Effects of Surface Roughness and Turbulence Intensity on the Aerodynamics Losses Produced by a Suction Surface of a Simulated Turbine Airfoil

2003 ◽  
Author(s):  
Qiang Zhang ◽  
Sang Woo Lee ◽  
Philip M. Ligrani
Keyword(s):  
Surface Roughness ◽  
Boundary Layers ◽  
Turbulence Intensity ◽  
Turbulent Transport ◽  
Three Dimensional ◽  
Intensity Level ◽  
Suction Surface ◽  
University Of Utah ◽  
Trailing Edges ◽  
Turbine Airfoils

The effects of surface roughness on the aerodynamic performance of turbine airfoils are investigated with different inlet turbulence intensity levels of 0.9 percent, 5.5 percent and 16.2 percent using the University of Utah Transonic Wind Tunnel. Three symmetric airfoils, each with the same shape and exterior dimensions, are employed with different rough surfaces created to match the roughness which exists on operating turbine vanes and blades subject to extended operating times and significant surface particulate deposition. The non-uniform, irregular, three-dimensional roughness is characterized using the equivalent sand grain roughness size. Mach numbers along the airfoil range from 0.4 to 0.7. Chord Reynolds numbers based on inlet and exit flow conditions are 0.54×106 and 1.02×106, respectively. The contributions of varying surface roughness and turbulence intensity level to aerodynamic losses, Mach number profiles, normalized kinetic energy profiles, and Integrated Aerodynamics Losses (IAL) are quantified. Results show that effects of changing the surface roughness condition on IAL values are substantial, whereas the effects of different inlet turbulence intensity levels are generally relatively small. Relative to smooth airfoils, these variations are due to: (i) augmentations of mixing and turbulent transport in the boundary layers which develop along the roughened airfoils, (ii) thicker boundary layers at the trailing edges of roughened airfoils, (iii) separation of flow streamlines at airfoil trailing edges, and (iv) increased turbulent diffusion in the transverse direction within the wakes of roughened airfoils as they advect downstream.

Effects of Surface Roughness and Turbulence Intensity on the Aerodynamic Losses Produced by the Suction Surface of a Simulated Turbine Airfoil

2004 ◽  
Vol 126 (2) ◽  
pp. 257-265 ◽  
Author(s):  
Qiang Zhang ◽  
Sang Woo Lee ◽  
Phillip M. Ligrani
Keyword(s):  
Surface Roughness ◽  
Turbulence Intensity ◽  
Reynolds Numbers ◽  
Aerodynamic Performance ◽  
Intensity Level ◽  
Flow Conditions ◽  
Suction Surface ◽  
Energy Profiles ◽  
Turbine Airfoils ◽  
Aerodynamic Losses

The effects of surface roughness on the aerodynamic performance of turbine airfoils are investigated with different inlet turbulence intensity levels of 0.9%, 5.5% and 16.2%. Three symmetric airfoils, each with the same shape and exterior dimensions, are employed with different rough surfaces. The nonuniform, irregular, 3-D roughness is characterized using the equivalent sand grain roughness size. Mach numbers along the airfoil range from 0.4 to 0.7. Chord Reynolds numbers based on inlet and exit flow conditions are 0.54×106 and 1.02×106, respectively. The contributions of varying surface roughness and turbulence intensity level to aerodynamic losses, Mach number profiles, normalized kinetic energy profiles, and Integrated Aerodynamics Losses (IAL) are quantified. Results show that effects of changing the surface roughness condition on IAL values are substantial, whereas the effects of different inlet turbulence intensity levels are generally relatively small.

Measurements and Prediction of the Effects of Surface Roughness on Profile Losses and Deviation in a Turbine Cascade

1998 ◽  
Vol 120 (1) ◽  
pp. 20-27 ◽  
Author(s):  
R. J. Kind ◽  
P. J. Serjak ◽  
M. W. P. Abbott
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Leading Edge ◽  
Computational Method ◽  
Roughness Height ◽  
Surface Boundary ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Roughness Effects ◽  
Profile Losses

