Measurement and Computation of Energy Separation in the Vortical Wake Flow of a Turbine Nozzle Cascade

1999 ◽  
Vol 121 (4) ◽  
pp. 703-708 ◽  
Author(s):  
W. E. Carscallen ◽  
T. C. Currie ◽  
S. I. Hogg ◽  
J. P. Gostelow
Keyword(s):  
Mach Number ◽  
Vortex Shedding ◽  
High Performance ◽  
Turbine Blades ◽  
Wake Flow ◽  
Energy Separation ◽  
Stagnation Temperature ◽  
Time Resolved ◽  
Exit Mach Number ◽  
Nozzle Guide

This paper describes the observation, measurement, and computation of vortex shedding behind a cascade of turbine nozzle guide vanes that have a blunt trailing edge. At subsonic discharge speeds, periodic wake vortex shedding was observed at all times at a shedding frequency in the range 7–11 kHz. At high subsonic speeds the wake was susceptible to strong energy redistribution. The effect was greatest around an exit Mach number of 0.95 and results are presented for that condition. An unusually cold flow on the wake centerline and hot spots at the edges of the wake were measured. These were found to be a manifestation of Eckert–Weise effect energy separation in the shed vortex street. Experimental identification of these phenomena was achieved using a new stagnation temperature probe of bandwidth approaching 100 kHz. Using phase-averaging techniques, it was possible to plot contours of time-resolved entropy increase at the downstream traverse plane. Computational work has been undertaken that gives qualitative confirmation of the experimental results and provides a more detailed explanation of the fine scale structure of the vortex wake. The topology of the wake vortical structures behind blunt trailing-edged turbine blades is becoming clearer. These measurements are the first instantaneous observations of the energy separation process occurring in turbine blade wake flows. This was also the first demonstration of the use of the probe in the frequency, Mach number, and temperature ranges typical of operation behind the rotors of high-performance turbomachines such as transonic fans.

scholarly journals Measurement and Computation of Energy Separation in the Vortical Wake Flow of a Turbine Nozzle Cascade

1998 ◽  
Author(s):  
W. E. Carscallen ◽  
T. C. Currie ◽  
S. I. Hogg ◽  
J. P. Gostelow
Keyword(s):  
Mach Number ◽  
Vortex Shedding ◽  
High Performance ◽  
Turbine Blades ◽  
Wake Flow ◽  
Energy Separation ◽  
Stagnation Temperature ◽  
Time Resolved ◽  
Exit Mach Number ◽  
Nozzle Guide

This paper describes the observation, measurement and computation of vortex shedding behind a cascade of turbine nozzle guide vanes which have a blunt trailing edge. At subsonic discharge speeds periodic wake vortex shedding was observed at all times at a shedding frequency in the range 7–11 kHz. At high subsonic speeds the wake was susceptible to strong energy redistribution. The effect was greatest around an exit Mach number of 0.95 and results are presented for that condition. An unusually cold flow on the wake center line and hot spots at the edges of the wake were measured. These were found to be a manifestation of Eckert-Weise effect energy separation in the shed vortex street. Experimental identification of these phenomena was achieved using a new stagnation temperature probe of bandwidth approaching 100 kHz. Using phase averaging techniques it was possible to plot contours of time-resolved entropy increase at the downstream traverse plane. Computational work has been undertaken which gives qualitative confirmation of the experimental results and provides a more detailed explanation of the fine scale structure of the vortex wake. The topology of the wake vortical structures behind blunt trailing-edged turbine blades is becoming clearer. These measurements are the first instantaneous observations of the energy separation process occurring in turbine blade wake flows. This was also the first demonstration of the use of the probe in the frequency, Mach number and temperature ranges typical of operation behind the rotors of high performance turbomachines such as transonic fans.

scholarly journals A Review on Turbine Trailing Edge Flow

2020 ◽  
Vol 5 (2) ◽  
pp. 10
Author(s):  
Claus Sieverding ◽  
Marcello Manna
Keyword(s):  
Vortex Shedding ◽  
Point Of View ◽  
Wake Flow ◽  
Energy Separation ◽  
Trailing Edge ◽  
Time Resolved ◽  
Unsteady Wake ◽  
Aerodynamic Parameters ◽  
Unsteady Wake Flow ◽  
Turbine Wake

The paper presents a state-of-the-art review of turbine trailing edge flows, both from an experimental and numerical point of view. With the help of old and recent high-resolution time resolved data, the main advances in the understanding of the essential features of the unsteady wake flow are collected and homogenized. Attention is paid to the energy separation phenomenon occurring in turbine wakes, as well as to the effects of the aerodynamic parameters chiefly influencing the features of the vortex shedding. Achievements in terms of unsteady numerical simulations of turbine wake flow characterized by vigorous vortex shedding are also reviewed. Whenever possible the outcome of a detailed code-to-code and code-to-experiments validation process is presented and discussed, on account of the adopted numerical method and turbulence closure.

