Boundary condition and fuel composition effects on injection processes of high-pressure sprays at the microscopic level

Detailed imaging of n-dodecane and ethanol sprays injected in a constant-flow, high-pressure, high-temperature optically accessible chamber was per-formed. High-speed, diffused back-illuminated long-distance microscopy was used to resolve the spray structure in the near-nozzle field. The effect of injection and ambient pressures, as well as fuel temperature and composition have been studied through measurements of the spray penetration rates, hydraulic delays and spreading angles. Additional information such as transient flow velocities have been extracted from the measurements and compared to a control-volume spray model. The analysis demonstrated the influence of outlet flow on spray development with lower penetration velocities and wider spreading angles during the transients (start and end of injection) than during the quasi-steady period of the injection. The effect of fuel com-position on penetration was limited, while spreading angle measurements showed wider sprays for ethanol. In contrast, varying fuel temperature led to varying penetration velocities, while spreading angle remained constant during the quasi-steady period of the injection. Fuel temperature affected injector performance, with shorter delays as fuel temperature was increased. The comparisons between predicted and measured penetration rates showed differences suggesting that the transient behavior of the spreading angle of the sprays modified spray development significantly in the near-field. The reasonable agreement between predicted and measured flow velocity at and after the end of injection suggested that the complete mixing assumptions made by the model were valid in the near nozzle region during this period, when injected flow velocities are reduced.The authors wish to thank Chris Carlen from Sandia National Laboratories for designing and manufacturing specific ultra-fast LEDs, as well as Jose Enrique del Rey and Juan Pablo Viera from CMT-Motores Termicos for their support during the experiments. Support for the research carried out by Julien Manin at CMT-Motores Termicos was provided by the U.S. Department of Energy, Office of Vehicle Technologies. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.Manin, J.; Bardi, M.; Pickett, LM.; Payri Marín, R. (2016). Boundary condition and fuel composition effects on injection processes of high-pressure sprays at the microscopic level. International Journal of Multiphase Flow. 83:267-278. https://doi.org/10.1016/j.ijmultiphaseflow.2015.12.001S2672788

Eulerian CFD modeling of nozzle geometry effects on ECN Sprays A and D: assessment and analysis

