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An experimental study of swirling supercritical hydrocarbon fuel jets / R. R. Rachedi in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 132 N° 8 (Août 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 8 (Août 2010) . - 09 p. Titre : An experimental study of swirling supercritical hydrocarbon fuel jets Type de document : texte imprimé Auteurs : R. R. Rachedi, Auteur ; L. C. Crook, Auteur ; P. E. Sojka, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Fuel  Jets  Nozzles  Sprays  Swirling  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An experimental investigation was conducted to examine the behavior of swirling supercritical hydrocarbon fuel (SCF) jets injected into nitrogen environments whose temperatures and pressures exceeded the fuel critical values. Measurements of jet full-cone angle, mass concentration field, and penetration length were made using a schlieren system; the images were captured by a high-speed digital camera and processed using the camera's software, plus MATLAB codes. Test parameters were the internal geometry of the pressure-swirl nozzle, fuel flow rate, and density ratio. The density ratio was varied by altering the reduced temperature of the injected fluid and nitrogen environment. SCF injections were studied at reduced temperatures (Tjet/Tcrit with both reported in Kelvin) ranging between 1.01 and 1.10, a reduced pressure (pjet/pcrit with both reported in bars) of 1.05, and fuel flowrates of 1.0 g/s, 2.0 g/s, and 3.0 g/s. The variable internal geometry pressure-swirl atomizer produced jets having swirl numbers (SN) of 0 (straight bore), 0.25, 0.50, and 1.00 (high swirl). As expected, increasing the swirl number for a SCF jet had by far the largest effect on jet cone angle, followed by a change in the density ratio; changing the fuel flow rate had very little effect. The SCF jet penetration length increased when either the fuel flow rate or density ratio increased. The mass concentration profiles demonstrated the jets to be self-similar in nature, and correlation to a Gaussian profile showed the mass concentration field to be independent of swirl number, density ratio, and fuel flow rate. Finally, it was found that there was a linear relationship between the jet half-width and the swirl number. The current study characterized the behavior of swirling hydrocarbon fuel SCF jets for the first time. Aspects of jet behavior similar to that of gas jets include: Gaussian mass concentration profiles and jet boundaries that scale with swirl number. Finally, CO2 was found to be a suitable surrogate fluid for hydrocarbon fuels since the behavior of the hydrocarbon SCF jets was similar to that of CO2 SCF jets. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] An experimental study of swirling supercritical hydrocarbon fuel jets [texte imprimé] / R. R. Rachedi, Auteur ; L. C. Crook, Auteur ; P. E. Sojka, Auteur . - 2011 . - 09 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 8 (Août 2010) . - 09 p. Mots-clés : Fuel  Jets  Nozzles  Sprays  Swirling  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An experimental investigation was conducted to examine the behavior of swirling supercritical hydrocarbon fuel (SCF) jets injected into nitrogen environments whose temperatures and pressures exceeded the fuel critical values. Measurements of jet full-cone angle, mass concentration field, and penetration length were made using a schlieren system; the images were captured by a high-speed digital camera and processed using the camera's software, plus MATLAB codes. Test parameters were the internal geometry of the pressure-swirl nozzle, fuel flow rate, and density ratio. The density ratio was varied by altering the reduced temperature of the injected fluid and nitrogen environment. SCF injections were studied at reduced temperatures (Tjet/Tcrit with both reported in Kelvin) ranging between 1.01 and 1.10, a reduced pressure (pjet/pcrit with both reported in bars) of 1.05, and fuel flowrates of 1.0 g/s, 2.0 g/s, and 3.0 g/s. The variable internal geometry pressure-swirl atomizer produced jets having swirl numbers (SN) of 0 (straight bore), 0.25, 0.50, and 1.00 (high swirl). As expected, increasing the swirl number for a SCF jet had by far the largest effect on jet cone angle, followed by a change in the density ratio; changing the fuel flow rate had very little effect. The SCF jet penetration length increased when either the fuel flow rate or density ratio increased. The mass concentration profiles demonstrated the jets to be self-similar in nature, and correlation to a Gaussian profile showed the mass concentration field to be independent of swirl number, density ratio, and fuel flow rate. Finally, it was found that there was a linear relationship between the jet half-width and the swirl number. The current study characterized the behavior of swirling hydrocarbon fuel SCF jets for the first time. Aspects of jet behavior similar to that of gas jets include: Gaussian mass concentration profiles and jet boundaries that scale with swirl number. Finally, CO2 was found to be a suitable surrogate fluid for hydrocarbon fuels since the behavior of the hydrocarbon SCF jets was similar to that of CO2 SCF jets. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Effervescent atomization of viscoelastic liquids / S. C. Geckler in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 6 (Juin 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 6 (Juin 2008) . - 11 p. Titre : Effervescent atomization of viscoelastic liquids : experiment and modeling Type de document : texte imprimé Auteurs : S. C. Geckler, Auteur ; P. E. Sojka, Auteur Année de publication : 2009 Article en page(s) : 11 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Fluids;  drops;  polymers;  sprays;  molecular  weight;  water;  stability;  tension Résumé : The effervescent atomization of viscoelastic liquids is reported. A total of 23 fluids, formulated from a 60wt% glycerine/40wt% water solvent to which were added varying concentrations (0.001–0.5wt%) of poly(ethylene oxide) polymers whose molecular weights ranged from 12,000 to 900,000, were sprayed through a conventional effervescent atomizer. Mean drop sizes were measured using a forward light scattering instrument. The drop size (D32) data show the expected decrease with an increase in air-liquid ratio by mass (ALR), the expected increase with an increase in polymer concentration, plus an increase with an increase in polymer molecular weight for most cases. However, no significant change in D32 was observed