An Advanced Single-Stage Turbine Facility for Investigating Nonaxisymmetric Contoured Endwalls in the Presence of Purge Flow

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Robin R. Jones ◽  
Oliver J. Pountney ◽  
Bjorn L. Cleton ◽  
Liam E. Wood ◽  
B. Deneys J. Schreiner ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Static Pressure ◽  
Optical Measurement ◽  
Single Stage ◽  
Test Facility ◽  
Pressure Distributions ◽  
Mainstream Flow ◽  
Planar Laser ◽  
Flow Interactions ◽  
Purge Flow

Abstract In modern gas turbines, endwall contouring (EWC) is employed to modify the static pressure field downstream of the vanes and minimize the growth of secondary flow structures developed in the blade passage. Purge flow (or egress) from the upstream rim-seal interferes with the mainstream flow, adding to the loss generated in the rotor. Despite this, EWC is typically designed without consideration of mainstream–egress interactions. The performance gains offered by EWC can be reduced, or in the limit eliminated, when purge air is considered. In addition, EWC can result in a reduction in sealing effectiveness across the rim seal. Consequently, industry is pursuing a combined design approach that encompasses the rim-seal, seal-clearance profile, and EWC on the rotor endwall. This paper presents the design of and preliminary results from a new single-stage axial turbine facility developed to investigate the fundamental fluid dynamics of egress–mainstream flow interactions. To the authors' knowledge, this is the only test facility in the world capable of investigating the interaction effects between cavity flows, rim seals, and EWC. The design of optical measurement capabilities for future studies, employing volumetric velocimetry (VV) and planar laser-induced fluorescence (PLIF), is also presented. The fluid-dynamically scaled rig operates at benign pressures and temperatures suited to these techniques and is modular. The facility enables expedient interchange of EWC (integrated into the rotor bling), blade-fillet and rim-seal geometries. The measurements presented in this paper include: gas concentration effectiveness and swirl measurements on the stator wall and in the wheel-space core; pressure distributions around the nozzle guide vanes (NGV) at three different spanwise locations; pitchwise static pressure distributions downstream of the NGV at four axial locations on the stator platform.

An Advanced Single-Stage Turbine Facility for Investigating Non-Axisymmetric Contoured Endwalls in the Presence of Purge Flow

2019 ◽  
Author(s):  
Robin R. Jones ◽  
Oliver J. Pountney ◽  
Bjorn L. Cleton ◽  
Liam E. Wood ◽  
B. Deneys J. Schreiner ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Static Pressure ◽  
Optical Measurement ◽  
Guide Vane ◽  
Single Stage ◽  
Test Facility ◽  
Pressure Distributions ◽  
Mainstream Flow ◽  
Purge Flow ◽  
Nozzle Guide

Abstract In modern gas turbines, endwall contouring (EWC) is employed to modify the static pressure field downstream of the vanes and minimise the growth of secondary flow structures developed in the blade passage. Purge flow (or egress) from the upstream rim-seal interferes with the mainstream flow, adding to the loss generated in the rotor. Despite this, EWC is typically designed without consideration of mainstream-egress interactions. The performance gains offered by EWC can be reduced, or in the limit eliminated, when purge air is considered. In addition, EWC can result in a reduction in sealing effectiveness across the rim seal. Consequently, industry is pursuing a combined design approach that encompasses the rim-seal, seal-clearance profile and EWC on the rotor endwall. This paper presents the design of, and preliminary results from a new single-stage axial turbine facility developed to investigate the fundamental fluid dynamics of egress-mainstream flow interactions. To the authors’ knowledge this is the only test facility in the world capable of investigating the interaction effects between cavity flows, rim seals and EWC. The design of optical measurement capabilities for future studies, employing volumetric velocimetry and planar laser induced fluorescence are also presented. The fluid-dynamically scaled rig operates at benign pressures and temperatures suited to these techniques and is modular. The facility enables expedient interchange of EWC (integrated into the rotor bling), blade-fillet and rim-seals geometries. The measurements presented in this paper include: gas concentration effectiveness and swirl measurements on the stator wall and in the wheel-space core; pressure distributions around the nozzle guide vanes at three different spanwise locations; pitchwise static pressure distributions downstream of the nozzle guide vane at four axial locations on the stator platform.

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.

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.

