Fundamental Analysis of the Secondary Flows and Jet-Wake in a Torque Converter Pump—Part I: Model and Flow in a Rotating Passage

2005 ◽  
Vol 127 (1) ◽  
pp. 66-74 ◽  
Author(s):  
R. Flack ◽  
K. Brun
Keyword(s):  
Suction Side ◽  
Torque Converter ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Experimental Results ◽  
Wake Flow ◽  
Rossby Number ◽  
Geometrical Parameters ◽  
Shell Side ◽  
The Core

Previously, experimental results for the velocity field in a torque converter pump showed strong jet/wake characteristics including backflows and circulatory secondary flows. To understand the fundamental flow behavior simplified analytical/numerical Navier-Stokes flow models were developed herein to independently analyze the pump pressure-to-suction side jet/wake flow, the core-to-shell side jet/wake flow, and the secondary flows. Parametric studies were undertaken to evaluate the effect that operating conditions and geometry had on the characteristics. Two relatively simple models were employed: (i) a rotating two-dimensional straight-walled duct to model the pressure-to-suction side jet/wake flow due to rotational Coriolis forces and (ii) a 180 deg flow bend to model the core-to-shell side jet/wake flow due to rapid radial/axial flow turning. The formation and development of the pump jet/wake flow was studied in detail. Results showed that the suction side wake, which was due to the counter-rotational tangential Coriolis force, was almost only a function of the modified Rossby number and independent of the Reynolds number. Increasing the modified Rossby number increased the pressure-to-suction side jet/wake flow. A geometric parameter that was seen to affect the pump flow was the backsweeping angle for the pressure-to-suction side jet/wake. Results showed that using backswept blades can completely eliminate the pressure-to-suction side jet/wake flow effect. Other geometrical parameters were tested but only a small to moderate influence on the jet/wake flow phenomena was found. Predicted trends compared favorably with experimental results.

Fundamental Analysis of the Secondary Flows and Jet-Wake in a Torque Converter Pump: Part 1 — Model and Flow in a Rotating Passage

2003 ◽  
Author(s):  
R. Flack ◽  
K. Brun
Keyword(s):  
Reynolds Number ◽  
Suction Side ◽  
Torque Converter ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Experimental Results ◽  
Wake Flow ◽  
Rossby Number ◽  
Shell Side ◽  
The Core

Previously, experimental results for the velocity field in a torque converter pump showed strong jet/wake characteristics including backflows and circulatory secondary flows. To understand the fundamental flow behavior simplified analytical/numerical Navier-Stokes flow models were developed herein to independently analyze the pump pressure-to-suction side jet/wake flow, the core-to-shell side jet/wake flow, and the secondary flows. Parametric studies were undertaken to evaluate the effect that operating conditions and geometry had on the characteristics. Two relatively simple models were employed: (i) a rotating 2-D straight-walled duct to model the pressure-to-suction side jet/wake flow due to rotational Coriolis forces and (ii) a 180° flow bend to model the core-to-shell side jet/wake flow due to rapid radial/axial flow turning. The formation and development of the pump jet/wake flow was studied in detail. Results showed that the core side wake and the suction side wake, both of which drive the formation of 3-D jet/wake flow in a mixed flow impeller were primarily dependent on two non-dimensional force parameters: the modified Rossby number and the Reynolds number. The suction side wake, which was due to the counter-rotational tangential Coriolis force, was almost only a function of the modified Rossby number and independent of the Reynolds number, while the core side wake, which was due to flow separation caused by rapid radial flow turning, was primarily a function of the Reynolds number. Increasing the modified Rossby number increased the pressure-to-suction side jet/wake flow; similarly, increasing the Reynolds number increased the core-to-shell side jet/wake flow. The geometric parameters that were seen to affect the pump flow were the back-weeping angle for the pressure-to-suction side jet/wake, and the passage length (or curvature) for the core-to-shell jet/wake. Results showed that using backswept blades can completely eliminate the pressure-to-suction side jet/wake flow effect. Other geometrical parameters were tested but only a small to moderate influence on the jet/wake flow phenomena was found. Predicted trends compared favorably with experimental results.

