Blockage and Distortion Effects on a Vane Island Type Diffuser Performance of Centrifugal Pumps for Various Flow Rates

2015 ◽  
Author(s):  
Qiaorui Si ◽  
Antoine Dazin ◽  
Patrick Dupont ◽  
Olivier Roussette ◽  
Gérard Bois
Keyword(s):  
Outer Part ◽  
Flow Distribution ◽  
Flow Structures ◽  
Inlet Section ◽  
Centrifugal Pumps ◽  
Mean Flow ◽  
Local Flow ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Island Type

Experimental investigation of mean flow velocity and pressure inside the vane-island type diffuser passage of a laboratory centrifugal pump model is presented in this paper. A three-hole directional probe was used to investigate hub to shroud flow properties at diffuser leading and trailing edge planes and at the mid-section between suction and pressure sides along the diffuser passage. All these measurements have been performed for five different flow conditions. The flow structures at the inlet section of the diffuser and along with the passage were analyzed in detail, with a focus on the flow distribution and the pressure recovery evolution of different diffuser part. Block age and distortion effects are analyzed using existing published Particle Image Velocimetry (PIV)measurements in the outer part of the impeller and around the diffuser throat in order to get a better understanding of the overall performances and local flow structures of such a diffuser design.

Vortices' Characteristics to Explain the Flange Height Effects on the Aerodynamic Performances of a Diffuser Augmented Wind Turbine

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Rym Chaker ◽  
Mouldi Kardous ◽  
Mahmoud Chouchen ◽  
Fethi Aloui ◽  
Sassi Ben Nasrallah
Keyword(s):  
Wind Velocity ◽  
Particle Image ◽  
Flow Direction ◽  
Pressure Coefficient ◽  
Inlet Section ◽  
Wind Tunnel Experiments ◽  
Piv Measurements ◽  
Velocity Increase ◽  
Image Velocimetry ◽  
Aerodynamic Performances

Flange height is between the geometric features that contribute efficiently to improve the diffuser aerodynamic performances. Results obtained from wind tunnel experiments, particle image velocimetry (PIV) measurements, and numerical simulations reveal that at the diffuser inlet section, the wind velocity increases as the flange height increases. Nevertheless, there is an optimal ratio (flange height/inlet section diameter, Hopt/Da ≈ 0.15) beyond it, the flange height effect on the velocity increase diminishes. This behavior can be explained by both the positions of the two contra-rotating vortices generated downstream of the diffuser and the pressure coefficient at their centers. Indeed, it was found that, as the flange height increases, the two vortices move away from each other in the flow direction and since the flange height exceeds (Hopt/Da), they became too distant from each other and from the flange. While the pressure coefficients at the vortices' centers increase with (H/Da), attain a maximum when (Hopt/Da) is reached, and then decrease. This suggests that the wind velocity increase depends on the pressure coefficient at the vortices' centers. Therefore, it depends on the vortices' locations which are in turn controlled by the flange height. In practice, this means that the diffuser could be more efficient if equipped with a control system able to hold the vortices too near from the flange.

scholarly journals Cross-plane stereo-PIV measurements in a refractive-index-matched environment of flow associated with barchan dunes immersed in a turbulent boundary layer

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Nathaniel Bristow ◽  
Gianluca Blois ◽  
James Best ◽  
Kenneth Christensen
Keyword(s):  
Boundary Layer ◽  
Refractive Index ◽  
Turbulent Boundary Layer ◽  
Coherent Structures ◽  
Fixed Bed ◽  
Flow Structures ◽  
Local Flow ◽  
Piv Measurements ◽  
Complex Interactions ◽  
Barchan Dunes