Vortex Tracking of Purge-Mainstream Interactions in a Rotating Turbine Stage

2021 ◽  
Author(s):  
Alex W. Mesny ◽  
Mark A. Glozier ◽  
Oliver J. Pountney ◽  
James A. Scobie ◽  
Yan Sheng Li ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Gas Turbines ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Horseshoe Vortex ◽  
Suction Surface ◽  
Vortex Filaments ◽  
Passage Vortex ◽  
Purge Flow

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 egress-mainstream 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. The pressure-side leg of the horseshoe vortex and a second vortex associated with the egress flow were identified by the experimental campaign. In the absence of purge flow the two vortices merged, forming the passage vortex. With the addition of purge flow, the two cores remained independent to 40% of the blade axial chord, while also demonstrating an increased radial migration and intensification of the passage vortex. The egress core was shown to remain closer to the suction-surface with purge flow. Importantly, where the vortex filaments demonstrated strong radial or tangential components of velocity, the circulation level calculated from axial planes underpredicted the true circulation by up to 50%.

APR+ Core Flow and Pressure Distributions Under the 4 Pump Unbalanced Flow Condition

2013 ◽  
Author(s):  
K. Kim ◽  
D. J. Euh ◽  
Y. J. Youn ◽  
I. C. Chu ◽  
H. S. Choi ◽  
...  
Keyword(s):  
Flow Condition ◽  
Static Pressure ◽  
Flow Path ◽  
Test Facility ◽  
Hydraulic Characteristics ◽  
Ensemble Averaging ◽  
Core Flow ◽  
Pressure Distributions ◽  
Fuel Assemblies ◽  
Reduced Scale

The core inlet flow rates and exit pressure distributions of an APR+ (Advanced Power Reactor Plus) reactor were evaluated experimentally in this study. The tests were performed in the ACOP (APR+ Core Flow & Pressure) test facility constructed with a linear reduced scale of 1/5 referring to the prototype plant. The major flow path inside the reactor vessel was designed with a preservation of a geometrically similar flow without hindering the dynamic similarity. The 257 core simulators with 771 pressure impulse lines were installed in the ACOP facility to measure the hydraulic characteristics at the inlet and outlet of the fuel assemblies. The pressure distributions along the major flow path were obtained by measuring the static pressure and differential pressures at 584 points. The hydraulic characteristics of the reactor flow under an unbalanced cold leg flow condition were investigated by using an ensemble averaging process of 5 independent tests. The details of these experiments and a data analysis were described in this paper.

Effect of Swirl on Pressure Recovery in Annular Diffusers

1980 ◽  
Vol 22 (6) ◽  
pp. 305-313 ◽  
Author(s):  
D. S. Kumar ◽  
K. L. Kumar
Keyword(s):  
Cross Sections ◽  
Static Pressure ◽  
Tangential Velocity ◽  
Pressure Recovery ◽  
Test Facility ◽  
Pressure Loss Coefficient ◽  
Pressure Distributions ◽  
Inlet Swirl ◽  
Total Pressure Loss Coefficient ◽  
Different Levels

Annular diffusers are likely to operate with varying amounts of swirl at the inlet. The work described in this paper is concerned mainly with an experimental investigation of subsonic turbulent swirling flows through annular diffusers having diverging hub and casing boundaries. The test facility was designed SO as to peImit different levels of inlet swirl. The static pressure distributions and the axial and tangential velocity profiles were measured with the help of a three-hole cobra probe suitably mounted at different cross sections along the diffuser length. The diffuser performance parameters such as static-pressure recovery, effectiveness, and the total pressure loss coefficient were then computed from the experimental observations. The behaviour of these parameters has been discussed to establish the effect of swirl. The presence of inlet swirl was found to increase the overall static-pressure recovery. A substantial increase in the pressure recovery occurred over the initial stages of diffusion and the gain was maintained thereafter. Improvement in effectiveness was more significant for otherwise stalled diffusers. Introduction of swirl was found to substantially reduce the chances of separation at the casing and to shift the stall from the casing to the hub for the stalled diffusers.

A New Test Facility for Investigating the Interaction Between Swirl Flow and Wall Cooling Films in Combustors

2009 ◽  
Author(s):  
B. Wurm ◽  
A. Schulz ◽  
H.-J. Bauer
Keyword(s):  
Gas Turbines ◽  
Static Pressure ◽  
Thermal Analyses ◽  
Thermal Studies ◽  
Swirl Flow ◽  
Operating Conditions ◽  
Test Facility ◽  
Wall Region ◽  
Test Rig ◽  
Combustor Liner

