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Artykuły w czasopismach na temat "Sprays from coaxial atomizers"
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Hardalupas, Y., i J. H. Whitelaw. "Interaction Between Sprays From Multiple Coaxial Airblast Atomizers". Journal of Fluids Engineering 118, nr 4 (1.12.1996): 762–71. http://dx.doi.org/10.1115/1.2835507.
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Phase Doppler measurements of size, velocity, liquid flux, and average mass fractions were obtained in sprays produced by three identical coaxial airblast atomizers, with their axes placed in a triangular arrangement at distances of two air jet diameters from each other; the arrangement simulates the spray interaction in the preburner of the space shuttle main engine with water and air respectively replacing the liquid oxygen and hydrogen of the preburner sprays. Each nozzle comprised a liquid jet with exit diameter of 2.3 mm centred in a 8.95 mm diameter air stream. Two liquid flowrates were examined, while the air flowrate was kept constant, resulting in Weber number at the exit of the nozzle around 1100, air-to-liquid momentum ratio 8.6 and 38, velocity ratio 24 and 51, mass flowrate ratio 0.35 and 0.75, liquid jet Reynolds number 10,000 and 21,000 and air jet Reynolds number around 108,000. The air flow characteristics were compared to the flow without liquid injection. Up to 10 air jet diameters from the nozzle exit, individual spray characteristics dominated and maximum Sauter mean diameters, typically around 150 μm, and liquid flux were observed on the geometrical axes of the nozzles. Spray merging was strong in the region between the nozzle axes, where the Sauter mean diameter reduced and the liquid flux and the mean and rms of the fluctuations of the axial velocity of the droplets and the air flow increased relative to the single spray. Downstream of 25 air jet diameters from the nozzle exit, the multiple sprays merged to a single spray-like flow produced by a nozzle located at the centre of the triangular region between the nozzle axes. Reduction of the liquid flowrate by 50 percent, improved atomization by 25 percent, shortened the axial distance from the nozzles where the individual spray characteristics disappeared by 30 percent and increased the air flow turbulence by 20 percent. Droplet coalescence was negligible for high liquid flowrates, but for reduced liquid flowrates coalescence became important and the Sauter mean diameter increased with the axial distance from the exit by around 15 percent. Spray merging increased the air flow turbulence and the local mass fraction distribution of the air in the region between the nozzle axes by around 50 and 40 percent respectively relative to the single sprays, resulting in a fuel rich region with increased gas flow turbulence which may influence the ignition process in the preburner of the space shuttle main engine.
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Utepov, Burxon, Tuygun Khaydarov, Nurmamat Rajabov, Gulnoza Murtazayeva, Bakhtiyor Tulaganov i Mirzoolim Avliyakulov. "Experimental studies of frequency of rotation of smooth rotating disk with coaxial-lateral air flow". E3S Web of Conferences 365 (2023): 04018. http://dx.doi.org/10.1051/e3sconf/202336504018.
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The article presents methods for determining the main parameters of a rotating atomizer sprayer. The choice of research methodology is justified based on the general pattern of liquid atomization by rotating atomizers, taking into account the influence of the air flow on them. The main indicators affecting the sprayed drops' dispersal are the air flow rate and the rotational speed of the pneumatic disk atomizer. Therefore, the correct choice of the method for determining the rotational speed ω of a pneumatic disk atomizer makes it possible, at a constant air flow rate, to obtain the required median-mass diameter of the atomized droplets. To obtain a high-quality air-droplet flow, there must be a combination between the initial speed of the main drops discharged from the spray disk's periphery and the fan installation's air flow speed.
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Eroglu, H., i N. Chigier. "Initial Drop Size and Velocity Distributions for Airblast Coaxial Atomizers". Journal of Fluids Engineering 113, nr 3 (1.09.1991): 453–59. http://dx.doi.org/10.1115/1.2909517.
