Laser-Doppler Velocimetry Measurements Inside a Backward Curved Centrifugal Fan

Laser-Doppler velocimetry (LDV) measurements are presented of relative mean velocity and turbulence intensity components inside the impeller passage of a centrifugal fan with twelve backward curved blades at design, under-design, and over-design flow rates. Additional LDV measurements were also performed at the volute outlet to examine the uniformity of the outlet flow for the three selected flow rates. Complementary flow visualization results in the tongue region are further presented. It is found that the number of characteristic flow regions and the average turbulence level increase with decreasing air flow rate. For the case of under-design flow rate, there are a through-flow region on the suction side, a reverse flow region on the pressure side, and a shear layer region in between. The corresponding average turbulence intensity is as high as 9.1% of blade tip velocity.

Download Full-text

Inertial Deposition Effects: A Study of Aerosol Mechanics in the Trachea Using Laser Doppler Velocimetry and Fluorescent Dye

Journal of Biomechanical Engineering ◽

10.1115/1.1516572 ◽

2002 ◽

Vol 124 (6) ◽

pp. 629-637 ◽

Cited By ~ 14

Author(s):

T. E. Corcoran ◽

Norman Chigier

Keyword(s):

Steady Flow ◽

Turbulence Intensity ◽

Axial Velocity ◽

Laser Doppler Velocimetry ◽

Aerosol Deposition ◽

Fluorescent Dye ◽

Laser Doppler ◽

Doppler Velocimetry ◽

Flow Rates ◽

Phase Doppler Interferometry

This study characterizes the axial velocity and axial turbulence intensity patterns noted in the tracheal portion of a cadaver-based throat model at two different steady flow rates (18.1 and 41.1 LPM.) This characterization was performed using Phase Doppler Interferometry (Laser Doppler Velocimetry). Deposition, as assessed qualitatively using fluorescent dye, is related to the position of the laryngeal jet within the trachea. The position of the jet is dependent on the downstream conditions of the model. It is proposed therefore that lung/airway conditions may have important effects on aerosol deposition within the throat. There is no correspondence noted between regions of high axial turbulence intensity and deposition.

Download Full-text

Laser-Doppler-Velocimetry Measurements in a Cascade of Compressor Blades at Stall

Journal of Turbomachinery ◽

10.1115/1.2841378 ◽

1998 ◽

Vol 120 (1) ◽

pp. 170-178 ◽

Cited By ~ 3

Author(s):

G. V. Hobson ◽

A. J. H. Williams ◽

H. J. Ganaim Rickel

Keyword(s):

Flow Visualization ◽

Laser Doppler Velocimetry ◽

Reverse Flow ◽

Separation Bubble ◽

Laser Sheet ◽

Leading Edge ◽

Flow Region ◽

Laser Doppler ◽

Laser Doppler Velocimeter ◽

Doppler Velocimetry

Compressor stall was simulated in the Low-Speed Cascade Wind Tunnel at the Turbopropulsion Laboratory of the Naval Postgraduate School. The test blades were of controlled-diffusion design with a solidity of 1.67, and stalling occurred at 10 deg of incidence above the design inlet air angle. All measurements were taken at a flow Reynolds number, based on chord length, of 700,000. Laser-sheet flow visualization techniques showed that the stalling process was unsteady and occurred over the whole cascade. Detailed laser-Doppler-velocimetry measurements over the suction side of the blades showed regions of continuous and intermittent reverse flow. The measurements of the continuous reverse flow region at the leading edge were the first data of their kind in the leading edge separation bubble. The regions of intermittent reverse flow, measured with laser-Doppler velocimeter, corresponded to the flow visualization studies. Blade surface pressure measurements showed a decrease in normal force on the blade, as would be expected at stall. Data are presented in a form that characterizes the unsteady positive and negative velocities about their mean, for both the continuous reverse flow regions and the intermittent reverse flow regions.