Investigation of the 3D Unsteady Rotor Pressure Field in a HP Turbine Stage

2002 ◽  
Author(s):  
E. Valenti ◽  
J. Halama ◽  
R. De´nos ◽  
T. Arts
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Pressure Field ◽  
Pressure Ratio ◽  
Turbine Stage ◽  
Time Resolved ◽  
Mach Number Distribution ◽  
Rotor Surface ◽  
Exit Mach Number ◽  
Unsteady Pressure Measurements

This paper presents steady and unsteady pressure measurements at three span locations (15, 50 and 85%) on the rotor surface of a transonic turbine stage. The data are compared with the results of a 3D unsteady Euler stage calculation. The overall agreement between the measurements and the prediction is satisfactory. The effects of pressure ratio and Reynolds number are discussed. The rotor time-averaged Mach number distribution is very sensitive to the pressure ratio of the stage since the incidence of the flow changes as well as the rotor exit Mach number. The time-resolved pressure field is dominated by the vane trailing edge shock waves. The incidence and intensity of the shock strongly varies from hub to tip due to the radial equilibrium of the flow at the vane exit. The decrease of the pressure ratio attenuates significantly the amplitude of the fluctuations. An increase of the pressure ratio has less significant effect since the change in the vane exit Mach number is small. The effect of the Reynolds number is weak for both the time-averaged and the time-resolved rotor static pressure at mid-span, while it causes an increase of the pressure amplitudes at the two other spans.

Loss Generation in Transonic Turbine Blading

2017 ◽  
Author(s):  
Penghao Duan ◽  
Choon S. Tan ◽  
Andrew Scribner ◽  
Anthony Malandra
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Mach Number ◽  
High Speed ◽  
Turbine Blades ◽  
Surface Boundary ◽  
Loss Model ◽  
Exit Mach Number ◽  
Loss Characteristic ◽  
Shock Loss

The measured loss characteristic in a high-speed cascade tunnel of two turbine blades of different designs showed distinctly different trend with exit Mach number ranging from 0.8 to 1.4. Assessments using steady RANS computation of the flow in the two turbine blades, complemented with control volume analyses and loss modelling, elucidate why the measured loss characteristic looks the way it is. The loss model categorizes the total loss in terms of boundary layer loss, trailing edge loss and shock loss; it yields results in good agreement with the experimental data as well as steady RANS computed results. Thus RANS is an adequate tool for determining the loss variations with exit isentropic Mach number and the loss model serves as an effective tool to interpret both the computational and experimental data. The measured loss plateau in Blade 1 for exit Mach number of 1 to 1.4 is due to a balance between a decrease of blade surface boundary layer loss and an increase in the attendant shock loss with Mach number; this plateau is absent in Blade 2 due to a greater rate in shock loss increase than the corresponding decrease in boundary layer loss. For exit Mach number from 0.85 to 1, the higher loss associated with shock system in Blade 1 is due to the larger divergent angle downstream of the throat than that in Blade 2. However when exit Mach number is between 1.00 and 1.30, Blade 2 has higher shock loss. For exit Mach number above around 1.4, the shock loss for the two blades is similar as the flow downstream of the throat is completely supersonic. In the transonic to supersonic flow regime, the turbine design can be tailored to yield a shock pattern the loss of which can be mitigated in near equal amount of that from the boundary layer with increasing exit Mach number, hence yielding a loss plateau in transonic-supersonic regime.

On Vortex Formation in the Wake Flows of Transonic Turbine Blades and Oscillating Airfoils

2005 ◽  
Vol 128 (3) ◽  
pp. 528-535 ◽  
Author(s):  
J. P. Gostelow ◽  
M. F. Platzer ◽  
W. E. Carscallen
Keyword(s):  
Vortex Shedding ◽  
Turbine Blades ◽  
Vortex Formation ◽  
Energy Separation ◽  
Bluff Bodies ◽  
Wake Flows ◽  
Blunt Trailing Edge ◽  
Speed Flow ◽  
New Synthesis ◽  
Transonic Turbine

This paper demonstrates similarities between the vortex shedding from blunt trailing-edge transonic turbine nozzle blades and from oscillating airfoils and bluff bodies. Under subsonic conditions the turbine nozzle cascade shed wake vortices in a conventional von Kármán vortex street. This was linked with a depressed base pressure and associated energy separation in the wake. Under transonic conditions a variety of different shedding configurations was observed with vortices shedding and pairing in several different ways. Similarities are addressed between the observed structures and those from vortex shedding in some other physical situations, such as the vortex wakes shed from cylinders and airfoils in sinusoidal heaving motion in low-speed flow. The established field of vortex-induced vibration has provided a developed classification scheme for the phenomena observed. The paper has brought together three previously independent fields of investigation and, by showing that the three are essentially related, has provided the basis for a new synthesis.

