Improving Turbine Efficiency Using Non-Axisymmetric End Walls: Validation in the Multi-Row Environment and With Low Aspect Ratio Blading

2002 ◽  
Author(s):  
N. W. Harvey ◽  
G. Brennan ◽  
D. A. Newman ◽  
M. G. Rose
Keyword(s):  
Turbine Stage ◽  
Flow Conditions ◽  
Original Design ◽  
Linear Cascade ◽  
Hp Model ◽  
Low Aspect Ratio ◽  
Turbine Efficiency ◽  
Met Expectations ◽  
End Wall ◽  
Stage Efficiency

This paper describes how the Intermediate Pressure (IP) turbine model rig of the Rolls-Royce Trent 500 engine was redesigned by applying non-axisymmetric end walls to both the vane and blade passages. The blading aerofoil shapes, the turbine operating point and the overall flow conditions were unaltered from the original design. The results from testing of the model rig are presented and compared with those obtained previously for the datum design. A feature of this is that the IP turbine was tested in a “two-shaft” arrangement with the (upstream) Trent 500 High Pressure (HP) model turbine. Previously, non-axisymmetric end wall profiling had been shown to achieve a 0.59 ± 0.25% improvement in the stage efficiency of the Trent 500 HP model turbine when tested as a single stage, Rose et al. [1]. This had exceeded the design expectation of 0.4% improvement, Brennan et al. [4] — based on previous linear cascade research at Durham University, see Harvey et al. [2] and Hartland et al. [3]. The IP and HP turbines with profiled end walls were tested together, while for the datum test both model turbines had blading with axisymmetric end walls. The results have met expectations with an improvement in the IP turbine stage efficiency of 0.9 ± 0.4% at the design point. The turbine characteristics are shown to change significantly from the datum test.

Improving the Efficiency of the Trent 500 HP Turbine Using Non-Axisymmetric End Walls: Part II — Experimental Validation

2001 ◽  
Author(s):  
M. G. Rose ◽  
N. W. Harvey ◽  
P. Seaman ◽  
D. A. Newman ◽  
D. McManus
Keyword(s):  
Design Methodology ◽  
Experimental Validation ◽  
Axial Flow ◽  
Cfd Analysis ◽  
Hot Wire ◽  
Flow Conditions ◽  
Linear Cascade ◽  
Turbine Efficiency ◽  
End Wall ◽  
Turbine Model

Part I of this paper described how the HP turbine model rig of the Rolls-Royce Trent 500 was redesigned by applying non-axisymmetric end walls to both the vane and blade passages, whilst leaving the turbine operating point and overall flow conditions unaltered. This paper describes the results obtained from testing of the model rig and compares them with those obtained for the datum design (with conventional axisymmetric end walls). Measured improvements in the turbine efficiency are shown to be in line with those expected from the previous linear cascade research at Durham University, see Harvey et al. [1] and Hartland et al. [2]. These improvements are observed at both design and off-design conditions. Hot wire traverses taken at the exit of the rotor show, unexpectedly, that the end wall profiling has caused changes across the whole of the turbine flow field. This result is discussed making reference to a preliminary 3-D CFD analysis. It is concluded that the design methodology described in part I of this paper has been validated, and that non-axisymmetric end wall profiling is now a major new tool for the reduction of secondary loss in turbines (and potentially all axial flow turbomachinery). Further work, though, is needed to fully understand the stage (and multistage) effects of end wall profiling.

