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Visualization and Experiment of Tip Vortex Phenomenon in Cooling Fan using Digital Particle Image velocimetry

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Journal of Thermal Science 2004年第4期13卷 321-327页

作者： Junlong Xie Xuejun Wang Guanghui Wu Keqi Wu Huazhong Univ Sci & Technol Sch Energy & Power Engn Wuhan 430074 Hubei Province Peoples R China

The Digital Particle Image velocimetry (DPIV) is an efficient method for measuring the internal flow field of a low-speed cooling fan. This paper studied the velocity field by means of PIV technology for a leading edge swept axial-flow fan without casing, and the tip vortex phenomenon was observed. Time-averaged velocity measurements were taken near the pressure surface, the suction surface and the tip of blade, etc. Moreover, the flow characteristics were visualized using numerical techniques. Experimental results showed that this tip vortex existed at the leading edge of the blade. The generating, developing and dissipating evolvement process of the tip vortex from the blade leading edge to downstream were discussed in detail. In addition, by comparing DPIV results and numerical results, a good agreement between them indicated a possibility to predict flow field using CFD tools. The experimental data provided in this paper are reliable for improving the aerodynamic characteristics of the open axial fan.

关键词： flow visualization open axial-flow fan digital particle image velocimetry tip vortex.

Borescopic particle image velocimetry in bubbling gas-solid fluidized beds

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Particuology 2019年第2期17卷 66-75页

作者： M. Banaei R. Dellaert N.G. Deen J.A.M. Kuipers M. van Sint Annaland Multiphase Reactors Group Department of Chemical Engineering & Chemistry Eindhoven University of Technology P.O. Box 513 5600 MB Eindhoven The Netherlands Dutch Polymer Institute (DPI) P.O. Box 902 5600 AX Eindhoven The Netherlands Multiphase and Reactive Flows Group. Department of Mechanical Engineering Eindhoven University of Technology P.O. Box 513 5600 MB Eindhoven The Netherlands

In this work, the borescopic particle image velocimetry (BPIV) technique was applied to a bubbling gas-solid fluidized bed, and the results were compared with published positron emission particle tracking (PEPT) measurement data. Before performing the experiments, the sensitivity of the BPIV results to the illumination power, light reflectivity of the particles, and location of the borescope was also investigated. The BPIV and PEPT results were in fair agreement;however, some discrepancies were observed.The difference between the two sets of results were mainly caused by the intrusiveness of BPIV, the fact that the local solids volume fraction was not accounted for in the BPIV analysis, and the intrinsic differences of these two methods. Therefore, measurement of the local solids volume fraction with the borescope is highly recommended for further development of the BPIV method, which will also enable measureme nt of the local solids mass fluxes in side dense gas-solid fluidized beds.

关键词： Borescopic particle image velocimetry Gas-solid bubbling fluidized bed Solid velocity profile Experimental investigation Hydrodynamics

Particle image velocimetry for an automatic cooling device using temperature-sensitive magnetic fluid

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维普期刊数据库

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Science China(Technological Sciences) 2008年第8期51卷 1203-1210页

作者： LIAN WenLei LI Qiang XUAN YiMin School of Power Engineering Nanjing University of Science&TechnologyNanjing 210094China

An automatic cooling device has been developed by using a temperature-sensitive magnetic fluid as the coolant. A particle image velocimetry (PIV) system was used to measure the flow velocity of the fluid inside the loop. The efficiency of the device under varying conditions such as the heat load and the power of cooling were ex- perimentally investigated. The effect of cooperation between external magnetic field and thermal field on the performance of the device was studied. As expected, a continuous flow induced by the thermal and magnetic field was observed in the loop, where heat was transferred by the circulating magnetic fluid. The synergic effect between the magnetic field and the temperature gradient has impact on the performance of the device.