Swirl stabilization of flames is typically used in combustors of aero engines and gas turbines for power generation. In the near wall region of the combustor liner, the swirling flow interacts in a very particular way with wall cooling films. This interaction and its effect on the local wall cooling performance gave reason to design and commission a new atmospheric test rig for detailed aerodynamic and thermal studies. The new test rig includes three burners in a planar arrangement. Special emphasis was placed on the simulation of realistic operating conditions as Reynolds number and temperature ratio. The liner cooling and the formation of a starter cooling film can be independently controlled. The rectangular flow channel is equipped with large windows to allow for laser optical diagnostics like PIV and 3-component LDA. The thermal analyses are based on highly resolved temperature mappings of the cooled surface utilizing infrared thermography. First experimental results are presented in terms of static pressure distributions on the combustor liner and PIV contour plots of the swirl flow. The static pressure pattern corresponds well to the up wash and downwash regions of the swirl flow.

scholarly journals Experimental Investigation on the Effect of Varying Purge Flow in a Newly Commissioned Single Stage Turbine Test Facility

2020 ◽  
Author(s):  
Daniel Payne ◽  
Vasudevan Kanjirakkad
Keyword(s):  
Pressure Ratio ◽  
Outer Radius ◽  
Single Stage ◽  
Rotor Blades ◽  
Test Facility ◽  
Rotating Disc ◽  
Radial Temperature ◽  
Turbine Performance ◽  
Purge Flow ◽  
Secondary Air

Abstract In order to produce efficient engines it is essential for gas tur-bine designers to understand the interaction between the primary and secondary air systems in critical parts of the engine. One of these is the first stage turbine, where the ingress of the hot an-nulus air into the rotor stator cavity could be catastrophic due to the increased heat load on the disc posts and on the rotor blades themselves (through reduced cooling). To ensure that this does not happen, contactless seals (rim seals) are built into the outer radius of the rotating disc. Additionally, a secondary air flow rate must be appropriately set in order to ‘purge’ the hot air that could be ingested into the rim seal cavity. However, this purge airflow could cause deterioration of the turbine performance as it re-joins the main annulus flow at the interface between the rim seal cavity and the main annulus. The deterioration in performance is pri-marily due to the difference in kinematic (flow velocity and mass flow) and thermodynamic (density, enthalpy) properties of the two stream of air. It is therefore essential to understand the optimum seal geometry and purge flow rates required to prevent the ingestion of the hot annulus air while maintaining the required turbine performance. In this paper we present experimental test results from a single stage turbine facility, the Rim Seal (RiSe) rig, at the University of Sussex. The turbine stage incorporates a model rotor-stator cavity system that is representative of the first stage turbine in a gas turbine engine. The facility is capable of generating disc cavity rotational Reynolds numbers of the order of 2.2 × 106 and axial Reynolds number of the order of 0.7 × 106, while operating at a pressure ratio of 2.5. The paper will present the salient features of the test facility, the various instrumentation employed, and the operating specifications of the stage. The paper will discuss the effect of varying the purge flow for a fixed operating point of the turbine. Results presented will include typical mission profiles, cavity radial temperature distribution, and the measured cavity sealing effectiveness.

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.

Integrated Outlet Guide Vane Design for an Aggressive S-Shaped Compressor Transition Duct

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
A. D. Walker ◽  
A. G. Barker ◽  
J. F. Carrotte ◽  
J. J. Bolger ◽  
M. J. Green
Keyword(s):  
Gas Turbines ◽  
Static Pressure ◽  
Pressure Field ◽  
Guide Vane ◽  
Integrated Design ◽  
Axial Compressor ◽  
Test Facility ◽  
Speed Test ◽  
Duct Geometry ◽  
System Length

Within gas turbines the ability to design shorter aggressive S-shaped ducts is advantageous from a performance and weight saving perspective. However, current design philosophies tend to treat the S-shaped duct as an isolated component, neglecting the potential advantages of integrating the design with the upstream or downstream components. In this paper, such a design concept is numerically developed in which the upstream compressor outlet guide vanes are incorporated into the first bend of the S-shaped duct. Positioning the vane row within the first bend imparts a strong radial gradient to the pressure field within the vane passage. Tangential lean and axial sweep are employed such that the vane geometry is modified to exactly match the resulting inclined static pressure field. The integrated design is experimentally assessed and compared to a conventional nonintegrated design on a fully annular low speed test facility incorporating a single stage axial compressor. Several traverse planes are used to gather five-hole probe data which allow the flow structure to be examined through the rotor, outlet guide vane and within the transition ducts. The two designs employ almost identical duct geometry, but integration of the vane row reduces the system length by 21%. Due to successful matching of the static pressure field, the upstream influence of the integrated vane row is minimal and the rotor performance is unchanged. Similarly, the flow development within both S-shaped ducts is similar such that the circumferentially averaged profiles at duct exit are almost identical, and the operation of a downstream component would be unaffected. Overall system loss remains nominally unchanged despite the inclusion of lean and sweep and a reduction in system length. Finally, the numerical design predictions show good agreement with the experimental data thereby successfully validating the design process.

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