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Author: Rustam Homi Sethna
Publisher:
ISBN:
Category :
Languages : en
Pages : 428
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Author: Rustam Homi Sethna
Publisher:
ISBN:
Category :
Languages : en
Pages : 428
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Author: Maximilian Kuhnhenn
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Miguel A. Balzán
Publisher:
ISBN:
Category : Atomizers
Languages : en
Pages : 314
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Book Description
An experimental investigation was conducted with the purpose of studying the effects of selected operating and design variables in the flow inside an effervescent atomizer. A series of tests were performed in a horizontally oriented, square conduit of 12.7 mm in diameter which constituted the mixing chamber of the effervescent atomizer. The operating fluids were water and air. The air was injected perpendicularly into a fully developed, turbulent water flow, whose bulk water velocity values ranged between 1.1 and 4.3 m/s. The gas mass flow rate values were in the range between 8 and 60 × 10-3 g/s. Three different gas injectors, with diameters of 0.27 mm, 0.52 mm and 1.59 mm were used. The combination of variables allowed the operation of the atomizer within the limits of what constitutes a bubbly flow in pipes. High-speed shadowgraphy was the technique used to investigate thoroughly the dynamics between the gas and liquid phases near the gas injection region as well as upstream the discharge nozzle. A set of original, empirical expressions used to estimate the incipient centerline and borderline trajectories of the gas phase, during its initial interaction with the liquid and based on dimensionless parameters, were introduced. The assessment of the correlations gave a strong prediction of the initial centerline and borderline trajectories of the gas jet in the flowing liquid. The effects that the gas injection velocity, liquid mean velocity and injection gas injection diameter have on the process of bubble generation were investigated. Four distinct regimes were identified: Single Bubbling (SB), Pulse (P), Elongated Jetting (EJ) and Atomizing Jetting (AJ). It was observed that the shift between regimes occurs gradually, producing the need to identify transitional regions: SBP and PTJ. Sets of independent dimensionless variables were used to categorize the proposed regimes in bubble formation maps. Empirical correlations that delimit the boundaries between ordered and chaotic bubble generation were determined. An introductory description of the forces involved in the bubbling process was conducted. The results indicated that the form-induced drag and added mass force were dominant detaching and cohesive force respectively. While there was agreement with previous works regarding the dominant breakup effect, the results obtained for the main attaching force were unique. Also, a novel methodology for the estimation of dynamic shape based drag and added mass coefficient was included. The morphological features of the gas jet were described through empirical correlations based on relevant dimensionless numbers associated to the variations of three fundamental design parameters: liquid cross-flow velocity, gas mass flow rate and the nozzle dimensions. The gas jet features were compared with representative statistical diameters from the population distribution, resulting in an estimation of the averaged Sauter mean diameter and maximum bubble diameter as a function of the gas jet dimensions. It was determined that the gas injection conditions play a fundamental role in the internal flow characteristics for an effervescent atomizer.
Author: Musbah Mahmud Misellati
Publisher:
ISBN:
Category : Atomization
Languages : en
Pages : 568
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Author: Carmen Sescu
Publisher:
ISBN:
Category : Atomization
Languages : en
Pages : 219
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In this research work the flow characteristics of a type of rotary atomizer, referred to as slinger injector, were experimentally and numerically investigated at relatively low rotational speeds. Although slinger injectors provide a good level of atomization at high rotational speeds where they are intended to operate (30,000 rpm or higher), a critical aspect in small gas turbines is related to the start-up phase, which typically takes place at speeds around 10,000 rpm. The quality of atomization is very important, especially at these low speeds where smaller mean fuel droplet diameters are desirable. The current work focused on the study of atomization provided by slinger injectors at rotational speed related pertinent to the start-up phase (up to 15,000 rpm). An optical measurement system was implemented to investigate the liquid atomization provided by the slinger injector. The qualitative behavior of fuel emerging from the slinger was evaluated to determine whether a satisfactory atomization was provided within a distance compatible with the size of a small gas turbine engine combustion chamber. The size of the droplets was measured using the Global Sizing Velocimetry (GSV) system. Visualization of the primary liquid breakup process, determination of breakup lengths, and measurement of droplet size were performed by varying rotational speed, liquid flow rate, injector hole shape, size and orientation, and number of holes. Photographs of the liquid breakup, various mean and representative diameters, droplet size histograms and cumulative volume distribution are presented. The findings of this thesis show that droplet size decrease with an increase in rotational speed, as expected. Moreover, hole