Pełny tekst źródłaStreszczenie:
Initial drop size and velocity distributions, after complete disintegration of coaxial liquid jets, were determined by phase Doppler measurements. The measured radial distributions of Sauter mean diameter (SMD) were compared with the photographs of the disintegrating liquid jet. The SMD distribution was found to be strongly affected by the structure and behavior of the preceding liquid intact jet. The results showed that SMD increases with increasing liquid supply pressure as well as with decreasing air supply pressure. The axial measurement stations were determined from the photographs of the coaxial liquid jet at very short distances (1–2 mm) downstream of the observed break-up locations. The droplets accelerated at these regions under the influence of the air velocity. Smaller droplets were found to reach higher velocities because of their larger drag-to-momentum ratio. In general, minimum droplet mean velocities were found at the center, and the maximum velocities were near the spray boundary. Size velocity correlations show that the velocity of larger drops did not change with drop size. Drop rms velocity distributions have double peaks whose radial positions coincide with the maximum mean velocity gradients.
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Zhang, Feichi, Simon Wachter, Thorsten Zirwes, Tobias Jakobs, Nikolaos Zarzalis, Dimosthenis Trimis, Thomas Kolb i Dieter Stapf. "Effect of nozzle upscaling on coaxial, gas-assisted atomization". Physics of Fluids 35, nr 4 (kwiecień 2023): 043302. http://dx.doi.org/10.1063/5.0141156.
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Mass flow scaling of gas-assisted coaxial atomizers from laboratory to industrial scale is of major interest for a wide field of applications. However, there is only scarce knowledge and research concerning the effect of atomizer scale-up on liquid breakup and spray characteristics. The main objective of this study is therefore to derive basic principles for liquid jet breakup using upscaled nozzles to increase the liquid mass flow rate [Formula: see text]. For that purpose, atomizers with the same geometrical setup but increased sizes have been designed and experimentally investigated for [Formula: see text], 50, 100, and 500 kg/h, while the aerodynamic Weber number Weaero and gas-to-liquid ratio GLR have been kept constant. The primary jet breakup was recorded via high-speed imaging, and the liquid core length LC and the frequency of the Kelvin–Helmholtz instability fK were extracted. Applying these results as reference data, highly resolved numerical simulations have been performed to gain a deeper understanding of the effect of mass flow scaling. In the case of keeping Weaero and GLR constant, it has been shown by both experiments and simulations that the breakup morphology, given by a pulsating liquid jet with the disintegration of fiber-type liquid fragments, remains almost unchanged with the degree of upscaling n. However, the normalized breakup length [Formula: see text] has been found to be considerably increased with increasing n. The reason has been shown to be the decreased gas flow velocity vgas at the nozzle exit with n, which leads to a decreased gas-to-liquid momentum flux ratio j and an attenuated momentum exchange between the phases. Accordingly, the calculated turbulence kinetic energy of the gas flow and the specific kinetic energy in the liquid phase decrease with n. This corresponds to a decreased fKHI with n or [Formula: see text], respectively, which has been confirmed by both experiments and simulations. The same behavior has been shown for two liquids with different viscosities and at different Weaero. The obtained results allow a first-order estimate of the liquid breakup characteristics, where the influence of nozzle upscaling can be incorporated into j and Reliq in terms of n.
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Sivakumar, D., i B. N. Raghunandan. "Hysteretic interaction of conical liquid sheets from coaxial atomizers: Influence on the spray characteristics". Physics of Fluids 10, nr 6 (czerwiec 1998): 1384–97. http://dx.doi.org/10.1063/1.869663.
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Lefebvre, A. "Discussion: “Interaction Between Sprays From Multiple Coaxial Airblast Atomizers” (Hardalupas, Y., and Whitelaw, J. H., 1996, ASME J. Fluids Eng., 118, pp. 762–771)". Journal of Fluids Engineering 118, nr 4 (1.12.1996): 645–46. http://dx.doi.org/10.1115/1.2835489.