关键词： temperature-sensitive magnetic fluid automatic cooling device particle image velocimetry (PIV)

Numerical simulation of flow separation over a backward-facing step with high Reynolds number

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Water Science and Engineering 2019年第2期12卷 145-154页

作者： Fang-fang Wang Shi-qiang Wu Sen-lin Zhu State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Nanjing Hydraulic Research Institute

Large eddy simulation (LES) explicitly calculates the large-scale vortex field and parameterizes the small-scale vortices.In this study,LES and κ-ε models were developed for a specific geometrical configuration of backward-facing step (BFS).The simulation results were validated with particle image velocimetry (PIV) measurements and direct numerical simulation (DNS).This LES simulation was carried out with a Reynolds number of 9000 in a pressurized water tunnel with an expansion ratio of 2.00.The results indicate that the LES model can reveal largescale vortex motion although with a larger grid-cell size.However,the LES model tends to overestimate the top wall separation and the Reynolds stress components for the BFS flow simulation without a sufficiently fine grid.Overall,LES is a potential tool for simulating separated flow controlled by large-scale vortices.

关键词： Large eddy simulation κ-ε model Backward-facing step Direct numerical simulation Large-scale vortices Particle image velocimetry

A Study of the Velocity Field during Evaporation of Sessile Water and Water/Ethanol Drops

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Journal of Bionic Engineering 2010年第4期7卷 321-328页

作者： John R.E.Christy Khellil Sefiane Euan Munro School of Engineering University of Edinburgh

Many studies have investigated evaporation of sessile drops in an attempt to understand the effect of wetting on theevaporation process.Recently interest has also increased in the deposition of particles from such drops,with evaporative massflux being deemed to be responsible for ring-like deposits,and counteraction of the mass flux by Marangoni convection explainingmore uniform deposition patterns.Understanding of such deposition processes is important in biological applications,such as the Litos test-system endorsed by the Russian Ministry of Health for diagnosis of urolithiasis and the evaporation ofcolloidal drops for depositing and organizing proteins and DNA.In most cases where deposition from evaporating drops hasbeen studied,velocity information is inferred from the final deposition pattern or from mathematical modeling based on simplifiedmodels of the physics of the evaporation process.In this study we have directly measured the flow velocities in the baseof sessile drops,using micro particle image velocimetry,viewing the drop from below,through the cover slide.For water drops,a radial pattern of flow was observed with a maximum velocity close to but not at the pinned outer edge.For ‘azeotropic’ethanol/water mixtures,the velocity field is more chaotic to begin with,passing through a phase involving three or four recirculationcells and finally having the same radial pattern as for water drops.

关键词： evaporation sessile drop velocimetry particle deposition μPIV

Experiment of gas plasma plume deflection by magnetic control

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航空动力学报 2020年第3期35卷 581-588页

作者： ZHAO Kai HU Jianbo LU Yongji LI Feng MING Ming SUN Baigang School of Energy and Power Engineering Beijing University of Aeronautics and AstronauticsBeijing 100191China School of Aviation Operations and Services Aviation University of Air ForceChangchun Jilin 130022China Department of Contract Tactics Air Force Command CollegeBeijing 100097China

To investigate the deflection effect of gas plasma plume controlled by magnetic field,a novel experimental scheme was presented.The Cs2CO3 catalytic ionization seeds were injected into the combustion chamber to obtain gas plasma on a high temperature magneto hydrodynamic(MHD)experiment rig.The plasma jet was deflected under the action of an external magnetic field,resulting in a thrust-vector effect.Particle image velocimetry(PIV)collected two-dimensional images of jet flow field.Through image processing and velocity vector analysis,the jet deflection angle can be obtained quantitatively.At 1800-2500 K,the jet deflection was verified experimentally under the condition of 0.45 T magnetic field strength.The results indicate that the jet deflection angle increases gradually with the increase of gas temperature,and above 2200 K,the jet deflection angle increase obviously.In the process of gas plasma jet,it is feasible to realize the jet deflection controlled by MHD by adding an external magnetic field.