On Vortex Formation in the Wake Flows of Transonic Turbine Blades and Oscillating Airfoils

2005 ◽  
Author(s):  
J. P. Gostelow ◽  
W. E. Carscallen ◽  
M. F. Platzer
Keyword(s):  
Vortex Shedding ◽  
Classification Scheme ◽  
Turbine Blades ◽  
Vortex Formation ◽  
Energy Separation ◽  
Bluff Bodies ◽  
Wake Flows ◽  
Speed Flow ◽  
New Synthesis ◽  
Transonic Turbine

This paper demonstrates similarities between the vortex shedding from blunt trailing-edged transonic turbine nozzle blades and from oscillating bluff bodies. Under subsonic conditions the turbine nozzle cascade shed wake vortices in a conventional von Ka´rma´n vortex-street. This was linked with a depressed base pressure and associated energy separation in the wake. Under transonic conditions a variety of different shedding configurations was observed with vortices shedding and pairing in several different ways. Similarities are addressed between the observed structures and those from vortex shedding in some other physical situations. The authors have investigated the similarity between the vortex wakes shed from cylinders and airfoils in sinusoidal heaving motion in low speed flow and the wakes shed from the turbine nozzle cascade in transonic flow. The established field of vortex-induced vibration has provided a developed classification scheme for the phenomena observed. The paper has brought together three previously unrelated fields of investigation and, by showing that the three are essentially related, has provided the basis for a new synthesis.

Influence of Loading Distribution on the Off-Design Performance of High-Pressure Turbine Blades

2006 ◽  
Author(s):  
D. Corriveau ◽  
S. A. Sjolander
Keyword(s):  
High Pressure ◽  
Mach Number ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Design Flow ◽  
Superior Performance ◽  
High Pressure Turbine ◽  
Design Performance ◽  
Mach Numbers ◽  
Exit Mach Number

Linear cascade measurements for the aerodynamic performance of a family of three transonic, high-pressure (HP) turbine blades have been presented previously by the authors. The airfoils were designed for the same inlet and outlet velocity triangles but varied in their loading distributions. The previous papers presented results for the design incidence at various exit Mach numbers, and for off-design incidence at the design exit Mach number of 1.05. Results from the earlier studies indicated that by shifting the loading towards the rear of the airfoil an improvement in the profile loss performance of the order of 20% could be obtained near the design Mach number at design incidence. Measurements performed at off-design incidence, but still at the design Mach number, showed that the superior performance of the aft-loaded blade extended over a range of incidence from about −5.0° to +5.0° relative to the design value. For the current study, additional measurements were performed at off-design Mach numbers from about 0.5 to 1.3 and for incidence values of −10.0°, +5.0° and + 10.0° relative to design. The corresponding Reynolds numbers, based on outlet velocity and true chord, varied from roughly 4 × 105 to 10 × 105. The measurements included midspan losses, blade loading distributions and base pressures. In addition, two-dimensional Navier-Stokes computations of the flow were performed to help in the interpretation of the experimental results. The results show that the superior loss performance of the aft-loaded profile, observed at design Mach number and low values of off-design incidence, does not extend readily to off-design Mach numbers and larger values of incidence. In fact, the measured midspan loss performance for the aft-loaded blade was found to be inferior to, or at best equal to, that of the baseline, mid-loaded airfoil at most combinations of off-design Mach number and incidence. However, based on the observations made at design and off-design flow conditions, it appears that aft-loading can be a viable design philosophy to employ in order to reduce the losses within a blade row provided the rearward deceleration is carefully limited. The loss performance of the front-loaded blade is inferior or at best equal to that of the other two blades for all operating conditions. As such, it appears that there is no advantage to front loading the airfoil for transonic high-pressure turbine blades. The results also provide a significant addition to the data available in the open literature on the off-design performance of transonic HP turbine airfoils.

Aerodynamic Performance of a Family of Three High Pressure Transonic Turbine Blades at Off-Design Incidence

2005 ◽  
Author(s):  
D. Corriveau ◽  
S. A. Sjolander
Keyword(s):  
High Pressure ◽  
Mach Number ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Blade Loading ◽  
Design Values ◽  
Outlet Flow ◽  
Exit Mach Number

