Experimental Investigations of Flows Through a Plane Cascade at Large Angles of Attack With Separations

1988 ◽  
Vol 110 (3) ◽  
pp. 323-328 ◽  
Author(s):  
Chuan-Gang Gu ◽  
Lai-Qin Luo ◽  
Yong-Miao Miao
Keyword(s):  
Measurement Techniques ◽  
Large Angle ◽  
Surface Velocity ◽  
Experimental Investigations ◽  
Reynolds Stresses ◽  
Hot Wire ◽  
Order Accuracy ◽  
High Turbulence ◽  
Flow Visualizations ◽  
New Formula

Measurements of various parameters in the flows through a cascade at different angles of attack have been performed. The parameters, such as Reynolds stresses (uu/U2, vv/U2, and uv/U2), pressure distribution on the blade surface, velocity distribution in the blade passage, position of the separation point, and so on, are measured at a large angle of attack with separations. In addition, the development of wake is also investigated. A new formula with second-order accuracy has been developed to analyze hot-wire signals in flows with high turbulence intensity. The hot-wire data are compared with those by conventional measurement techniques and by flow visualizations. The results are satisfactory.

Leakage Flow Investigations on a Through-Wall Crack Related to Thermal Fatigue of Nuclear Power Plant Piping

2017 ◽  
Author(s):  
Stefan Schmid ◽  
Rudi Kulenovic ◽  
Eckart Laurien
Keyword(s):  
Experimental Data ◽  
Nuclear Power ◽  
Numerical Models ◽  
Measurement Techniques ◽  
Experimental Investigations ◽  
Leakage Flow ◽  
Test Rig ◽  
Reduced Pressure ◽  
Flow Rates ◽  
Set Up

For the validation of empirical models to calculate leakage flow rates in through-wall cracks of piping, reliable experimental data are essential. In this context, the Leakage Flow (LF) test rig was built up at the IKE for measurements of leakage flow rates with reduced pressure (maximum 1 MPA) and temperature (maximum 170 °C) compared to real plant conditions. The design of the test rig enables experimental investigations of through-wall cracks with different geometries and orientations by means of circular blank sheets with integrated cracks which are installed in the tubular test section of the test rig. In the paper, the experimental LF set-up and used measurement techniques are explained in detail. Furthermore, first leakage flow measurement results for one through-wall crack geometry and different imposed fluid pressures at ambient temperature conditions are presented and discussed. As an additional aspect the experimental data are used for the determination of the flow resistance of the investigated leak channel. Finally, the experimental results are compared with numerical results of WinLeck calculations to prove specifically in WinLeck implemented numerical models.

Preliminary Evaluation of Turbulence Level Influence in Heat Transfer Measurements

2004 ◽  
Author(s):  
Carlo Carcasci ◽  
Luca Innocenti ◽  
Marco Surace
Keyword(s):  
Heat Transfer ◽  
Initial Level ◽  
Measurement Techniques ◽  
Preliminary Evaluation ◽  
Turbulence Level ◽  
Hot Wire ◽  
Aluminum Foams ◽  
Transfer Coefficients ◽  
Perforated Plates ◽  
Heat Transfer Coefficients

Heat transfer coefficients have often been experimentally measured, taking into account Nusselt number as a function of Reynolds and Prandtl number. Most experimenters spend their effort to control turbulence level, set it to different values, or keep it unchanged during the tests, as it’s not easy to predict how its initial level may change final results. The aim of this work is to add some comprehension on how different turbulence incoming levels may affect heat transfer measurements, and when it’s possible or not to neglect such effects. Experimental setup features different duct geometries, and thermocromic liquid crystals coupled with hot-wire anemometers are used as main measurement techniques. Tests were performed for Reynolds number from 10000 to 50000 and turbulence level from 3% to 12%. Several turbulence manipulators were adopted, including aluminum foams and multi-perforated plates, and results show some interesting dependences of heat transfer from both turbulence level and grid features.