关键词： gas plasma plume deflection magnetic fluid thrust vector particle image velocimetry

Experimental investigation on flow characteristics in circular tube inserted with rotor-assembled strand using PIV

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Chinese Journal of Chemical Engineering 2019年第1期27卷 1-9页

作者： Lichen He Weimin Yang Changfeng Guan Hua Yan Lin Zheng Xiahua Zuo College of Mechanical and Electrical Engineering Beijing University of Chemical Technology

Rotor-assembled strand works as a typical tube insert to achieve heat transfer augmentation and scale inhibition in a heat exchanger.In this work, the PIV experiment regarding the flow fields in a circular tube inserted with rotor-assembled strand was conducted and the flow characteristics on transverse section and longitudinal section were analyzed.The results showed that swirling flow was produced in the tube inserted with rotors and it was particularly strong within the swing diameter of the rotor on the section that contains the rotor;the average turbulence intensity and the radial velocity were improved notably; the velocity vectors on the longitudinal section remained along the direction of a straight line; both the swirling flow and average turbulence intensity were higher for the rotor with three blades than for the rotor with two blades except that the radial velocity was approximate, but they were all reduced by enlarging the lead of the rotor.Characterization of the flow patterns in a circular tube contributes to understanding the heat transfer efficiency and scale inhibition performance of the rotor-assembled strand and provides guidance for its application.

关键词： Particle image velocimetry (PIV) Swirling flow Rotor-assembled strand Circular tube

Chaotic characteristics of pseudoplastic fluid induced by 6PBT impeller in a stirred vessel

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Chinese Journal of Chemical Engineering 2019年第2期27卷 293-297页

作者： Deyu Luan Yiming Chen Hong Wang Yue Wang Xing Wei College of Electromechanical Engineering Qingdao University of Science and Technology

Xanthan gum solutions with different mass concentrations were used to study the chaotic characteristics induced by the impeller of perturbed six-bent-blade turbine(6 PBT) in a stirred vessel. Based on the velocity time series obtained by the experiment of particle image velocimetry(PIV), with the software MATLAB(R2016a), the distributions of the largest Lyapunov exponent(LLE) and Kolmogorov entropy(K entropy) of the system, as two important parameters for characterizing the chaotic degree, were investigated respectively. Results showed that both of the LLE and K entropy increased with the increasing speed at the beginning. As the speed was up to 200 r·min-1, the two parameters reached the maximal values meanwhile, corresponding to 0.535 and 0.834, respectively, which indicated that the chaotic degree of the flow field was up to the highest level. When the speed was increased further, both of the LLE and K entropy decreased on the contrary, which meant that the chaotic degree was decreasing. It was also observed that the chaotic characteristics of flow field were hardly affected by the fluid rheology and the detecting positions. The research results will enhance the understanding of the chaotic mixing mechanism and provide a theoretical reference for optimizing impeller structure.

关键词： Chaos Pseudoplastic fluids Largest Lyapunov exponent (LLE) Kolmogorov entropy (K entropy) Particle image velocimetry (PIV) 6PBT impeller

Experimental investigation on the effect of surface characterization of electrodes on the gas bubble dynamics in electrolyte flow and performance of FLA batteries by using PIV

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Chinese Journal of Chemical Engineering 2021年第5期34卷 30-39页

作者： Saeed Nahidi Iraj Jafari Gavzan Seyfolah Saedodin Mahmoud Salari Department of Mechanical Engineering Semnan UniversitySemnanIran Department of Mechanical Engineering Imam Hossein UniversityTehranIran

In the flooded lead_acid batteries(FLAB),gas bubbles are initially formed on the surface of the electrodes,which are produced by electrochemical reactions,and then released into the electrolyte.In the present investigation,the effect of surface characterization of electrodes of FLAB on the gas bubble dynamic parameters in the electrolyte flow at different charging/discharging rates(C-rates)are studied utilizing particle image velocimetry(PIV)method.The results show that the capacity of FLAB have a linear behavior due to changes in each of the two parameters of the surface characterization of electrodes and the Crate.At all State of charges(SOCs)of FLAB cells in different tests,increasing average roughness(Ra)and average wavelength of the roughness(λa)in the electrode surfaces,results in an increase in average bubble diameter and bubble rising velocity.Nevertheless,a sharp decrease in the void fraction of bubbles within the electrolyte was observed due to the increment inλa and Ra.Also,the effect of the rising movement of gas bubbles within the electrolyte on the average electrolyte velocity pattern in the gap between the electrodes by changing the surface characterization of electrodes are investigated in detail.

关键词： Particle image velocimetry (PIV) Flooded lead_acid batteries (FLAB) Insoluble gas bubble Electrochemical reactions Surface characterization of electrodes