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Hardalupas, Y., i J. H. Whitelaw. "Characteristics of sprays produced by coaxial airblast atomizers". Journal of Propulsion and Power 10, nr 4 (lipiec 1994): 453–60. http://dx.doi.org/10.2514/3.23795.
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Hallstrom, Anders, i Jeffrey B. Danner. "SPRAYS FROM NOZZLES AND ROTARY ATOMIZERS". Atomization and Sprays 4, nr 3 (1994): 263–73. http://dx.doi.org/10.1615/atomizspr.v4.i3.20.
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Gavaises, M., i C. Arcoumanis. "Modelling of sprays from high-pressure swirl atomizers". International Journal of Engine Research 2, nr 2 (kwiecień 2001): 95–117. http://dx.doi.org/10.1243/1468087011545370.
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Tratnig, Andreas, i Günter Brenn. "Drop size spectra in sprays from pressure-swirl atomizers". International Journal of Multiphase Flow 36, nr 5 (maj 2010): 349–63. http://dx.doi.org/10.1016/j.ijmultiphaseflow.2010.01.008.
Pełny tekst źródłaRozprawy doktorskie na temat "Sprays from coaxial atomizers"
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Seidu, Iddrisu. "Analytical and Numerical Validation of Nozzle Spray Measurement Data Obtained from a Newly Developed Production System". Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1446504762.
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Athul, Joseph. "Spray morphology and droplet characteristics in gas centered swirl coaxial (GCSC) atomizers". Thesis, 2019. https://etd.iisc.ac.in/handle/2005/4404.
Pełny tekst źródłaStreszczenie:
Studies on liquid atomization and spray formation in coaxial type atomizers are necessary to improve the performance of liquid propellant rocket engines. Recess ratio, expressed as the ratio of orifice recess length to inner orifice diameter, is one of the geometrical parameters that influences the characteristics of sprays discharging from coaxial atomizers. The present thesis reports an experimental investigation on the atomization and spray formation processes in recessed gas-centered swirl coaxial (GCSC) atomizers through the analysis of spray morphologies and measurements of size and velocity characteristics of spray droplets. A GCSC atomizer discharges a swirling liquid film and a gas jet via its annular and central orifices, respectively. Specific attention is given to elucidate the role of atomizer recess ratio of the GCSC atomizer on the characteristics of the spray that results from the breakup of the annular swirling liquid sheet by the central gas jet.
The experiments are carried out in a spray test facility using water and air as the experimental fluids. The measurements of pressure drop across the atomizer orifices and fluid flow rates are made in the test facility. The images of sprays at different flow conditions are captured using the technique of backlighted shadowgraphy. Laser-based optical diagnostic systems (Phase Doppler Interferometry and Spraytec) are used to measure the size and velocities of spray droplets at different spatial locations of the spray below the atomizer exit. In the present study, the spray condition from the GCSC atomizers is expressed in terms of the gas-to-liquid momentum flux ratio, J.
The quantitative variations of the spray cone angle and the streamwise breakup length of the annular liquid sheet, with the atomizer recess ratio, RR are presented for different GCSC atomizer flow conditions. An increase in RR of the GCSC atomizer results in a smaller spray cone angle and a longer sheet breakup length. A power law analysis of the experimental data shows that the sensitivity of the sheet breakup to J is more in case of higher recess ratio GCSC atomizers. The formation of a fully developed spray (spray free from ligament/droplet clusters and non-spherical droplets) in GCSC atomizers is quantified. For a given J, an increase in RR significantly reduces the cone angle of spray. The distance from the atomizer exit to the fully developed spray zone decreases with increase in J. Among the tested GCSC atomizers with varying RR (RR = 1, 2 and 3), a fully developed spray is rapidly seen for sprays discharging from the atomizer with RR = 2. The generation of more axially directed ligaments for the sprays discharging from higher RR (RR = 3) atomizer makes the fully developed spray to begin at a farther distance from the atomizer exit, compared to that from the atomizer with RR = 2.
