scholarly journals Hydraulic Study of Bubble Migration in Liquid Titanium Alloy Melt during Vertical Centrifugal Casting Process

2019 ◽  
Vol 38 (2019) ◽  
pp. 309-316
Author(s):  
Qin Xu ◽  
Xing Wang ◽  
Shiping Wu
Keyword(s):  
Centrifugal Casting ◽  
Gas Bubbles ◽  
Casting Process ◽  
Initial Position ◽  
Gas Bubble ◽  
Bubble Generation ◽  
Mould Wall ◽  
Line Parallel ◽  
Complex Cavity ◽  
Liquid Titanium

AbstractThe bubble migration in liquid titanium melt during vertical centrifugal casting process has been investigated by hydraulic experiments. Results show that the gas bubble in the simple cavity ultimately migrates like a line parallel to the wall in the opposite direction to the rotational casting mould. The deviation distance of the bubble in the simple geometry cavity tends to increase with the increment of the mould rotational speed during the migration process. And the gas bubble is much easier to migrate like a line when its initial position is nearer to the casting mould wall which is opposite to the mould rotational direction. The migration trajectories of bubbles located at different position in the complex cavity are more complicated than that in the simple cavity. The casting mould in the complex cavity can hamper both the radial movement and the circular movement of the bubble. And gas bubbles will gather, re-nucleate and form new bigger bubbles beside the casting mould wall. The re-formed gas bubbles in the complex cavity become bigger than which escape from bubble generation chamber.

scholarly journals Bubble evolution in the titanium alloy melt under vertical centrifugal field

2020 ◽  
Vol 40 (2) ◽  
pp. 16-23
Author(s):  
Qin Xu ◽  
Xing Wang ◽  
Shiping Wu
Keyword(s):  
Rotational Speed ◽  
Complex Geometry ◽  
Initial Position ◽  
Blocking Effect ◽  
Migration Process ◽  
Centrifugal Field ◽  
Bubble Generation ◽  
Complex Cavity ◽  
Liquid Titanium ◽  
Bubble Evolution

The bubble evolution in the liquid titanium melt under vertical centrifugal field has been studied by the hydraulic experiment simulation. The bubble migration process in the simple and complex cavities, the bubble morphology, bubble dimensional size diversification under different mould rotational speed has been investigated. The results show that the mould wall has a blocking effect on the bubble migration. The bubble migration in the simple cavity deviates from the line between the bubble initial position and the rotation shaft of the casting mould. Also, the bubbles in the complex cavity gather, re-nucleate and form new big ones for the blocking effect of the complex geometry shape on the radial movement of the bubble. The shape of bubbles in both the simple and complex cavity during the migration process is not a perfect sphere, but an elliptical shape. The critical size of bubble released from the bubble generation chamber decreases with the increment of the mould rotational speed. The diameter of the gas bubbles in the simple cavity during the migration process become bigger and bigger for the pressure difference at different positions of the cavity in the vertical centrifugal field.

Laboratory Results of Cleaning Produced Water by Gas Flotation

1980 ◽  
Vol 20 (03) ◽  
pp. 175-190 ◽  
Author(s):  
W.T. Strickland
Keyword(s):  
Bubble Size ◽  
Contact Process ◽  
Gas Bubbles ◽  
Small Scale ◽  
Supersaturated Solution ◽  
Gas Bubble ◽  
Laboratory Studies ◽  
Bubble Generation ◽  
Gas Concentration ◽  
Attachment Efficiency

