Investigation of the Effect of Rotation on the Flow in a Two-Pass Cooling System With Smooth and Ribbed Walls Using PIV

2011 ◽  
Author(s):  
Michael Schroll ◽  
Lena Lange ◽  
Martin Elfert
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Cooling System ◽  
Angular Position ◽  
Axial Flow ◽  
Strong Impact ◽  
Pass System ◽  
Flow Maps ◽  
Rotation Numbers ◽  
Two Component

A rotating cooling system with a 180 deg turn is investigated experimentally using the 2C PIV technique to measure the flow inside. This cooling configuration consists of two ducts of arbitrary cross-sections representing a two-pass front part of an idealized but nevertheless engine relevant turbine blade cooling design. The system has been investigated with ribbed walls in both passages for cooling enhancement as well as with smooth walls as a reference version in order to identify the effects induced by ribs. The rib orientation on the walls is 45 deg. With a rib height of 0.1 of hydraulic duct diameter and a pitch of 10 times rib height, a representative well-established rib lay-out was selected. This paper presents measurements of the axial flow during rotation of this two-pass system for rotation numbers up to 0.1. Together with previously obtained stationary results [1], this data completes the investigation of the secondary flow field with rotational results acquired with a two-component PIV measuring technique with improved sequencer technique [2]. The Two-Pass Cooling System was analyzed on the rotating test rig using two-component Particle Image Velocimetry (2C PIV) a non-intrusive optical planar measurement technique. PIV is capable of obtaining complete flow maps of the instantaneous as well as averaged flow field even at high turbulence levels, which are typical for the narrow serpentine-shaped ribbed cooling systems. An in-house developed synchronization device enables very accurate control of the laser flashes and image acquisition with regard to the angular position of the measurement plane (light sheet) and thereby very accurately stabilizes the position of the channel within the image during PIV recording which then leads to very accurate mean velocities. The presented investigations were conducted in stationary and rotating mode. The results demonstrate the combined interaction of different vortices induced by several effects such as the inclination of ribs, Coriolis forces due to rotation and inertial forces within the bend. Additionally, a flow separation was observed at the divider wall downstream of the bend (in the second pass) that has a strong impact on the flow field depending on the rotational speed. The axial flow maps presented in this paper in combination with the secondary flow maps published previously are of sufficient high quality and spatial resolution to serve as a benchmark test case for the validation of flow solvers. The turbulent channel flow was investigated at a Reynolds number of 50,000 and at rotation numbers of 0.0 and 0.1.

PIV Measurement of Secondary Flow in a Rotating Two-Pass Cooling System With an Improved Sequencer Technique

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
Martin Elfert ◽  
Michael Schroll ◽  
Wolfgang Förster
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Cooling System ◽  
Flow Direction ◽  
Rotational Flow ◽  
Complex Flow ◽  
Reference Length ◽  
Rotation Numbers ◽  
Piv Measurement ◽  
Image Position