Fundamental Analysis of the Secondary Flows and Jet-Wake in a Torque Converter Pump: Part 2 — Flow in a Curved Stationary Passage and Combined Flows

2003 ◽  
Author(s):  
R. Flack ◽  
K. Brun
Keyword(s):  
Secondary Flow ◽  
Suction Side ◽  
Torque Converter ◽  
Secondary Flows ◽  
Wake Flow ◽  
Streamwise Vorticity ◽  
Shell Side ◽  
The Core ◽  
Flow Circulation ◽  
Vorticity Component

Previously, experimental results for the velocity field in a torque converter pump showed strong jet/wake characteristics including backflows and circulatory secondary flows. Navier-Stokes flow models were developed herein to independently analyze the pump pressure-to-suction side jet/wake flow, the core-to-shell side jet/wake flow, and the secondary flows. Two relatively simple models were employed: (i) a rotating 2-D straight-walled duct and (ii) a 180° flow bend. Parametric studies were undertaken to evaluate the effect that operating conditions and geometry had on the characteristics. Using the modified equations for the generation of streamwise vorticity and the results from the two-dimensional jet/wake model for the normal and binormal vorticity components, trends for the secondary flows in the torque converter pump were predicted. Predicted secondary flows in the torque converter pump circulated in the counter-clockwise direction (positive streamwise vorticity) in the pump mid-plane and in the clockwise direction (negative streamwise vorticity) in the pump exit plane. These trends agreed with experimental observations. Both the Reynolds number and the modified Rossby number were seen to have a significant influence on the streamwise vorticity and, thus, on the magnitude of the secondary flow velocities. The pump mid-plane counter-clockwise secondary flow circulation was primarily caused by the interaction of the pressure-to-suction side jet/wake non-uniform flow (and the associated normal vorticity component) with the high radial/axial flow turning angle the flow underwent while passing through blade passage. Similarly, the pump exit plane clockwise secondary flow circulation was caused by the core-to-shell side jet/wake non-uniform flow (and the associated binormal vorticity component) being rotated about a fixed centerline (pump shaft). Thus, the pump streamwise vorticity, which was responsible for the generation circulatory secondary flows, was directly related to the pump jet/wake phenomena.

Fundamental Analysis of the Secondary Flows and Jet-Wake in a Torque Converter Pump—Part II: Flow in a Curved Stationary Passage and Combined Flows

2005 ◽  
Vol 127 (1) ◽  
pp. 75-82 ◽  
Author(s):  
R. Flack ◽  
K. Brun
Keyword(s):  
Reynolds Number ◽  
Secondary Flow ◽  
Suction Side ◽  
Torque Converter ◽  
Secondary Flows ◽  
Wake Flow ◽  
Streamwise Vorticity ◽  
Shell Side ◽  
The Core ◽  
Vorticity Component

