Phase-Doppler Anemometry Measurements in Water-Air Impinging Jet Flows

2016 ◽  
Author(s):  
Yakang Xia ◽  
Lyes Khezzar ◽  
Mohamed Alshehhi
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Liquid Droplet ◽  
Air Flow ◽  
Turbulent Jets ◽  
Spray Angle ◽  
Jet Flows ◽  
High Speed Photography ◽  
Phase Doppler Anemometry ◽  
Radial Profiles

Flow visualization using high speed photography is used to study the structure of two liquid and one air impinging turbulent jets. The break up structure is discussed and the resulting spray angle at large air flow rates is obtained. The spray angle increases with the air flow rate except for the case when the water jet velocity is so small that the flow rate of air does not have significant effects on the spray angle. Phase Doppler Anemometry measurements of liquid droplet sizes and velocities are also given in terms of radial profiles at several axial locations from the point of impingement.

Experimental Characterization of a Modified Airlift Pump

2014 ◽  
Author(s):  
Afshin Goharzadeh ◽  
Keegan Fernandes
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
High Speed ◽  
Water Flow Rate ◽  
High Speed Photography ◽  
Two Phase ◽  
Inner Diameter ◽  
Airlift Pump ◽  
Flow Map ◽  
Churn Flow

This paper presents an experimental investigation on a modified airlift pump. Experiments were undertaken as a function of air-water flow rate for two submergence ratios (ε=0.58 and 0.74), and two different riser geometries (i) straight pipe with a constant inner diameter of 19 mm and (ii) enlarged pipe with a sudden expanded diameter of 19 to 32 mm. These transparent vertical pipes, of 1 m length, were submerged in a transparent rectangular tank (0.45×0.45×1.1 m3). The compressed air was injected into the vertical pipe to lift the water from the reservoir. The flow map regime is established for both configurations and compared with previous studies. The two phase air-water flow structure at the expansion region is experimentally characterized. Pipeline geometry is found to have a significant influence on the output water flow rate. Using high speed photography and electrical conductivity probes, new flow regimes, such as “slug to churn” and “annular to churn” flow, are observed and their influence on the output water flow rate and efficiency are discussed. These experimental results provide fundamental insights into the physics of modified airlift pump.

The Application of PIV in the Study of Impeller-Diffuser Interaction in Centrifugal Fan: Part I — Impeller-Vaneless Diffuser Interaction

2001 ◽  
Author(s):  
Tarek Mekhail ◽  
Zhang Li ◽  
Du Zhaohui ◽  
Willem Jansen ◽  
Chen Hanping
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
High Speed ◽  
Maximum Flow ◽  
Image Processing Technique ◽  
High Speed Photography ◽  
Centrifugal Fan ◽  
Performance Measurements ◽  
Vaneless Diffuser ◽  
Unstable Flow

Abstract The PIV (Particle Image Velocimetry) technology is a brand-new technique of measuring velocity. It started in the 1980’s with the development of high-speed photography and the image processing technique of computers. This article deals with PIV applied to the study of unsteady impeller-vaneless diffuser interaction in centrifugal fen. Experiments were carried out at The Turbomachinery Laboratory of Shanghai Jiaotong University. The test rig consists of a centrifugal, shrouded impeller, diffuser and volute casing all made of plexiglass. A series of performance measurements were carried out at different speeds and different vaneless diffuser widths. PIV measurements were applied to measure the unsteady flow at the exit part of the impeller and the inlet part of the diffuser for the case of the same width vaneless diffuser. The absolute flow field is measured at medium flow rate and at maximum flow rate. It is informative to capture the whole flow field at the same instant of time, and it might be more revealing to observe the unstable flow in real time.