diameter, hole shape and flow rates affect the slinger atomization. For a given flow rate and a given rotational speed, the experimental data show that the droplet sizes decrease by increasing the hole diameter. The droplets increase in size when the flow rates is increased for a given hole size. The atomization was found to be characteristically different for a slit compared to a circular hole injector. However, the orientation of the emerging jet relative to the axis of rotation insignificantly influenced the slinger atomization for the cases studied. A correlation equation was obtained for a slinger with circular hole, estimating the Sauter mean diameter as a function of the rotational speed of the slinger, the hole diameter, the liquid flow rate and the liquid properties. Two-dimensional and three-dimensional numerical simulations of the internal flow and the external near-field flow for a slinger atomizer were conducted. The simulations were carried out using the commercial Computational Fluid Dynamics code FLUENT, wherein the Volume of Fluid model was used to track the interface between the two phases. A User Defined Function was developed to take into account the centrifugal and Coriolis forces needed for FLUENT computations. The numerical simulations focused on the study of formation of the liquid film along the channel injector wall, and on the upstream characteristics of the liquid jet near the exit of the atomizer. The numerical simulations were in qualitative agreement with the experiment, showing that an annular jet exiting from the channel collapses and the liquid breaks up into droplets a short distance from the exist. The results show that the Volume of Fluid model is appropriate for developing simulation models of the working of a slinger atomizer.
Author: Arthur Lefebvre
Publisher: CRC Press
ISBN: 1482227851
Category : Nature
Languages : en
Pages : 434
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Book Description
Atomization and Sprays examines the atomization of liquids and characteristics of sprays. It explains the physical processes of atomization as well as guidelines for designing atomizers. In addition, it demonstrates how the importance of the size and velocity of a particle contributes to improved spray characterization. Coverage includes general co
Author: L.P. Bayvel
Publisher: Routledge
ISBN: 1351434950
Category : Science
Languages : en
Pages : 488
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Book Description
Covering the basics of liquid atomization, this book familiarizes readers with the physical processes of liquid atomization, the main types of atomizers and their design, measurements of spray characteristics, experimental investigations of atomizers, and application of atomizers. It demonstrates how to calculate and design atomizers and how to mea
Author: Yuriy I Khavkin
Publisher: CRC Press
ISBN: 9781560329756
Category : Technology & Engineering
Languages : en
Pages : 490
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Book Description
In this book, prominent Russian scientist Yuriy I. Khavkin shows that the droplet sizes in swirl atomizers depend only on the specific energy of the liquid drops and on viscosity. The new theory based only on two parameters is shown to be far simpler and in better agreement with experimental data than any previous presentations. The following topics are included in the book: · The solution of the Navier-Stokes equation for a liquid rotating flow · Atomizers for gas turbine combustion chambers · Atomizers for high capacity steam boilers · Atomizers for liquid-propellant rocket engines · Quality of liquid atomization by non-swirl atomizers · A unique table of experimental data of 232 atomizers, enables the reader to find an atomizer with the flow rate from 5 kg/h to 15,000 kg/h Readers will also learn: · To create an atomizer with the given mean droplet size · To create an atomizer with the given droplet size distribution · To create an atomizer with the given limits of flow rate control. The book is intended for the design engineer, as well as the theoretical scientist.
Author: RC. Derksen
Publisher:
ISBN:
Category : Controlled droplet applications
Languages : en
Pages : 20
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Book Description
A one-dimensional imaging probe was used to measure samples of the spray distribution produced by four different rotary atomizers operating at several different flow rates and rotary speeds using tap water and vegetable oil as carriers. The operating characteristics of the laser imaging probe affected the data collection results. The warm-up interval, effective sampling width, droplet velocity, and spray density were the most critical factors. Each rotary atomizer produced a range of droplet sizes for which uniformity depended on the operating conditions and liquid carrier. At water flow rates below 0.5 L/min, the Micron Micromax produced the most uniform droplet distributions. At rates above 0.5 L/min of water, the Spraying Systems RotoJet produced the most uniform droplet distributions. A larger selection of volume median diameters was produced using vegetable oil rather than water as the carrier. The uniformity of the droplet distributions is controlled better with oil. The RotoJet produced the most uniform droplet distribution with oil in comparison with the other atomizers. There was little difference between water and oil as carries in the drift potential at low rotational speeds. However, at higher operating speeds the drift potential was reduced by using oil as the liquid carrier.
Author: Dennis Cooper
Publisher:
ISBN:
Category :
Languages : en
Pages :
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