scholarly journals Measurements of the Flow Field Within a Compressor Outlet Guide Vane Passage

1993 ◽  
Author(s):  
J. F. Carrotte ◽  
K. F. Young ◽  
S. J. Stevens
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Guide Vane ◽  
Pressure Probe ◽  
Streamwise Vorticity ◽  
Measured Velocity ◽  
Tip Leakage ◽  
Blade Row ◽  
Flow Features ◽  
Novel Design

A series of tests have been carried out to investigate the flow in a Compressor Outlet Guide Vane (OGV) blade row downstream of a single stage rotor. The subsequent flow field that developed within an OGV passage was measured, at intervals of 10% axial chord, using a novel design of miniature 5 hole pressure probe. In addition to indicating overall pressure levels and the growth of regions containing low energy fluid, secondary flow features were identified from calculated axial vorticity contours and flow vectors. Close to each casing the development of classical secondary flow was observed, but towards the centre of the annulus large well defined regions of opposite rotation were measured. These latter flows were due to the streamwise vorticity at inlet to the blade row associated with the skewed inlet profile. Surface static pressures were also measured and used to obtain the blade pressure force at 3 spanwise locations. These values were compared with the local changes in flow momentum calculated from the measured velocity distributions. With the exception of the flow close to the outer casing, which is affected by rotor tip leakage, good agreement was found between these quantities indicating relatively weak radial mixing.

Measurements of the Flow Field Within a Compressor Outlet Guide Vane Passage

1995 ◽  
Vol 117 (1) ◽  
pp. 29-37 ◽  
Author(s):  
J. F. Carrotte ◽  
K. F. Young ◽  
S. J. Stevens
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Guide Vane ◽  
Pressure Probe ◽  
Streamwise Vorticity ◽  
Measured Velocity ◽  
Tip Leakage ◽  
Blade Row ◽  
Flow Features ◽  
Novel Design

A series of tests have been carried out to investigate the flow in a Compressor Outlet Guide Vane (OGV) blade row downstream of a single-stage rotor. The subsequent flow field that developed within an OGV passage was measured, at intervals of 10 percent axial chord, using a novel design of miniature five-hole pressure probe. In addition to indicating overall pressure levels and the growth of regions containing low-energy fluid, secondary flow features were identified from calculated axial vorticity contours and flow vectors. Close to each casing the development of classical secondary flow was observed, but toward the center of the annulus large well-defined regions of opposite rotation were measured. These latter flows were due to the streamwise vorticity at inlet to the blade row associated with the skewed inlet profile. Surface static pressures were also measured and used to obtain the blade pressure force at three spanwise locations. These values were compared with the local changes in flow momentum calculated from the measured velocity distributions. With the exception of the flow close to the outer casing, which is affected by rotor tip leakage, good agreement was found between these quantities indicating relatively weak radial mixing.

Improving Efficiency of a High Work Turbine Using Non-Axisymmetric Endwalls: Part II—Time-Resolved Flow Physics

2008 ◽  
Author(s):  
P. Schuepbach ◽  
R. S. Abhari ◽  
M. G. Rose ◽  
T. Germain ◽  
I. Raab ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Guide Vane ◽  
Axial Flow ◽  
Fast Response ◽  
Secondary Flows ◽  
Streamwise Vorticity ◽  
Time Resolved ◽  
Flow Physics ◽  
High Work

This paper is the second part of a two part paper that reports on the improvement of efficiency of a one-and-half stage high work axial flow turbine. The first part covered the design of the endwall profiling as well as a comparison with steady probe data, this part covers the analysis of the time-resolved flow physics. The focus is on the time-resolved flow physics that lead to a total-to-total stage efficiency improvement of Δηtt = 1.0% ± 0.4%. The investigated geometry is a model of a high work (Δh/U2 = 2.36), axial shroudless HP turbine. The time-resolved measurements have been acquired upstream and downstream of the rotor using a Fast Response Aerodynamic Probe (FRAP). The paper contains a detailed analysis of the secondary flow field that is changed between the axisymmetric and the non-axisymmetric endwall profiling cases. The flowfield at exit of the first stator is improved considerably due to non-axisymmetric endwall profiling and results in reduced secondary flow and a reduction of loss at both hub and tip, as well as a reduced trailing shed vorticity. The rotor has reduced losses and a reduction of secondary flows mainly at the hub. At the rotor exit the flow field with non-axisymmetric endwalls is more homogenous due to the reduction of secondary flows in the two rows upstream of the measurement plane. This confirms that non-axisymmetric endwall profiling is an effective tool for reducing secondary losses in axial turbines. Using a frozen flow assumption the time-resolved data is used to estimate the axial velocity gradients, which are then used to evaluate the streamwise vorticity and dissipation. The non-axisymmetric endwall profiling of the first nozzle guide vane show reductions of dissipation and streamwise vorticity due to reduced trailing shed vorticity. This smaller vorticity explains the reduction of loss at mid-span, which is shown in the first part of the two part paper. This leads to the conclusion that non-axisymmetric endwall profiling also has the potential of reducing trailing shed vorticity.