Abstract Laboratory studies were conducted to determine the factors governingflotation-cell performance. It was learned that oil removal is increased byincreasing collision and attachment efficiencies and gas/liquid contact time.Collision efficiency is increased by increasing oil-drop size and gasconcentration and by decreasing gas-bubble size. Several factors (crude type, pH, temperature, etc.) were found to change attachment efficiency. Nocorrelation between basic system properties and attachment efficiency wasfound. Some of these important parameters are determined by the cell design, whereas others are characteristics of the feed. Thus, the same type (design)cell will produce different effluent oil concentrations for different feeds.Also, the effluent from a given cell will change when the feed characteristicschange. Introduction Flotation cells are used widely throughout industry to remove oil fromoil/water mixtures produced from underground reservoirs. This is becauseflotation cells have proved to be a practical and reliable means of oilremoval. Small-scale pilot tests have been attempted to predict the performanceof a full-scale unit, but these have not been too successful. Therefore, laboratory studies were initiated to increase the knowledge of this process.The process of flotation consists of four basic steps:bubble generation inoily water,contact between a gas bubble and an oil drop suspended in thewater,attachment of the oil drop to the gas bubble, andrising of thegas/oil combination to the water surface where the oil can be removed byskimming. Research was conducted to investigate these basic steps and todetermine the fundamental mechanisms and parameters that govern the process.Both the theoretical and experimental results are discussed in this paper. Theory Bubble Generation There are three common methods of bubble generation:dissolution of gasfrom a supersaturated solution (dissolved gas flotation),mechanical mixingof gas and liquid (dispersed gas flotation), anddirect gas injection bymeans of a sparger. The method of bubble generation and important because itdetermines the bubble size and gas concentration for a given feed. As shown inthe section on bubble-drop contact, bubble size and gas concentration influencethe collision efficiency and, thus, the rate of oil recovery. Bubble/Drop Contact Gas bubbles and oil drops must come into contact for flotation to occur.This contact process is basically one of hydrodynamics. Since both oil and gasare less dense than water (with the exception of a few very heavy crudes), theyboth tend to rise relative to water. Gas bubbles are generally larger than oildrops (gas bubbles are usually larger than 100 m and oil drops in producedwater are usually smaller than 30 m), and the density difference between gasand water is much greater than between oil and water. For these two reasons, gas bubbles rise more rapidly than the oil drops and overtake them. This leadsto the possibility of bubble-drop contact. On the other hand, a fluid flowpattern is established around a moving gas bubble that tends to deflect oildrops, which reduces the possibility of contact. SPEJ P. 175

Investigation of Functionally Graded Aluminium A356 Alloy and A356-10%SiCp Composite for Hydro Turbine Bucket Application

2016 ◽  
Vol 26 ◽  
pp. 30-46 ◽  
Author(s):  
Williams S. Ebhota ◽  
Akhil S. Karun ◽  
Freddie L. Inambao
Keyword(s):  
Heat Treatment ◽  
Tensile Stress ◽  
Centrifugal Casting ◽  
A356 Alloy ◽  
Casting Process ◽  
Ultimate Tensile Stress ◽  
Functionally Graded ◽  
Cnc Machining ◽  
Mould Material ◽  
Turbine Bucket

The study investigates the application of centrifugal casting process in the production of a complex shape component, Pelton turbine bucket. The bucket materials examined were functionally graded aluminium A356 alloy and A356-10%SiCp composite. A permanent mould for the casting of the bucket was designed with a Solidworks software and fabricated by the combination of CNC machining and welding. Oil hardening non-shrinking die steel (OHNS) was chosen for the mould material. The OHNS was heat treated and a hardness of 432 BHN was obtained. The mould was put into use, the buckets of A356 Alloy and A356-10%SiCp composite were cast, cut and machined into specimens. Some of the specimens were given T6 heat treatment and the specimens were prepared according to the designed investigations. The micrographs of A356-10%SiCp composite shows more concentration of SiCp particles at the inner periphery of the bucket. The maximum hardness of As-Cast A356 and A356-10%SiCp composite were 60 BRN and 95BRN respectively, recorded at the inner periphery of the bucket. And these values appreciated to 98BRN and 122BRN for A356 alloy and A356-10%SiCp composite respectively after heat treatment. The prediction curves of the ultimate tensile stress and yield tensile stress show the same trend as the hardness curves.

