Parametric Study of the Frequency of Bubble Formation at a Single Orifice With Liquid Cross-Flow

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Miguel A. Balzan ◽  
Franz Hernandez ◽  
Carlos F. Lange ◽  
Brian A. Fleck
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Liquid Velocity ◽  
Bubble Formation ◽  
Cross Flow ◽  
Average Frequency ◽  
Jet Breakup ◽  
Mass Flow Rates ◽  
Experimental Values ◽  
Processing Techniques

The bubble formation frequency from a single-orifice nozzle subjected to the effects of a crossflowing liquid was investigated using high-speed shadowgraphy, combined with image analysis and signal processing techniques. The effects of the nozzle dimensions, orientation within the conduit, liquid cross-flow velocity, and gas mass flow rate were evaluated. Water and air were the working fluids. Existing expressions in the literature were compared to the experimental values obtained. The expressions showed modest agreement with the experimental mean average frequency magnitude. It was found that increasing the gas injection diameter could decrease the bubbling frequency approximately 12% until reaching a certain value (0.52 mm). Further increasing the nozzle dimensions increase the frequency by around 20%. Bubbling frequency is more sensitive to the liquid velocity where changes up to 63% occurred when the velocity was raised from 3.1 to 4.3 m/s. Increasing gas mass flow rates decreased the gas jet breakup frequency in all cases. This phenomenon was primarily attributed to changes in the bubbling mode from discrete bubbling to pulsating and jetting modes. The nozzle orientation plays a role in modifying the bubbling frequency, having a higher magnitude when oriented against gravity.

Numerical Investigation of Local Cooling Enhancement Using Pin-Finned Channel With Incremental Impingement

2017 ◽  
Author(s):  
Susheel Singh ◽  
Sumanta Acharya ◽  
Forrest Ames
Keyword(s):  
Aspect Ratio ◽  
Mass Flow ◽  
Cross Flow ◽  
Surface Cooling ◽  
Local Cooling ◽  
Stagnation Region ◽  
Flow Rates ◽  
Pin Fins ◽  
Mass Flow Rates ◽  
The Impact

Flow and heat transfer in a low aspect ratio pin-finned channel, representative of an internally cooled turbine airfoil, is investigated using Large Eddy Simulations (LES). To achieve greater control of surface cooling distribution, a novel approach has been recently proposed in which coolant is injected incrementally through a series of holes located immediately behind a specially designed cutout region downstream of the pin-fins. Sheltering the coolant injection behind the pin-fins avoids the impact of the cross-flow buildup that deflects the impingement jet and isolates the surface from cooling. The longitudinal and transverse spacing of the pin-fins, arranged in a staggered fashion, is X/D = 1.046 and S/D = 1.625, respectively. The aspect ratio (H/D) of pin-fin channel is 0.5. Due to the presence of the sequential jets in the configuration, the local cooling rates can be controlled by controlling the jet-hole diameter which impacts the jet mass flow rate. Hence, four different hole diameters, denoted as Large (L), Medium (M) , Small (S), Petite (P) are tested for impingement holes, and their effects are studied. Several patterns of the hole-size distributions are studied. It is shown that the peak Nusselt number in the stagnation region below the jet correlates directly with the jet-velocity, while downstream the Nusselt numbers correlate with the total mass flow rates or the average channel velocity. The local cooling parameter defined as (Nu/Nu0)(1-ε) correlates with the jet/channel mass flow rates.

Bubble Formation From Porous Plates in Liquid Cross-Flow

2018 ◽  
Author(s):  
Thomas Shepard ◽  
Eric Ruud ◽  
Henry Kinane ◽  
Deify Law ◽  
Kohl Ordahl
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Bubble Diameter ◽  
Bubble Formation ◽  
Cross Flow ◽  
Rectangular Channels ◽  
Gas Liquid Flow ◽  
Liquid Flows ◽  
Processing Techniques ◽  
The Impact

Controlling bubble diameter and bubble size distribution is important for a variety of applications and active fields of research. In this study the formation of bubbles from porous plates in a liquid cross-flow is examined experimentally. By injecting air through porous plates of various media grades (0.2 to 100) into liquid flows in rectangular channels of varying aspect ratio (1–10) and gas/liquid flow rates the impact of the various factors is presented. Image processing techniques were used to measure bubble diameters and capture their formation from the porous plates. Mean bubble diameters ranged from 0.06–1.21 mm. The present work expands upon the work of [1] and further identifies the relative importance of wall shear stress, air injector pore size and gas to liquid mass flow ratio on bubble size and size distribution.

