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.

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

1996 ◽  
Author(s):  
D. Ristic ◽  
B. Lakshminarayana
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Axial Flow ◽  
Flow Region ◽  
Radial Pressure ◽  
Blade Surface ◽  
Suction Surface ◽  
Field Development

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 one axial station on the endwall and blade 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 blade surface were found to be very thin and laminar, except on the suction surface downstream of 70% 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 turbulent and much thicker, especially near the suction corner of the casing surface, caused by the secondary flow. The secondary flow region near the suction casing surface corner indicated the presence of the passage vortex detached from the blade surface. The boundary layer code accurately predicts the three-dimensional boundary layers on both vane surfaces in regions where the influence of secondary flow is small.

scholarly journals Behavior of Three-Dimensional Boundary Layers in a Radial Inflow Turbine Scroll

1993 ◽  
Author(s):  
Kazuo Hara ◽  
Masato Furukawa ◽  
Masahiro Inoue
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Radial Pressure ◽  
Inlet Region ◽  
Flow Phenomena ◽  
Dimensional Boundary ◽  
Radial Inflow Turbine ◽  
The One ◽  
Circumferential Nonuniformity

A detailed experimental investigation was carried out to examine the three-dimensional boundary layer characteristics in a radial inflow turbine scroll. Some basic flow phenomena and growth of secondary flow were also investigated. In the inlet region of the scroll, the incoming boundary layer begins to have the skewed nature, namely the radially inward secondary flow caused by the radial pressure gradient. From the inlet region to the one third of the scroll circumference, the secondary flow grows so strongly that the most of the low momentum fluid in the incoming boundary layer are transported to the nozzle region. The succeeding elimination of the low momentum fluid in the boundary layer suppresses growth of the boundary layer further downstream, where the boundary layer shows a similarity of velocity profile. The distributions of the boundary layer properties in the scroll correspond well to those of the flow properties at the nozzle. The behavior of the boundary layer in the scroll is found to affect the circumferential nonuniformity of the nozzle flow field.

Behavior of Three-Dimensional Boundary Layers in a Radial Inflow Turbine Scroll

1994 ◽  
Vol 116 (3) ◽  
pp. 446-452 ◽  
Author(s):  
K. Hara ◽  
M. Furukawa ◽  
M. Inoue
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Radial Pressure ◽  
Flow Properties ◽  
Inlet Region ◽  
Flow Phenomena ◽  
Dimensional Boundary ◽  
Radial Inflow Turbine ◽  
Circumferential Nonuniformity

A detailed experimental investigation was carried out to examine the three-dimensional boundary layer characteristics in a radial inflow turbine scroll. Some basic flow phenomena and growth of secondary flow were also investigated. In the inlet region of the scroll, the incoming boundary layer begins to have a skewed nature, namely the radially inward secondary flow caused by the radial pressure gradient. From the inlet region to one third of the scroll circumference, the secondary flow grows so strongly that most of the low-momentum fluid in the incoming boundary layer is transported to the nozzle region. The succeeding elimination of the low-momentum fluid in the boundary layer suppresses growth of the boundary layer farther downstream, where the boundary layer shows a similar velocity profile. The distributions of the boundary layer properties in the scroll correspond well to those of the flow properties at the nozzle. The behavior of the boundary layer in the scroll is found to affect the circumferential nonuniformity of the nozzle flow field.

Review: Laminar-to-Turbulent Transition of Three-Dimensional Boundary Layers on Rotating Bodies

1994 ◽  
Vol 116 (2) ◽  
pp. 200-211 ◽  
Author(s):  
Ryoji Kobayashi
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Speed Ratio ◽  
Stream Velocity ◽  
Turbulent Transition ◽  
Centrifugal Instability ◽  
Crossflow Instability ◽  
Dimensional Boundary ◽  
Axisymmetric Bodies

The laminar-turbulent transition of three-dimensional boundary layers is critically reviewed for some typical axisymmetric bodies rotating in still fluid or in axial flow. The flow structures of the transition regions are visualized. The transition phenomena are driven by the compound of the Tollmien-Schlichting instability, the crossflow instability, and the centrifugal instability. Experimental evidence is provided relating the critical and transition Reynolds numbers, defined in terms of the local velocity and the boundary layer momentum thickness, to the local rotational speed ratio, defined as the ratio of the circumferential speed to the free-stream velocity at the outer edge of the boundary layer, for the rotating disk, the rotating cone, the rotating sphere and other rotating axisymmetric bodies. It is shown that the cross-sectional structure of spiral vortices appearing in the transition regions and the flow pattern of the following secondary instability in the case of the crossflow instability are clearly different than those in the case of the centrifugal instability.

