Unsteady Flow Field of an Axial-Flow Turbine Rotor at a Low Reynolds Number

2006 ◽  
Vol 129 (2) ◽  
pp. 360-371 ◽  
Author(s):  
Takayuki Matsunuma
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Unsteady Flow ◽  
Low Reynolds Number ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Frame Of Reference ◽  
Flow Angle ◽  
Low Reynolds ◽  
Secondary Vortices

The unsteady flow field of an annular turbine rotor was investigated experimentally using a laser Doppler velocimetry (LDV) system. Detailed measurements of the time-averaged and time-resolved distributions of the velocity, flow angle, turbulence intensity, etc., were carried out at a very low Reynolds number condition, Reout=3.5×104. The data obtained were analyzed from the viewpoints of both an absolute (stationary) frame of reference and a relative (rotating) frame of reference. The effect of the turbine nozzle wake and secondary vortices on the flow field inside the rotor passage was clearly captured. It was found that the nozzle wake and secondary vortices are suddenly distorted at the rotor inlet, because of the rotating potential field of the rotor. The nozzle flow (wake and passage vortices) and the rotor flow (boundary layer, wake, tip leakage vortex, and passage vortices) interact intensively inside the rotor passage.

Unsteady Flow Field of an Axial-Flow Turbine Rotor at a Low Reynolds Number

2006 ◽  
Author(s):  
Takayuki Matsunuma
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Unsteady Flow ◽  
Low Reynolds Number ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Frame Of Reference ◽  
Flow Angle ◽  
Low Reynolds ◽  
Secondary Vortices

The unsteady flow field of an annular turbine rotor was investigated experimentally using a laser Doppler velocimetry (LDV) system. Detailed measurements of the time-averaged and time-resolved distributions of the velocity, flow angle, and turbulence intensity, etc. were carried out at a very low Reynolds number condition, Reout = 3.5 × 104. The data obtained were analyzed from the viewpoints of both an absolute (stationary) frame of reference and a relative (rotating) frame of reference. The effect of the turbine nozzle wake and secondary vortices on the flow field inside the rotor passage was clearly captured. It was found that the nozzle wake and secondary vortices are suddenly distorted at the rotor inlet, because of the rotating potential field of the rotor. The nozzle flow (wake and passage vortices) and the rotor flow (boundary layer, wake, tip leakage vortex, and passage vortices) interact intensively inside the rotor passage.

LDV Measurements of Unsteady Midspan Flow in a Turbine Rotor at Low Reynolds Number

2003 ◽  
Author(s):  
Takayuki Matsunuma ◽  
Yasukata Tsutsui
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Reynolds Stress ◽  
Low Reynolds Number ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Mean Flow ◽  
Suction Surface ◽  
Flow Angle ◽  
Low Reynolds

In this study, the unsteady flow field at midspan in an axial-flow turbine rotor at low Reynolds number (Reout,RT = 3.6×104) was investigated experimentally using a laser Doppler velocimetry (LDV) system. The time-averaged and time-dependent distributions of velocity, flow angle, vorticity, turbulence intensity, and Reynolds stress were analyzed in terms of both absolute and relative frames of reference. In the relative frame of reference, the nozzle wake had a slip velocity relative to the mean flow, which caused the wake fluid to migrate across the rotor passage and accumulate on the rotor suction surface. The effect of the nozzle wake on the flow field inside the rotor was determined qualitatively and quantitatively. The flow separation occurred at the rotor suction surface because of the low Reynolds number. The position of the separation onset fluctuated periodically as much as about 10% of the rotor axial-chord by the rotor-stator interaction. The turbulence in the wake region was anisotropy, and it exhibited strong Reynolds stress.

scholarly journals Effects of Low Reynolds Number on Wake-Generated Unsteady Flow of an Axial-Flow Turbine Rotor

2005 ◽  
Vol 2005 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Takayuki Matsunuma ◽  
Yasukata Tsutsui
Keyword(s):  
Reynolds Number ◽  
Energy Dissipation ◽  
Flow Field ◽  
Unsteady Flow ◽  
Power Law ◽  
Turbulence Intensity ◽  
Low Reynolds Number ◽  
Axial Flow ◽  
Reynolds Numbers ◽  
Low Reynolds

The unsteady flow field downstream of axial-flow turbine rotors at low Reynolds numbers was investigated experimentally using hot-wire probes. Reynolds number, based on rotor exit velocity and rotor chord lengthReout,RT, was varied from3.2×104to12.8×104at intervals of1.0×104by changing the flow velocity of the wind tunnel. The time-averaged and time-dependent distributions of velocity and turbulence intensity were analyzed to determine the effect of Reynolds number. The reduction of Reynolds number had a marked influence on the turbine flow field. The regions of high turbulence intensity due to the wake and the secondary vortices were increased dramatically with the decreasing Reynolds number. The periodic fluctuation of the flow due to rotor-stator interaction also increased with the decreasing Reynolds number. The energy-dissipation thickness of the rotor midspan wake at the low Reynolds numberReout,RT=3.2×104was1.5times larger than that at the high Reynolds numberReout,RT=12.8×104. The curve of the−0.2power of the Reynolds number agreed with the measured energy-dissipation thickness at higher Reynolds numbers. However, the curve of the−0.4power law fitted more closely than the curve of the−0.2power law at lower Reynolds numbers below6.4×104.

