Nonaxisymmetric Turbine End Wall Design: Part II—Experimental Validation

The Durham Linear Cascade has been redesigned with the non-axisymmetric profiled end wall described in the first part of this paper, with the aim of reducing the effects of secondary flow. The design intent was to reduce the passage vortex strength and to produce a more uniform exit flow angle profile in the radial direction with less over turning at the wall. The new end wall has been tested in the linear cascade and a comprehensive set of measurements taken. These include traverses of the flow field at a number of axial planes and surface static pressure distributions on the end wall. Detailed comparisons have been made with the CFD design predictions, and also for the results with a planar end wall. In this way an improved understanding of the effects of end wall profiling has been obtained. The experimental results generally agree with the design predictions, showing a reduction in the strength of the secondary flow at the exit and a more uniform flow angle profile. In a turbine stage these effects would be expected to improve the performance of any downstream blade row. There is also a reduction in the overall loss, which was not given by the CFD design predictions. Areas where there are discrepancies between the CFD calculations and measurement are likely to be due to the turbulence model used. Conclusions for how the three-dimensional linear design system should be used to define end wall geometries for improved turbine performance are presented.

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Investigation of a Novel Secondary Flow Feature in a Turbine Cascade With End Wall Profiling

Journal of Turbomachinery ◽

10.1115/1.1812321 ◽

2005 ◽

Vol 127 (1) ◽

pp. 209-214 ◽

Cited By ~ 20

Author(s):

Grant Ingram ◽

David Gregory-Smith ◽

Neil Harvey

Keyword(s):

Secondary Flow ◽

Secondary Flows ◽

Pressure Probe ◽

Unexpected Result ◽

Full Potential ◽

Flow Angle ◽

Passage Vortex ◽

Flow Feature ◽

New Feature ◽

End Wall

A novel secondary flow feature, previously unreported for turbine blading as far as the authors are aware, has been discovered. It has been found that it is possible to separate part of the inlet boundary layer on the blade row end wall as it is being over-turned and rolled up into the passage vortex. This flow feature has been discovered during a continuing investigation into the aerodynamic effects of non-axisymmetric end wall profiling. Previous work, using the low speed linear cascade at Durham University, has shown the potential of end wall profiling for reducing secondary losses. The latest study, the results of which are described here, was undertaken to determine the limits of what end wall profiling can achieve. The flow has been investigated in detail with pressure probe traversing and surface flow visualization. This has found that the inlet boundary locally separates, on the early suction side of the passage, generating significant extra loss which feeds directly into the core of the passage vortex. The presence of this new feature gives rise to the unexpected result that the secondary flow, as determined by the exit flow angle deviations and levels of secondary kinetic energy, can be reduced while at the same time the loss is increased. CFD was found to calculate the secondary flows moderately well compared with measurements. However, CFD did not predict this new feature, nor the increase in loss it caused. It is concluded that the application of non-axisymmetric end wall profiling, although it has been shown to be highly beneficial, can give rise to adverse features that current CFD tools are unable to predict. Improvements to CFD capability are required in order to be able to avoid such features, and obtain the full potential of end wall profiling.

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Investigation of a Novel Secondary Flow Feature in a Turbine Cascade With End Wall Profiling

Volume 5: Turbo Expo 2004, Parts A and B ◽

10.1115/gt2004-53589 ◽

2004 ◽

Cited By ~ 2

Author(s):

Grant Ingram ◽

David Gregory-Smith ◽

Neil Harvey

Keyword(s):