for polymer solutions whose molecular weights ranged from 12,000 to 35,000, suggesting the presence of a critical molecular weight below which spray performance is unaltered. This argues for two different factors controlling drop size: Polymer molecular weight is most influential at the highest polymer concentrations while polymer concentration is most influential at the lowest polymer concentrations. Analysis of the spray formation process was carried out using a ligament formation model previously developed for the effervescent atomization of Newtonian liquids coupled with a linear stability model for the breakup of viscoelastic liquid jets. The jet breakup model assumes that an unrelaxed axial tension exists within the fluid. A comparison of model predictions and experimental data indicates that the model predicts the observed dependencies of mean drop size on ALR, polymer concentration, and polymer molecular weight. Quantitative agreement is within 10–50% of experimental values in all cases. Finally, a shortcoming of the model is noted and a means of avoiding this limitation reported. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27318 [...] [article] Effervescent atomization of viscoelastic liquids : experiment and modeling [texte imprimé] / S. C. Geckler, Auteur ; P. E. Sojka, Auteur . - 2009 . - 11 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 6 (Juin 2008) . - 11 p. Mots-clés : Fluids;  drops;  polymers;  sprays;  molecular  weight;  water;  stability;  tension Résumé : The effervescent atomization of viscoelastic liquids is reported. A total of 23 fluids, formulated from a 60wt% glycerine/40wt% water solvent to which were added varying concentrations (0.001–0.5wt%) of poly(ethylene oxide) polymers whose molecular weights ranged from 12,000 to 900,000, were sprayed through a conventional effervescent atomizer. Mean drop sizes were measured using a forward light scattering instrument. The drop size (D32) data show the expected decrease with an increase in air-liquid ratio by mass (ALR), the expected increase with an increase in polymer concentration, plus an increase with an increase in polymer molecular weight for most cases. However, no significant change in D32 was observed for polymer solutions whose molecular weights ranged from 12,000 to 35,000, suggesting the presence of a critical molecular weight below which spray performance is unaltered. This argues for two different factors controlling drop size: Polymer molecular weight is most influential at the highest polymer concentrations while polymer concentration is most influential at the lowest polymer concentrations. Analysis of the spray formation process was carried out using a ligament formation model previously developed for the effervescent atomization of Newtonian liquids coupled with a linear stability model for the breakup of viscoelastic liquid jets. The jet breakup model assumes that an unrelaxed axial tension exists within the fluid. A comparison of model predictions and experimental data indicates that the model predicts the observed dependencies of mean drop size on ALR, polymer concentration, and polymer molecular weight. Quantitative agreement is within 10–50% of experimental values in all cases. Finally, a shortcoming of the model is noted and a means of avoiding this limitation reported. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27318 [...]

Non-Newtonian drops spreading on a flat surface / A. Dechelette in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 07 p. Titre : Non-Newtonian drops spreading on a flat surface Type de document : texte imprimé Auteurs : A. Dechelette, Auteur ; P. E. Sojka, Auteur ; C. R. Wassgren, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : force;  surface  tension;  flow  (dynamics);  viscosity;  Reynolds  number;  drops;  water Résumé : The objective of this study is to develop a computational model that accurately describes the dynamic behavior of a non-Newtonian power-law film formed after a drop impinges on a flat surface. The non-Newtonian drop deposition and spreading process is described by a model based on one developed for Newtonian liquids. The effects of variations in non-Newtonian liquid rheological parameters, such as Ren (the non-Newtonian Reynolds number), n (the flow behavior index), and We (the Weber number), are studied in detail. Results show that a reduction in the viscous forces results in enhanced spreading of the film followed by a more rapid recession. An increase in surface tension results in reduced spreading of the film, followed by a more rapid recession. Model predictions of film diameter as a function of time were larger than corresponding experimental values obtained as part of this study. However, the discrepancy never exceeded 21%, demonstrating that the model accurately predicts the phenomena of interest. This comparison also shows that the results are in best agreement for large non-Newtonian Reynolds numbers and small non-Newtonian Ohnesorge numbers (We/Ren). DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Non-Newtonian drops spreading on a flat surface [texte imprimé] / A. Dechelette, Auteur ; P. E. Sojka, Auteur ; C. R. Wassgren, Auteur . - 2011 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 07 p. Mots-clés : force;  surface  tension;  flow  (dynamics);  viscosity;  Reynolds  number;  drops;  water Résumé : The objective of this study is to develop a computational model that accurately describes the dynamic behavior of a non-Newtonian power-law film formed after a drop impinges on a flat surface. The non-Newtonian drop deposition and spreading process is described by a model based on one developed for Newtonian liquids. The effects of variations in non-Newtonian liquid rheological parameters, such as Ren (the non-Newtonian Reynolds number), n (the flow behavior index), and We (the Weber number), are studied in detail. Results show that a reduction in the viscous forces results in enhanced spreading of the film followed by a more rapid recession. An increase in surface tension results in reduced spreading of the film, followed by a more rapid recession. Model predictions of film diameter as a function of time were larger than corresponding experimental values obtained as part of this study. However, the discrepancy never exceeded 21%, demonstrating that the model accurately predicts the phenomena of interest. This comparison also shows that the results are in best agreement for large non-Newtonian Reynolds numbers and small non-Newtonian Ohnesorge numbers (We/Ren). DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]