Improving Efficiency of a High Work Turbine Using Nonaxisymmetric Endwalls—Part II: Time-Resolved Flow Physics

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
P. Schüpbach ◽  
R. S. Abhari ◽  
M. G. Rose ◽  
T. Germain ◽  
I. Raab ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Guide Vane ◽  
Axial Flow ◽  
Fast Response ◽  
Secondary Flows ◽  
Streamwise Vorticity ◽  
Time Resolved ◽  
Flow Physics ◽  
High Work

This paper is the second part of a two part paper that reports on the improvement of efficiency of a one and a half stage high work axial flow turbine. The first part covered the design of the endwall profiling, as well as a comparison with steady probe data; this part covers the analysis of the time-resolved flow physics. The focus is on the time-resolved flow physics that leads to a total-to-total stage efficiency improvement of 1.0%±0.4%. The investigated geometry is a model of a high work (Δh/U2=2.36), axial shroudless HP turbine. The time-resolved measurements have been acquired upstream and downstream of the rotor using a fast response aerodynamic probe (FRAP). This paper contains a detailed analysis of the secondary flow field that is changed between the axisymmetric and the nonaxisymmetric endwall profiling cases. The flowfield at the exit of the first stator is improved considerably due to the nonaxisymmetric endwall profiling and results in reduced secondary flow and a reduction in loss at both hub and tip, as well as a reduced trailing shed vorticity. The rotor has reduced losses and a reduction in secondary flows mainly at the hub. At the rotor exit, the flow field with nonaxisymmetric endwalls is more homogenous due to the reduction in secondary flows in the two rows upstream of the measurement plane. This confirms that nonaxisymmetric endwall profiling is an effective tool for reducing secondary losses in axial turbines. Using a frozen flow assumption, the time-resolved data are used to estimate the axial velocity gradients, which are then used to evaluate the streamwise vorticity and dissipation. The nonaxisymmetric endwall profiling of the first nozzle guide vane show reductions in dissipation and streamwise vorticity due to the reduced trailing shed vorticity. This smaller vorticity explains the reduction in loss at midspan, which is shown in the first part of the two part paper. This leads to the conclusion that nonaxisymmetric endwall profiling also has the potential of reducing trailing shed vorticity.

scholarly journals Incidence Angle and Pitch-Chord Effects on Secondary Flows Downstream of a Turbine Cascade

1992 ◽  
Author(s):  
A. Perdichizzi ◽  
V. Dossena
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Incidence Angle ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Pressure Probe ◽  
Turbine Cascade ◽  
Oil Flow ◽  
Secondary Velocity ◽  
Secondary Flow Field

This paper describes the results of an experimental investigation of the three-dimensional flow downstream of a linear turbine cascade at off-design conditions. The tests have been carried out for five incidence angles from −60 to +35 degrees, and for three pitch-chord ratios: s/c = 0.58,0.73,0.87. Data include blade pressure distributions, oil flow visualizations, and pressure probe measurements. The secondary flow field has been obtained by traversing a miniature five hole probe in a plane located at 50% of an axial chord downstream of the trailing edge. The distributions of local energy loss coefficients, together with vorticity and secondary velocity plots show in detail how much the secondary flow field is modified both by incidence and cascade solidity variations. The level of secondary vorticity and the intensity of the crossflow at the endwall have been found to be strictly related to the blade loading occurring in the blade entrance region. Heavy changes occur in the spanwise distributions of the pitch averaged loss and of the deviation angle, when incidence or pitch-chord ratio is varied.