The spray from a recessed GCSC atomizer comprises two distinct spray morphologies: a central dense spray of finer droplets and an outer coarse spray of bigger droplets. The radial boundary between the two spray morphologies is marked by a jump in the mean drop size of the spray recorded along the radial direction. The mean drop size of the central spray decreases with increase in J, whereas that of the outer coarse spray is independent of J. The reduced spray cone angle and enhanced interaction in the sprays discharging from a high RR GCSC atomizer facilitate the migration of bigger droplets from the annular film breakup region to the central fine spray. The mean drop size recorded at the spray axis increases substantially with increase in RR from 2 to 3. The radial profiles of the mean velocities of spray droplets at different J are presented. The measured radial and tangential velocities of the spray droplets are two orders of magnitude smaller than that of their axial velocity, suggesting that the spray flow discharging from recessed GCSC atomizers is axially dominated. For the sprays with high J, the profile of the mean axial velocity of the spray droplets exhibits trends similar to that of a self-similar free gas jet.
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Kulkarni, Varun. "Breakup Behaviour Of Liquid Sheets Discharging From Gas Centered Swirl Coaxial Atomizers". Thesis, 2009. https://etd.iisc.ac.in/handle/2005/1119.
Pełny tekst źródłaStreszczenie:
This thesis aims at studying the breakup of swirling liquid sheets discharging from the outer orifice of gas centered swirl coaxial atomizers. Such atomizers are considered as propellant injection systems for semi-cryogenic liquid rocket engines. A gas centered swirl coaxial type atomizer discharges an annular swirling liquid sheet which is atomized by a gaseous jet issuing from the central orifice of the atomizer. The primary objectives of this work were to understand the fluid dynamic interaction process between the outer liquid sheet and the central gas jet and its role on the breakup process of the liquid sheet. Cold flow experiments were carried out by constructing custom made gas centered swirl coaxial atomizers. Two different atomizer configurations with varying swirl effect were studied. The jets were injected into ambient atmospheric air medium with tap water and air as experimental fluids. The flow conditions were described in terms of Weber number (Wel) and Reynolds number (Reg) for liquid sheet and the air jet respectively. Spray images were captured by employing an image acquisition system comprising a high resolution digital camera and a strobe lamp. The captured spray images at different combinations of Wel and Reg were analyzed to extract quantitative measurements of breakup length (Lb), spray cone angle (θs), spray width (SW) and two-dimensional
surface profile of liquid sheets. Quantitative analysis of the variation of Lb with Reg with different values of Wel suggested that low inertia liquid sheets undergo an efficient breakup process. High inertia liquid sheets ignore the presence of central air jet at lower values of Reg however undergo air jet breakup at higher values of Reg. Qualitative analysis of experimental observations revealed that the entrainment process, established between the inner surface of the liquid sheet and the boundary of central jet, triggers the air assisted sheet breakup by drawing the liquid sheet closer to the spray axis. The entrainment process may be developing corrugations on the surface of liquid sheet which promotes the production of thick liquid ligaments from the sheet surface. The level of surface corrugations on the liquid sheet, quantified by means of tortuosity of liquid sheet profile, increases with increasing Reg. Limited studies on the effect of variation swirl intensity on the air assisted breakup process of liquid sheets did not show any significant influence for the atomizers examined in the present work.
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Kulkarni, Varun. "Breakup Behaviour Of Liquid Sheets Discharging From Gas Centered Swirl Coaxial Atomizers". Thesis, 2009. http://hdl.handle.net/2005/1119.