Measurements of pressure distributions, profile losses, and flow deviation were carried out on a planar turbine cascade in incompressible flow to assess the effects of partial roughness coverage of the blade surfaces. Spanwise-oriented bands of roughness were placed at various locations on the suction and pressure surfaces of the blades. Roughness height, spacing between roughness elements, and band width were varied. A computational method based on the inviscid/viscous interaction approach was also developed; its predictions were in good agreement with the experimental results. This indicates that good predictions can be expected for a variety of cascade and roughness configurations from any two-dimensional analysis that couples an inviscid method with a suitable rough surface boundary-layer analysis. The work also suggests that incorporation of the rough wall skin-friction law into a three-dimensional Navier–Stokes code would enable good predictions of roughness effects in three-dimensional situations. Roughness was found to have little effect on static pressure distribution around the blades and on deviation angle, provided that it does not precipitate substantial flow separation. Roughness on the suction surface can cause large increases in profile losses; roughness height and location of the leading edge of the roughness band are particularly important. Loss increments due to pressure-surface roughness are much smaller than those due to similar roughness on the suction surface.

Numerical Investigation of Three-Dimensional Separation in an Axial Flow Compressor: The Influence of Free-Stream Turbulence Intensity and Endwall Boundary Layer State

2016 ◽  
Author(s):  
Ashley D. Scillitoe ◽  
Paul G. Tucker ◽  
Paolo Adami
Keyword(s):  
Boundary Layer ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Boundary Layer Transition ◽  
Surface Boundary ◽  
Suction Surface ◽  
Corner Separation ◽  
Free Stream Turbulence

Regions of three-dimensional separations are an inherent flow feature of the suction surface - endwall corner in axial compressors. These corner separations can cause a significant total pressure loss and reduce the compressor’s efficiency. This paper uses wall-resolved LES to investigate the loss sources in a corner separation, and examines the influence of the inflow turbulence on these sources. Different subgrid scale (SGS) models are tested and the choice of model is found to be important. The σ SGS model, which performed well, is then used to perform LES of a compressor endwall flow. The time-averaged data is in good agreement with measurements. The viscous and turbulent dissipation are used to highlight the sources of loss, with the latter being dominant. The key loss sources are seen to be the 2D laminar separation bubble and trailing edge wake, and the 3D flow region near the endwall. Increasing the free-stream turbulence intensity (FST) changes the suction surface boundary layer transition mode from separation induced to bypass. However, it doesn’t significantly alter the transition location and therefore the corner separation size. Additionally, the FST doesn’t noticeably interact with the corner separation itself, meaning that in this case the corner separation is relatively insensitive to the FST. The endwall boundary layer state is found to be significant. A laminar endwall boundary layer separates much earlier leading to a larger passage vortex. This significantly alters the endwall flow and loss. Hence, the need for accurate boundary measurements is clear.

Turbine Blade Surface Deterioration by Erosion

2004 ◽  
Author(s):  
Awatef A. Hamed ◽  
Widen Tabakoff ◽  
Richard B. Rivir ◽  
Kaushik Das ◽  
Puneet Arora
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Low Pressure ◽  
Impact Angle ◽  
Rotor Blades ◽  
Material Surface ◽  
Surface Erosion ◽  
Blade Surface ◽  
Suction Surface ◽  
Particle Trajectories

This paper presents the results of a combined experimental and computational research program to investigate turbine vane and blade material surface deterioration caused by solid particle impacts. Tests are conducted in the erosion wind tunnel for coated and uncoated blade materials at various impact conditions. Surface roughness measurements obtained prior and subsequent to the erosion tests are used to characterize the change in roughness caused by erosion. Numerical simulations for the three dimensional flow field and particle trajectories through a low pressure gas turbine are employed to determine the particle impact conditions with stator vanes and rotor blades using experimentally-based particle restitution models. Experimental results are presented for the measured blade material/coating erosion and surface roughness. The measurements indicate that both erosion and surface roughness increase with impact angle and particle size. Computational results are presented for the particle trajectories though the first stage of a low-pressure turbine of a high bypass turbofan engine. The trajectories indicate that the particles impact the vane pressure surface and the aft part of the suction surface. The impacts reduce the particle momentum through the stator but increase it through the rotor. Vane and blade surface erosion patterns are predicted based on the computed trajectories and the experimentally measured blade coating erosion characteristics.