Improving Turbine Stage Efficiency and Sealing Effectiveness Through Modifications of the Rim Seal Geometry

2012 ◽  
Author(s):  
I. Popović ◽  
H. P. Hodson
Keyword(s):  
Large Scale ◽  
Outer Part ◽  
Turbine Stage ◽  
Linear Cascade ◽  
Seal Design ◽  
Swirl Velocity ◽  
Different Types ◽  
Recirculation Zones ◽  
Secondary Air ◽  
Stage Efficiency

This paper presents an investigation of a range of engine realistic rim seals starting from a simple axial seal to different types of overlapping seals. The experiments were performed in a large-scale linear cascade equipped with a secondary air system capable of varying independently both the mass fraction as well as the swirl velocity of the leakage air. The experimental results were also complemented by CFD to provide better insight in the flow physics. It has been found that the key feature of the rim seals that affect their impact on overall loss generation and their ability to provide good sealing effectiveness was the location and the size of the recirculation zones within the rim seal. The requirements for good sealing and reduced spoiling effects on the main gaspath flow often led to contradictory designs. In general, the recirculation zones were found to improve sealing by reducing the effect of the pitchwise (circumferential) variation in the pressure distribution due to the blade’s potential field, and thus reduce ingestion. However, at the same time the recirculation zones tend to increase the loss generation. The best compromise was found when the outer part of the seal and its interface with the rotor platform was as smooth as possible to minimize the spoiling losses, while the recirculation zones were confined to the inner part of the seal to maintain acceptable levels of sealing effectiveness. A new rim seal design, which utilizes the best attributes of the above mentioned designs was developed. Linear cascade tests showed the losses due to the leakage-mainstream interaction were reduced by 33% compared to the datum seal design. Further validation was performed by examining the new configuration using unsteady full-stage calculations under engine realistic conditions. These calculations suggest an improvement of nearly 0.2% in the stage efficiency.

Investigations Into Heat Transfer and Aerodynamic Performance of a Worn Squealer Tipped Turbine Stage

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Xin Yan ◽  
Mingliang Ye ◽  
Kun He
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Gas Turbine ◽  
Aerodynamic Performance ◽  
Wear Depth ◽  
Turbine Stage ◽  
Original Design ◽  
Design Case ◽  
Starting Location ◽  
Stage Efficiency

Abstract Heat transfer and aerodynamic performance in worn squealer tip gap of a high-pressure gas turbine stage were numerically investigated. Effects of the starting location of wear and wear depth on tip heat transfer coefficient distributions and stage efficiency were analyzed to evaluate the aero-thermal performance degradations in the gas turbine stage after wear. At three starting locations of wear and five wear depths, flow patterns in worn squealer tip gap of the turbine stage were visualized and compared with the original design case. The results show that the counter-rotating vortex systems in tip cavity, as well as the interactions between leakage vortex and passage vortex, are significantly affected by the degree of wear damage. The starting location of wear and wear depth have pronounced influences on heat transfer and aerodynamic performance in squealer tip gap. After wear, the stage efficiency is decreased by about 0.3–1%, as the wear depth is equal to clearance gap size. In the serious worn case, thermal load on tip cavity floor is increased by about 60%, while the heat transfer on rims is reduced by about 20%. However, compared with the original design case, the area-averaged heat transfer coefficient on shroud is reduced by 5% at most.

Influence of Tip Geometry on Over Tip Leakage in Shrouded Rotor Blades With Cooling

2017 ◽  
Author(s):  
Jeffrey Tessier ◽  
Gregory Vogel
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
Turbine Blades ◽  
Honeycomb Structure ◽  
Rotor Blades ◽  
Turbine Stage ◽  
Turbine Efficiency ◽  
Physical Effects ◽  
Efficiency Effects ◽  
Stage Efficiency

Gas turbine blades can be shrouded and designed with “knife edges” to reduce over tip leakages as an attempt to improve turbine stage efficiency. The smaller the tip gap is, the less the amount of leakage and consequently the higher the turbine efficiency. However a zero tip gap between the rotating blade and the stationary casing is simply not practical and not achievable for typical engine operations. One approach often consists of making the stationary shroud at the casing of abradable coating or of softer material in a honeycomb structure. In some cases, it is also common practice to pretrench the honeycomb structure to a certain height to reduce rubbing that could naturally occur with brand new hardware. This paper details the physical effects occurring between trenched and un-trenched configurations and quantifies the potential loss in turbine stage efficiency and power under such changes. Because front turbine stages are also cooled, this paper is also detailing the physical effects that are occurring between trenched and un-trenched configurations for a shrouded cooled turbine blade and the associated impact on performance. Since gas turbine are set to run at a specific gas mass flow, the differences between un-trenched and trenched for un-cooled and cooled are compared at the same given gas mass flow conditions. The paper concludes with key considerations for cooled turbine stage efficiency effects with and without trench.