Pełny tekst źródłaStreszczenie:
This thesis aims at studying the breakup of swirling liquid sheets discharging from the outer orifice of gas centered swirl coaxial atomizers. Such atomizers are considered as propellant injection systems for semi-cryogenic liquid rocket engines. A gas centered swirl coaxial type atomizer discharges an annular swirling liquid sheet which is atomized by a gaseous jet issuing from the central orifice of the atomizer. The primary objectives of this work were to understand the fluid dynamic interaction process between the outer liquid sheet and the central gas jet and its role on the breakup process of the liquid sheet. Cold flow experiments were carried out by constructing custom made gas centered swirl coaxial atomizers. Two different atomizer configurations with varying swirl effect were studied. The jets were injected into ambient atmospheric air medium with tap water and air as experimental fluids. The flow conditions were described in terms of Weber number (Wel) and Reynolds number (Reg) for liquid sheet and the air jet respectively. Spray images were captured by employing an image acquisition system comprising a high resolution digital camera and a strobe lamp. The captured spray images at different combinations of Wel and Reg were analyzed to extract quantitative measurements of breakup length (Lb), spray cone angle (θs), spray width (SW) and two-dimensional
surface profile of liquid sheets. Quantitative analysis of the variation of Lb with Reg with different values of Wel suggested that low inertia liquid sheets undergo an efficient breakup process. High inertia liquid sheets ignore the presence of central air jet at lower values of Reg however undergo air jet breakup at higher values of Reg. Qualitative analysis of experimental observations revealed that the entrainment process, established between the inner surface of the liquid sheet and the boundary of central jet, triggers the air assisted sheet breakup by drawing the liquid sheet closer to the spray axis. The entrainment process may be developing corrugations on the surface of liquid sheet which promotes the production of thick liquid ligaments from the sheet surface. The level of surface corrugations on the liquid sheet, quantified by means of tortuosity of liquid sheet profile, increases with increasing Reg. Limited studies on the effect of variation swirl intensity on the air assisted breakup process of liquid sheets did not show any significant influence for the atomizers examined in the present work.
Części książek na temat "Sprays from coaxial atomizers"
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Athul Joseph, P. Nandagopalan, T. John Tharakan i D. Sivakumar. "Effect of Orifice Recess on the Droplet Size Distribution of Sprays Discharging from Gas-Centered Swirl Coaxial Atomizers". W Fluid Mechanics and Fluid Power – Contemporary Research, 1091–100. New Delhi: Springer India, 2016. http://dx.doi.org/10.1007/978-81-322-2743-4_103.
Pełny tekst źródłaStreszczenia konferencji na temat "Sprays from coaxial atomizers"
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Hardalupas, Y., R. F. Tsai i J. H. Whitelaw. "Spray Unsteadiness in Coaxial Airblast Atomizers". W ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0195.
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Abstract Experiments have been performed with two coaxial atomizers, the first with an annular stream of air surrounding a central jet of water and the second a commercial airblast atomizer with air swirl. They quantify the deterministic unsteadiness of the droplet flow caused by the break-up process in terms of the mean and temporal fluctuations of the droplet surface area and provide links between atomizing air and liquid flow conditions and the amplitude of the droplet flow unsteadiness with distance from the nozzle exit. Time dependent measurements of droplet surface area in the spray were obtained by image processing of high speed photographs to detect the temporal fluctuations of the attenuation of the incident light and by a Mie scattering technique to detect the intensity of the light scattered by droplets illuminated by a laser sheet. Mie scattering was preferred, because of improved measurement accuracy and lower cost. The spray unsteadiness due to the break-up process was quantified in terms of the spectrum of the energy of the fluctuations of the droplet surface area within a frequency range associated with the break-up process. With the coaxial atomizer, the energy of the deterministic unsteadiness varied between 50% and 65% of the total energy of the spectrum and remained in the droplet flow at least up to 150 liquid jet diameters downstream of the break-up region and its energy increased with the reduction of the air or liquid flowrates, although higher energy was correlated with faster attenuation with the downstream distance from the exit plane, caused by the redistribution of droplets by the gas flow turbulence.
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Oide, Shunsaku, Masanao Iwakura, Mai Takaoka, Shunsuke Kasuga i Shigeru Hayashi. "Low-NOx Combustion of Fuel Spray-Air Mixtures From a Converging Splitter in a Co-Swirling Annular Air Flow". W ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-65205.