Hot Wire Measurements at the Exit of a Centrifugal Compressor Impeller

1979 ◽  
Vol 193 (1) ◽  
pp. 341-347
Author(s):  
A. Goulas ◽  
R. C. Baker
Keyword(s):  
Centrifugal Compressor ◽  
Magnetic Tape ◽  
Reynolds Stresses ◽  
Hot Wire ◽  
Mean Velocity ◽  
Isentropic Flow ◽  
Compressor Impeller ◽  
The Mean

Hot wire measurements at the exit of a small centrifugal compressor impeller are reported. Three different hot wire readings were obtained and stored on a magnetic tape for each point by gating the analogue hot wire signal with a pulse which indicated circumferential position. The combination of the three readings yielded the mean velocity and some Reynolds stresses at each point. The measurements show a ‘jet-wake’ profile towards the shroud and ‘isentropic’ flow near the hub.

Investigations of Turbulent Flow in a Centrifugal Compressor Vaned Diffuser by 3-Component Laser Velocimetry

1998 ◽  
Author(s):  
D. Stahlecker ◽  
G. Gyarmathy
Keyword(s):  
Centrifugal Compressor ◽  
Reynolds Stresses ◽  
Vaned Diffuser ◽  
Time Resolved ◽  
Plane Flow ◽  
Diffuser Flow ◽  
Sheer Stress ◽  
High Turbulence ◽  
Approach Velocity ◽  
System Time

The unsteady 3D impeller exit and vaned diffuser flow of a high-subsonic centrifugal compressor has been investigated with an LDV system. Time-resolved 3D velocity measurements were taken along a streampath at 8 positions from impeller exit downwards through the vaned diffuser and at 18 positions from hub to casing at each station. The compressor was operated at its best point at a rim Mach number of Mu = 0.75. Time-resolved (phase averaged) angle and velocity profiles are presented for 2 positions along the streampath. The time-averaged velocity, deterministic fluctuation intensity, turbulence intensity, and in-plane Reynolds sheer stress profiles, presented for all stations, show the evolution of flow and permit comparisons to in-house CFD calculations to be made. The flow leaving the impeller enters the diffuser with an asymmetric and distorted velocity profile. It is shown that the deterministic fluctuations caused by the jet/wake are quickly damped along the streampath. The results illustrate the deceleration of the flow arriving near the hub in the diffuser channel. The deceleration is accompanied by a sharp increase of turbulence. Near the casing, where the approach velocity is low, no deceleration occurs and the Reynolds stresses are high. Turbulence in the in-plane flow can be regarded as isotropic whereas the axial fluctuations clearly show a high amount of anisotropicity. The narrow diffuser passage required special optical measures for permitting close-to-wall LDV measurements. The experiences are described.

Results of the Study Rotor Wheels Supersonic Microturbines with a Large Angle of Rotation of the Flow

2015 ◽  
Vol 752-753 ◽  
pp. 884-889 ◽  
Author(s):  
Andrey Yu. Fershalov ◽  
Mikhail Yu. Fershalov ◽  
Yuriy Ya. Fershalov ◽  
Timofey V. Sazonov
Keyword(s):  
Mach Number ◽  
Gas Flow ◽  
Large Angle ◽  
Experimental Investigations ◽  
Flow Rates ◽  
Ratio Speed ◽  
Supersonic Gas Flow ◽  
Angle Of Rotation

The article presents the results of experimental investigations of rotor wheels supersonic microturbines with a large angle of rotation of the flow. The characteristics of the studied rotor wheels. The analysis of the results of the study ratio speed of rotor wheels, depending on the Mach number. Recommendations for the design working wheels microturbines operating at high supersonic gas flow rates.

The Swirling Turbulent Plume

1974 ◽  
Vol 41 (2) ◽  
pp. 337-342 ◽  
Author(s):  
J. P. Narain ◽  
M. S. Uberoi
Keyword(s):  
Surrounding Medium ◽  
Experimental Investigations ◽  
Swirl Ratio ◽  
Reynolds Stresses ◽  
Ambient Fluid ◽  
Densimetric Froude Number ◽  
Swirl Velocity ◽  
The Mean ◽  
Turbulent Plume ◽  
Integrated Conservation

An entrainment model for an axisymmetric buoyant swirling turbulent plume in a quiescent homogeneous density surrounding medium has been developed. The streamwise similarity of the mean axial velocity, swirl velocity, turbulent Reynolds stresses, and the density difference between the plume and the ambient fluid are assumed. Consistent with various integrated conservation equations, the entrainment is found to be a function of the Reynolds stress, the form of various similarity profiles, the local densimetric Froude number, and the swirl ratio of the swirling plume. While the swirl alone always increases the rate of entrainment across the boundaries of the plume, it also interacts with the buoyancy forces to cause a slight detrainment of the fluid from the plume. The numerical results for the decays of axial and swirling velocities and the spread of the jet agree reasonably well with the existing experimental investigations.