Improving Turbine Stage Efficiency and Sealing Effectiveness Through Modifications of the Rim Seal Geometry

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Ivan Popovíc ◽  
Howard P. Hodson
Keyword(s):  
Large Scale ◽  
Outer Part ◽  
Turbine Stage ◽  
Linear Cascade ◽  
Seal Design ◽  
Swirl Velocity ◽  
Different Types ◽  
Recirculation Zones ◽  
Secondary Air ◽  
Stage Efficiency

This paper presents an investigation of a range of engine realistic rim seals starting from a simple axial seal to different types of overlapping seals. The experiments were performed in a large-scale linear cascade equipped with a secondary air system capable of varying independently both the mass fraction as well as the swirl velocity of the leakage air. The experimental results were also complemented by computationally fluid dynamics (CFD) to provide better insight in the flow physics. It has been found that the key feature of the rim seals that affect their impact on overall loss generation and their ability to provide good sealing effectiveness was the location and the size of the recirculation zones within the rim seal. The requirements for good sealing and reduced spoiling effects on the main gaspath flow often led to contradictory designs. In general, the recirculation zones were found to improve sealing by reducing the effect of the pitchwise (circumferential) variation in the pressure distribution due to the blade's potential field, and thus reduce ingestion. However, at the same time the recirculation zones tend to increase the loss generation. The best compromise was found when the outer part of the seal and its interface with the rotor platform was as smooth as possible to minimize the spoiling losses, while the recirculation zones were confined to the inner part of the seal to maintain acceptable levels of sealing effectiveness. A new rim seal design, which utilizes the best attributes of the above mentioned designs was developed. Linear cascade tests showed the losses due to the leakage-mainstream interaction were reduced by 33% compared to the datum seal design. Further validation was performed by examining the new configuration using unsteady full-stage calculations under engine realistic conditions. These calculations suggest an improvement of nearly 0.2% in the stage efficiency.

Diabatic Nozzle Flow with Constant Small Stage Efficiency

1960 ◽  
Vol 64 (598) ◽  
pp. 632-635 ◽  
Author(s):  
R. A. A. Bryant
Keyword(s):  
Gas Flow ◽  
Nozzle Flow ◽  
Flow Conditions ◽  
One Dimensional ◽  
Real Flow ◽  
Stage Efficiency ◽  
Frictional Effects

The concept of small stage efficiency is introduced when studying one-dimensional gas flow in nozzles in order to permit a closer approximation of real flow conditions than is possible from an isentropic analysis. It is more or less conventional to assume the flow conditions are adiabatic whenever the small stage efficiency is used. That is to say, small stage efficiency is generally considered in relation to flows contained within adiabatic boundaries, in which case it becomes a measure of the heat generated by internal frictional effects alone.

Effect of Wake Passing on Unsteady Aerodynamic Performance in a Turbine Stage

2006 ◽  
Author(s):  
K. Yamada ◽  
K. Funazaki ◽  
K. Hiroma ◽  
M. Tsutsumi ◽  
Y. Hirano ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Suction Side ◽  
Turbine Stage ◽  
Three Dimensional Flow ◽  
Unsteady Aerodynamic ◽  
Unsteady Effect ◽  
Unsteady Rans ◽  
Wake Passing ◽  
Stage Efficiency