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A unique burner consisting of a pressure swirl atomizer, a converging outer shroud, a coaxially assembled converging splitter, and coaxial swirlers at the inlets of the inner and outer circuits is being developed for low-NOx emissions (below 0.5 g/kg-fuel) at the higher inlet air temperatures and better flame stability at the lower inlet air temperatures. Liquid fuel is atomized only into the air flowing in the inner circuit and the resulting mixture jet is injected into the combustion chamber from the exit of the splitter, surrounded by the annular swirling air jet from the outer circuit. Emissions measurements, direct flame imaging, and Mie scattering imaging of the sprays were conducted for inner swirler vane angles of 40 and 50 degrees and a fixed outer swirler vane angle of 45 degrees at inlet air temperatures of 453 to 753 K (a 100-degree step) and atmospheric pressure. A lifted flame was stabilized with the flame front at a distance from the burner exit. Direct flame images were successfully used to correlate the NOx emissions with flame structure. Additionally, local gas sampling was done at 753 K. The measured distributions of equivalence ratio and of chemical species concentrations in the combustion chamber were used to explain the lower NOx emissions for the smaller vane angle.
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Broumand, Mohsen, Murray J. Thomson, Sean Yun i Zekai Hong. "Spray Characterization of a Preheated Bio-Oil Surrogate at Elevated Pressures". W ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-80430.
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Abstract Atomization plays an important role in the gasification or combustion of bio-oils, where the atomizer parameters need to be properly controlled to efficiently atomize a highly viscous liquid at elevated pressures with imparting the least amount of kinetic energy to the discharged droplets because of evaporation and chemical reaction constraints. With a focus on bio-oil deployments in micro gas turbines (MGTs), an aqueous surrogate of a preheated bio-oil, injected from an original equipment manufacturer (OEM) twin-fluid atomizer, is used in the present study for spray size and velocity measurements at elevated pressures. The experiments were conducted in High Pressure Spray Facility of the National Research Council of Canada (NRC) using various optical diagnostics including laser sheet imaging (LSI), phase Doppler anemometry (PDA), and laser diffraction (LD). A scaling strategy was adopted to conserve the ranges of gas-to-liquid momentum flux ratio, M, at different working pressures, P. Over the range of conditions studied, it is found out that the cone angle of sprays is insensitive to P, but they decrease with increasing M. For a constant value of M, droplet mean diameters increase and their corresponding velocities decrease with increasing P, attributed to the effect of gas-to-liquid density ratio on the primary breakup of a liquid jet in a coaxial gas stream. Therefore, to predict the Sauter mean diameter of spray droplets, D32, a correlation previously reported in the literature is modified by including the effect of system air density at elevated pressures, and a novel correlation is proposed based on four dimensionless groups, namely gas Weber number and gas-to-liquid momentum flux ratio, density ratio, and viscosity ratio. The detailed results obtained in the present study could be used to define the optimal parameters required for twin-fluid atomization of high viscosity liquids with various atomization gases under realistic operating conditions and to enhance the capabilities of their numerical simulations.
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Rashid, Mohd Syazwan Firdaus Mat, Ahmad Hussein Abdul Hamid, Zulkifli Abdul Ghaffar i Khairil Azizi Mohamad Zaki. "An experimental investigation on spray characteristics emanating from liquid–liquid coaxial swirl atomizer". W THE 4TH INTERNATIONAL MEETING OF ADVANCES IN THERMOFLUIDS (IMAT 2011). AIP, 2012. http://dx.doi.org/10.1063/1.4704267.
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Sankar, Subramanian V., Kevin E. Maher, Didier M. Robart i William D. Bachalo. "Rapid Characterization of Fuel Atomizers Using an Optical Patternator". W ASME 1997 Turbo Asia Conference. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-aa-001.