scholarly journals Numerical and Experimental Analysis of Secondary Flow in Modern State-of-the-Art Low Pressure Guide Vane Rows

1995 ◽  
Author(s):  
Ernst Lindner
Keyword(s):  
Aspect Ratio ◽  
Secondary Flow ◽  
Total Pressure ◽  
Guide Vane ◽  
Numerical Results ◽  
Flow Behaviour ◽  
Inlet Guide Vane ◽  
Streamwise Vorticity ◽  
Pressure Losses ◽  
Turbine Guide Vane

To enhance the performance of the inlet guide vane and the annular duct of a jet engine, a detailed investigation of annular cascades with two different types of turbine guide vane rows is made. The first one is a leaned guide vane with an aspect ratio of two and a half and a transition duct ahead of the vane. To avoid the losses associated to the decelerating transition duct an alternative vane is designed and investigated with the same inlet and exit conditions. In this case the chord of the vane is increased to the effect that the vane begins immediately at the enterance of the diverging annulus and so a continuously accelerated flow is achieved. To maintain a good performance for this configuration a bowed-type vane with an aspect ratio of one is designed. The aim of the investigation is to obtain detailed informations on the secondary flow behaviour with particular regard to the development of the total pressure losses and the streamwise vorticity of the vortices inside and behind the blade rows. In the first step a three-dimensional, structured, explicit finite-volume flow-solver with a k–ε turbulence model is validated against the measurements, which were made in cross-sections behind the blades. Having proved that the numerical results are very close to the experimental ones, the secondary flow behaviour inside and behind the blade rows is analysed in the second step. By calculating the streamwise vorticity from the numerical results the formation of horse-shoe vortex, passage-vortex and the trailing edge vortex shed is investigated. The differences of the vortical motion and the formation of the total pressure losses between the two configurations of turbine guide vane rows are discussed.

Experimental Investigations and Numerical Validation of an Outlet Guide Vane With an Engine Mount Recess

2008 ◽  
Author(s):  
Johan Hja¨rne ◽  
Valery Chernoray ◽  
Jonas Larsson
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Guide Vane ◽  
Test Facility ◽  
Experimental Investigations ◽  
Flow Angle ◽  
Sst Model ◽  
Engine Mount ◽  
Inlet Conditions ◽  
Secondary Flow Field

This paper presents experiments and CFD calculations of a Low Pressure Turbine/Outlet Guide Vane (LPT/OGV) equipped with an engine mount recess (a bump) tested in the Chalmers linear LPT/OGV cascade. The investigated characteristics include performance for the design point in terms of total pressure loss and turning as well as a detailed description of the downstream development of the secondary flow field. The numerical simulations are performed for the same inlet conditions as in the test-facility with engine-like properties in terms of Reynolds number, boundary-layer thickness and inlet flow angle. The objective is to validate how accurately and reliably the secondary flow field and losses can be predicted for an LPT/OGV equipped with a bump. Three different turbulent models as implemented in FLUENT, the k-ε realizable model, the kω-SST model and the RSM are validated against detailed measurements. From these results it can be concluded that the kω-SST model predicts both the secondary flow field and the losses most accurately.

Effects of Off-Design Operating Conditions on the Blade Row Interaction in a HP Turbine Stage

2007 ◽  
Author(s):  
G. Persico ◽  
P. Gaetani ◽  
C. Osnaghi
Keyword(s):  
Flow Field ◽  
Strong Dependence ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Pressure Probe ◽  
Turbine Stage ◽  
Mixing Rate ◽  
Aerodynamic Pressure ◽  
Blade Row ◽  
Blade Row Interaction

An extensive experimental analysis on the subject of the unsteady periodic flow in a highly subsonic HP turbine stage has been carried out at the Laboratorio di Fluidodinamica delle Macchine (LFM) of the Politecnico di Milano (Italy). In this paper the blade row interaction is progressively enforced by increasing the stator and rotor blade loading and by reducing the stator-rotor axial gap from 100% (very large to smooth the rotor inlet unsteadiness) to 35% (design configuration) of the stator axial chord. The time-averaged three-dimensional flow field in the stator-rotor gap was investigated by means of a conventional five-hole probe for the nominal (0°) and an highly positive (+22°) stator incidences. The evolution of the viscous flow structures downstream of the stator is presented to characterize the rotor incoming flow. The blade row interaction was evaluated on the basis of unsteady aerodynamic measurements at the rotor exit, performed with a fast-response aerodynamic pressure probe. Results show a strong dependence of the time-averaged and phase-resolved flow field and of the stage performance on the stator incidence. The structure of the vortex-blade interaction changes significantly as the magnitude of the rotor inlet vortices increases, and very different residual traces of the stator secondary flows are found downstream of the rotor. On the contrary, the increase of rotor loading enhances the unsteadiness in the rotor secondary flows but has a little effect on the vortex-vortex interaction. For the large axial gap, a reduction of stator-related effects at the rotor exit is encountered when the stator incidence is increased as a result of the different mixing rate within the cascade gap.