Barchan dunes are crescent-shaped bedforms that form in aeolian (i.e., wind-driven) environments (including both Earth and other planets, such as Mars) as well as subaqueous environments. Under the forcing of the aloft turbulent boundary layer, they migrate downstream at a rate inversely proportional to their size, which results in complex interactions between neighboring dunes of disparate scales. In particular, it has been observed that dunes will interact at a distance, causing changes in morphology without contacting each other, which is thought to be driven by the way dunes modify the local flow field Bristow et al. (2018); Assis and Franklin (2020). In this study, the coherent structures formed in the wakes of barchan dunes are investigated using measurements of the flow over fixed-bed (i.e., solid) barchan models, both in the wake of an isolated barchan and the interdune region between interacting barchans (Fig. 1(a)). Furthermore, the interactions between the flow structures shed by the dunes and the structures in the incoming boundary layer are analyzed.

scholarly journals On the Effects of Tip Clearance and Operating Condition on the Flow Structures Within an Axial Turbomachine Rotor Passage

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Yuanchao Li ◽  
Huang Chen ◽  
David Tan ◽  
Joseph Katz
Keyword(s):  
Particle Image ◽  
Suction Side ◽  
Tip Clearance ◽  
Flow Structures ◽  
Narrow Gap ◽  
Piv Measurements ◽  
Tip Leakage ◽  
Image Velocimetry ◽  
Stereo Particle Image Velocimetry ◽  
Turbomachine Rotor

Abstract Effects of tip clearance size and flowrate on the flow around the tip of an axial turbomachine rotor are studied experimentally. Visualizations and stereo-particle image velocimetry (PIV) measurements in a refractive index-matched facility compare the performance, leakage velocity, and the trajectory, growth rate, and strength of the tip leakage vortex (TLV) for gaps of 0.49% and 2.3% of the blade chord, and two flowrates. Enlarging the tip clearance delays the TLV breakup in the aft part of the rotor passage at high flowrates but causes earlier breakup under pre-stall conditions. It also reduces the entrainment of endwall boundary layer vorticity from the separation point where the leakage and passage flows meet. Reducing the flowrate or tip gap shifts the location of the TLV detachment from the blade suction side (SS) upstream to points where the leakage velocity is 70–80% of the tip speed. Once detached, the growth rates of the total shed circulation are similar for all cases, i.e., varying the gap or flowrate mostly shifts the detachment point. The TLV migration away from the SS decreases with an increasing gap but not with the flowrate. Two mechanisms dominate this migration: initially, the leakage jet pushes the TLV away from the blade at 50% of the leakage velocity. Further downstream, the TLV is driven by its image on the other side of the endwall. Differences in migration rate are caused by the smaller distance between the TLV and its image for the narrow gap, and the increase in initial TLV strength with decreasing flowrate and gap.

Flow Field and Turbulence Characterization of a Counter Impinging Jet Reactor Using Particle Image Velocimetry

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Victor A. Miller ◽  
Mirko Gamba
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Field ◽  
Reynolds Stress ◽  
Particle Image ◽  
Impinging Jet ◽  
Reynolds Numbers ◽  
Inlet Section ◽  
Turbulent Stress ◽  
Mean Flow ◽  
Image Velocimetry

We characterize the three dimensional structure and quantify turbulence quantities in a counter-impinging jet reactor with trapezoidal cross-section to test the feasibility of achieving stratified mixing. Dye flow-visualization and particle image velocimetry (PIV) velocity field measurements are made in the inlet section of the reactor. Two-component velocity measurements are made on three sets of orthogonal planes for Rej = 1000, 1800, 2600, and 3700; the overall structure of the flow field is found to be qualitatively similar for the Reynolds numbers studied, but the precise trajectory of the mean flow is found to be sensitive to inflow boundary conditions. Reynolds stresses and anisotropic invariants are calculated; the turbulent kinetic energy decreases linearly with increasing distance downstream in the reactor and it decreases at the same relative rate for all Reynolds numbers studied; anisotropic invariants and Reynolds stress maps indicate a turbulent stress state that tends toward isotropy downstream of the inlets. Turbulent stress maps indicate that the Reynolds stress components are stratified in the reactor channel, becoming uniform as a function of z by y/Dh = 4.