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Planar laser scattering (PLS) and planar laser-induced fluorescence (PLIF) techniques are currently being used for rapid characterization of fuel sprays associated with gas turbine atomizers, Diesel injectors, and automotive fuel injectors. These techniques can be use used for qualitative, quantitative, and rapid measurement of fuel mass, spray geometry, and Sauter mean diameters in various sprays. The spatial distribution of the fuel mass can be inferred directly from the PLIF image, and the Sauter mean diameter can be measured by simultaneously recording the PLIF and PLS images, and then ratioing the two. A spray characterization system incorporating the PLS and/or PLIF techniques has been loosely termed an Optical Patternator, and in this study, it has been used to characterize both steady and pulsed sprays. The results obtained with the Optical Patternator have been directly validated using a Phase Doppler Particle Analyzer (PDPA).
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Ibrahim, Ashraf A., i Milind A. Jog. "Modeling of Gas-Liquid Flow in Pressure Swirl Atomizers". W ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81579.
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Pressure swirl or simplex atomizers are commonly used in a number of industrial applications for liquid atomization, including fuel injection systems for gas turbine engines, spray drying, and paint sprays. Computational modeling of the two-phase flow in the atomizer coupled with a non-linear analysis of instability of liquid sheet exiting from the atomizer has been carried out. The Volume-of-Fluid method is employed to determine the two-phase gas-liquid flow inside the atomizer. Results are validated using available experimental data for film thickness at exit, spray angle, and discharge coefficient. The predictions of breakup length using the non-linear model are compared with available experimental measurements which show excellent agreement. The effect of flow conditions and nozzle geometry on the flow field and sheet breakup are investigated. The coupled internal flow simulation and sheet instability analysis provides a comprehensive approach to modeling atomization from a pressure-swirl atomizer.
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Matsuura, Kazuaki, Shunya Uesaka, Tomoyuki Iwasaki, Yoji Kurosawa, Hideshi Yamada, Takeshi Yamamoto i Shigeru Hayashi. "Visualization of pilot flame of an optically-accessible coaxially-staged aero-engine lean-burn fuel injector". W ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4752.
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The visualization of the pilot flame of a coaxially-staged aero-engine lean-burn fuel injector, not only downstreambut also inside of the pilot nozzle, was successfully performed at realistic aero-engine conditions. Optical access toward the inside of the nozzle was achieved through the inner and outer shrouds, both of which were made of transparent quartz. The image distortion caused by complex contours of the two shrouds was corrected by a method based on optical ray tracing, which realized precise determination of spatial intensity distribution of optical signals. Line-of-sight OH chemiluminescence, cross-sectional OH-LIF, kerosene LIF and kerosene Mie scattering were employed as diagnostic tools. The effects of pilot local air-to-fuel ratio on spray flame structure were revealed, both inside and downstream of the pilot nozzle under stable combustions. As the pilot mixture got rich, the main reaction zone moved from inside of the pilot nozzle to the region near the injector lip downstream of the injector exit. The OH-LIF signal was detected near the central axis surrounded by the fuel spray. It was also observed near the back-step of the pilot nozzle for the rich cases. The experiments under combustion oscillation were also conducted and the correlation of phenomena inside and downstream of the pilot nozzle was captured. It was clarified that the reaction enhancement in the outer part of the lip vortex region was caused by the convectionof rich mixture, which appeared near the pilot atomizer lip at 150~210deg earlier oscillation phase angle.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4752
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Schäfer, Dominik, Fabian Hampp, Oliver Lammel i Manfred Aigner. "Investigation of Spray Formation and Turbulent Droplet Transport in High Momentum Jet Stabilized Combustor Injection Systems". W ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-15231.