Secondary Flow ◽

Secondary Flows ◽

Pressure Probe ◽

Unexpected Result ◽

Full Potential ◽

Flow Angle ◽

Passage Vortex ◽

Flow Feature ◽

New Feature ◽

End Wall

A novel secondary flow feature, previously unreported for turbine blading as far as the authors are aware, has been discovered. It has been found that it is possible to separate part of the inlet boundary layer on the blade row end wall as it is being over-turned and rolled up into the passage vortex. This flow feature has been discovered during a continuing investigation into the aerodynamic effects of non-axisymmetric end wall profiling. Previous work, using the low speed linear cascade at Durham University, has shown the potential of end wall profiling for reducing secondary losses. The latest study, the results of which are described here, was undertaken to determine the limits of what end wall profiling can achieve. The flow has been investigated in detail with pressure probe traversing and surface flow visualization. This has found that the inlet boundary locally separates, on the early suction side of the passage, generating significant extra loss which feeds directly into the core of the passage vortex. The presence of this new feature gives rise to the unexpected result that the secondary flow, as determined by the exit flow angle deviations and levels of secondary kinetic energy, can be reduced while at the same time the loss is increased. CFD was found to calculate the secondary flows moderately well compared with measurements. However, CFD did not predict this new feature, nor the increase in loss it caused. It is concluded that the application of non-axisymmetric end wall profiling, although it has been shown to be highly beneficial, can give rise to adverse features that current CFD tools are unable to predict. Improvements to CFD capability are required in order to be able to avoid such features, and obtain the full potential of end wall profiling.

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Improving the Efficiency of the Trent 500-HP Turbine Using Nonaxisymmetric End Walls—Part I: Turbine Design

Journal of Turbomachinery ◽

10.1115/1.1450766 ◽

2003 ◽

Vol 125 (3) ◽

pp. 497-504 ◽

Cited By ~ 31

Author(s):

G. Brennan ◽

N. W. Harvey ◽

M. G. Rose ◽

N. Fomison ◽

M. D. Taylor

Keyword(s):

Large Scale ◽

Three Dimensional ◽

Design System ◽

Turbine Cascade ◽

Linear Cascade ◽

Definition Of ◽

Turbine Design ◽

Shrouded Rotor ◽

End Wall ◽

Turbine Model

This paper describes the redesign of the HP turbine of the Rolls-Royce Trent 500 engine, making use of nonaxisymmetric end walls. The original, datum turbine used conventional axisymmetric end walls, while the vane and (shrouded) rotor aerofoil profiles were nominally the same for the two designs. Previous research on the large-scale, low-speed linear cascade at Durham University (see Hartland et al., 1998, “Non-Axisymmetric End Wall Profiling in a Turbine Cascade,” ASME 98–GT-525), had already demonstrated significant potential for reducing turbine secondary losses using nonaxisymmetric end walls-by about one third. This paper shows how a methodology was derived from the results of this research and applied to the design of the single-stage Trent 500-HP turbine (model rig). In particular, the application of a new linear design system for the parametric definition of these end wall shapes (described in Harvey et al., 1999, “Non-Axisymmetric Turbine End Wall Design: Part I Three-Dimensional Linear Design System,” ASME 99–GT-337) is discussed in detail.

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Effects of Periodic Wake Passing Upon Aerodynamic Loss of a Turbine Cascade: Part I — Measurements of Wake-Affected Cascade Loss by Use of a Pneumatic Probe

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery ◽

10.1115/99-gt-093 ◽

1999 ◽

Author(s):

Ken-ichi Funazaki ◽

Nobuaki Tetsuka ◽

Tadashi Tanuma

Keyword(s):

Turbine Cascade ◽

Flow Angle ◽

Linear Cascade ◽

Local Loss ◽

Aerodynamic Loss ◽

Free Stream Turbulence ◽

Pressure Distributions ◽

Wake Turbulence ◽

Wake Passing ◽

Profile Loss

This paper reports on an experimental investigation of aerodynamic loss of a low-speed linear turbine cascade which is subjected to periodic wakes shed from moving bars of the wake generator. In this case, parameters related to the wake, such as wake passing frequency (wake Strouhal number) or wake turbulence characteristics, are varied to see how these wake-related parameters affect the local loss distribution or mass-averaged loss coefficient of the turbine cascade. Free-stream turbulence intensity is changed by use of a turbulence grid. In Part I of this paper a focus is placed on the measurements by use of a pneumatic five-hole yawmeter, which provides time-averaged stagnation pressure distributions downstream of the moving bars as well as of the turbine cascade. Spanwise distributions of wake-affected exit flow angle are also measured. From this study it is found that the wake passing greatly affects not only the profile loss but secondary loss of the linear cascade. Noticeable change in exit flow angle is also identified.

