Influence of Unsteady Wakes on the Secondary Flows in the Linear T106 Turbine Cascade

2016 ◽  
Author(s):  
Ilker Kirik ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Secondary Flow ◽  
High Speed ◽  
Base Flow ◽  
Secondary Flows ◽  
Pressure Probe ◽  
Hot Wire ◽  
Flow Angle ◽  
Secondary Flow Field

The present work extends previous investigations on the secondary flows around a steady and unsteady base flow to detailed time-averaged and time-resolved flow field measurements up- and downstream of the cascade. As a representative of modern low pressure turbine rotors of moderate aerodynamic loading, the LPT cascade T106 with parallel sidewalls was chosen for these investigations. Previous investigations have shown that the intensity of secondary flows in the endwall region within a first test set-up was fairly low due to the thin endwall boundary layer at the inlet of the cascade which impeded to study the influence of periodically incoming wakes on the temporal development of the secondary flow field. For that reason a new test-up was built providing a thicker inlet boundary. Measurements have been performed in the High-Speed Cascade Wind Tunnel of the University of the Federal Armed Forces Munich under realistic Mach and Reynolds numbers. In order to simulate real turbomachinery situtations, a wake generator is installed generating temporally representative wakes in the inlet plane of the cascade by a moving bar system. The inlet conditions were determined using a hot wire and a Pitot probe. Detailed measurements of the three-dimensional flow field were carried out downstream of the cascade with a triple hot wire probe, a conventional five hole pressure probe, and a dynamic pressure probe equipped with a single Kulite sensor. All measurements were performed with and without moving bars. Based on previous investigations, a pitch of the moving bars of 40 mm and a circumferential speed of 20 m/s was chosen as the configuration with the highest influence on the secondary flow field. It is shown that the intended increase of the inlet boundary layer was achieved by putting plates on top of each other in the inlet plane endwalls. This leads to more pronounced secondary flow parameters in the spanwise distribution of the pitchwise averaged secondary flow angle (Δβ2,sec) and the secondary losses (ζ2,sec).

Experimental Investigations on Effects of Unsteady Wakes on the Secondary Flows in the Linear T106 Turbine Cascade

2015 ◽  
Author(s):  
Ilker Kirik ◽  
Reinhard Niehuis
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Base Flow ◽  
Secondary Flows ◽  
Experimental Investigations ◽  
Pressure Probe ◽  
Hot Wire ◽  
Hot Wire Anemometry ◽  
Unsteady Inflow ◽  
Secondary Flow Field

The present work extends previous investigations on the secondary flows around a steady base flow to detailed time-averaged and time-resolved flow field measurements up- and downstream of a low pressure turbine (LPT) cascade. Unsteady inflow was generated by a moving bar system. The inlet conditions were determined using single hot wire anemometry and a pitot probe. Further detailed measurements of the three-dimensional flow field were carried out downstream of the cascade with triple hot wire anemometry, a conventional five hole pressure probe, and a dynamic pressure probe equipped with a single Kulite sensor. All measurements have been performed with and without moving bars. Cases with different Strouhal numbers and flow coefficients have been considered by varying the pitch of the moving bars between 40 mm and 80 mm and circumferential speed between 10m/s and 20m/s in order to investigate the influence of unsteady inflow in particular on the secondary flow field near the endwalls. It turned out that the effects of the incoming wakes are evident in the time-accurate data in terms of their interaction with secondary flow vortices. On a time-averaged basis, however, the influence of the incoming wakes on the secondary flow field turned out to be small for the small inlet boundary layer.

scholarly journals The Secondary Flow Field of a Turbine Cascade With 3D Airfoil Design and Endwall Contouring at Off-Design Incidence

1999 ◽  
Author(s):  
Arno Duden ◽  
Leonhard Fottner
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
High Speed ◽  
Secondary Flows ◽  
Turbine Cascade ◽  
Flow Angle ◽  
Radial Extent ◽  
Endwall Contouring ◽  
End Wall ◽  
Secondary Flow Field

A highly loaded turbine cascade with prismatic airfoils and straight endwalls was redesigned with the objective of reducing the secondary flow by applying end wall contouring and 3D airfoil design in the endwall regions. When tested at design conditions the flow field showed distinct improvements. The radial extent of the secondary flows was reduced and a decrease in secondary losses was observed (Duden et al., 1998). As an extension of this investigation, the effects of positive and negative incidence on the performance of the redesigned cascade have been evaluated and compared to the original cascade. The investigations were carried out in a high speed cascade wind tunnel. At negative incidence the redesigned cascade was observed to reduce the radial variation of the circumferential exit flow angle but to increase the magnitude of the secondary losses. At positive incidence, in comparison to the flowfield in the reference cascade, the radial extent of the secondary flows and the magnitude of the secondary losses were greatly reduced. The benefits provided by the 3D airfoil design and endwall contouring were even more obvious at positive incidence than at the design conditions.