Velocity characteristics in a multiphase pump under different tip clearances

2020 ◽  
pp. 095765092094653
Author(s):  
Guangtai Shi ◽  
Zongku Liu ◽  
Yexiang Xiao ◽  
Helin Li ◽  
Xiaobing Liu
Keyword(s):  
Velocity Distribution ◽  
Flow Rate ◽  
High Speed ◽  
Stokes Equations ◽  
Design Flow ◽  
Tip Clearance ◽  
High Speed Photography ◽  
Hydraulic Loss ◽  
Impeller Blade ◽  
Multiphase Pump

To investigate the effect of tip clearance on the velocity distribution in a multiphase pump, the internal flow and velocity distribution characteristics in pump under different tip clearances are studied using experimental and numerical methods. Simulations based on the Reynolds-Averaged Navier-Stokes equations (RANS) and the standard k-ε turbulence model are carried out using ANSYS CFX. Under conditions of inlet gas void fraction (IGVF) is 5% at the flow rate of 0.6Q, 0.7Q and 0.8Q (Q is the design flow rate), the accuracy of the numerical method is verified by comparing with the experimental data using high-speed photography. Results show that the leakage flow interacts with the main flow and evolves into the tip leakage vortex (TLV). Due to the TLV, the pressure, velocity, turbulent kinetic energy (TKE), vorticity and streamlines on the S2 stream surface in the impeller and diffuser are changed greatly under different tip clearances. The velocities at the impeller outlet and diffuser inlet along the radial direction are also changed. The axial velocity distribution is similar to the meridional velocity distribution at the impeller blade outlet. While the relative velocity and absolute velocity distribution show the opposite trends. In addition, the vorticity is larger near the tip separated vortex and the hydraulic loss in pump is also increased due to the TLV.

scholarly journals Research on the Deposition Characteristics of Integrated Prefabricated Pumping Station

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 760
Author(s):  
Kai Wang ◽  
Jianbin Hu ◽  
Houlin Liu ◽  
Zixu Zhang ◽  
Li Zou ◽  
...  
Keyword(s):  
Deposition Rate ◽  
Flow Rate ◽  
High Speed ◽  
Particle Diameter ◽  
High Speed Photography ◽  
Pump Operation ◽  
Pumping Station ◽  
Movement Trajectories ◽  
Pump Station ◽  
The Right

Based on the discrete phase model (DPM) solid–liquid two-phase flow model and MATLAB image processing technology, an integrated prefabricated pumping station was taken as the research object to study deposition characteristics under different flow rates, different particle diameters, and different liquid levels. Considering the incomplete symmetry of the internal flow of the prefabricated pumping station, deposition characteristics of the prefabricated pumping station under single/double pumps were also analyzed. Double pumps were symmetrically distributed in the integrated prefabricated pump station, and the movement trajectories of particles at the bottom of the pump pit under the closing inlet valve were measured through the use of a high-speed photography experiment. Results showed that with the increase of the flow rate, the deposition rate of the separated prefabricated pumping station decreased. With an increase of the particle diameter, the movement of particles was farther away from the vertical barrier weir. In the range of particle diameter of 6 to 10 mm, the deposition rate decreased with the increase of the particle diameter. With the increase of the liquid level, the deposition rate decreased, first, and then increased again. In the case of the single pump operation, the deposition rate of the right pump operation was smaller than that of the left pump operation. The variation of the deposition rate when the right pump operated was basically the same as that when the dual pumps operated. The movement path of particle N1 was longer. With the decrease of the flow rate and the increase of the particle diameter, the following feature of the particle decreased, and it was easier to impact the walls and edges, which caused long-term deposition. The research results could provide some suggestions for the design of anti-deposition performance of prefabricated pumping station.

Vortex ring-like structures in gasoline fuel sprays under cold-start conditions

2009 ◽  
Vol 10 (4) ◽  
pp. 195-214 ◽  
Author(s):  
S Begg ◽  
F Kaplanski ◽  
S Sazhin ◽  
M Hindle ◽  
M Heikal
Keyword(s):  
Vortex Ring ◽  
High Speed ◽  
Phenomenological Study ◽  
Theoretical Models ◽  
High Speed Photography ◽  
Fuel Injector ◽  
Fuel Injectors ◽  
Fuel Sprays ◽  
Phase Doppler Anemometry ◽  
Ring Model