Air Bubble Injection Into a Liquid Stream in a Minichannel

2013 ◽  
Author(s):  
Randy Samaroo ◽  
Masahiro Kawaji
Keyword(s):  
High Speed ◽  
Liquid Velocity ◽  
Bubble Formation ◽  
Video Camera ◽  
Velocity Profiles ◽  
Bubble Behavior ◽  
Particle Image Velocimetry Technique ◽  
Air Bubble ◽  
Cfd Models ◽  
Laminar And Turbulent Flow

Air bubble injection experiments have been performed to obtain a better understanding and detailed data on bubble behavior and liquid velocity profiles to be used for validation of 3-D Interface Tracking Models and CFD models. Two test sections used were vertical rectangular minichannels with a width and gap of 20 mm × 5.1 mm and 20 mm × 1.9 mm, respectively. Subcooled water at near atmospheric pressure flowed upward under laminar and turbulent flow conditions accompanied by air bubbles injected from a small hole on one of the vertical walls. The experiments yielded data on bubble formation and departure, and interactions with laminar or turbulent water flow. Instantaneous and ensemble-average liquid velocity profiles have been obtained using a Particle Image Velocimetry technique and a high speed video camera.

Experimental Investigation of Liquid Jet Breakup in a Cross Flow of a Swirling Air Stream

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Tushar Sikroria ◽  
Abhijit Kushari ◽  
Saadat Syed ◽  
Jeffery A. Lovett
Keyword(s):  
Experimental Investigation ◽  
Momentum Flux ◽  
High Speed ◽  
Cross Flow ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Breakup Process ◽  
Breakup Length ◽  
Jet Breakup ◽  
Penetration Behavior

This paper presents the results of an experimental investigation of liquid jet breakup in a cross flow of air under the influence of swirl (swirl numbers 0 and 0.2) at a fixed air flow Mach number 0.12 (typical gas turbine conditions). The experiments have been conducted for various liquid to air momentum flux ratios (q) in the range of 1 to 25. High speed (@ 500 fps) images of the jet breakup process are captured and those images are processed using matlab to obtain the variation of breakup length and penetration height with momentum flux ratio. Using the high speed images, an attempt has been made to understand the physics of the jet breakup process by identification of breakup modes—bag breakup, column breakup, shear breakup, and surface breakup. The results show unique breakup and penetration behavior which departs from the continuous correlations typically used. Furthermore, the images show a substantial spatial fluctuation of the emerging jet resulting in a wavy nature related to effects of instability waves. The results with 15 deg swirl show reduced breakup length and penetration related to the nonuniform distribution of velocity that offers enhanced fuel atomization in swirling fuel nozzles.

scholarly journals Geometric optimization of cross-flow heat exchanger based on dynamic controllability

2008 ◽  
Vol 12 (3) ◽  
pp. 75-84
Author(s):  
Sorour Alotaibi ◽  
Asad Alebrahim
Keyword(s):  
Aspect Ratio ◽  
Mass Flow ◽  
Numerical Solutions ◽  
Cross Flow ◽  
Internal Flow ◽  
Geometric Optimization ◽  
Transient Model ◽  
The Face ◽  
Mass Flow Rates ◽  
Water Mass Flow Rate

The operation of heat exchangers and other thermal equipments in the face of variable loads is usually controlled by manipulating inlet fluid temperatures or mass flow rates, where the controlled variable is usually one of the output temperatures. The aim of this work is to optimize the geometry of a tube with internal flow of water and an external cross-flow of air, based on its controllability characteristics. Controllability is a useful concept both from theoretical and practical perspective since it tells us if a particular output can be controlled by a particular input. This concept can also provide us with information about the easiest operating condition to control a particular output. A transient model of a tube in cross-flow is developed, where an implicit formulation is used for transient numerical solutions. The aspect ratio of the tube is optimized, subject to volume constraints, based on the optimum operation in terms of controllability. The reported optimized aspect ratio, water mass flow rate and controllability are studied for deferent external properties of the tube.

Theoretical Analysis of CO2 Bubble Formation in Anode Flow Field of μDMFC

2014 ◽  
Vol 635-637 ◽  
pp. 346-353 ◽  
Author(s):  
Miao Miao Li ◽  
Jun Geng ◽  
Ru Peng Zhu
Keyword(s):  
Mathematical Model ◽  
Theoretical Analysis ◽  
Flow Field ◽  
Flow Velocity ◽  
Liquid Velocity ◽  
Bubble Formation ◽  
Cross Flow ◽  
Carbon Paper ◽  
Gas Velocity ◽  
Cross Flow Velocity

A mathematical model was established and validated to predict the microbubble diameter when it departing from the carbon paper and moving into the channel of μDMFC. Single bubble behaviors were studied using the model, which took the gas velocity, liquid cross-flow velocity, micro porous diameter and other parameters into account. Results indicate that the microbubble departure diameter decreases with the increasing liquid velocity, and increases with the increasing micro porous diameter and increasing gas velocity.

scholarly journals Experimental and Numerical Investigation the Effect of Grooves Impeller on Rotating Stall of High Speed Blower