The flow field characteristics of a two-pass cooling system with an engine-similar layout have been investigated experimentally using the nonintrusive particle image velocimetry (PIV). It consists of a trapezoidal inlet duct, a nearly rectangular outlet duct, and a sharp 180 deg turn. The system has been investigated with smooth and ribbed walls. Ribs are applied on two opposite walls in a symmetric orientation inclined with an angle of 45 deg to the main flow direction. The applied rib layout is well proven and optimized with respect to heat transfer improvement versus pressure drop penalty. The system rotates about an axis orthogonal to its centerline. The configuration was analyzed with the planar two-component PIV technique, which is capable of obtaining complete maps of the instantaneous as well as the averaged flow field even at high levels of turbulence, which are typically found in sharp turns, in ribbed ducts, and, especially, in rotating ducts. In the past, a slip between motor and channel rotation causes additional non-negligible uncertainties during PIV measurements due to an unstable image position. These were caused by the working principle of the standard programmable sequencer unit used in combination with unsteady variations in the rotation speed. Therefore, a new sequencer was developed using FPGA-based hardware and software components from National Instruments (NI), which revealed a significant increase in the stability of the image position. Furthermore, general enhancements of the operability of the PIV system were achieved. The presented investigations of the secondary flow were conducted in stationary and, with the new sequencer technique applied, in rotating mode. Especially in the bend region, vortices with high local turbulence were found. The ribs also change the fluid motion as desired by generating additional vortices impinging the leading edge of the first pass. The flow is turbulent and isothermal; no buoyancy forces are active. The flow was investigated at a Reynolds number of Re=50,000, based on the reference length d (see Fig. 3). The rotation numbers are Ro=0.0 (nonrotating) and 0.1. Engine relevant rotation numbers are in order of 0.1 and higher. A reconstruction of some test rig components, especially the model mounting, has become necessary to reach higher values of the rotational speed compared with previous investigations such as the work of Elfert et al. (2008, “Detailed Flow Investigation Using PIV in a Rotating Square-Sectioned Two-Pass Cooling System With Ribbed Walls,” ASME Turbo Expo, Berlin, Germany, Jun. 9–13, Paper No. GT-2008-51183). This investigation is aimed to analyze the complex flow phenomena caused by the interaction of several vortices, generated by rotation, flow turning, or inclined wall ribs. The flow maps obtained with PIV are of good quality and high spatial resolution and therefore provide a test case for the development and validation of numerical flow simulation tools with special regard to the prediction of flow turbulence under the rotational flow regime, which is typical of turbomachinery. Future work will include the investigation of buoyancy effects to the rotational flow. This implicates wall heating, which results from the heater glass in order to provide transparent models.

Experimental and Numerical Investigation of Stator Exit Flow Field of an Automotive Torque Converter

1996 ◽  
Vol 118 (4) ◽  
pp. 835-843 ◽  
Author(s):  
B. V. Marathe ◽  
B. Lakshminarayana ◽  
Y. Dong
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Complex Flow ◽  
Rate Of Decay

The objective of this investigation is to understand the nature of the complex flow field inside each element of the torque converter through a systematic experimental and numerical investigation of the flow field. A miniature five-hole probe was used to acquire the data at the exit of the stator at several operating conditions. The flow field is found to be highly three dimensional with substantial flow deviations, and secondary flow at the exit of the stator. The secondary flow structure, caused by the upstream radial variation of the through flow, induces flow overturning near the core. Flow separation near the shell causes flow underturning in this region. The rate of decay of stator wake is found to be slower than that observed in the wakes of axial flow turbine nozzles. The flow predictions by a Navier–Stokes code are in good agreement with the pressure and the flow field measured at the exit of the stator at the design and the off-design conditions.

scholarly journals Experimental Investigation of the Flow Field in a Multistage Axial Flow Compressor

1996 ◽  
Vol 2 (4) ◽  
pp. 247-258 ◽  
Author(s):  
B. Lakshminarayana ◽  
N. Suryavamshi ◽  
J. Prato ◽  
R. Moritz
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Axial Flow ◽  
Suction Side ◽  
Mean Velocity ◽  
Axial Flow Compressor ◽  
Total Temperature ◽  
Single Sensor ◽  
Flow Compressor ◽  
Thermocouple Probe

The nature of the flow field in a three stage axial flow compressor, including a detailed survey at the exit of an embedded stator as well as the overall performance of the compressor is presented and interpreted in this paper. The measurements include area traverse of a miniature five hole probe (1.07 mm dia) downstream of stator 2, radial traverses of a miniature five hole probe at the inlet, downstream of stator 3 and at the exit of the compressor at various circumferential locations, area traverse of a low response thermocouple probe downstream of stator 2, radial traverses of a single sensor hot-wire probe at the inlet, and casing static pressure measurements at various circumferential and axial locations across the compressor at the peak efficiency operating point. Mean velocity, pressure and total temperature contours as well as secondary flow contours at the exit of the stator 2 are reported and interpreted. Secondary flow contours show the migration of fluid particles toward the core of the low pressure regions located near the suction side casing endwall corner.

