The Interaction of Turbine Inter-Platform Leakage Flow With the Mainstream Flow

2005 ◽  
Vol 129 (2) ◽  
pp. 303-310 ◽  
Author(s):  
Kevin Reid ◽  
John Denton ◽  
Graham Pullan ◽  
Eric Curtis ◽  
John Longley
Keyword(s):  
Three Dimensional ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Turbine Performance ◽  
Leakage Flow Rate ◽  
Single Piece ◽  
Flow Through ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Leakage Fraction

Individual nozzle guide vanes (NGV’s) in modern aeroengines are often cast as a single piece with integral hub and casing endwalls. When in operation, there is a leakage flow through the chord-wise interplatform gaps. An investigation into the effect of this leakage flow on turbine performance is presented. Efficiency measurements and NGV exit area traverse data from a low-speed research turbine are reported. Tests show that this leakage flow can have a significant impact on turbine performance, but that below a threshold leakage fraction this penalty does not rise with increasing leakage flow rate. The effect of various seal clearances are also investigated. Results from steady-state simulations using a three-dimensional multiblock Reynolds-averaged Navier-Stokes solver are presented with particular emphasis paid to the physics of the mainstream/leakage interaction and the loss generation.

The Interaction of Turbine Inter-Platform Leakage Flow With the Mainstream Flow

2005 ◽  
Author(s):  
Kevin Reid ◽  
John Denton ◽  
Graham Pullan ◽  
Eric Curtis ◽  
John Longley
Keyword(s):  
Three Dimensional ◽  
Leakage Flow ◽  
Turbine Performance ◽  
Leakage Flow Rate ◽  
Single Piece ◽  
Flow Through ◽  
Aero Engines ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Leakage Fraction

Individual nozzle guide vanes (NGVs) in modern aero engines are often cast as a single piece with integral hub and casing endwalls. When in operation there is a leakage flow through the chord-wise inter-platform gaps. An investigation into the effect of this leakage flow on turbine performance is presented. Efficiency measurements and NGV exit area traverse data from a low speed research turbine are reported. Tests show that this leakage flow can have a significant impact on turbine performance, but that below a threshold leakage fraction this penalty does not rise with increasing leakage flow rate. The effect of various seal clearances are also investigated. Results from steady-state simulations using a three-dimensional multiblock RANS solver are presented with particular emphasis paid to the physics of the mainstream/leakage interaction and the loss generation.

Study of Losses in a Leakage Flow Through the Passage of Shrouded Turbine Blades With Swirl Velocity

2001 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano
Keyword(s):  
Turbine Blades ◽  
Three Dimensional ◽  
Major Effect ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Complex Flow ◽  
Local Pressure ◽  
Leakage Flow Rate ◽  
Calculation Results

In this paper the study of the flows over shrouded turbine blades with staggered-seals is presented by computing the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations along with a compressible non-linear k-ε turbulence model. The swirl of the blade is coupled into the calculation. A multi-zone technique is used to generate the grids in the complex flow channel. The calculation results show that the leakage flow rate in the seal-channel is dominated by the pressure difference. It was also observed that the circumferential momentum transfer in the channel is very slow in the region in front of the seal tooth. The major effect of the rotating blade is the increase of local pressure distribution along the shrouded tip clearance path. However, the swirl motion of the blade tip does not significantly change the flow pattern in the axial-radial plane.

A Numerical Analysis of Bidirectional Ducted Tidal Turbines in Yawed Flow

2013 ◽  
Vol 47 (4) ◽  
pp. 23-35 ◽  
Author(s):  
Clarissa S.K. Belloni ◽  
Richard H.J. Willden ◽  
Guy T. Houlsby
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Navier Stokes ◽  
External Diameter ◽  
Tidal Turbines ◽  
Turbine Performance ◽  
Ducted Turbine ◽  
Flow Through ◽  
Porous Disc

AbstractThe paper presents a computational study of ducted bidirectional tidal turbines using three-dimensional Reynolds-averaged Navier-Stokes simulations. We model the outer duct as a solid body and use a porous disc to represent the turbine rotor, a simplification that captures changes in linear momentum and thus the primary interaction of the turbine with the flow through and around the duct while greatly reducing computational complexity. The duct is modeled using linearly converging and diverging sections and a short straight pipe at the duct throat.We investigate the performance of bare and ducted turbines and relate these to the flows through the devices. For the ducted turbine under investigation, we show a substantial decrease in power generated relative to a bare turbine of diameter equal to the external diameter of the duct. In the case of ducted turbines with concave duct exteriors, we observe two external flow regimes with increasing turbine thrust: nozzle-contoured and separation dominated regimes. Maximum power occurs within the separation dominated flow regime due to the additional channel blockage created by the external separation.The ducts of ducted tidal turbines have been argued to provide a flow straightening effect, allowing modest yaw angles to be readily accommodated. We present a comparison of bare and ducted turbine performance in yawed flow. We show that while bare turbine performance decreases in yawed flow, ducted turbine performance increases. This is due to both a flow straightening effect and also an increase in effective blockage as ducts present greater projected frontal area when approached nonaxially.