2018 ◽  
Vol 8 (04) ◽  
Author(s):  
Muna S. Kassim ◽  
Fouad A. Saleh ◽  
Alaa Th. Aliwi
Keyword(s):  
Numerical Investigation ◽  
Mass Flow ◽  
High Speed ◽  
Static Pressure ◽  
Rotating Stall ◽  
High Mass ◽  
Ansys Fluent ◽  
Flow Rates ◽  
Frontal Wall ◽  
Mass Flow Rates

Experimental and numerical investigation to study the influence of add (one groove and two grooves) to the unshroud impeller onto the rotating stall as well fluctuations of pressure at a high speed blower of centrifugal. Experimental test rig which includes blower of centrifugal, transducer of pressure as well measurement instrumentations are constructed and designed for this study. A data acquisition system (hardware) as well its (software) have been developed into transferring the signal than transducer of pressure to the computer. The experimental work has been implemented through measuring the variation of static pressure as well fluctuation of pressure for two cases of the impeller (with one groove and with two grooves). Static pressure has been taken in different points arranged onto the frontal-wall of a volute casing along one track for two cases of the impeller. This track is angular track about the impeller. The results of experimental show that the fluctuations of pressure for different mass flow rates are nature of non-periodical and the mass flow rates decrease with the fluctuations of pressure increase. Also, the results indicate that the impeller with two grooves show high mass flow rates comparison with the impeller with one groove. Simulation of numerical has been implemented onto blower of centrifugal to analysis both field of flow as well fluctuations of pressure through using ANSYS (FLUENT 15). The simulation of numerical has been carried out through solve the continuity as well momentum equations with the moving reference framework technicality inside a blower. The numerical simulation results show good agreement with the results of experimental.

Calibration of a V-Cone for Low Mass Flows for Small Core Compressor Research

2020 ◽  
Author(s):  
Julia E. Stephens ◽  
Sameer Kulkarni
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Flow Rates ◽  
Turbofan Engines ◽  
Mass Flow Rates ◽  
Low Mass ◽  
Mass Flows ◽  
Multistage Axial Compressor

Abstract Advancements in core compressor technologies are necessary for next generation, high Overall Pressure Ratio (OPR) turbofan engines. High pressure compressors (HPCs) for future engines are being designed with exit corrected mass flow rates less than 2.25 kg/s (5 lbm/s). In order to accurately measure the performance of these advanced designs, high accuracy measurements are needed in test facilities. The W7 High Speed Multistage Axial Compressor Facility at NASA Glenn Research Center has been used to acquire data for advanced compressor designs. This facility utilizes an advanced differential pressure flow meter called a V-Cone. The facility has historically tested components with physical mass flow rates in the range of 27 to 45 kg/s (60 to 100 lbm/s). As such, when the V-Cone was calibrated prior to installation, the calibrations focused on higher mass flow rates, and uncertainties in that regime range from 0.5% to 0.85%. However, for low mass flow rates under 9 kg/s (20 lbm/s), expected in tests of advanced high OPR HPCs rear stages, the uncertainties of the V-Cone exceed 2.5%. To address this, using a method similar to that utilized by the National Institute of Standards and Technology, an array of Critical Flow Venturi Nozzles (CFVs) was installed in the W7 test section and used to calibrate the V-Cone in 0.5 kg/s (1 lbm/s) increments up to 10.5 kg/s (23 lbm/s). This effort details the measurements and uncertainties associated with this calibration which resulted in a final uncertainty of the V-Cone measurements under 1%.

Utilization of Gas-Liquid Cylindrical Cyclone (GLCC©) Compact Separator for Solids Removal—Part II: Operational Envelope for Carry-Over

2009 ◽  
Author(s):  
S. Omarov ◽  
L. Gomez ◽  
S. Wang ◽  
R. Mohan ◽  
O. Shoham ◽  
...  
Keyword(s):  
Experimental Data ◽  
Mass Flow ◽  
Liquid Velocity ◽  
Solid Mass ◽  
Efficient Operation ◽  
Flow Rates ◽  
Wide Range ◽  
Mass Flow Rates ◽  
Carry Over ◽  
Operational Envelope

The operational envelope for particle (solid and liquid) carry-over (OPEN-CO) in the GLCC© has been studied experimentally and theoretically. The experimental data were acquired for a wide range of flow conditions, including: inlet superficial gas and liquid velocities between 15–35 ft/s and 0.1–1.2 ft/s, respectively, solid particle sizes of 5, 25 and 50 microns, and solid mass flow rates between 6.61lbm/min and 15.43 lbm/min. An uncertainty analysis of the experimental data revealed uncertainties less than 1% and less that 8.5% for the superficial liquid velocity and the superficial gas velocity measurements, respectively. Results from the experimental data show that as the density of the slurry increases (higher solid mass flow rates), the OPEN-CO shifts up. A mechanistic model was developed for the prediction of OPEN-CO, based on particle trajectory. The model assumes that the particle (liquid and solid) density is the same as the slurry density. Model predictions agree well with the experimental data. The developed model can be used for design and efficient operation of the GLCC© for gas-liquid-solid flow (gas slurry separation).

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