Time Resolved Flow Field Investigations of Low Reynolds number Transient Maneuvers

2016 ◽  
Author(s):  
Hauke Ehlers ◽  
Robert Konrath ◽  
Marcel Börner ◽  
Ralf Wokoeck ◽  
Rolf Radespiel
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Low Reynolds Number ◽  
Time Resolved ◽  
Field Investigations ◽  
Low Reynolds

Low Pressure Turbine Lapse Rate Study: CFD Model vs. Rig Data

2002 ◽  
Author(s):  
J.-S. Liu ◽  
M. L. Celestina ◽  
G. B. Heitland ◽  
D. B. Bush ◽  
M. L. Mansour ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Fluid Dynamic ◽  
Low Reynolds Number ◽  
Low Pressure ◽  
Lapse Rate ◽  
Bypass Transition ◽  
Blade Row ◽  
Low Reynolds ◽  
Lp Turbine

As an aircraft engine operates from sea level take-off (SLTO) to altitude cruise, the low pressure (LP) turbine Reynolds number decreases. As Reynolds number is reduced the condition of the airfoil boundary layer shifts from bypass transition to separated flow transition. This can result in a significant loss. The LP turbine performance fall-off from SLTO to altitude cruise, due to the loss increase with reduction in Reynolds number, is referred to as a lapse rate. A considerable amount of research in recent years has been focused on understanding and reducing the loss associated with the low Reynolds number operation. A recent 3-1/2 stage LP turbine design completed a component rig test program at Honeywell. The turbine rig test included Reynolds number variation from SLTO to altitude cruise conditions. While the rig test provides detailed inlet and exit condition measurements, the individual blade row effects are not available. Multi-blade row computational fluid dynamics (CFD) analysis is used to complement the rig data by providing detailed flow field information through each blade row. A multi-blade row APNASA model was developed and solutions were obtained at the SLTO and altitude cruise rig conditions. The APNASA model predicts the SLTO to altitude lapse rate within 0.2 point compared to the rig data. The global agreement verifies the modeling approach and provides a high confidence level in the blade row flow field predictions. Additional Reynolds number investigation with APNASA will provide guidance in the LP turbine Reynolds number research areas to reduce lapse rate. To accurately predict the low Reynolds number flow in the LP turbine is a challenging task for any computational fluid dynamic (CFD) code. The purpose of this study is to evaluate the capability of a CFD code, APNASA, to predict the sensitivity of the Reynolds number in LP turbines.

Experimental Investigation of Steady and Unsteady Flow Field Downstream of an Automotive Torque Converter Turbine and Inside the Stator: Part I—Flow at Exit of Turbine

1997 ◽  
Vol 119 (3) ◽  
pp. 624-633 ◽  
Author(s):  
B. V. Marathe ◽  
B. Lakshminarayana ◽  
D. G. Maddock
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Separation Zone ◽  
Torque Converter ◽  
Frame Of Reference ◽  
Flow Properties ◽  
Ensemble Averaging ◽  
Suction Surface ◽  
Flow Angle ◽  
Periodic Components

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 inside the stator with a view toward improving its performance. The measurements were conducted in a stationary frame of reference using a high-frequency response five-hole probe, 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 the temporal-spatial domain by ensemble averaging technique. The flow properties (e.g., pressure and velocity) were resolved into mean, periodic, aperiodic, and unresolved components. A velocity profile similar to that of a fully developed flow was observed at all radii. The periodic data in relative reference frame revealed a small separation zone near the suction surface in the core region. The rms values of the unresolved component were found to be significantly higher in this region. The secondary flow vectors show underturning, radially inward flow in the entire passage with a small region of overturning near the separation zone. The overall flow at the turbine exit was nearly two dimensional in nature except in the zone of flow separation. The unsteady flow data show that unresolved and aperiodic components dominate the unsteadiness in the pressure, whereas the periodic components dominate the unsteadiness in velocities and flow angles. Pressure and velocity fluctuations were moderate, whereas the flow angle fluctuations were found to be high. The overall flow at the exit of turbine was found to be highly unsteady.

2E1 Active Control of Reattaching Flow Field at Low Reynolds Number Turbulent Flow Region

2013 ◽  
Vol 2013 (0) ◽  
pp. 143-144
Author(s):  
Naoto YAMAGUCHI ◽  
Isao TERUYA ◽  
Masaaki ISHIKAWA ◽  
Yuta MURO
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Turbulent Flow ◽  
Active Control ◽  
Low Reynolds Number ◽  
Flow Region ◽  
Low Reynolds
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