Linear cascade measurements for the aerodynamic performance of three transonic High Pressure (HP) turbine blades have been presented previously by Corriveau and Sjolander [1] [2] for the design incidence. The airfoils were designed for the same inlet and outlet velocity triangles but varied in their loading distributions. Results from the earlier studies indicated that by shifting the loading towards the rear of the airfoil an improvement in the profile loss performance of the order of 20% could be obtained near the design Mach number of 1.05. The measurements have been extended to off-design incidence to investigate the effects of incidence on the performance of HP turbine blades having differing loading distributions. The additional measurements were performed for incidence values of −10.0°, +5.0°, and +10.0° relative to the design incidence. In addition, two-dimensional Navier-Stokes numerical simulations of the cascade flow were performed in order to help in the interpretation of the experimental results. The exit Mach number was kept at the design value of 1.05. The corresponding Reynolds numbers, based on outlet velocity and true chord, is roughly 10 × 105. The measurements include midspan losses, outlet flow angles, blade loading distributions and base pressures. The results show that the superior loss performance of the aft-loaded profile, observed at design incidence and Mach number, could also be seen for off-design values of incidence ranging from about −5.0° to +5.0°. However, it was found that for incidences greater than about +5.0° the performance of the aft-loaded blade deteriorated rapidly. The front-loaded airfoil showed generally similar performance to that of the baseline mid-loaded airfoil up to an incidence of +5.0°, at which point its performance also deteriorates significantly.

Investigation of Vortex Shedding and Wake-Wake Interaction in a Transonic Turbine Stage Using Laser-Doppler-Velocimetry and Particle-Image-Velocimetry

2005 ◽  
Vol 128 (1) ◽  
pp. 178-187 ◽  
Author(s):  
E. Göttlich ◽  
J. Woisetschläger ◽  
P. Pieringer ◽  
B. Hampel ◽  
F. Heitmeir
Keyword(s):  
Vortex Shedding ◽  
Particle Image ◽  
Rotor Blades ◽  
Laser Doppler ◽  
Turbine Stage ◽  
Time Resolved ◽  
Guide Vanes ◽  
Wake Interaction ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

The current paper presents a time-resolved experimental flow investigation in a highly loaded transonic gas turbine stage operating continuously under engine representative conditions. The measurement was performed with a two-component laser-doppler-velocimeter (LDV) and a three-component stereoscopic particle-image-velocimeter (3C-PIV). Unsteady velocity data were obtained in axis perpendicular planes (LDV) and tangential planes (3C-PIV) between stator and rotor as well as downstream of the rotor. The results of the time-resolved investigation at several radii show the vortex shedding process from the trailing edges of nozzle guide vanes and rotor blades. This vortex shedding was found to be phase locked to higher harmonics of the blade passing frequency. Pressure waves evoked by reflection of the trailing edge shocks of the vanes on the passing rotor blades interact with the boundary layers on the rear suction side of the vanes and on the rotor blade surfaces while running upstream and downstream the flow. They are responsible for this phase-locking phenomenon of the shedding vortices. At midspan, the vortices shedding from stator and rotor blades were also observed by PIV. The in-plane vorticity distribution was used to discuss the wake-wake interaction indicating that wake segments from the nozzle guide vanes were chopped by the rotor blades. These chopped segments are still visible in the distributions as a pair of counter rotating vortices. The nozzle wake segments are transported through the rotor passages by the flow, influencing the vortex street of the rotor blades as they pass by with the higher velocity of the main flow. A comparison with a numerical simulation is also given.

Effect of Airfoil Shape and Turning Angle on Turbine Airfoil Aerodynamic Performance at Transonic Conditions

2011 ◽  
Author(s):  
Santosh Abraham ◽  
Kapil Panchal ◽  
Srinath V. Ekkad ◽  
Wing Ng ◽  
Barry J. Brown ◽  
...  
Keyword(s):  
Mach Number ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Flow Characteristics ◽  
Airfoil Surface ◽  
Turning Angle ◽  
Gas Turbine Blades ◽  
Mach Numbers ◽  
Exit Mach Number ◽  
Turbine Airfoils

Performance data for high turning gas turbine blades under transonic Mach numbers is significantly lacking in literature. Performance of three gas turbine airfoils with varying turning angles at transonic flow conditions was investigated in this study. Midspan total pressure loss, secondary flow field and static pressure measurements on the airfoil surface in a linear cascade setting were measured. Airfoil curvature and true chord were varied to change the loading vs. chord for each airfoil. Airfoils A, D and E are designed to operate at different velocity triangles. Velocity triangle requirements (inlet/exit Mach number and gas angles) come from 1D and 2D models that include calibrated loss systems. One of the goals of this study was to use the experimental data to confirm/refine loss predictions for the effect of various Mach numbers and gas turning angles. The cascade exit Mach numbers were varied within a range from 0.6 to 1.1. The airfoil turning angle ranges from 120° to 138°. A realistic inlet/exit Mach number ratio, that is representative of that seen in a real engine, was obtained by reducing the inlet span with respect to the exit span of the airfoil, thereby creating a quasi 2D cascade. In order to compare the experimental results and study the detailed flow characteristics, 3D viscous compressible CFD analysis was also carried out.

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