Flow Bistability Downstream of Three-Dimensional Double Backward Facing Steps at Zero-Degree Sideslip

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Benjamin B. Herry ◽  
Laurent Keirsbulck ◽  
Larbi Labraga ◽  
Jean-Bernard Paquet
Keyword(s):  
Three Dimensional ◽  
Sensitivity Study ◽  
Wind Tunnels ◽  
Mean Flow ◽  
Unstable Flow ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Oil Flow ◽  
Zero Degree ◽  
And Control

The flow downstream of a three-dimensional double backward facing step (3D DBWFS) is investigated for Reynolds number Reh ranging from 5×103 to8×104 (based on the first step height h). The flow is studied both qualitatively by means of laser tomoscopy and oil-flow visualizations and quantitatively by means of particle image velocimetry (PIV) measurements. In particular, the results show a mean flow asymmetry. A sensitivity study around zero degree sideslip has shown that the flow is bistable for this geometry. This bistability has been observed in two different wind tunnels for very different upstream conditions. As a main consequence, the zero degree drift angle could be a relevant validation case of unstable flow computation. More tests are carried out to understand and control this particular flow feature.

PIV Measurements in the Condenser Region of a Gas-Loaded Thermosyphon

2008 ◽  
Author(s):  
Martin Cleary ◽  
Ronan Grimes ◽  
Marc Hodes ◽  
Mark T. North
Keyword(s):  
Vapor Phase ◽  
Particle Image ◽  
Flow Structures ◽  
Evaporator Temperature ◽  
Piv Measurements ◽  
3 Dimensional ◽  
Quantitative Measurements ◽  
Passive Devices ◽  
Image Velocimetry ◽  
Heat Loads

Thermosyphons are passive devices used to transfer heat via a liquid-vapor phase change cycle. By adding a secondary non-condensable gas (NCG) to the vapor phase of the thermosyphon it is possible to provide some control over the evaporator temperature as heat load and or ambient temperature vary. The objective of this paper is to perform measurements on the vapor phase in the condenser region of a gas-loaded thermosyphon using particle image velocimetry (PIV). An optically-accessible water/air thermosyphon with a 34.5 mm diameter was designed, constructed and characterized for a range of fill ratios, heat loads, coolant temperatures and masses of NCG. Smoke particles, added with the NCG, were used to seed the flow. The flow field in the condenser was found to be unsteady except with low masses of NCG. It was found that there was no discernable vapor/NCG front present. A large amount of mixing of the vapor and NCG and recirculation of the NCG was observed. Due to the complex 3-dimensional non-axisymmetric nature of the flow it is very difficult to obtain useful quantitative measurements, however, PIV was found to be a very useful tool in visualizing the flow providing an insight in to the flow structures in the condenser.

scholarly journals Stereoscopic PIV measurements using low-cost action cameras

2021 ◽  
Vol 62 (3) ◽  
Author(s):  
Theo Käufer ◽  
Jörg König ◽  
Christian Cierpka
Keyword(s):  
Continuous Wave ◽  
Low Cost ◽  
Frame Rate ◽  
Processing Scheme ◽  
Piv Measurements ◽  
Stereoscopic Piv ◽  
Cost Action ◽  
Image Velocimetry ◽  
Frequency Generator ◽  
Educational Applications

Abstract Recently, large progress was made in the development towards low-cost PIV (Particle Image Velocimetry) for industrial and educational applications. This paper presents the use of two low-cost action cameras for stereoscopic planar PIV. A continuous wave laser or alternatively an LED was used for illumination and pulsed by a frequency generator. A slight detuning of the light pulsation and camera frame rate minimizes systematic errors by the rolling shutter effect and allows for the synchronization of both cameras by postprocessing without the need of hardware synchronization. The setup was successfully qualified on a rotating particle pattern in a planar and stereoscopic configuration as well as on the jet of an aquarium pump. Since action cameras are intended to be used at outdoor activities, they are small, very robust and work autarkic. In conjunction with the synchronization and image pre-processing scheme presented herein, those cameras enable stereoscopic PIV in harsh environments and even on moving experiments. Graphic abstract

Sign in / Sign up

Export Citation Format

Share Document