Improving Efficiency of a High Work Turbine Using Non-Axisymmetric Endwalls: Part II—Time-Resolved Flow Physics

2008 ◽  
Author(s):  
P. Schuepbach ◽  
R. S. Abhari ◽  
M. G. Rose ◽  
T. Germain ◽  
I. Raab ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Guide Vane ◽  
Axial Flow ◽  
Fast Response ◽  
Secondary Flows ◽  
Streamwise Vorticity ◽  
Time Resolved ◽  
Flow Physics ◽  
High Work

This paper is the second part of a two part paper that reports on the improvement of efficiency of a one-and-half stage high work axial flow turbine. The first part covered the design of the endwall profiling as well as a comparison with steady probe data, this part covers the analysis of the time-resolved flow physics. The focus is on the time-resolved flow physics that lead to a total-to-total stage efficiency improvement of Δηtt = 1.0% ± 0.4%. The investigated geometry is a model of a high work (Δh/U2 = 2.36), axial shroudless HP turbine. The time-resolved measurements have been acquired upstream and downstream of the rotor using a Fast Response Aerodynamic Probe (FRAP). The paper contains a detailed analysis of the secondary flow field that is changed between the axisymmetric and the non-axisymmetric endwall profiling cases. The flowfield at exit of the first stator is improved considerably due to non-axisymmetric endwall profiling and results in reduced secondary flow and a reduction of loss at both hub and tip, as well as a reduced trailing shed vorticity. The rotor has reduced losses and a reduction of secondary flows mainly at the hub. At the rotor exit the flow field with non-axisymmetric endwalls is more homogenous due to the reduction of secondary flows in the two rows upstream of the measurement plane. This confirms that non-axisymmetric endwall profiling is an effective tool for reducing secondary losses in axial turbines. Using a frozen flow assumption the time-resolved data is used to estimate the axial velocity gradients, which are then used to evaluate the streamwise vorticity and dissipation. The non-axisymmetric endwall profiling of the first nozzle guide vane show reductions of dissipation and streamwise vorticity due to reduced trailing shed vorticity. This smaller vorticity explains the reduction of loss at mid-span, which is shown in the first part of the two part paper. This leads to the conclusion that non-axisymmetric endwall profiling also has the potential of reducing trailing shed vorticity.

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.

scholarly journals Experimental Investigation of the Flow Field in a Multistage Axial Flow Compressor

1994 ◽  
Author(s):  
B. Lakshminarayana ◽  
N. Suryavamshl ◽  
J. Prato ◽  
R. Moritz
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Axial Flow ◽  
Suction Side ◽  
Temporal Variations ◽  
Hot Wire ◽  
Suction Surface ◽  
Mean Velocity ◽  
Axial Flow Compressor ◽  
Flow Compressor

The nature of the flow field in a three stage axial flow compressor, including a detailed survey at the exit of an embedded stator as well as the overall performance of the compressor is presented and interpreted in this paper. The measurements include area traverse of a miniature five hole probe (1.07 mm dia) downstream of stator 2, radial traverses of a miniature five hole probe at the inlet, downstream of stator 3 and at the exit of the compressor at various circumferential locations, area traverse of a low response thermocouple probe downstream of stator 2, radial traverses of a single sensor hot-wire probe at the inlet, and casing static pressure measurements at various circumferential and axial locations across the compressor at the peak efficiency operating point. Spectral analysis of the hot-wire data reveal the existence of several harmonics of all three rotor blade passing frequencies at the inlet of the compressor. Mean velocity, pressure and total temperature contours as well as secondary flow contours at the exit of the stator 2 are reported and interpreted. Hub clearance flow is shown to eliminate the suction surface corner separation. Secondary flow contours show the migration of fluid particles toward the core of the low pressure regions located near the suction side casing endwall corner. The RMS value of the spatial fluctuations in mean velocity downstream of the second stator (which appear as temporal variations to the subsequent rotor) have been derived and shown to be significant.

Experimental and Numerical Investigation of Stator Exit Flow Field of an Automotive Torque Converter

1994 ◽  
Author(s):  
B. V. Marathe ◽  
B. Lakshminarayana ◽  
Y. Dong
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Complex Flow ◽  
Rate Of Decay

The objective of this investigation is to understand the nature of the complex flow field inside each element of the torque converter through a systematic experimental and numerical investigation of the flow field. A miniature five-hole probe was used to acquire the data at the exit of the stat or at several operating conditions. The flow field is found to be highly three-dimensional with substantial flow deviations, and secondary flow at the exit of the stator. The secondary flow structure, caused by the upstream radial variation of the through flow, induces flow overturning near the core. Flow separation near the shell causes flow underturning in this region. The rate of decay of stator wake is found to be slower than that observed in the wakes of axial flow turbine nozzles. The flow predictions by a Navier-Stokes code are in good agreement with the pressure and the flow field measured at the exit of the stator at the design and the off-design conditions.