Analysis of the Flow in Vaneless Diffusers With Large Width-to-Radius Ratios

1996 ◽  
Author(s):  
Hua-Shu Dou ◽  
Shimpei Mizuki
Keyword(s):  
Boundary Layer ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Flow Region ◽  
Rotating Stall ◽  
Wake Flow ◽  
Layer Versus ◽  
Dimensional Boundary ◽  
Vaneless Diffusers ◽  
Large Width

The flow in vaneless diffusers with large width-to-radius ratios is analyzed by using three-dimensional boundary-layer theory. The variations of the wall shear angle in the layer and the separation radius of the turbulent boundary layer versus various parameters are calculated and compared with experimental data. The effect of the separation point on the performance of vaneless diffusers and the mechanism of rotating stall are discussed. It is concluded that when the flow rate becomes very low, the reverse flow zone on the diffuser walls extends toward the entry region of diffusers. When the rotating jet-wake flow with varying total pressure passes through the reverse flow region near the impeller outlet, rotating stall is generated. The influences of the radius ratio on the reverse flow occurrence as well as on the overall performance are also discussed.

On vortex boundary layers

1985 ◽  
Vol 400 (1819) ◽  
pp. 253-261 ◽  
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Three Dimensional ◽  
Radial Pressure ◽  
Outer Flow ◽  
The Core ◽  
Dimensional Boundary ◽  
Radial Pressure Gradient ◽  
Potential Vortex ◽  
Vortex Axis

Flow visualization is used to study the flow that results when a potential vortex rotates normal to a stationary horizontal disc. Viscosity is seen to remove the singularity on the vortex axis and lead to the development of a three-dimensional boundary layer. The flow remains laminar below a Reynolds number, Re , of about 10 4 , where Re is based on radius and velocity at the disc edge. With further increases in Re the boundary layer becomes turbulent but relaminarizes as it is advected radially inwards by the highly favourable radial pressure gradient associated with the outer flow. The radius of the zone of relaminarized fluid decreases with increasing Re . Close to the axis the flow effuses vertically to form the core of the vortex which, for Re < 10 4 , is observed to undergo a massive disruption, either of the axisymmetric or helical form. The sense of the helix was observed on some occasions to be with that of the outer flow and on others to be opposite that of the outer flow.

Some Effects of Non-Axisymmetric End Wall Profiling on Axial Flow Compressor Aerodynamics: Part I—Linear Cascade Investigation

2008 ◽  
Author(s):  
N. W. Harvey
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Computational Study ◽  
Design Method ◽  
Axial Flow ◽  
Flow Region ◽  
Original Design ◽  
Suction Surface ◽  
Secondary Loss ◽  
End Wall