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End-Wall Film Cooling Through Fan-Shaped Holes With Different Area Ratios

Journal of Turbomachinery ◽

10.1115/1.2464140 ◽

2006 ◽

Vol 129 (2) ◽

pp. 212-220 ◽

Cited By ~ 7

Author(s):

Giovanna Barigozzi ◽

Giuseppe Franchini ◽

Antonio Perdichizzi

Keyword(s):

Secondary Flow ◽

Mass Flow ◽

Film Cooling ◽

Three Dimensional ◽

Wide Band ◽

Lateral Spreading ◽

Area Ratio ◽

Adiabatic Effectiveness ◽

Flow Effects ◽

End Wall

The present paper reports on the aerothermal performance of a nozzle vane cascade, with film-cooled end walls. The coolant is injected through four rows of cylindrical holes with conical expanded exits. Two end-wall geometries with different area ratios have been compared. Tests have been carried out at low speed (M=0.2), with coolant to mainstream mass flow ratio varied in the range 0.5–2.5%. Secondary flow assessment has been performed through three-dimensional (3D) aerodynamic measurements, by means of a miniaturized five-hole probe. Adiabatic effectiveness distributions have been determined by using the wide-band thermochromic liquid crystals technique. For both configurations and for all the blowing conditions, the coolant share among the four rows has been determined. The aerothermal performances of the cooled vane have been analyzed on the basis of secondary flow effects and laterally averaged effectiveness distributions; this analysis was carried out for different coolant mass flow ratios. It was found that the smaller area ratio provides better results in terms of 3D losses and secondary flow effects; the reason is that the higher momentum of the coolant flow is going to better reduce the secondary flow development. The increase of the fan-shaped hole area ratio gives rise to a better coolant lateral spreading, but appreciable improvements of the adiabatic effectiveness were detected only in some regions and for large injection rates.

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Design Optimization of Profiled Endwall With Consideration of Cooling and Rim Seal Flow Effects

Volume 2B: Turbomachinery ◽

10.1115/gt2016-57219 ◽

2016 ◽

Author(s):

Huimin Tang ◽

Shuaiqiang Liu ◽

Hualing Luo

Keyword(s):

High Pressure ◽

Flow Field ◽

Secondary Flow ◽

Three Dimensional ◽

Great Influence ◽

Optimization Procedure ◽

Secondary Flows ◽

High Pressure Turbine ◽

Operation Condition ◽

Turbine Performance

Profiled endwall is an effective method to improve aerodynamic performance of turbine. This approach has been widely studied in the past decade on many engines. When automatic design optimisation is considered, most of the researches are usually based on the assumption of a simplified simulation model without considering cooling and rim seal flows. However, many researchers find out that some of the benefits achieved by optimization procedure are lost when applying the high-fidelity geometry configuration. Previously, an optimization procedure has been implemented by integrating the in-house geometry manipulator, a commercial three-dimensional CFD flow solver and the optimization driver, IsightTM. This optimization procedure has been executed [12] to design profiled endwalls for a turbine cascade and a one-and-half stage axial turbine. Improvements of the turbine performance have been achieved. As the profiled endwall is applied to a high pressure turbine, the problems of cooling and rim seal flows should be addressed. In this work, the effects of rim seal flow and cooling on the flow field of two-stage high pressure turbine have been presented. Three optimization runs are performed to design the profiled endwall of Rotor-One with different optimization model to consider the effects of rim flow and cooling separately. It is found that the rim seal flow has a significant impact on the flow field. The cooling is able to change the operation condition greatly, but barely affects the secondary flow in the turbine. The influences of the profiled endwalls on the flow field in turbine and cavities have been analyzed in detail. A significant reduction of secondary flows and corresponding increase of performance are achieved when taking account of the rim flows into the optimization. The traditional optimization mechanism of profiled endwall is to reduce the cross passage gradient, which has great influence on the strength of the secondary flow. However, with considering the rim seal flows, the profiled endwall improves the turbine performance mainly by controlling the path of rim seal flow. Then the optimization procedure with consideration of rim seal flow has also been applied to the design of the profiled endwall for Stator Two.