scholarly journals Flow Analysis in a Spiral Inducer Impeller

1993 ◽  
Author(s):  
J. H. G. Howard ◽  
B. R. Hutchinson ◽  
R. B. Broberg
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Flow Rates ◽  
Flow Swirl ◽  
Upstream Flow ◽  
Secondary Flow Field

The flow within an axial-flow spiral inducer impeller is complex and three-dimensional. The long but tightly-spiralled passages give rise to secondary flow fields strongly influenced by the blade walls. Flow analysis in such an impeller is carried out by a three-dimensional viscous flow code and compared with previously published LDV measurements. Due to the extreme blade angles of the inducer, an unconventional meshing strategy is required in order to prevent high mesh non-orthogonality. Details of that strategy are provided. Tip clearance modelling was not incorporated in this first stage of investigation. Despite this, the flow analysis reveals the pattern of development of the secondary flow field along the length of the high solidity passage consistent with the LDV data but in much greater detail than was possible with the limited capability of the measurement system. Predicted flow patterns upstream suggest preconditions for the initiation of the observed induction of upstream flow swirl at reduced flow rates.

PIV-Measurement of Secondary Flow in a Rotating Two-Pass Cooling System With an Improved Sequencer Technique

2010 ◽  
Author(s):  
M. Elfert ◽  
M. Schroll ◽  
W. Fo¨rster
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Cooling System ◽  
Flow Direction ◽  
Flow Simulation ◽  
Rotational Flow ◽  
Complex Flow ◽  
Reference Length ◽  
Piv Measurement ◽  
Image Position

The flow field characteristics of a two-pass cooling system with an engine-similar lay-out have been investigated experimentally using the non-intrusive Particle Image Velocimetry (PIV). It consists of a trapezoidal inlet duct, a nearly rectangular outlet duct, and a sharp 180 degree turn. The system has been investigated with smooth and ribbed walls. Ribs are applied on two opposite walls in a symmetric orientation inclined with an angle of 45 degrees to the main flow direction. The applied rib lay-out is well-proved and optimized with respect to heat transfer improvement versus pressure drop penalty. The system rotates about an axis orthogonal to its centreline. The configuration was analyzed with the planar two-component PIV technique (2C PIV), which is capable of obtaining complete maps of the instantaneous as well as the averaged flow field even at high levels of turbulence, which are typically found in sharp turns, in ribbed ducts and, especially, in rotating ducts. In the past, slip between motor and channel rotation causes additional not negligible uncertainties during PIV measurements due to unstable image position. These were caused by the working principle of the standard programmable sequencer unit used in combination with unsteady variations of the rotation speed. Therefore, a new sequencer was developed using FPGA-based hardware and software components from National Instruments which revealed a significant increase of the stability of the image position. Furthermore, general enhancements of the operability of the PIV system were achieved. The presented investigations of the secondary flow were conducted in stationary and, with the new sequencer technique applied, in rotating mode. Especially in the bend region vortices with high local turbulence were found. The ribs also change the fluid motion as desired by generating additional vortices impinging the leading edge of the first pass. The flow is turbulent and isothermal, no buoyancy forces are active. The flow was investigated at Reynolds number of Re = 50,000, based on the reference length d (see Fig. 3). The rotation number is Ro = 0 (non-rotating) and 0.1. Engine relevant rotation numbers are in order of 0.1 and higher. A reconstruction of some test rig components, especially the model mounting, has become necessary to reach higher values of the rotational speed compared to previous investigations like in Elfert [2008]. This investigation is aimed to analyze the complex flow phenomena caused by the interaction of several vortices, generated by rotation, flow turning or inclined wall ribs. The flow maps obtained with PIV are of good quality and high spatial resolution and therefore provide a test case for the development and validation of numerical flow simulation tools with special regard to prediction of flow turbulence under rotational flow regime as typical for turbomachinery. Future work will include the investigation of buoyancy effects to the rotational flow. This implicates wall heating which result from the heater glass in order to provide transparent models.

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