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Abstract This work investigates the influence of coaxial air flow on droplet distribution, velocity, and size generated by a pressure-swirl atomizer. The experiments were performed inside a generic test section with large optical access at atmospheric conditions. The flow conditions replicate the mixing duct sections of high momentum jet stabilized combustors for gas turbines, e.g. high axial air velocities without swirl generation and high preheat temperatures. High momentum jet stabilized combustors based on the FLOX® burner concept are used successfully in gas turbines due to its fuel and load flexibility and very low pollutant emissions. In previous and ongoing studies, different model combustors have been under investigation mainly with the focus of broadening fuel flexibility and operational limits. Operation with different liquid fuel injection systems in high pressure experiments showed a significant impact from the injector shape and injection strategy on the fuel air mixing behavior, the flame position and stability, and thus NOx emissions. This experiment will give a more detailed understanding of the turbulent mixing and interaction of primary and secondary atomization with the surrounding air in such burners. The setup will also allow for the testing of different injection systems for various burner configurations by the variation of injection type, location, fuel, and air flow properties. In the present experiments a pressure-swirl atomizer was set to a constant pressure drop and mass flow. Liquid fuel was replaced by deionized water due to safety concerns. The coaxial air mass flow was preheated up to 473 K and set to bulk velocities of 20 m/s, 50 m/s, and 80 m/s. Particle Image Velocimetry (PIV) was used to characterize the flow field downstream of the point of injection. The droplet size and velocity distributions were quantified by double frame shadow imaging combined with a long-distance microscope with a resolution below 1 μm per pixel. Moreover, the formation of ligaments as well as primary spray break-up was visualized. The results show a significant change of the spatial droplet distribution with increasing co-flow velocity for a given atomizer geometry. The spray cone angle widens at high co-flow velocities due to the formation of a pronounced recirculation zone behind the backward facing step of the injector near the nozzle orifice. This also leads to a change in the initial droplet momentum and the spatial distribution of large droplets. Smaller droplets are concentrated to the center of the spray due to turbulent transport. These findings assist the ongoing developments of liquid fuel injection systems for high momentum jet based combustors and provide validation data for numerical simulations of primary and secondary atomization.
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Parsons, J. A., i A. K. Jasuja. "Effect of Air Pressure Upon Spray Angle/Width Characteristics of Simplex Pressure Swirl Atomizers". W ASME 1986 International Gas Turbine Conference and Exhibit. American Society of Mechanical Engineers, 1986. http://dx.doi.org/10.1115/86-gt-176.
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This paper examines the spatial distribution characteristics of fuel sprays emanating from simplex pressure swirl atomizers of the type commonly used in the gas turbine engine. Three different atomizers were tested on kerosine at chamber gas pressures up to 1377 KN/m2 and fuel pressure drops up to 3448 KN/m2. A non-intrusive, still photographic technique was developed for recording the spray profiles over the entire range of test conditions. Analysis of the experimental data shows that the closing in of the spray boundaries due to an increase in air pressure is a result of the aerodynamic interaction between the fuel spray and its gaseous environment — the nozzle hydrodynamics apparently exercising no influence. Experimental data collected in the study reveals the influence of gas pressure (Pa) upon the half width (y) of the spray envelope at a downstream distance of 30mm from the nozzle face to be described adequately by the expression y α Pa-0.26.
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Farago, Zoltan, i Norman Chigier. "Parametric Experiments on Coaxial Airblast Jet Atomization". W ASME 1990 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1990. http://dx.doi.org/10.1115/90-gt-081.
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Experiments using high speed, high magnification, and high contrast photography on airblast coaxial atomizers were carried out to study the wave characteristics of liquid surfaces, ligament breakup, and droplet formation. Liquid flow rate was changed from 4 to 50 kg/h, corresponding to a velocity range of 1.5 to 18 m/s, and a Reynolds number range of 1400 to 18000. Air flow rate was varied from 8 to 70 kg/h, corresponding to a velocity range of 22 to 180 m/s, and a Reynolds number range of 13000 to 105000. Tube wall thicknesses of 145 and 320 microns were used. Under different flow conditions, different jet instabilities (capillary, helical and Kelvin-Helmholtz) and different dominant mechanisms of ligament formation were observed. One of the most surprising experimental results is that, under certain flow conditions, the coaxial round liquid jet, surrounded by an axisymmetric annular air stream, forms a flat curling liquid sheet. This liquid sheet breaks into droplet clouds with a frequency of a few thousand Hertz and emits strong oscillations and fluctuating, highly non-axisymmetric vibrations.