Three-Dimensional Blade Boundary Layer and Endwall Flow Development in the Nozzle Passage of a Single Stage Turbine

1998 ◽  
Vol 120 (3) ◽  
pp. 570-578 ◽  
Author(s):  
D. Ristic ◽  
B. Lakshminarayana
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Axial Flow ◽  
Flow Region ◽  
Radial Pressure ◽  
Suction Surface ◽  
Field Development ◽  
Dimensional Boundary

The three-dimensional viscous flow field development in the nozzle passage of an axial flow turbine stage was measured using a “x” hot-wire probe. The measurements were carried out at two axial stations on the endwall and vane surfaces and at several spanwise and pitchwise locations. Static pressure measurements and flow visualization, using a fluorescent oil technique, were also performed to obtain the location of transition and the endwall limiting streamlines. The boundary layers on the vane surface were found to be very thin and mostly laminar, except on the suction surface downstream of 70 percent axial chord. Strong radial pressure gradient, especially close to the suction surface, induces strong radial flow velocities in the trailing edge regions of the blade. On the endwalls, the boundary layers were much thicker, especially near the suction corner of the casing surface, caused by the secondary flow. The secondary flow region near the suction surface-casing corner indicated the presence of the passage vortex detached from the vane surface. The boundary layer code accurately predicts the three-dimensional boundary layers on both vane surfaces and endwall in the regions where the influence of the secondary flow is small.

Influence of Surface Roughness on Three-Dimensional Separation in Axial Compressors

2004 ◽  
Vol 126 (4) ◽  
pp. 455-463 ◽  
Author(s):  
Semiu A. Gbadebo ◽  
Tom P. Hynes ◽  
Nicholas A. Cumpsty
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Leading Edge ◽  
Major Effect ◽  
Surface Flow ◽  
Design Flow ◽  
Flow Coefficient ◽  
Navier Stokes ◽  
Suction Surface

Surface roughness on a stator blade was found to have a major effect on the three-dimensional (3D) separation at the hub of a single-stage low-speed axial compressor. The change in the separation with roughness worsened performance of the stage. A preliminary study was carried out to ascertain which part of the stator suction surface and at what operating condition the flow is most sensitive to roughness. The results show that stage performance is extremely sensitive to surface roughness around the leading edge and peak-suction regions, particularly for flow rates corresponding to design and lower values. Surface flow visualization and exit loss measurements show that the size of the separation, in terms of spanwise and chordwise extent, is increased with roughness present. Roughness produced the large 3D separation at design flow coefficient that is found for smooth blades nearer to stall. A simple model to simulate the effect of roughness was developed and, when included in a 3D Navier–Stokes calculation method, was shown to give good qualitative agreement with measurements.

The Influence of Deterministic Surface Roughness and Free-Stream Turbulence on Transitional Boundary Layers: Heat Transfer Distributions and a New Transition Onset Correlation

2021 ◽  
Author(s):  
Christoph Gramespacher ◽  
Matthias Stripf ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Flat Plate ◽  
Boundary Layers ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Reynolds Numbers ◽  
Data Set ◽  
Length Scales ◽  
Free Stream Turbulence

Abstract Heat transfer measurements in transitional flat plate boundary layers subjected to surface roughness, strong pressure gradients and free stream turbulence are presented. The surfaces considered, consist of a smooth reference and twenty six deterministic surface topographies that vary in roughness element aspect ratio, height and density. They are designed to cover the full range of roughness regimes from smooth over transitionally rough to fully rough. For each surface, two pressure distributions, characteristic for a suction and a pressure side turbine vane, are investigated. Inlet Reynolds numbers range from 3.0 · 105 to 6.0 · 105 and inlet turbulence intensity is varied between 1% to 8%. Furthermore, different turbulence Reynolds numbers, i.e. turbulence length scales, are realized while the incident turbulence intensity is kept constant. Additionally, the turbulence intensity and Reynolds stress distributions in the free-stream along the flat plate are measured using x-wire probes. Results show a strong influence of roughness and turbulence intensity on the onset of transition. The new data set is used to develop an improved correlation considering the roughness height, density and shape as well as the turbulence intensity and turbulent length scales.