Gas bubble induced scalings in geothermal systems

2021 ◽  
Author(s):  
Lilly Zacherl ◽  
Thomas Baumann
Keyword(s):  
Ph Value ◽  
Saturation Index ◽  
Gas Bubbles ◽  
Gas Bubble ◽  
Geothermal Systems ◽  
Injection Wells ◽  
Term Operation ◽  
Maintenance Schedule ◽  
Local Experience ◽  
Maintenance Schedules

<p>Scalings in geothermal systems are affecting the efficiency and safety of geothermal systems. An operate-until-fail maintenance scheme might seem appropriate for subsurface installations where the replacement of pumps and production pipes is costly and regular maintenance comprises a complete overhaul of the installations. The situation is different for surface level installations and injection wells. Here, monitoring of the thickness of precipitates is the key to optimized maintenance schedules and long-term operation.</p><p>A questionnaire revealed that operators of geothermal facilities start with a standardized maintenance schedule which is adjusted based on local experience. Sensor networks, numerical modelling and predictive maintenance are not yet applied. In this project we are aiming to close this gap with the development of a non-invasive sensor system coupled to innovative data acquisition and evaluation and an expert system to quantitatively predict the development of precipitations in geothermal systems and open cooling towers.</p><p>Previous investigations of scalings in the lower part of production pipes of a geothermal facility suggest that the disruption of the carbonate equilibrium is triggered by the formation of gas bubbles in the pump and subsequent stripping of CO<sub>2</sub>. Although small in it's overall effect on pH-value and saturation index, significant amounts of precipitates are forming at high volumetric flow rates. To assess the kinetics of gas bubble induced precipitations laboratory experiments were run. The experiment addresses precipitations at surfaces and at the gas bubbles themselves.</p>

scholarly journals Effect of the Filling Ratio on the Solidified Structure in Horizontal Centrifugal Casting Process

2015 ◽  
Vol 101 (9) ◽  
pp. 488-493 ◽  
Author(s):  
Hisao Esaka ◽  
Yoshimasa Kataoka ◽  
Kei Shinozuka
Keyword(s):  
Centrifugal Casting ◽  
Casting Process ◽  
Filling Ratio

Properties and CA4GE-Engine Test of TiAl-Based Alloy Valves by Permanent Mold Casting

2010 ◽  
Vol 139-141 ◽  
pp. 557-560
Author(s):  
Wen Bin Sheng ◽  
Chun Xue Ma ◽  
Wan Li Gu
Keyword(s):  
Tial Alloy ◽  
Centrifugal Casting ◽  
Casting Process ◽  
Vacuum Arc ◽  
Permanent Mold ◽  
Casting Method ◽  
Arc Melting ◽  
Vacuum Arc Melting ◽  
Mold Casting ◽  
Induction Skull Melting

TiAl-based alloy valves were manufactured by combining charges compressed /vacuum arc melting (VA)/ induction skull melting (ISM) procedure with permanent mold centrifugal casting method. Microstructures, compositions and mechanical properties of as-cast and hot isostatical pressed (HIPed) valves are detected. Results show that the permanent mold centrifugal casting process obviously refines the size of grain in TiAl alloy and the tensile strength of as-cast and HIPed valves are 550MPa and 580MPa at 20°C, 370MPa and 470MPa at 815°C, respectively. As-cast specimens show ~0% elongation at 20°C and 1~2% at 815°C, while HIPed ones show an elongation of 1~2% at room temperature and about 10% at 815°C. Furthermore, a 200-hour test was carried out with CA4GE-engine, which demonstrated the possibility of as-cast TiAl alloy valves for the substitution of present steel ones.

Nuclei and Cavitation

1970 ◽  
Vol 92 (4) ◽  
pp. 681-688 ◽  
Author(s):  
J. William Holl
Keyword(s):  
Bubble Growth ◽  
Scale Effects ◽  
Gas Bubbles ◽  
Gas Content ◽  
Gas Bubble ◽  
Cavitation Nuclei ◽  
The Stability

This paper is a review of existing knowledge on cavitation nuclei. The lack of significant tensions in ordinary liquids is due to so-called weak spots or cavitation nuclei. The various forms which have been proposed for nuclei are gas bubbles, gas in a crevice, gas bubble with organic skin, and a hydrophobic solid. The stability argument leading to the postulation of the Harvey model is reviewed. Aspects of bubble growth are considered and it is shown that bubbles having different initial sizes will undergo vaporous cavitation at different liquid tensions. The three modes of growth, namely vaporous, pseudo, and gaseous are presented and implications concerning the interpretation of data are considered. The question of the source of nuclei and implications concerning scale effects are made. The measurement of nuclei is considered together with experiments on the effect of gas content on incipient cavitation.