Previously, experimental results for the velocity field in a torque converter pump showed strong jet/wake characteristics including backflows and circulatory secondary flows. Navier-Stokes flow models were developed herein to independently analyze the pump pressure-to-suction side jet/wake flow, the core-to-shell side jet/wake flow, and the secondary flows. Two relatively simple models were employed: (i) a rotating two-dimensional straight-walled duct and (ii) a 180 deg flow bend. Parametric studies were undertaken to evaluate the effect that operating conditions and geometry had on the characteristics. Results from the model showed that the core side wake, which was due to flow separation caused by rapid radial flow turning, was primarily a function of the Reynolds number; increasing the Reynolds number increased the core-to-shell side jet/wake flow. The passage length (or curvature) strongly affected the core-to-shell jet/wake. Using the modified equations for the generation of streamwise vorticity and the results from the two-dimensional jet/wake model for the normal and binormal vorticity components, trends for the secondary flows in the torque converter pump were predicted. Predicted secondary flows in the torque converter pump circulated in the counterclockwise direction (positive streamwise vorticity) in the pump midplane and in the clockwise direction (negative streamwise vorticity) in the pump exit plane. These trends agreed with experimental observations. Both the Reynolds number and the modified Rossby number were seen to have a significant influence on the streamwise vorticity and, thus, on the magnitude of the secondary flow velocities. The pump midplane counter-clockwise secondary flow circulation was primarily caused by the interaction of the pressure-to-suction side jet/wake nonuniform flow (and the associated normal vorticity component) with the high radial/axial flow turning angle the flow underwent while passing through blade passage. Similarly, the pump exit plane clockwise secondary flow circulation was caused by the core-to-shell side jet/wake nonuniform flow (and the associated binormal vorticity component) being rotated about a fixed centerline (pump shaft). Thus, the pump streamwise vorticity, which was responsible for the generation circulatory secondary flows, was directly related to the pump jet/wake phenomena.

scholarly journals Flow Field in the Turbine Rotor Passage in an Automotive Torque Converter Based on the High Frequency Response Rotating Five-hole Probe Measurement Part I: Flow Field at the Design Condition (Speed Ratio 0.6)

2001 ◽  
Vol 7 (4) ◽  
pp. 253-269 ◽  
Author(s):  
Y. F. Liu ◽  
B. Lakshminarayana ◽  
J. Burningham
Keyword(s):  
Pressure Drop ◽  
Flow Field ◽  
Flow Separation ◽  
Suction Side ◽  
Torque Converter ◽  
Turbine Rotor ◽  
Stagnation Pressure ◽  
Wake Flow ◽  
Speed Ratio ◽  
The Core

The relative flow field in an automotive torque converter turbine was measured at three locations inside the passage (turbine 1/4 chord, mid-chord, and 4/4 chord) using a highfrequency response rotating five-hole-probe. “Jet-Wake” flow structure was found in the turbine passage. Possible flow separation region was observed at the core/suction side at the turbine1/4chord and near the suction side at the turbine mid-chord. The mass averaged stagnation pressure drop is almost evenly distributed along the turbine flow path at the design condition(SR=0.6). The pressure drop due to centrifugal and Coriolis forces is found to be appreciable. The rotary stagnation pressure distribution indicates that there are higher losses at the first half of the turbine passage than at the second half. The major reasons for these higher losses and inefficiency are possible flow separation and a mismatch between the pump exit and the turbine inlet flow field. The fuel economy of a torque converter can be improved through redesign of the core region and by properly matching the pump and the turbine. The Part I of the paper deals with the design speed ratio(SR=0.6), and Part II deals with the off-design condition(SR=0.065)and the effects of speed ratio.

scholarly journals Flow Characteristics at the Pump-Turbine Interface of a Torque Converter at Extreme Speed Ratios

2003 ◽  
Vol 9 (6) ◽  
pp. 419-426 ◽  
Author(s):  
A. Habsieger ◽  
R. D. Flack
Keyword(s):  
Flow Field ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
High Velocity ◽  
Torque Converter ◽  
Speed Ratio ◽  
Shell Side ◽  
The Core ◽  
Velocity Gradients ◽  
Coupling Point

The average velocity field at the pump–turbine interface in a scaled version of a truck torque converter was studied. Seven different turbine-to-pump rotational-speed ratios were examined, ranging from near stall (0.065) to overspeed (1.050) so as to determine the effect of the speed ratio on the flow field and on the mass flow rate. Laser velocimetry was used to measure the flow velocity through the pump's exit and the turbine's inlet plane. At the pump's exit, as the speed ratio increases, the high velocities move to the pressure-shell corner and then to both the core-suction and the pressureshell corners. Concentrated velocity gradients are largest at the lowest speed ratio, but areas of velocity gradients are largest near the coupling point. Near the coupling point, the flow field is most nonuniform, which yields a highly periodic flow into the turbine inlet. Above the coupling point, the high velocity remains in the pressure-shell corner but separation is seen to develop at the highest speed ratio. At the turbine's inlet, reverse flow is seen at low speed ratios and is an indicator of flow leakage through the core. Velocity gradients are very large at low speed ratios. As the speed ratio increases to the coupling point, the high velocities remain on the shell side. Above the coupling point, the high-velocity flow migrates from the shell side to the core side. The mass flow rate decreases significantly and nonlinearly with the increase of the speed ratio, but for speed ratios greater than 1.000, the negative slope decreases.