Download Full-text

Laser-Doppler Velocimetry Measurements in a Cascade of Compressor Blades at Stall

Volume 1: Turbomachinery ◽

10.1115/96-gt-484 ◽

1996 ◽

Author(s):

Garth V. Hobson ◽

Andrew J. H. Williams ◽

Humberto J. Ganaim Rickel

Keyword(s):

Flow Visualization ◽

Laser Doppler Velocimetry ◽

Reverse Flow ◽

Separation Bubble ◽

Laser Sheet ◽

Leading Edge ◽

Flow Region ◽

Laser Doppler ◽

Laser Doppler Velocimeter ◽

Doppler Velocimetry

Compressor stall was simulated in the Low Speed Cascade Wind Tunnel at the Turbopropulsion Laboratory. The test blades were of controlled-diffusion design with a solidity of 1.67, and stalling occurred at 10 degrees of incidence above the design inlet air angle. All measurements were taken at a flow Reynolds number, based on chord length, of 700 000. Laser-sheet flow visualization techniques showed that the stalling process was unsteady and occurred over the whole cascade. Detailed laser-Doppler-velocimetry measurements over the suction side of the blades showed regions of continuous and intermittent reverse flow. The measurements of the continuous reverse flow region at the leading edge were the first data of their kind in the leading edge separation bubble. The regions of intermittent reverse flow, measured with laser Doppler velocimeter, corresponded to the flow visualization studies. Blade surface pressure measurements showed a decrease in normal force on the blade as would be expected at stall. Data is presented in a form which characterizes the unsteady positive and negative velocities about their mean, for both the continuous reverse flow regions and the intermittent reverse flow regions.

Download Full-text

Cryogenic flow rate measurement with a laser Doppler velocimetry standard

Measurement Science and Technology ◽

10.1088/1361-6501/aa9dd1 ◽

2018 ◽

Vol 29 (3) ◽

pp. 034009 ◽

Cited By ~ 1

Author(s):

R Maury ◽

A Strzelecki ◽

C Auclercq ◽

Y Lehot ◽

S Loubat ◽

...

Keyword(s):

Flow Rate ◽

Laser Doppler Velocimetry ◽

Laser Doppler ◽

Doppler Velocimetry ◽

Rate Measurement ◽

Flow Rate Measurement ◽

Cryogenic Flow

Download Full-text

An LDV Study of the Influence of the Radiator on a Cooling Module Fan

Volume 1: Fora, Parts A and B ◽

10.1115/fedsm2002-31426 ◽

2002 ◽

Author(s):

Robert J. Martinuzzi ◽

Gregory A. Kopp ◽

Brian Havel

Keyword(s):

Laser Doppler Velocimetry ◽

Reverse Flow ◽

Low Flow ◽

Doppler Velocimetry ◽

Flow Conditions ◽

Flow Rates ◽

Cooling Fan ◽

Outlet Flow ◽

Flow Through ◽

Cooling Module

The influence of the radiator on the flow through an automotive cooling fan module was investigated using Laser Doppler Velocimetry for three different flow conditions. It is found that at the nominal design point, the radiator acts as an effective flow straightener. At low flow rates, fan induced pre-swirl is significant, but the radiator helps reduce reverse flow through the fan. Under ram air conditions the upstream inlet distortions persist through the module resulting in a highly distorted outlet flow.

Download Full-text

Flow Field Investigation in a Low-Solidity Inducer by Laser-Doppler Velocimetry

Journal of Turbomachinery ◽

10.1115/1.2927427 ◽

1990 ◽

Vol 112 (1) ◽

pp. 91-97 ◽

Cited By ~ 3

Author(s):

A. Boccazzi ◽

A. Perdichizzi ◽

U. Tabacco

Keyword(s):

Flow Field ◽

Flow Rate ◽

Reverse Flow ◽

Field Investigation ◽

Design Flow ◽

Laser Doppler ◽

Laser Doppler Velocimeter ◽

Pressure Probe ◽

Specific Work ◽

Flow Angle

The results of an experimental investigation of the flow field within a low-solidity inducer at design and off-design flow rates are presented and discussed; particular attention is devoted to the analysis of the flow field, at the tip in front of the leading edge, for the flow rate close to the back-flow onset. The flow field was measured by means of a laser-Doppler velocimeter at four different axial positions upstream, within, and downstream of the inducer. Axial, tangential, and relative flow angle distributions, in the measuring planes, are presented for three different flow coefficients. At the lower flow rate, the plots show the presence of reverse flow in the region close to the hub downstream of the trailing edge. For the same flow rate, quite low axial velocities are detected at the tip. This is in agreement with pressure probe traverses carried out in a slightly downstream section; these measurements also show radial inward velocities of the same order of magnitude as the axial velocities. Circumferentially averaged losses were evaluated from specific work and total head rise given by pressure probes.

Download Full-text