Reducing the Perfomance Penalty Due to Turbine Inter-Platform Gaps

2006 ◽  
Author(s):  
Kevin Reid ◽  
John Denton ◽  
Graham Pullan ◽  
Eric Curtis ◽  
John Longley
Keyword(s):  
Single Unit ◽  
Numerical Calculations ◽  
Leakage Flow ◽  
Performance Improvements ◽  
Significant Performance ◽  
Flow Through ◽  
Aero Engines ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Stage Efficiency

Individual nozzle guide vanes (NGV’s) in modern aero engines are often cast as a single unit with integral hub and casing endwalls. When in operation there is a leakage flow through the chord-wise inter-platform gaps. A previous paper [1] has shown that these gaps can result in a stage efficiency penalty of 0.5% – 1.5% depending upon how well they are sealed. In this paper, numerical calculations are used to re-design the inter-platform gaps with the aim of minimizing their effect on the mainstream aerodynamics and hence reduce the efficiency penalty. Experiments using a full scale, low speed model turbine and an improved gap-design show that significant performance improvements are possible regardless of how well the gap is sealed.

Numerical investigation into the effects of a radial gap on hydraulic turbine performance

2001 ◽  
Vol 215 (1) ◽  
pp. 99-107
Author(s):  
K Sato ◽  
L He
Keyword(s):  
Three Dimensional ◽  
Hydraulic Turbine ◽  
Turbine Rotor ◽  
Navier Stokes ◽  
Vaned Diffuser ◽  
Dual Time Stepping ◽  
The Difference ◽  
Nozzle Guide ◽  
Radial Gap ◽  
Nozzle Guide Vanes

The effects of the rotor/stator blade row interaction on the performance of radial turbine stages are investigated numerically. A three-dimensional unsteady incompressible Navier-Stokes method based on the dual-time stepping and the pseudocompressibility method is developed for the performance prediction. A centrifugal pump with a vaned diffuser is calculated for validation purposes, and the predicted unsteady flow results show reasonable agreement with the experimental data. The method is applied to analysis of hydraulic turbine stages. A generic turbine rotor is combined with a row of nozzle guide vanes with three settings of radial gap and numerical flow simulations are conducted for the performance evaluations. The predicted efficiency of the hydraulic turbine stages deteriorates if the radial gap between blade rows is reduced although the difference is very small. The entropy rises along the streamlines suggest that the differences in the stage efficiency level can be largely attributed to the loss generated in the nozzle vane passages.

scholarly journals Aerodynamics of Turbine Rim-Seal Ingestion

1997 ◽  
Author(s):  
Nicholas J. Hills ◽  
Tony Green ◽  
Alan B. Turner ◽  
John W. Chew
Keyword(s):  
Three Dimensional ◽  
Coolant Flow ◽  
Theoretical Modelling ◽  
Flow Rates ◽  
Guide Vanes ◽  
Flow Mechanisms ◽  
Flow Through ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Good Agreement

This paper describes the theoretical modelling of the flow in a rotor-stator wheelspace with ingestion through the rim-seal. The predictions are compared with experimental measurements of pressure taken for an axial clearance rim-seal downstream of a set of nozzle guide vanes. The mainstream pressure asymmetry caused by the guide vanes was measured in the absence of coolant flow. Using this data, three-dimensional CFD calculations were carried out, providing both predictions of the cavity pressures and insight into the flow mechanisms involved. The CFD predictions gave good agreement with experiment at low coolant flow rates. However, at high coolant flow rates, disagreement with the experimental results is evident, suggesting that the interaction between the coolant flow and the mainstream flow through the nozzle guide vanes could no longer be ignored.

