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.

Experimental and Numerical Investigation of the Influence of Rotor Blades on Hot Gas Ingestion Into the Upstream Cavity of an Axial Turbine Stage

2000 ◽  
Author(s):  
Dieter Bohn ◽  
Bernd Rudzinski ◽  
Norbert Sürken ◽  
Wolfgang Gärtner
Keyword(s):  
Carbon Dioxide ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Positive Influence ◽  
Rotor Blades ◽  
Gas Concentration ◽  
Hot Gas ◽  
Carbon Dioxide Gas ◽  
Static Pressure Distribution ◽  
Nozzle Guide

The phenomenon of hot gas ingestion through turbine rim seals is experimentally and numerically investigated for a complete stage with nozzle guide vanes and uncooled helicopter turbine rotor blades. In the experimental part, two different geometrical rim seal configurations are examined: 1. a simple axial gap between rotor and stator disk and 2. an axial gap between the rotor disk and a rim seal lip at the periphery of the stator disk. The results obtained are compared to experiments carried out for the same geometry but without rotor blades. The influence of the presence of rotor blades on hot gas ingestion is examined for different parameters such as nondimensional seal flow rate, Reynolds number in the turbine annulus and rotational speed. For the determination of the sealing efficiency measurements of carbon dioxide gas concentration are carried out in the wheelspace. The static pressure distribution in the cavity is measured by means of pressure taps at the stator disk. It is shown that for configuration 1 the presence of rotor blades causes a considerable drop in sealing efficiency whereas for configuration 2 the sealing efficiency increases significantly. In the numerical part results of three-dimensional unsteady CFD calculations for configuration 2 are compared to steady calculations for the same configuration without blades. Predictions of hot gas ingestion and carbon dioxide gas concentration in the hub region and inside the cavity are presented. Special emphasis is put on unsteady effects arising from rotor movement. A local ingestion zone rotating at approximately half rotor speed is numerically predicted. As indicated by the experimental results the rotor blades have a positive influence on the predicted sealing efficiency.

scholarly journals Influence of Rim Seal Geometry on Hot Gas Ingestion Into the Upstream Cavity of an Axial Turbine Stage

1999 ◽  
Author(s):  
Dieter Bohn ◽  
Bernd Rudzinski ◽  
Norbert Sürken ◽  
Wolfgang Gärtner
Keyword(s):  
Mach Number ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Main Flow ◽  
Rotor Blades ◽  
Flow Rates ◽  
Hot Gas ◽  
Carbon Dioxide Gas ◽  
Industrial Gas Turbines ◽  
Rotor Disk

The ingestion of hot gas at the rim seal of a turbine has been investigated for a complete stage with nozzle guide vanes and rotor blades for two types of geometry: 1. the simple axial gap between a flat rotor disk and a flat stator disk, commonly used for industrial gas turbines and 2. an axial lip of the rim seal on the stator combined with a flat rotor disk, often found in aero engine applications. The clearance of the axial gap has been varied for the second type. The efficiency of the rim seal has been examined for different seal flow rates, rotational Reynolds numbers and Mach numbers in the main flow. For the determination of the sealing effectiveness carbon dioxide gas concentration measurements have been carried out in the wheelspace. The distribution of the static pressure in the vicinity of the seal and inside the wheelspace has been measured by means of pressure taps at the stator disk. It is shown that the external flow Mach number in the main flow has a significant effect on the sealing efficiency. As Mach number increases sealing efficiency goes down. The rotational Reynolds number has a distinct effect on the rim seal efficiency depending on the examined configuration. Even for high seal flow rates the ingestion of hot gas can not be fully avoided. The experimental results were the motivation for a three-dimensional CFD approach neglecting the influence of the rotor blades. The results give further insight into aerodynamic features of the ingestion phenomenon.

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.

Measurement of Turbine Rotor Blade Flows

1981 ◽  
Vol 103 (2) ◽  
pp. 400-405 ◽  
Author(s):  
R. P. Dring ◽  
H. D. Joslyn
Keyword(s):  
Rotor Blade ◽  
Static Pressure ◽  
Turbine Rotor ◽  
Measurement Methods ◽  
Incident Flow ◽  
Airfoil Surface ◽  
Turbine Rotor Blade ◽  
Pressure Distributions ◽  
Different Types ◽  
Flow Phenomena

Measurement methods for obtaining various types of experimental data on a turbine rotor blade are discussed in this paper. A variety of different types of measurements have been taken in the rotating frame of reference, including: airfoil surface static pressure distributions, the radial distribution of total pressure in the incident flow, flow visualization of surface streamlines, and radial-circumferential traversing of a pneumatic probe aft of the rotor. Typical results are presented/showing interesting flow phenomena present on the rotor. In particular, results are shown which demonstrate the various viscous and inviscid mechanisms that give rise to strong radial flows.