The Development of Wake Flow in a Centrifugal Impeller

1980 ◽  
Vol 102 (2) ◽  
pp. 382-389 ◽  
Author(s):  
M. W. Johnson ◽  
J. Moore
Keyword(s):  
Three Dimensional ◽  
Suction Side ◽  
Secondary Flows ◽  
Wake Flow ◽  
Centrifugal Impeller ◽  
Three Dimensional Flow ◽  
Cross Sectional ◽  
Flow Measurements ◽  
Compressor Impeller ◽  
Rotating Impeller

Three-dimensional flow, leading to the formation and the growth of a wake in a centrifugal impeller, has been studied. Results of flow measurements in a 1 m dia, shrouded, centrifugal compressor impeller running at 500 rpm are presented. Relative velocities and rotary stagnation pressures (p* = p + 1/2ρW2 − 1/2ρω2r2) were measured, on five cross-sectional planes between the inlet and outlet of the impeller, using pressure probes which were traversed within the rotating impeller passage. Particular attention was given to the convection of low p* fluid by secondary flows and to the formation of the wake in the shroud/suction-side corner region of the passage.

scholarly journals Experimental Investigation of Steady and Unsteady Flow Field Downstream of an Automotive Torque Converter Turbine and Stator

1995 ◽  
Vol 2 (2) ◽  
pp. 67-84 ◽  
Author(s):  
B. V. Marathe ◽  
B. Lakshminarayana
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Unsteady Flow ◽  
Torque Converter ◽  
Mean Value ◽  
Frame Of Reference ◽  
Secondary Flows ◽  
Flow Properties ◽  
The Core ◽  
Stationary Frame

The objective of this investigation is to understand the steady and the unsteady flow field at the exit of an automotive torque converter turbine and stator with a view towards improving it's performance. A high frequency response five-hole probe was designed and built to measure the three-dimensional steady and unsteady flow fields. The measurements were conducted in a stationary frame of reference and the data were processed to derive the flow properties in the relative (turbine) frame of reference. The experimental data were processed in the frequency domain by spectrum analysis and in temporal-spatial domain by ensemble averaging technique. The data show that the flow field is highly unsteady with high unresolved unsteadiness (approx. 17-21% of mean value) and significant blade-to-blade periodic component approx. 6% of mean value). The unresolved unsteadiness and periodic unsteadiness increase with an increase in the radius from the shell to the core whereas the aperiodic unsteadiness does not show any systematic variation with the radius. The experimental data reveal the presence of a low momentum region near the core due to possible flow separation and reattachment inside the turbine passage. Data also show the presence of strong secondary flow near the core and weak secondary flow near the shell at the exit of the turbine. These secondary flows generate high levels of turbulence. A comparison of the flow properties upstream and downstream of the stator in the stationary frame of reference indicate the presence of high losses near the core due to high turbulence levels and large secondary flows, and high losses near the shell due to possible corner separation near the shell suction surface inside the stator blade passage. The unsteadiness in the flow properties upstream of the stator is high. The rms value of the unsteady total velocity is approx. 20% of the steady state value. Periodic and aperiodic unsteadiness were also found significant.