In the present work, unsteady RANS simulations were performed to clarify several interesting features of the unsteady three-dimensional flow field in a turbine stage. The unsteady effect was investigated for two cases of axial spacing between stator and rotor, i.e. large and small axial spacing. Simulation results showed that the stator wake was convected from pressure side to suction side in the rotor. As a result, another secondary flow, which counter-rotated against the passage vortices, was periodically generated by the stator wake passing through the rotor passage. It was found that turbine stage efficiency with the small axial spacing was higher than that with the large axial spacing. This was because the stator wake in the small axial spacing case entered the rotor before mixing and induced the stronger counter-rotating vortices to suppress the passage vortices more effectively, while the wake in the large axial spacing case eventually promoted the growth of the secondary flow near the hub due to the migration of the wake towards the hub.

Improving Efficiency of a High Work Turbine Using Non-Axisymmetric Endwalls: Part I—Endwall Design and Performance

2008 ◽  
Author(s):  
T. Germain ◽  
M. Nagel ◽  
I. Raab ◽  
P. Schuepbach ◽  
R. S. Abhari ◽  
...  
Keyword(s):  
Numerical Optimization ◽  
Axial Flow ◽  
Loss Reduction ◽  
Numerical Investigations ◽  
Turbine Efficiency ◽  
Transition Modeling ◽  
And Performance ◽  
High Work ◽  
Stage Efficiency ◽  
Probe Measurements

This paper is the first part of a two part paper reporting the improvement of efficiency of a one-and-half stage high work axial flow turbine by non-axisymmetric endwall contouring. In this first paper the design of the endwall contours is described and the CFD flow predictions are compared to five-hole-probe measurements. The endwalls have been designed using automatic numerical optimization by means of an Sequential Quadratic Programming (SQP) algorithm, the flow being computed with the 3D RANS solver TRACE. The aim of the design was to reduce the secondary kinetic energy and secondary losses. The experimental results confirm the improvement of turbine efficiency, showing a stage efficiency benefit of 1%±0.4%, revealing that the improvement is underestimated by CFD. The secondary flow and loss have been significantly reduced in the vane, but improvement of the midspan flow is also observed. Mainly this loss reduction in the first row and the more homogeneous flow is responsible for the overall improvement. Numerical investigations indicate that the transition modeling on the airfoil strongly influences the secondary loss predictions. The results confirm that non-axisymmetric endwall profiling is an effective method to improve turbine efficiency, but that further modeling work is needed to achieve a good predictability.

The Influence of Shroud and Cavity Geometry on Turbine Performance — An Experimental and Computational Study: Part II — Exit Cavity Geometry

2007 ◽  
Author(s):  
Budimir Rosic ◽  
John D. Denton ◽  
Eric M. Curtis ◽  
Ashley T. Peterson
Keyword(s):  
Computational Study ◽  
Experimental Program ◽  
Leakage Flow ◽  
Cfd Analysis ◽  
Stage Model ◽  
Low Aspect Ratio ◽  
Turbine Performance ◽  
Air Turbine ◽  
End Wall ◽  
Dominant Influence

The geometry of the exit shroud cavity where the rotor shroud leakage flow re-enters the main passage flow is very important due to the dominant influence of the leakage flow on the aerodynamics of low aspect ratio turbines. The work presented in this paper investigates, both experimentally and numerically, possibilities for the control of shroud leakage flow by modifications to the exit shroud cavity. The processes through which the leakage flow affects the mainstream aerodynamics identified in the first part of this study were used to develop promising strategies for reducing the influence of shroud leakage flow. The experimental program of this study was conducted on a three-stage model air turbine, which was extensively supported by CFD analysis. Three different concepts for shroud leakage flow control in the exit cavity were analysed and tested: a) profiled exit cavity downstream end-wall, b) axial deflector, and c) radial deflector concept. Reductions in aerodynamic losses associated with shroud leakage were achieved by controlling the position and direction at which the leakage jet re-enters the mainstream when it leaves the exit shroud cavity. Suggestions are made for an optimum shroud and cavity geometry.

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