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[EN] The selective catalytic reduction (SCR) is a technology employed for NOx reduction purposes which is based on the injection of an Urea Water Solution (UWS) into the exhaust line. Conversion of this injected urea into ammonia is a key step to ensure high SCR efficiency. In order to study this phenomenon, a three-dimensional model of the urea-water injection process has been created to recreate realistic conditions. A Lagrangian-Eulerian approach has been followed to model liquid and gas phases, respectively. Droplet evaporation as well as relevant chemical processes have been included to recreate the thermolysis and hydrolysis phenomena, and the results have been validated against literature data. Then, the validated model has been applied to recreate an in-house experimental facility that measured spray macroscopic and microscopic characteristics by means of diffused back illumination (DBI) visualization. Probability density functions of the UWS droplet sizes as well as the velocity distributions have been obtained at three different regions of interest to be compared with the experimental data set. Contours of isocyanic acid and ammonia mass fractions have been included to show the chemical transformation from urea into its products. The model accurately replicates the experimental results, and it stands as a good methodology to predict the main spray characteristics as well as the chemical processes that take place in actual SCR systems. ; This research has been partially funded by Spanish Ministerio de Ciencia, Innovacion y Universidades through project RTI2018099706-B-100. Additionally, the experimental hardware was purchased through FEDER and Generalitat Valenciana under project IDIFEDER/2018/037. Additionally, the Ph.D. student J.M.-G. has been funded by a grant from the Government of Generalitat Valenciana with reference ACIF/2020/259 and financial support from The European Union. ; Payri, R.; Bracho Leon, G.; Marti-Aldaravi, P.; Marco-Gimeno, J. (2021). Numerical Analysis of Urea to Ammonia ...

In this research, two Engine Combustion Network (ECN) mono-orifice nozzles, referred to as Spray C and Spray D. respectively, were analyzed by performing visualization tests through Schlieren and Diffused Backlight Illumination (DBI) techniques under a wide range of ambient conditions in a non-reactive atmosphere. Spray C presents a straight nozzle designed with a sharp fillet in opposition to Spray D that has similar hydraulic properties, but with a convergent nozzle construction and a smoother corner. The experiments were carried out injecting two distinct fuels at different injection pressure ranges, from 50 MPa to 150 MPa with n-dodecane and to 200 MPa for diesel. The images were processed with Matlab home-built routines to calculate parameters as spray penetration, spreading angle, quasi steady liquid length, as well as the spray penetration derivative respect to the square root of time, presented in this document as R-parameter. The results showed a clear influence of nozzle geometry in all measured parameters, due mainly to the nature of Spray C to cavitation, which increase the spreading angle and consequently a reduction in vapor penetration. On the other hand, fuel properties also affected spray penetration due to its dependency on viscous forces expressed in terms of the Reynolds number and its volatility in case of liquid length. This last parameter was calculated employing two processing methodologies, finding a good general agreement between them. ; This work was supported by "Ministerio de Economia y Competitividad" of the Spanish Government in the frame of the projects "Estudio de la interaccion chorro-pared en condiciones realistas de motor", Ref. TRA2015-67679-c2-1-R. Moreover, the optical equipment employed in the project was purchased with investment from "Ministerio de Economia y Competitividad" FEDER-ICTS-2012-06. ; Gimeno, J.; Bracho Leon, G.; Marti-Aldaravi, P.; Peraza, JE. (2016). Experimental study of the injection conditions influence over n-dodecane and diesel sprays with two ECN ...

[EN] Due to environmental problems, research on fuel economy and pollutant emissions in internal combustion engines has drawn the attention of automobile manufacturers and researchers. The diesel engine is one of the most efficient alternatives and one of the main areas of the study in these engines is spray mixing, recognized as a critical factor in combustion control and the reduction of its related contaminants. The studies about fuel sprays rely on experimental data of the rate of injection, which can only be obtained with high-cost equipment. The aim of this paper is to validate for different fuels a method for the determination of the rate of injection based on spray momentum measurements and the total injected mass. After a proper tuning of the test momentum flux device, the injection rate results were validated using the Bosch tube method. The technique was validated for four different fuels, diesel, biodiesel, GTL (Gas-to-liquid) and Farnesane, in order to identify the consequences of the fuel properties on the injection performance characteristics and the estimation method. The results of rate of injection following the procedures presented showed good accuracy when compared to experimental values. These methods can be employed to estimate this parameter when experimental facilities for this purpose are not available. ; Authors wish to thank the financial support provided by: i) the Spanish Ministry of Science, Innovation and Universities to the project RECUPERA, Ref. Ref.: RTI2018-095923-B-C21 and ii) the government of Castilla-La Mancha community to the project ASUAV, Ref. SBPLY/19/180501/000116. Authors also want to thank: i) the companies REPSOL, SASOL and AMYRIS by the fuels supply, ii) the technical support provided by Nissan Europe Technology Centre Spain. ; Payri, R.; Bracho Leon, G.; Soriano, JA.; Fernández-Yáñez, P.; Armas, O. (2020). Nozzle rate of injection estimation from hole to hole momentum flux data with different fossil and renewable fuels. Fuel. 279:1-10. ...