Rotating Probe Measurements of the Pump Passage Flow Field in an Automotive Torque Converter

2000 ◽  
Vol 123 (1) ◽  
pp. 81-91 ◽  
Author(s):  
Y. Dong ◽  
B. Lakshminarayana
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Flow Pattern ◽  
Flow Separation ◽  
Torque Converter ◽  
Wake Flow ◽  
Speed Ratio ◽  
Relative Pressure ◽  
Rotating Frame ◽  
The Core

The relative flow in an automotive torque converter pump passage was measured at three locations inside the passage (mid-chord, 3/4-chord, and 4/4-chord) using a miniature high-frequency response five-hole probe in the pump rotating frame. A custom-designed brush-type slip-ring unit is used in the rotating probe system to transmit the amplified signal from the probe in the rotating frame to the stationary frame. At speed ratio of 0.6, a weak “jet-wake” flow pattern is observed at the pump mid-chord. High flow loss is observed in the core-suction corner due to the “wake” flow caused by the flow separation. A strong clockwise secondary flow is found to dominate the flow structure at the pump mid-chord. The Coriolis force and the through flow velocity deficit near the core at the pump inlet are the main reasons for this secondary flow. The jet-wake flow pattern at the 3/4-chord is enhanced by the upstream secondary flow. A jet-wake flow pattern is also observed at the pump 4/4-chord, with concentration of the flow near the passage pressure side. The secondary flow changes its direction of rotation from the 3/4-chord to 4/4-chord. This is mostly caused by the passage meridional curvature and the flow concentration. High loss is found in the core-suction corner wake flow due to a low kinetic energy flow accumulation and the flow separation. Finally, the pump flow field is assessed through the mass-averaged total pressure and relative pressure loss parameter. The data are also analyzed to assess the effect of the speed ratio on the flow field.

Spatial Social Choice

2019 ◽  
pp. 207-244
Author(s):  
Norman Schofield
Keyword(s):  
United States ◽  
Stochastic Model ◽  
Social Choice ◽  
Spatial Models ◽  
The United States ◽  
Multinomial Logit ◽  
Experimental Results ◽  
The Core ◽  
Voting Game ◽  
Voter Choice

A key concept of social choice is the idea of the Condorcet point or core. For example, consider a voting game with four participants so any three will win. If voters have Euclidean preferences, then the point at the center will be unbeaten. Earlier spatial models of social choice focused on deterministic voter choice. However, it is clear that voter choice is intrinsically stochastic. This chapter employs a stochastic model based on multinomial logit to examine whether parties in electoral competition tend to converge toward the electoral center or respond to activist pressure to adopt more polarized policies. The chapter discusses experimental results of the idea of the core explores empirical analyses of elections in Israel and the United States.

scholarly journals Investigation of Separation Phenomena in a Radial Pump at Reduced Flow Rate by Large-Eddy Simulation

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Antonio Posa ◽  
Antonio Lippolis ◽  
Elias Balaras
Keyword(s):  
Reverse Flow ◽  
Leading Edge ◽  
Suction Side ◽  
Secondary Flows ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Turbulent Statistics ◽  
Large Eddy ◽  
Radial Pump ◽  
Reduced Flow

Turbopumps operating at reduced flow rates experience significant separation and backflow phenomena. Although Reynolds-Averaged Navier–Stokes (RANS) approaches proved to be usually able to capture the main flow features at design working conditions, previous numerical studies in the literature verified that eddy-resolving techniques are required in order to simulate the strong secondary flows generated at reduced loads. Here, highly resolved large-eddy simulations (LES) of a radial pump with a vaned diffuser are reported. The results are compared to particle image velocimetry (PIV) experiments in the literature. The main focus of the present work is to investigate the separation and backflow phenomena occurring at reduced flow rates. Our results indicate that the effect of these phenomena extends up to the impeller inflow: they involve the outer radii of the impeller vanes, influencing significantly the turbulent statistics of the flow. Also in the diffuser vanes, a strong spanwise evolution of the flow has been observed at the reduced load, with reverse flow, located mainly on the shroud side and on the suction side (SS) of the stationary channels, especially near the leading edge of the diffuser blades.

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