Numerical Investigations on Leakage Performance of the Rotating Labyrinth Honeycomb Seal

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Jun Li ◽  
Shengru Kong ◽  
Xin Yan ◽  
Shinnosuke Obi ◽  
Zhengping Feng
Keyword(s):  
Flow Rate ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Cell Diameter ◽  
Leakage Flow ◽  
Steam Turbines ◽  
Honeycomb Seal ◽  
Leakage Flow Rate ◽  
Honeycomb Cell

Three-dimensional Reynolds-averaged Navier–Stokes (RANS) solutions from CFX were utilized to investigate the leakage flow characteristics in the labyrinth honeycomb seal of steam turbines. At first, the accuracy and reliability of the utilized RANS approach was demonstrated using the published experimental data of the honeycomb seal. It showed that the utilized numerical method has sufficient precision to predict the leakage performance in seals. Then a range of sealing clearances, cell diameters, cell depths, rotation speeds, and pressure ratios were investigated to determine how these factors affect the leakage flow rate of the labyrinth honeycomb seal. The computed leakage flow rate increased with increasing sealing clearance and pressure ratios. Furthermore, the results show that the studied labyrinth honeycomb seal has the optimum sealing performance in the case of honeycomb cell diameter equals labyrinth step width, and the ratio of the honeycomb cell depth to honeycomb cell diameter is 0.93 under the designed condition. The flow pattern of each case is also illustrated to describe the leakage flow characteristics in labyrinth honeycomb seals.

The Extension of a Solution-Adaptive Three-Dimensional Navier–Stokes Solver Toward Geometries of Arbitrary Complexity

1993 ◽  
Vol 115 (2) ◽  
pp. 283-295 ◽  
Author(s):  
W. N. Dawes
Keyword(s):  
Guide Vane ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Wide Range ◽  
Nozzle Guide Vane ◽  
Recent Developments ◽  
Nozzle Guide

This paper describes recent developments to a three-dimensional, unstructured mesh, solution-adaptive Navier–Stokes solver. By adopting a simple, pragmatic but systematic approach to mesh generation, the range of simulations that can be attempted is extended toward arbitrary geometries. The combined benefits of the approach result in a powerful analytical ability. Solutions for a wide range of flows are presented, including a transonic compressor rotor, a centrifugal impeller, a steam turbine nozzle guide vane with casing extraction belt, the internal coolant passage of a radial inflow turbine, and a turbine disk cavity flow.

The Impact of Gas Modeling in the Numerical Analysis of a Multistage Gas Turbine

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Filippo Rubechini ◽  
Michele Marconcini ◽  
Andrea Arnone ◽  
Massimiliano Maritano ◽  
Stefano Cecchi
Keyword(s):  
Gas Turbine ◽  
Flow Direction ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Ratio Distribution ◽  
Real Gas ◽  
Turbine Performance ◽  
Wall Boundary Conditions ◽  
Heavy Duty Gas Turbine ◽  
The Impact

In this work a numerical investigation of a four stage heavy-duty gas turbine is presented. Fully three-dimensional, multistage, Navier-Stokes analyses are carried out to predict the overall turbine performance. Coolant injections, cavity purge flows, and leakage flows are included in the turbine modeling by means of suitable wall boundary conditions. The main objective is the evaluation of the impact of gas modeling on the prediction of the stage and turbine performance parameters. To this end, four different gas models were used: three models are based on the perfect gas assumption with different values of constant cp, and the fourth is a real gas model which accounts for thermodynamic gas properties variations with temperature and mean fuel∕air ratio distribution in the through-flow direction. For the real gas computations, a numerical model is used which is based on the use of gas property tables, and exploits a local fitting of gas data to compute thermodynamic properties. Experimental measurements are available for comparison purposes in terms of static pressure values at the inlet∕outlet of each row and total temperature at the turbine exit.

Experimental and Numerical Investigations on the Aerodynamic Performance of the Three-Stage Turbine With Consideration of the Leakage Flow Effect

2016 ◽  
Author(s):  
Yang Chen ◽  
Jun Li ◽  
Chaoyang Tian ◽  
Gangyun Zhong ◽  
Xiaoping Fan ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotor Blade ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Leakage Flows ◽  
Wheel Disk

The aerodynamic performance of three-stage turbine with different types of leakage flows was experimentally and numerically studied in this paper. The leakage flows of three-stage turbine included the shroud seal leakage flow between the rotor blade tip and case, the diaphragm seal leakage flow between the stator blade diaphragm and shaft, as well as the shaft packing leakage flow and the gap leakage flow between the rotor blade curved fir-tree root and wheel disk. The total aerodynamic performance of three-stage turbine including leakage flows was firstly experimentally measured. The detailed flow field and aerodynamic performance were also numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and S-A turbulence model. The numerical mass flow rate and efficiency showed well agreement with experimental data. The effects of leakage flows between the fir-tree root and the wheel disk were studied. All leakage mass flow fractions, including the mass flow rate in each hole for all sets of root gaps were given for comparison. The effect of leakage flow on the aerodynamic performance of three-stage was illustrated and discussed.

Sign in / Sign up

Export Citation Format

Share Document