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Excess Streamwise Vorticity and Its Role in Secondary Flow

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/pime_proc_1987_201_144_02 ◽

1987 ◽

Vol 201 (6) ◽

pp. 413-420 ◽

Cited By ~ 1

Author(s):

P W James

Keyword(s):

Secondary Flow ◽

Gas Turbines ◽

Three Dimensional ◽

Point Of View ◽

Streamwise Vorticity ◽

Three Dimensional Flow ◽

Approximate Methods ◽

Blade Row ◽

Flow Through ◽

Loss Term

The purpose of this paper is, firstly, to show how the concept of excess secondary vorticity arises naturally from attempts to recover three-dimensional flow details lost in passage-averaging the equations governing the flow through gas turbines. An equation for the growth of excess streamwise vorticity is then derived. This equation, which allows for streamwise entropy gradients through a prescribed loss term, could be integrated numerically through a blade-row to provide the excess vorticity at the exit to a blade-row. The second part of the paper concentrates on the approximate methods of Smith (1) and Came and Marsh (2) for estimating this quantity and demonstrates their relationship to each other and to the concept of excess streamwise vorticity. Finally the relevance of the results to the design of blading for gas turbines, from the point of view of secondary flow, is discussed.

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Forces and Surface Pressure on a Blade Moving in Front of the Admission Region

Journal of Fluids Engineering ◽

10.1115/1.4002468 ◽

2010 ◽

Vol 132 (12) ◽

Cited By ~ 7

Author(s):

Soo-Yong Cho ◽

Chong-Hyun Cho ◽

Kook-Young Ahn ◽

Young-Cheol Kim

Keyword(s):

Cross Section ◽

Performance Test ◽

Nozzle Flow ◽

Flow Angle ◽

Linear Cascade ◽

Blade Row ◽

Partial Admission ◽

Additional Losses ◽

Rotational Direction ◽

Admission Region

The partial admission technique is widely used to control the output power of turbines. In some cases, it has more merits than full admission. However, additional losses, such as expansion, mixing, or pumping, are generated in partial admission as compared with full admission. Thus, an experiment was conducted in a linear cascade apparatus having a partial admission region in order to investigate the effect of partial admission on a blade row. The admission region was formed by a spouting nozzle installed at the inlet of the linear cascade apparatus. Its cross section was rectangular and its size is 200×200 mm2. The tested blade was axial-type and its chord was 200 mm. Nineteen identical blades were applied to the linear cascade for the partial admission experiment. The blades moved along the rotational direction in front of the admission region, and then operating forces and surface pressures on the blades were measured at the steady state. The experiment was conducted at a Reynolds number of 3×105 based on the chord. The nozzle flow angle was set to 65 deg with a solidity of 1.38 for performance test at the design point. In addition, another two different solidities of 1.25 and 1.67 were applied. From the experimental results, when the solidity was decreased, the maximum rotational force increased but the maximum axial force decreased.

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Comparison of Steady and Unsteady Secondary Flows in a Turbine Stator Cascade

Volume 1: Turbomachinery ◽

10.1115/89-gt-79 ◽

1989 ◽

Cited By ~ 1

Author(s):

Gregory J. Hebert ◽

William G. Tiederman

Keyword(s):

Secondary Flows ◽

Rotor Blades ◽

Velocity Measurements ◽

Flow Loop ◽

Suction Surface ◽

Linear Cascade ◽

Turbine Stator ◽

Passage Vortex ◽

Blade Row ◽

Secondary Flow Structure

The effect of periodic rotor wakes on the secondary flow structure in a turbine stator cascade was investigated. A mechanism simulated the wakes shed from rotor blades bypassing cylindrical rods across the inlet to a linear cascade installed in a recirculating water flow loop. Velocity measurements showed a passage vortex, similar to that seen in steady flow, during the time associated with undisturbed fluid. However, as the rotor wake passed through the blade row, a large crossflow toward the suction surface was observed in the midspan region. This caused the development of two large areas of circulation between the midspan and endwall regions, significantly distorting and weakening the passage vortices.

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