A phenomenological study of vortex ring-like structures in gasoline fuel sprays is presented for two types of production fuel injectors: a low-pressure, port fuel injector (PFI) and a high-pressure atomizer that injects fuel directly into an engine combustion chamber (G-DI). High-speed photography and phase Doppler anemometry (PDA) were used to study the fuel sprays. In general, each spray was seen to comprise three distinct periods: an initial, unsteady phase; a quasi-steady injection phase; and an exponential trailing phase. For both injectors, vortex ring-like structures could be clearly traced in the tail of the sprays. The location of the region of maximal vorticity of the droplet and gas mixture was used to calculate the temporal evolution of the radial and axial components of the translational velocity of the vortex ring-like structures. The radial components of this velocity remained close to zero in both cases. The experimental results were used to evaluate the robustness of previously developed models of laminar and turbulent vortex rings. The normalized time, , and normalized axial velocity, , were introduced, where tinit is the time of initial observation of vortex ring-like structures. The time dependence of on was approximated as and for the PFI and G-DI sprays respectively. The G-DI spray compared favourably with the analytical vortex ring model, predicting , in the limit of long times, where α = 3/2 in the laminar case and α = 3/4 when the effects of turbulence are taken into account. The results for the PFI spray do not seem to be compatible with the predictions of the available theoretical models.

Air Entrainment and Bubble Generation by a Hydrofoil in a Turbulent Channel Flow

2019 ◽  
Author(s):  
Ichiro Kumagai ◽  
Kakeru Taguchi ◽  
Chiharu Kawakita ◽  
Tatsuya Hamada ◽  
Yuichi Murai
Keyword(s):  
Channel Flow ◽  
Flow Rate ◽  
High Speed ◽  
Air Flow ◽  
Air Entrainment ◽  
Air Bubbles ◽  
Air Flow Rate ◽  
Bubble Generation ◽  
Gas Liquid Flow ◽  
Entrained Air

Abstract Air entrainment and bubble generation by a hydrofoil bubble generator for ship drag reduction have been investigated using a small high-speed channel tunnel with the gap of 20 mm in National Maritime Research Institute (NMRI). A hydrofoil (NACA4412, chord length = 40 mm) was installed in the channel and an air induction pipe was placed above the hydrofoil. The flow rate of the entrained air was quantitatively measured by thermal air flow sensors at the inlet of the air induction pipe. The gas-liquid flow around the hydrofoil was visualized by a backlight method and recorded by a high-speed video camera. As the flow velocity in the channel increased, the negative pressure generated above the suction side of the hydrofoil lowered the hydrostatic pressure in the channel, then the atmospheric air was entrained into the channel flow. The entrained air was broken into small air bubbles by the turbulent flow in the channel. The threshold of air entrainment, the air flow rate, and gas-liquid flow pattern depends on Reynolds number, angle of attack (AOA), and hydrofoil type. We identified at least three modes of air entrainment behavior: intermittent air entrainment, stable air entrainment, and air entrainment with a ventilated cavity. At high flow speed in our experimental condition (9 m/s), a large volume of air bubbles was generated by this hydrofoil system (e.g. air flow rate was 50 l/min for NACA4412 at AOA 16 degrees), which has a high potential to reduce ship drag.

Three-Dimensional Shear Driven Thin Liquid Film in a Duct

2006 ◽  
Author(s):  
H. Lan ◽  
M. Friedrich ◽  
B. F. Armaly ◽  
J. A. Drallmeier
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Flow Rate ◽  
High Speed ◽  
Volume Flow Rate ◽  
Incident Light ◽  
Thin Liquid Film ◽  
Air Flow ◽  
Three Dimensional ◽  
Vof Model