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.

Incidence Angle and Pitch–Chord Effects on Secondary Flows Downstream of a Turbine Cascade

1993 ◽  
Vol 115 (3) ◽  
pp. 383-391 ◽  
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 deg, 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 percent 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 by 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.

Three Dimensional Clocking Effects in a One and a Half Stage Transonic Turbine

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
O. Schennach ◽  
J. Woisetschläger ◽  
B. Paradiso ◽  
G. Persico ◽  
P. Gaetani
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Fast Response ◽  
Secondary Flows ◽  
Pressure Probe ◽  
Time Resolved ◽  
Flow Angle ◽  
Aerodynamic Pressure ◽  
Velocity Flow ◽  
Transonic Turbine

This paper presents an experimental investigation of the flow field in a high-pressure transonic turbine with a downstream vane row (1.5 stage machine) concerning the airfoil indexing. The objective is a detailed analysis of the three-dimensional aerodynamics of the second vane for different clocking positions. To give an overview of the time-averaged flow field, five-hole probe measurements were performed upstream and downstream of the second stator. Furthermore in these planes additional unsteady measurements were carried out with laser Doppler velocimetry in order to record rotor phase-resolved velocity, flow angle, and turbulence distributions at two different clocking positions. In the planes upstream of the second vane, the time-resolved pressure field has been measured by means of a fast response aerodynamic pressure probe. This paper shows that the secondary flows of the second vane are significantly modified by the different clocking positions, in connection with the first vane modulation of the rotor secondary flows. An analysis of the performance of the second vane is also carried out, and a 0.6% variation in the second vane loss coefficient has been recorded among the different clocking positions.

Volumetric Velocimetry Measurements of Purge–Mainstream Interaction in a One-Stage Turbine

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
A. J. Carvalho Figueiredo ◽  
B. D. J. Schreiner ◽  
A. W. Mesny ◽  
O. J. Pountney ◽  
J. A. Scobie ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Suction Side ◽  
Secondary Flows ◽  
Blade Passage ◽  
One Stage ◽  
Passage Vortex ◽  
Purge Flow ◽  
Secondary Flow Field

Abstract Air-cooled gas turbines employ bleed air from the compressor to cool vulnerable components in the turbine. The cooling flow, commonly known as purge air, is introduced at low radius, before exiting through the rim-seal at the periphery of the turbine discs. The purge flow interacts with the mainstream gas path, creating an unsteady and complex flowfield. Of particular interest to the designer is the effect of purge on the secondary-flow structures within the blade passage, the extent of which directly affects the aerodynamic loss in the stage. This paper presents a combined experimental and computational fluid dynamics (CFD) investigation into the effect of purge flow on the secondary flows in the blade passage of an optically accessible one-stage turbine rig. The experimental campaign was conducted using volumetric velocimetry (VV) measurements to assess the three-dimensional inter-blade velocity field; the complementary CFD campaign was carried out using unsteady Reynolds-averaged Navier–Stokes (URANS) computations. The implementation of VV within a rotating environment is a world first and offers an unparalleled level of experimental detail. The baseline flow-field, in the absence of purge flow, demonstrated a classical secondary flow-field: the rollup of a horseshoe vortex, with subsequent downstream convection of a pressure-side and suction-side leg, the former transitioning in to the passage vortex. The introduction of purge, at 1.7% of the mainstream flowrate, was shown to modify the secondary flow-field by enhancing the passage vortex, in both strength and span-wise migration. The computational predictions were in agreement with the enhancement revealed by the experiments.

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.

Endwall Effusion Cooling System Behaviour Within a High-Pressure Turbine Cascade: Part 1—Aerodynamic Measurements

2010 ◽  
Author(s):  
Marco Sacchi ◽  
Daniele Simoni ◽  
Marina Ubaldi ◽  
Pietro Zunino ◽  
Stefano Zecchi
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Secondary Flow ◽  
Measurement Techniques ◽  
Secondary Flows ◽  
Turbine Cascade ◽  
High Pressure Turbine ◽  
Tangential Plane ◽  
Cooling Effects ◽  
Secondary Flow Field