Static Pressure Distributions Over 2D Mast/Sail Geometries

1989 ◽  
Vol 26 (04) ◽  
pp. 333-337
Author(s):  
Stuart Wilkinson
Keyword(s):  
Reynolds Number ◽  
Static Pressure ◽  
Incidence Angle ◽  
Flow Regimes ◽  
Two Dimensional ◽  
Test Program ◽  
Flow Parameters ◽  
Pressure Distributions

A variable-camber aerofoil with integral pressure tappings has been built to investigate the nature of the flows around two-dimensional, highly cambered, sail-like aerofoil sections with circular masts. Data have been obtained in the form of static pressure distributions over representative ranges of Reynolds number, camber ratio, incidence angle, mast diameter/chord ratio and mast angle. Two sail shapes—based on the NACA a = 0.8 and NACA 63 mean-line camber distributions—were involved in the test program. All flow regimes present have been identified and related to the salient model and flow parameters.

Thrust Force Measurements in an Axial Steam Turbine Test Rig: Effect of Disk Balance Holes

2021 ◽  
Author(s):  
Diganta Narzary ◽  
David Stasenko ◽  
Nikhil Rao
Keyword(s):  
Steam Turbine ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Velocity Ratio ◽  
Open Disk ◽  
Test Rig ◽  
Axial Thrust ◽  
Pressure Distributions ◽  
Face Seals ◽  
Rotor Disk

Abstract A full-size, full-speed, axial flow steam turbine test rig capable of measuring turbine thrust, and static pressures in the rotor-stator disk cavity was built and commissioned. The test rig was operated in a single-stage configuration for the test results first reported in Stasenko et al. [1], and now in this paper. The stage has stationary axial face seals radially inward of the airfoils, near the rotor disk rim. The face seals divide the rotor-stator cavity into inner and outer circumferential cavities, both of which were instrumented with static pressure probes on the stator radial wall. Axial thrust was measured with load cells in every thrust bearing pad. The test rig was operated over a range of three nominal stage pressure ratios (designated as LPR, MPR, and HPR), five nominal stage velocity ratios (0.25–0.6), and five admission fractions (0.38–0.88). This latest group of tests was conducted without rotor disk balance holes, which were mechanically plugged, and will be compared to the original block of tests with disk balance holes opened. In the upstream disk cavity, the two disk balance hole configurations shared many similar pressure characteristics: nearly uniform pressures in the inner cavity, circumferential pressure distributions in the outer cavity that corresponded with the direction of axial thrust, and radial pressure distributions in the outer cavity that were a direct function of rotor speed. General trends of thrust coefficients with the disk holes plugged were correlated to stage pressure ratio, stage velocity ratio, admission fraction, and leakage mass flow rate. Those trends were consistent with the first block of tests with open disk balance holes, although there was an offset toward more operating conditions with negative aggregate thrust coefficients. This suggests that the rotating disk induces a low-pressure gradient in the inner (upstream) cavity, and the opened disk balance holes tend to equalize the inner cavity static pressure toward the higher static pressure on the exit side of the disk. Additionally, thrust coefficients tended to become less negative (or more positive) with stage pressure ratio and with velocity ratio, but tended to become more negative with admission fraction. Significant thrust coefficient reductions were realized with the open disk balance hole configuration, and were determined to be consistently speed-dependent.

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.

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.

scholarly journals Negative Incidence Flow Over a Turbine Rotor Blade

1983 ◽  
Author(s):  
H. David Joslyn ◽  
Robert P. Dring
Keyword(s):  
Gas Turbines ◽  
Large Scale ◽  
Three Dimensional ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Surface Flow ◽  
Separated Flows ◽  
Turbine Rotor Blade ◽  
Pressure Surface ◽  
Pressure Distributions

The operation of variable cycle gas turbines at negative incidence can result in highly three dimensional separated flows on the turbine rotor pressure surface. These flows can impact both performance and durability. The present program was conducted to experimentally study the behavior of surface flow on a large scale axial flow turbine rotor with incidence varying up to and including negative incidence separation. Fullspan pressure distributions and surface flow visualization were acquired over a range of incidence. The data indicate that at large negative incidence, pressure surface separation occurred and extended to 60 percent chord at midspan. These separated flows were simulated at midspan by applying potential flow theory to match the measured pressure distributions.

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