Turbine Blade Surface Deterioration by Erosion

2004 ◽  
Vol 127 (3) ◽  
pp. 445-452 ◽  
Author(s):  
Awatef A. Hamed ◽  
Widen Tabakoff ◽  
Richard B. Rivir ◽  
Kaushik Das ◽  
Puneet Arora
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Low Pressure ◽  
Impact Angle ◽  
Rotor Blades ◽  
Material Surface ◽  
Surface Erosion ◽  
Blade Surface ◽  
Suction Surface ◽  
Particle Trajectories

This paper presents the results of a combined experimental and computational research program to investigate turbine vane and blade material surface deterioration caused by solid particle impacts. Tests are conducted in the erosion wind tunnel for coated and uncoated blade materials at various impact conditions. Surface roughness measurements obtained prior and subsequent to the erosion tests are used to characterize the change in roughness caused by erosion. Numerical simulations for the three-dimensional flow field and particle trajectories through a low-pressure gas turbine are employed to determine the particle impact conditions with stator vanes and rotor blades using experimentally based particle restitution models. Experimental results are presented for the measured blade material/coating erosion and surface roughness. The measurements indicate that both erosion and surface roughness increase with impact angle and particle size. Computational results are presented for the particle trajectories through the first stage of a low-pressure turbine of a high bypass turbofan engine. The trajectories indicate that the particles impact the vane pressure surface and the aft part of the suction surface. The impacts reduce the particle momentum through the stator but increase it through the rotor. Vane and blade surface erosion patterns are predicted based on the computed trajectories and the experimentally measured blade coating erosion characteristics.

The Effects of Secondary Flow and Passive Injection on the Motion of Solid Particles Entrained in Flow Through a Curved Converging Channel

1999 ◽  
Vol 121 (2) ◽  
pp. 359-364
Author(s):  
James J. Ventresca ◽  
Wilfred T. Rouleau
Keyword(s):  
Secondary Flow ◽  
Boundary Layers ◽  
Particle Deposition ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Solid Particles ◽  
Surface Boundary ◽  
Suction Surface ◽  
Particle Trajectories ◽  
Flow Through

The three-dimensional effects of secondary flow, passive injection, and particle size on the motion of solid particles entrained in a laminar, incompressible flow through a curved, converging, rectangular passage were numerically investigated. Emphasis was placed on observing the physical mechanisms that cause particles 5 μm and smaller in diameter to deposit on passage surfaces and to concentrate near the endwalls and mid-span at the passage exit. Particle trajectories were calculated for 5, 30, and 300 μm diameter solid particles. It was observed that the paths of 5 μm particles were similar to the streamlines of the three-dimensional flow in the channel until the particles encountered the boundary layers on the blade surfaces and endwalls, where they would graze the surfaces (contributing to particle deposition) and concentrate at the exit of the channel. Particles of 30 μm diameter, however, were only slightly affected by secondary flows, but were affected enough to be made to concentrate at the exit near the endwall and mid-span surfaces. Particles of 300 μm diameter were not affected by secondary flows at all. The particle trajectories showed that the passage secondary flow convected particles across endwalls toward the pressure and suction surface boundary layers of the blades. It was observed that small particles were made to decelerate and/or concentrate in the boundary layers near the passage exit. It was found that this concentration of particles along the suction surface and endwalls could be significantly reduced by means of passive injection. (Passive injection is a method of inducing the flow of jets in the curved portion of an airfoil shaped surface due to the pressure difference on opposing sides. This is accomplished by means of holes or slots that have been drilled through the surface at strategic locations.)

Influence of Surface Roughness on Three-Dimensional Separation in Axial Compressors

2004 ◽  
Author(s):  
Semiu A. Gbadebo ◽  
Tom P. Hynes ◽  
Nicholas A. Cumpsty
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Leading Edge ◽  
Major Effect ◽  
Surface Flow ◽  
Design Flow ◽  
Flow Coefficient ◽  
Navier Stokes ◽  
Suction Surface

Surface roughness on a stator blade was found to have a major effect on the three-dimensional (3D) separation at the hub of a single-stage low-speed axial compressor. The change in the separation with roughness worsened performance of the stage. A preliminary study was carried out to ascertain which part of the stator suction surface and at what operating condition the flow is most sensitive to roughness. The results show that stage performance is extremely sensitive to surface roughness around the leading edge and peak-suction regions, particularly for flow rates corresponding to design and lower values. Surface flow visualization and exit loss measurements show that the size of the separation, in terms of spanwise and chordwise extent, is increased with roughness present. Roughness produced the large 3D separation at design flow coefficient that is found for smooth blades nearer to stall. A simple model to simulate the effect of roughness was developed and, when included in a 3D Navier-Stokes calculation method, was shown to give good qualitative agreement with measurements.

Sign in / Sign up

Export Citation Format

Share Document