The secondary flow field in a large-scale high-pressure turbine cascade with micro-holed endwall cooling has been investigated at the Genova Laboratory of Aerodynamics and Turbomachinery in cooperation with Avio S.p.A in the framework of the European Project AITEB-2. The experimental investigation has been performed for the baseline configuration, with a smooth solid endwall installed, and for the cooled configuration with a micro-holed endwall providing micro-jets ejection from the wall. Two different cooling flow rates were investigated and the experimental results are reported in the paper. Different measurement techniques have been employed to analyze the secondary flow field along the channel and in a downstream tangential plane. Particle Image Velocimetry has been utilized to quantify the blade-to-blade velocity components in a plane located close to the endwall and in the midspan plane. Hot-wire measurements have been performed in a tangential plane downstream of the blade trailing edges in order to survey the micro-jets effects on the secondary flows behavior. The total pressure distributions, for the different blowing conditions, have been measured in the downstream tangential plane by means of a Kiel pneumatic probe. The results, represented in color plots of velocity, pressure loss coefficient and turbulent kinetic energy distributions, allow the identification of the endwall effusion cooling effects on location and strength of the secondary vortical structures. The thermal investigation of the effusion system is discussed in Part 2 of the paper.

Blade Row Interaction in a One and a Half Stage Transonic Turbine Focusing on Three Dimensional Effects: Part II—Clocking Effects

2008 ◽  
Author(s):  
O. Schennach ◽  
B. Paradiso ◽  
G. Persico ◽  
P. Gaetani ◽  
J. Woisetschla¨ger
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Three Dimensional ◽  
Field Measurements ◽  
Fast Response ◽  
Secondary Flows ◽  
Pressure Probe ◽  
Flow Angle ◽  
Aerodynamic Pressure ◽  
Transonic Turbine

The paper presents an experimental investigation of the flow field in a high-pressure transonic turbine with a downstream vane row (1.5 stage machine) concerning the airfoil indexing. The objective is a detailed analysis of the three dimensional flow field downstream of the high pressure turbine for different vane clocking positions. To give an overview of the time averaged flow field, measurements by means of a pneumatic five hole probe were performed upstream and downstream of the second stator. Furthermore in this planes additional unsteady measurements were carried out with Laser Doppler Velocimetry in order to record rotor phase resolved velocity, flow angle and turbulence distributions at two different clocking positions. In the measurement plane upstream the second vane the time resolved pressure field has been analyzed by means of a Fast Response Aerodynamic Pressure Probe. The paper shows that the secondary flows of the second vane are significantly modified for different clocking positions, in connection with the first vane modulation of the rotor secondary flows. An analysis of the performance of the second vane is also carried out.

On the definition of the secondary flow in three-dimensional cascades

2009 ◽  
Vol 223 (6) ◽  
pp. 667-676 ◽  
Author(s):  
G Persico ◽  
P Gaetani ◽  
V Dossena ◽  
G D'Ippolito ◽  
C Osnaghi
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Secondary Flow ◽  
Boundary Layers ◽  
Complex Geometry ◽  
Flow Direction ◽  
Flow Analysis ◽  
Secondary Flows ◽  
Streamwise Vorticity ◽  
Reference Flow

The present article proposes a novel methodology to evaluate secondary flows generated by the annulus boundary layers in complex cascades. Unlike two-dimensional (2D) linear cascades, where the reference flow is commonly defined as that measured at midspan, the problem of the reference flow definition for annular or complex 3D linear cascades does not have a general solution up to the present time. The proposed approach supports secondary flow analysis whenever exit streamwise vorticity produced by inlet endwall boundary layers is of interest. The idea is to compute the reference flow by applying slip boundary conditions at the endwalls in a viscous 3D numerical simulation, in which uniform total pressure is prescribed at the inlet. Thus the reference flow keeps the 3D nature of the actual flow except for the contribution of the endwall boundary layer vorticity. The resulting secondary field is then derived by projecting the 3D flow field (obtained from both an experiment and a fully viscous simulation) along the local reference flow direction; this approach can be proficiently applied to any complex geometry. This method allows the representation of secondary velocity vectors with a better estimation of the vortex extension, since it offers the opportunity to visualize also the region of the vortices, which can be approximated as a potential type. Furthermore, a proficient evaluation of the secondary vorticity and deviation angle effectively induced by the annulus boundary layer is possible. The approach was preliminarily verified against experimental data in linear cascades characterized by cylindrical blades, not reported for the sake of brevity, showing a very good agreement with the standard methodology based only on the experimental midspan flow field. This article presents secondary flows obtained by the application of the proposed methodology on two annular cascades with cylindrical and 3D-designed blades, stressing the differences with other definitions. Both numerical and experimental results are considered.

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