Sources of Excitation in Tube Banks Due to Vortex Shedding

1986 ◽  
Vol 200 (4) ◽  
pp. 293-301 ◽  
Author(s):  
R S Hill ◽  
K C Shim ◽  
R I Lewis
Keyword(s):  
Vortex Shedding ◽  
Velocity Fluctuation ◽  
Power Spectra ◽  
Vortex Street ◽  
Experimental Investigations ◽  
Causal Mechanism ◽  
Hot Wire ◽  
Tube Bank ◽  
Vortex Streets ◽  
Tube Banks

This paper describes experimental investigations of vortex shedding patterns in staggered and in-line tube banks consisting of four rows with transverse pitch to diameter ratios PT/d of 2.67 and longitudinal pitch to diameter ratios PL/d of 2.31. Single hot wire probes were used to obtain velocity power spectra in order to identify discrete frequencies of velocity fluctuation. Double hot wire probes provided phase correlations which could indicate conclusively the presence of vortex streets. Quite different results were obtained for the staggered and in-line geometries. While vortex street fluctuations were observed in both, an additional higher frequency fluctuation was observed in the staggered tube bank, the causal mechanism for which remains obscure.

scholarly journals Flow in a Pelton Turbine Bucket: Numerical and Experimental Investigations

2005 ◽  
Vol 128 (2) ◽  
pp. 350-358 ◽  
Author(s):  
Alexandre Perrig ◽  
François Avellan ◽  
Jean-Louis Kueny ◽  
Mohamed Farhat ◽  
Etienne Parkinson
Keyword(s):  
Homogeneous Model ◽  
Free Surface Flow ◽  
Flow Patterns ◽  
Surface Flow ◽  
Experimental Investigations ◽  
Pressure Measurements ◽  
Two Phase ◽  
Pelton Turbine ◽  
Flow Visualizations ◽  
Turbine Bucket

The aim of the paper is to present the results of investigations conducted on the free surface flow in a Pelton turbine model bucket. Unsteady numerical simulations, based on the two-phase homogeneous model, are performed together with wall pressure measurements and flow visualizations. The results obtained allow defining five distinct zones in the bucket from the flow patterns and the pressure signal shapes. The results provided by the numerical simulation are compared for each zone. The flow patterns in the buckets are analyzed from the results. An investigation of the momentum transfer between the water particles and the bucket is performed, showing the regions of the bucket surface that contribute the most to the torque. The study is also conducted for the backside of the bucket, evidencing a probable Coanda interaction between the bucket cutout area and the water jet.

Experimental Investigation of the Flow in the Pipe Diffuser of a Centrifugal Compressor Stage Under Selected Parameter Variations

2009 ◽  
Author(s):  
Uwe Zachau ◽  
Reinhard Niehuis ◽  
Herwart Hoenen ◽  
David C. Wisler
Keyword(s):  
Centrifugal Compressor ◽  
Measurement Techniques ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Test Facility ◽  
Experimental Investigations ◽  
Pressure Side ◽  
Compressor Stage ◽  
Diffuser Flow ◽  
Parameter Variations

On a centrifugal compressor test facility various experimental investigations have been carried out contributing a valuable gain in knowledge on the fundamental flow physics within passage type diffusers. An extensive measurement series using various steady, unsteady and laser optical measurement techniques has been performed to detect the unsteady, highly three dimensional diffuser flow under various realistic operating conditions. Zachau et al. [1] presented the test facility and the results gathered under nominal conditions. As a follow-up the results of investigated parameter variations are now presented, covering bleed variations, impeller tip clearance and impeller-diffuser misalignment studies. The data is compared to the benchmark created from the nominal baseline data sets and evaluated with respect to the compressor stage performance. Zachau et al. [1] found that under nominal conditions the flow in the pipe diffuser separates on the pressure side in the first half of the pipe. In the last 30% of the pipe hardly any deceleration of the flow takes place. From this, special attention is given to the investigated parameter variations regarding a first proposal for a diffuser design change, which consists in shortening the diffuser. The results for each parameter variation are evaluated in detail in direct comparison to the nominal baseline configuration underlining the conclusion made earlier that the diffuser flow always separates on the pressure side with negligible deceleration in the last third of the diffusing pipe.

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