Non-axisymmetric end wall profiling is now a well established design methodology in axial flow turbines, used principally to improve their aerodynamic efficiency by reducing secondary loss. However, profiled end walls (PEWs) have yet to find an in-service application in a gas turbine compressor. This two-part paper presents the results of a number of studies, both experimental and computational, into the potential aerodynamic benefits of applying PEWs in axial flow compressors. The first paper reports research carried out using a linear compressor stator cascade at Cambridge University. The datum geometry was based on previous research with this cascade. The PEW geometry was generated using a method that had been proven to reduce secondary loss in turbine blade rows. Data was taken on the datum and PEW geometries in the form of exit area traverses and surface static pressure measurements. The experiments demonstrated improvements to the exit flow field in terms of local reductions in the loss and under-turning in the secondary flow region due to the PEW. It was found that the original design method had over estimated the benefits of the PEW. The datum and PEW geometries were further analysed using state-of-the-art CFD (Computational Fluid Dynamics). The CFD is shown to achieve very good agreement with measurement at the design condition and a reasonable, qualitative match at off-design. It is concluded that the PEW geometry, though not optimum, effected predictable changes to the compressor stator flow field. The mechanisms for these effects are discussed and conclusions are drawn for taking the work forward. In particular, a mechanism is identified whereby the PEW enhances the cross-flow on the end wall and the subsequent radial migration of the secondary flow adjacent to the aerofoil suction surface. The control of corner stall by means of this flow mechanism is highlighted as a possible area for further investigation. This is followed up in the second paper, which presents a computational study of applying PEWs to a multi-stage HP compressor.

Measurement of Three-Dimensional Boundary Layers

1969 ◽  
Vol 73 (705) ◽  
pp. 796-798 ◽  
Author(s):  
B. K. Rogers ◽  
M. R. Head
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Present Form ◽  
Mean Flow ◽  
Flat Surfaces ◽  
Dimensional Boundary ◽  
Flow Directions

The instrument described here is designed to measure mean flow directions and velocities in the three-dimensional boundary layer. Its particular advantage is the small amount of interference it introduces, while allowing measurements to be made close to the surface and providing an acceptably large traverse distance normal to it. In its present form it is restricted, however, to flat surfaces where space beneath the surface is not at a premium.

The boundary layer beneath a Rankine-like vortex

1987 ◽  
Vol 411 (1840) ◽  
pp. 177-192 ◽  
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Radial Pressure ◽  
Reynolds Numbers ◽  
Tangential Component ◽  
Plane Boundary ◽  
Outer Flow ◽  
Law Of The Wall ◽  
Dimensional Boundary ◽  
Transitory State

An experimental investigation is made of the three-dimensional boundary layer that results when a Rankine-like vortex is bounded by a fixed plane boundary, in particular by a horizontal disc coaxial with, and perpendicular to, the axis of rotation of the vortex. A laser-Doppler anemometer is used to make velocity traverses through both the vortex and the boundary layer, for Reynolds numbers, Re , ranging from 5000 to 30000, where Re is based on velocity and radius at the disc edge. The boundary layer is laminar at Re = 5000 and the data agree well with the theory of Belcher et al . ( J . Fluid Mech . 52, 753-780 (1972)); at Re = 10000 the layer is in a transitory state, while for Re ≽ 15000 it is turbulent over some of the disc. The radial pressure gradient associated with the outer flow has a stabilizing effect on the boundary layer and, for 10000 ≼ Re ≼ 30000, acts to revert it to a laminar state, but with diminishing effect as Re increases. In spite of the high threedimensionality of the layer, the tangential component of velocity conforms to the same law-of-the-wall as its streamwise counterpart in two-dimensional turbulent boundary layers.

Analysis of the Flow in Vaneless Diffusers With Large Width-to-Radius Ratios

1998 ◽  
Vol 120 (1) ◽  
pp. 193-201 ◽  
Author(s):  
H.-S. Dou ◽  
S. Mizuki
Keyword(s):  
Boundary Layer ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Flow Region ◽  
Rotating Stall ◽  
Wake Flow ◽  
Layer Versus ◽  
Dimensional Boundary ◽  
Vaneless Diffusers ◽  
Large Width

The flow in vaneless diffusers with large width-to-radius ratios is analyzed by using three-dimensional boundary-layer theory. The variations of the wall shear angle in the layer and the separation radius of the turbulent boundary layer versus various parameters are calculated and compared with experimental data. The effect of the separation point on the performance of vaneless diffusers and the mechanism of rotating stall are discussed. It is concluded that when the flow rate becomes very low, the reverse flow zone on the diffuser walls extends toward the entry region of diffusers. When the rotating jet-wake flow with varying total pressure passes through the reverse flow region near the impeller outlet, rotating stall is generated. The influences of the radius ratio on the reverse flow occurrence as well as on the overall performance are also discussed.

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