Excess Streamwise Vorticity and Its Role in Secondary Flow

1987 ◽  
Vol 201 (6) ◽  
pp. 413-420 ◽  
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.

A Geometry Generation Framework for Contoured Endwalls

2019 ◽  
Author(s):  
L. E. Wood ◽  
R. R. Jones ◽  
O. J. Pountney ◽  
J. A. Scobie ◽  
D. A. S. Rees ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Aerodynamic Loss ◽  
Construction Methods ◽  
Novel Approach ◽  
Wide Range ◽  
Blade Row ◽  
Flow Features ◽  
Flow Effects ◽  
Geometric Variation

Abstract The mainstream, or primary, flow in a gas turbine annulus is characteristically two-dimensional over the mid-span region of the blading, where the radial flow is almost negligible. Contrastingly, the flow in the endwall and tip regions of the blading is highly three-dimensional, characterised by boundary layer effects, secondary flow features and interaction with cooling flows. Engine designers employ geometric contouring of the endwall region in order to reduce secondary flow effects and subsequently minimise their contribution to aerodynamic loss. Such is the geometric variation of vane and blade profiles — which has become a proprietary art form — the specification of an effective endwall geometry is equally unique to each blade-row. Endwall design methods, which are often directly coupled to aerodynamic optimisers, are widely developed to assist with the generation of contoured surfaces. Most of these construction methods are limited to the blade-row under investigation, while few demonstrate the controllability required to offer a universal platform for endwall design. This paper presents a Geometry Generation Framework (GGF) for the generation of contoured endwalls. The framework employs an adaptable meshing strategy, capable of being applied to any vane or blade, and a versatile function-based approach to defining the endwall shape. The flexibility of this novel approach is demonstrated by recreating a selection of endwalls from the literature, which were selected for their wide-range of contouring approaches.

scholarly journals Investigation on the Flow Field Entropy Structure of Non-Synchronous Blade Vibration in an Axial Turbocompressor

Entropy ◽  
2020 ◽  
Vol 22 (12) ◽  
pp. 1372
Author(s):  
Mingming Zhang ◽  
Anping Hou
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Guide Vane ◽  
Leading Edge ◽  
Inlet Guide Vane ◽  
Tip Leakage Flow ◽  
Good Correspondence ◽  
Blade Vibration ◽  
Tip Leakage ◽  
Spiral Vortex

In order to explore the inducing factors and mechanism of the non-synchronous vibration, the flow field structure and its formation mechanism in the non-synchronous vibration state of a high speed turbocompressor are discussed in this paper, based on the fluid–structure interaction method. The predicted frequencies fBV (4.4EO), fAR (9.6EO) in the field have a good correspondence with the experimental data, which verify the reliability and accuracy of the numerical method. The results indicate that, under a deviation in the adjustment of inlet guide vane (IGV), the disturbances of pressure in the tip diffuse upstream and downstream, and maintain the corresponding relationship with the non-synchronous vibration frequency of the blade. An instability flow that developed at the tip region of 90% span emerged due to interactions among the incoming main flow, the axial separation backflow, and the tip leakage vortices. The separation vortices in the blade passage mixed up with the tip leakage flow reverse at the trailing edge of blade tip, presenting a spiral vortex structure which flows upstream to the leading edge of the adjacent blade. The disturbances of the spiral vortexes emerge to rotate at 54.5% of the rotor speed in the same rotating direction as a modal oscillation. The blade vibration in the turbocompressor is found to be related to the unsteadiness of the tip flow. The large pressure oscillation caused by the movement of the spiral vortex is regarded as the one of the main drivers for the non-synchronous vibration for the present turbocompressor, besides the deviation in the adjustment of IGV.

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