formed between adjacent rotating and stationary discs, with purge air supplied at low radius before exiting into the mainstream gas-path through a rim-seal at the disc periphery. An aerodynamic penalty is incurred as the purge flow egress interacts with the mainstream. This study presents unparalleled three-dimensional velocity data from a single-stage turbine test rig, specifically designed to investigate egressmainstream interaction using optical measurement techniques. Volumetric Velocimetry is applied to the rotating environment with phase-locked measurements used to identify and track the vortical secondary flow features through the blade passage. A baseline case without purge flow is compared to experiments with a 1.7% purge mass fraction; the latter was chosen to ensure a fully sealed wheel-space. A non-localised vortex tracking function is applied to the data to identify the position of the core centroids. The strength of the secondary-flow vortices was determined by using a circulation criterion on rotated planes aligned to the vortex filaments........[abridged]

Numerical investigation of non-uniform flow in twin-silo combustors and impact on axial turbine stage performance

2021 ◽  
pp. 095765092199394
Author(s):  
Hafiz M Hassan ◽  
Adeel Javed ◽  
Asif H Khoja ◽  
Majid Ali ◽  
Muhammad B Sajid
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Internal Flow ◽  
Large Temperature ◽  
Clear Understanding ◽  
Gas Temperature ◽  
Turbine Stage ◽  
Flow Angle ◽  
Axial Turbine ◽  
Stage Performance

A clear understanding of the flow characteristics in the older generation of industrial gas turbines operating with silo combustors is important for potential upgrades. Non-uniformities in the form of circumferential and radial variations in internal flow properties can have a significant impact on the gas turbine stage performance and durability. This paper presents a comprehensive study of the underlying internal flow features involved in the advent of non-uniformities from twin-silo combustors and their propagation through a single axial turbine stage of the Siemens v94.2 industrial gas turbine. Results indicate the formation of strong vortical structures alongside large temperature, pressure, velocity, and flow angle deviations that are mostly located in the top and bottom sections of the turbine stage caused by the excessive flow turning in the upstream tandem silo combustors. A favorable validation of the simulated exhaust gas temperature (EGT) profile is also achieved via comparison with the measured data. A drop in isentropic efficiency and power output equivalent to 2.28% points and 2.1 MW, respectively is observed at baseload compared to an ideal straight hot gas path reference case. Furthermore, the analysis of internal flow topography identifies the underperforming turbine blading due to the upstream non-uniformities. The findings not only have implications for the turbine aerothermodynamic design, but also the combustor layout from a repowering perspective.

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.

Experimental Investigation of Turbine Stage Flow Field and Performance at Varying Cavity Purge Rates and Operating Speeds

2016 ◽  
Author(s):  
Johan Dahlqvist ◽  
Jens Fridh
Keyword(s):  
Mach Number ◽  
Flow Field ◽  
High Speed ◽  
Control Volume ◽  
Spatial Average ◽  
Turbine Stage ◽  
Wide Range ◽  
Annulus Flow ◽  
Purge Flow ◽  
Secondary Air

The aspect of hub cavity purge has been investigated in a high-pressure axial low-reaction turbine stage. The cavity purge is an important part of the secondary air system, used to isolate the hot main annulus flow from cavities below the hub level. A full-scale cold-flow experimental rig featuring a rotating stage was used in the investigation, quantifying main annulus flow field impact with respect to purge flow rate as it was injected upstream of the rotor. Five operating speeds were investigated of which three with respect to purge flow, namely a high loading case, the peak efficiency, and a high speed case. At each of these operating speeds, the amount of purge flow was varied across a very wide range of ejection rates. Observing the effect of the purge rate on measurement plane averaged parameters, a minor outlet swirl decrease is seen with increasing purge flow for each of the operating speeds while the Mach number is constant. The prominent effect due to purge is seen in the efficiency, showing a similar linear sensitivity to purge for the investigated speeds. An attempt is made to predict the efficiency loss with control volume analysis and entropy production. While spatial average values of swirl and Mach number are essentially unaffected by purge injection, important spanwise variations are observed and highlighted. The secondary flow structure is strengthened in the hub region, leading to a generally increased over-turning and lowered flow velocity. Meanwhile, the added volume flow through the rotor leads to higher outlet flow velocities visible in the tip region, and an associated decreased turning. A radial efficiency distribution is utilized, showing increased impact with increasing rotor speed.

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

2016 ◽  
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 ◽  
Engine Components ◽  
First Time

In gas turbines, hot mainstream flow can be ingested into the wheel-space formed between stator and rotor discs 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 discs, are used to minimise ingress and therefore reduce the amount of purge flow required to seal the wheel-space and cool the discs. 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 disc. 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.

scholarly journals Aero-Thermal Design and Testing of Advanced Turbine Blades

1997 ◽  
Author(s):  
M. Haendler ◽  
D. Raake ◽  
M. Scheurlen
Keyword(s):  
Gas Turbines ◽  
Full Range ◽  
Turbine Blades ◽  
Design Procedure ◽  
Thermal Design ◽  
Test Facility ◽  
Optical Pyrometer ◽  
Electrical Systems ◽  
Operation Conditions ◽  
Improved Performance

Based on the experience gained with more than 80 machines operating worldwide in 50 and 60 Hz electrical systems respectively, Siemens has developed a new generation of advanced gas turbines which yield substantially improved performance at a higher output level. This “3A-Series” comprises three gas turbine models ranging from 70 MW to 240 MW for 50 Hz and 60 Hz power generation applications. The first of the new advanced gas turbines with 170 MW and 3600 rpm was tested in the Berlin factory test facility under the full range of operation conditions. It was equipped with various measurement systems to monitor pressures, gas and metal temperatures, clearances, strains, vibrations and exhaust emissions. This paper presents the aero-thermal design procedure of the highly thermal loaded film cooled first stage blading. The predictions are compared with the extensive optical pyrometer measurements taken at the Siemens test facility on the V84.3A machine under full load conditions. The pyrometer was inserted at several locations in the turbine and radially moved giving a complete surface temperature information of the first stage vanes and blades.

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