251 267 27 3 ; S ; [EN] Accurate experimental data are often needed to validate computational fluid dynamics models. These models regularly rely on experimental results from single-orifice axially drilled nozzles that do not fully represent real injectors, as the difference in inclination angles creates turbulent conditions at the nozzle outlet, consequences of which on the spray development are not yet fully understood. In this work, near-field visualization was done for two nozzle inclination angles in non-vaporizing conditions. Spray tip penetration, spreading angle, and axis angle fluctuations are reported. Three hypotheses are analyzed: liquid jet breakup mechanism, internal flow development, and cavitation. Experiments were carried out using n-Dodecane, testing a single orifice axially drilled and a three-orifice injector, from the Engine Combustion Network. The spray was observed with a diffused back-illumination technique and a long distance microscope, only visualizing the first 6 mm of spray tip penetration, for three injection pressures and four gas densities at ambient temperature. The multi-orifice injector produced a spray with wider spreading angle, which resulted in smaller penetration values. Additionally, higher spray axis angle fluctuations were observed for the multi-orifice injector, which increased for higher injection pressure and, to a lesser extent, with decreasing chamber density. Further analysis was performed with spreading angle fluctuations measurements, where results showed good agreement with spray axis angle fluctuations trends, implying that complex internal flow structures, and even incipient cavitation, could be present in the multi-orifice injector and be the cause of these spray axis angle fluctuations. This work was sponsored by "Ministerio de Economia y Competitividad" of the Spanish Government in the frame of the project " Estudio de la interaccion chorro-pared en condiciones realistas de motor," reference TRA2015-67679-c2-1-R. Additionally, the optical equipment used for ...

[EN] Accurate experimental data are often needed to validate computational fluid dynamics models. These models regularly rely on experimental results from single-orifice axially drilled nozzles that do not fully represent real injectors, as the difference in inclination angles creates turbulent conditions at the nozzle outlet, consequences of which on the spray development are not yet fully understood. In this work, near-field visualization was done for two nozzle inclination angles in non-vaporizing conditions. Spray tip penetration, spreading angle, and axis angle fluctuations are reported. Three hypotheses are analyzed: liquid jet breakup mechanism, internal flow development, and cavitation. Experiments were carried out using n-Dodecane, testing a single orifice axially drilled and a three-orifice injector, from the Engine Combustion Network. The spray was observed with a diffused back-illumination technique and a long distance microscope, only visualizing the first 6 mm of spray tip penetration, for three injection pressures and four gas densities at ambient temperature. The multi-orifice injector produced a spray with wider spreading angle, which resulted in smaller penetration values. Additionally, higher spray axis angle fluctuations were observed for the multi-orifice injector, which increased for higher injection pressure and, to a lesser extent, with decreasing chamber density. Further analysis was performed with spreading angle fluctuations measurements, where results showed good agreement with spray axis angle fluctuations trends, implying that complex internal flow structures, and even incipient cavitation, could be present in the multi-orifice injector and be the cause of these spray axis angle fluctuations. ; This work was sponsored by "Ministerio de Economia y Competitividad" of the Spanish Government in the frame of the project " Estudio de la interaccion chorro-pared en condiciones realistas de motor," reference TRA2015-67679-c2-1-R. Additionally, the optical equipment used for the project was ...

[EN] Currently, diesel engines are calibrated using more and more complex multiple injection strategies. Under these conditions, the characteristics of the flow exiting the fuel injector are strongly affected by the transient interaction between the needle, the sac volume and the orifices, which are not yet clear. In the current paper, a methodology combining a 1D injector model and 3D-CFD simulations is proposed. First, the characteristics of the nozzle flow have been experimentally assessed in transient conditions by means of injection rate and momentum flux measurements. Later, the 3D-CFD modeling approach has been validated at steady-state fixed lift conditions. Finally, a previously developed 1D injector model has been used to extract the needle lift profiles and transient pressure boundary conditions used for the full-transient 3D-CFD simulations, using adaptive mesh refinement (AMR) strategies to be able to simulate the complete injection rate starting from 1 mu m lift. ; This work was partly sponsored by "Ministerio de Economia y Competitividad'', of the Spanish Government, in the frame of the Project "Estudio de la interaccion chorro-pared en condiciones realistas de motor'', Reference TRA2015-67679-c2-1-R. The authors would like also to thank the computer resources, technical expertise and assistance provided by Universidad de Valencia in the use of the supercomputer "Tirant''. Mr. Jaramillo's Thesis is funded by "Conselleria d'Educacio, Cultura i Esports'' of Generalitat Valenciana in the frame of the program "Programa VALI + D para investigadores en formacion, Reference ACIF/2015/040. ; Salvador, FJ.; De La Morena, J.; Bracho Leon, G.; Jaramillo-Císcar, D. (2018). Computational investigation of diesel nozzle internal flow during the complete injection event. Journal of the Brazilian Society of Mechanical Sciences and Engineering. 40(3):153-167. https://doi.org/10.1007/s40430-018-1074-z ; S ; 153 ; 167 ; 40 ; 3 ; Hall CAS, Lambert JG, Balogh SB (2014) EROI of different fuels and the implications for ...