A Preliminary Study of Fabrication Technology for Dynamic Compression Plates Using Centrifugal Casting Process

2021 ◽  
Vol 18 (2) ◽  
Author(s):  
A.K. Nasution ◽  
D. Gustiani ◽  
A. Handoko ◽  
Mukhtar ◽  
Zulkarnain ◽  
...  
Keyword(s):  
Low Income ◽  
Dynamic Compression ◽  
Centrifugal Casting ◽  
Casting Machine ◽  
Casting Process ◽  
Low Income Countries ◽  
Silicon Alloy ◽  
Horizontal Type ◽  
Preliminary Study ◽  
Cast Pipe

The high cost of health services in low-income countries has caused them to produce implants and medical devices at low cost. This research highlights a preliminary study of the design concept, mould design, and fabrication of horizontal type centrifugal casting machines for the manufacture of dynamic compression plates materials. Normally, dynamic compression plate is produced from materials such as 316L stainless steel, cobalt, and titanium alloys. In this work, aluminium-silicon alloy was used in this preliminary study. Aluminium-silicon alloy was melted at a temperature of 730 °C and poured into a mould with a rotational speed of 1500 rpm. Tensile, hardness and microstructure investigation were carried out to discern the mechanical properties of the cast product from the horizontal type centrifugal casting machine. Results showed the measured value of tensile strength is not significantly different in the two zones of cast pipe, the butt zone of fall of molten metal (specimen A) was 147 MPa, and the butt-end zone (specimen B) was 142 MPa. The hardness value for the as-cast pipe obtained from the outside, middle, and inside, was 104.0, 92.9, and 80.3 HV, respectively. Evaluation of microporosity in fractures (from tensile test) results from horizontal type centrifugal castings showed a small distribution. Meanwhile, the calculation of the contour hole processing time for DCP with eight holes is 38 minutes per implant.

An Electrochemically Actuated Micro Dosing System With Improved Dosing Control

1999 ◽  
Author(s):  
Sebastian Böhm ◽  
Wouter Olthuis ◽  
Piet Bergveld
Keyword(s):  
Driving Force ◽  
Gas Bubbles ◽  
Back Reaction ◽  
Integrated Sensor ◽  
Bubble Generation ◽  
Sensor Actuator ◽  
The Past ◽  
Electrolyte Mixture ◽  
Measured Impedance ◽  
Oxygen Gas

Abstract In this contribution a micromachined electrochemically-actuated micro dosing system is presented, which accurately can manipulate fluids in microsystems in the nanoliter range. The driving force to actively dispense liquids is provided by the electrochemical generation of gas bubbles (hydrogen and oxygen) by the electrolysis of an electrolyte. As these bubbles expand, they indirectly drive liquid out of a liquid filled reservoir, which is in hydraulic contact with the electrolyte in the bubble reservoir. The dosing system consists basically of a micromachined channel/reservoir structure in silicon, realized by dry reactive ion etching (DRIE). On top of this silicon fluidic board, a Pyrex® cover is bonded on which a set of electrodes is structured. These electrodes are applied for the generation of gas bubbles and at the same time, to measure the impedance of the gas/electrolyte mixture that is formed after bubble generation. It will be shown that this measured impedance reflects the gas bubble fraction in the bubble reservoir and that this parameter can be applied in determining the dosed amount of fluid. Besides the integrated sensor/actuator electrodes, measures have been taken to reduce the catalytic back reaction from the hydrogen oxygen gas mixture to water, as have been observed in the past.

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