Measurements and predictions of three-dimensional shear driven thin liquid films by turbulent air flow in a duct are reported. FLUENT - CFD code is used to perform the numerical simulations and the Reynolds Averaged Navier-Stokes and continuity equations along with the Volume of Fluid (VOF) model and the realizable k-ε turbulence model are implemented for this task. Film thickness and width are reported as a function of air flow rate, liquid film volume flow rate and surface tension, and a comparison with preliminary measured results is made. The thickness of the shear driven liquid film is measured using an interferometric technique that makes use of the phase shift between the reflection of incident light from the top and bottom surfaces of the thin liquid film. The spatial resolution is determined based on the spot size of the incident light, which for the current configuration of the transmitting optics is approximately 10 microns. The resulting fringe pattern is imaged using a high-speed imaging camera operating at 2000 frames per second. The technique has proved successful in measuring thickness between 100 and 900 microns in these shear driven films. Simulation results reveal that higher gas flow velocity decreases the film thickness but increases its width, while higher liquid film flow rate increases the film thickness and increases its width. Reasonable comparison appears to exist between preliminary measured and simulated results.

Experiments and Modeling of a Liquid Droplet Transported by a Gas Stream Impinging on a Heated Surface: Evaporative Regime

2009 ◽  
Author(s):  
Ryan P. Anderson ◽  
Alfonso Ortega
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Single Phase ◽  
Heat Dissipation ◽  
Liquid Droplet ◽  
Heated Surface ◽  
Thin Liquid Film ◽  
Spray Cooling ◽  
High Speed Photography ◽  
Transfer Coefficients

Understanding the transport mechanisms involved in a single droplet impinging on a heated surface is imperative to the complete understanding of droplet and spray cooling. Evidence in the literature suggests that gas assisted sprays and mist flows are more efficient than sprays consisting only of liquid droplets. There has been few if any fundamental studies on gas-assisted droplets or spray cooling, in which a carrier gas or vapor stream propels the droplet to the target surface. The current work extends previous studies of a droplet impinging on a heated surface conducted by the same group from the single phase regime into the evaporative regime. For both regimes, understanding the transport physics due to the heat transfer from the heated surface to the droplet and then by convection and evaporation to the airflow is of fundamental importance. High-speed photography was used to capture the spreading process and yielded results that correlated well with previously published isothermal and single-phase results. The heat transfer was measured with a fitting approach by which the instantaneous temperature profile was matched to an analytic solution to determine the instantaneous value of the centerline heat transfer coefficient. A very large increase in the heat dissipation was observed when compared to previously published single-phase results. Heat transfer was optimized at Reynolds numbers that produced an optimally thin liquid film and high heat and mass transfer coefficients on the surface of the film.

Experimental Validation of Methods Providing Boundary Conditions to Simulate the Evaporation Process of Water Injected Into High Speed Air Flow

2013 ◽  
Author(s):  
P. S. Nagabhushan ◽  
A. Rossetti ◽  
B. Barabas ◽  
J. P. Schnitzler ◽  
A. Kefalas ◽  
...  
Keyword(s):  
Experimental Data ◽  
Boundary Conditions ◽  
Gas Turbines ◽  
High Speed ◽  
Air Flow ◽  
Computational Cost ◽  
Spray Angle ◽  
Diameter Distribution ◽  
Particle Injection ◽  
Lagrange Approach

Water injection into a high speed air flow has been recently investigated by many scientists and is still an important field of research in gas turbine technology. To study the behavior of droplets in gas turbines, expensive experimental tests and their validation with analytical and Computational Fluid Dynamics (CFD) models are necessary. The Euler-Lagrange approach can be used to tackle these problems due to their capability in tracking particles along the domain, relative ease in formulating and applying them to the current industrial problems in terms of acceptable computational cost. However, providing spray boundary conditions using Euler-Lagrange approach is quite challenging because the spray pattern depends upon various parameters like spray angle, velocity, diameter distribution etc. In this paper, to obtain these parameters, two different approaches are described. The first approach depends on an analytical model for velocity and spray angle injection conditions and the second approach depends on an Euler free surface simulation. For diameter distribution, Rosin Rammler distribution function and experimental data are used. When combined together these lead to four particle injection conditions. The results achieved from all the four cases are compared with the experimental data of water droplet evaporation in a high speed air flow obtained from a hot air test rig operating at conditions of real gas turbines.

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