This is the author's version of a work that was accepted for publication in International Journal of Engine Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published as https://doi.org/10.1177/1468087419882500.[EN] Diesel spray modeling is a multi-scale problem with complex interactions between different flow regions, that is, internal nozzle flow, near-nozzle region and developed spray, including evaporation and combustion. There are several modeling approaches that have proven particularly useful for some spray regions although they have struggled at other areas, while Eulerian modeling has shown promise in dealing with all characteristics at a reasonable computational effort for engineering calculations. In this work, the sigma -Y single-fluid diffuse-interface model, based on scale separation assumptions at high Reynolds and Weber numbers, is used to simulate the engine combustion network Sprays A and D within a Reynolds-averaged Navier-Stokes turbulence modeling approach. The study is divided into two parts. First of all, the larger diameter Spray D is modeled from the nozzle flow till evaporative spray conditions, obtaining successful prediction of numerous spray metrics, paying special attention to the near-nozzle region where spray dispersion and interfacial surface area can be validated against measurements conducted at the Advanced Photon Source at Argonne National Laboratory, including both the ultra-small-angle X-ray scattering and the X-ray radiography. Afterwards, an analysis of the modeling predictions is made in comparison with previous results obtained for Spray A, considering the nozzle geometry effects in the modeling behavior.The authors thank the freely shared X-ray radiography and ultra-small-angle X-ray scattering measurements performed at Argonne National Laboratory by the following authors: Daniel J. Duke, Jan Ilavsky, Katarzyna E. Matusik., Brandon A. Sforzo., Alan L. Kastengren and Christopher F. Powell. They also thankfully acknowledge the computer resources at Picasso and the technical support provided by Universidad de Malaga (UMA; RES-FI-2018-1-0039).Pandal, A.; García-Oliver, JM.; Pastor Enguídanos, JM. (2020). Eulerian CFD modeling of nozzle geometry effects on ECN Sprays A and D: assessment and analysis. International Journal of Engine Research. 21(1):73-88. https://doi.org/10.1177/1468087419882500S7388211PAYRI, R., GARCIA, J., SALVADOR, F., & GIMENO, J. (2005). Using spray momentum flux measurements to understand the influence of diesel nozzle geometry on spray characteristics. Fuel, 84(5), 551-561. doi:10.1016/j.fuel.2004.10.009Payri, R., Salvador, F. J., Gimeno, J., & Zapata, L. D. (2008). Diesel nozzle geometry influence on spray liquid-phase fuel penetration in evaporative conditions. Fuel, 87(7), 1165-1176. doi:10.1016/j.fuel.2007.05.058Payri, R., Salvador, F. J., Gimeno, J., & de la Morena, J. (2009). Effects of nozzle geometry on direct injection diesel engine combustion process. Applied Thermal Engineering, 29(10), 2051-2060. doi:10.1016/j.applthermaleng.2008.10.009Payri, F., Payri, R., Salvador, F. J., & Martínez-López, J. (2012). A contribution to the understanding of cavitation effects in Diesel injector nozzles through a combined experimental and computational investigation. Computers & Fluids, 58, 88-101. doi:10.1016/j.compfluid.2012.01.005Kastengren, A. L., Powell, C. F., Wang, Y., Im, K.-S., & Wang, J. (2009). X-RAY RADIOGRAPHY MEASUREMENTS OF DIESEL SPRAY STRUCTURE AT ENGINE-LIKE AMBIENT DENSITY. Atomization and Sprays, 19(11), 1031-1044. doi:10.1615/atomizspr.v19.i11.30Pickett, L. M., Manin, J., Kastengren, A., & Powell, C. (2014). Comparison of Near-Field Structure and Growth of a Diesel Spray Using Light-Based Optical Microscopy and X-Ray Radiography. SAE International Journal of Engines, 7(2), 1044-1053. doi:10.4271/2014-01-1412Dahms, R. N., Manin, J., Pickett, L. M., & Oefelein, J. C. (2013). Understanding high-pressure gas-liquid interface phenomena in Diesel engines. Proceedings of the Combustion Institute, 34(1), 1667-1675. doi:10.1016/j.proci.2012.06.169Arienti, M., & Sussman, M. (2017). A numerical study of the thermal transient in high-pressure diesel injection. International Journal of Multiphase Flow, 88, 205-221. doi:10.1016/j.ijmultiphaseflow.2016.09.017Vallet, A., Burluka, A. A., & Borghi, R. (2001). DEVELOPMENT OF A EULERIAN MODEL FOR THE «ATOMIZATION» OF A LIQUID JET. Atomization and Sprays, 11(6), 24. doi:10.1615/atomizspr.v11.i6.20Siebers, D. L. (2008). Recent Developments on Diesel Fuel Jets Under Quiescent Conditions. Flow and Combustion in Reciprocating Engines, 257-308. doi:10.1007/978-3-540-68901-0_5Oefelein, J., Dahms, R., & Lacaze, G. (2012). Detailed Modeling and Simulation of High-Pressure Fuel Injection Processes in Diesel Engines. SAE International Journal of Engines, 5(3), 1410-1419. doi:10.4271/2012-01-1258Demoulin, F.-X., Reveillon, J., Duret, B., Bouali, Z., Desjonqueres, P., & Menard, T. (2013). TOWARD USING DIRECT NUMERICAL SIMULATION TO IMPROVE PRIMARY BREAK-UP MODELING. Atomization and Sprays, 23(11), 957-980. doi:10.1615/atomizspr.2013007439Desantes, J. M., Garcia-Oliver, J. M., Pastor, J. M., & Pandal, A. (2016). A COMPARISON OF DIESEL SPRAYS CFD MODELING APPROACHES: DDM VERSUS E-Y EULERIAN ATOMIZATION MODEL. Atomization and Sprays, 26(7), 713-737. doi:10.1615/atomizspr.2015013285Desantes, J. M., García-Oliver, J. M., Pastor, J. M., Pandal, A., Baldwin, E., & Schmidt, D. P. (2016). Coupled/decoupled spray simulation comparison of the ECN spray a condition with the -Y Eulerian atomization model. International Journal of Multiphase Flow, 80, 89-99. doi:10.1016/j.ijmultiphaseflow.2015.12.002Garcia-Oliver, J. M., Pastor, J. M., Pandal, A., Trask, N., Baldwin, E., & Schmidt, D. P. (2013). DIESEL SPRAY CFD SIMULATIONS BASED ON THE Σ-Υ EULERIAN ATOMIZATION MODEL. Atomization and Sprays, 23(1), 71-95. doi:10.1615/atomizspr.2013007198Navarro-Martinez, S. (2014). Large eddy simulation of spray atomization with a probability density function method. International Journal of Multiphase Flow, 63, 11-22. doi:10.1016/j.ijmultiphaseflow.2014.02.013Pandal, A., Pastor, J. M., García-Oliver, J. M., Baldwin, E., & Schmidt, D. P. (2016). A consistent, scalable model for Eulerian spray modeling. International Journal of Multiphase Flow, 83, 162-171. doi:10.1016/j.ijmultiphaseflow.2016.04.003Pandal, A., Payri, R., García-Oliver, J. M., & Pastor, J. M. (2017). Optimization of spray break-up CFD simulations by combining Σ-Y Eulerian atomization model with a response surface methodology under diesel engine-like conditions (ECN Spray A). Computers & Fluids, 156, 9-20. doi:10.1016/j.compfluid.2017.06.022Pandal, A., García-Oliver, J. M., Novella, R., & Pastor, J. M. (2018). A computational analysis of local flow for reacting Diesel sprays by means of an Eulerian CFD model. International Journal of Multiphase Flow, 99, 257-272. doi:10.1016/j.ijmultiphaseflow.2017.10.010Payri, R., Ruiz, S., Gimeno, J., & Martí-Aldaraví, P. (2015). Verification of a new CFD compressible segregated and multi-phase solver with different flux updates-equations sequences. Applied Mathematical Modelling, 39(2), 851-861. doi:10.1016/j.apm.2014.07.011Salvador, F. J., Gimeno, J., Pastor, J. M., & Martí-Aldaraví, P. (2014). Effect of turbulence model and inlet boundary condition on the Diesel spray behavior simulated by an Eulerian Spray Atomization (ESA) model. International Journal of Multiphase Flow, 65, 108-116. doi:10.1016/j.ijmultiphaseflow.2014.06.003Demoulin, F.-X., Beau, P.-A., Blokkeel, G., Mura, A., & Borghi, R. (2007). A NEW MODEL FOR TURBULENT FLOWS WITH LARGE DENSITY FLUCTUATIONS: APPLICATION TO LIQUID ATOMIZATION. Atomization and Sprays, 17(4), 315-345. doi:10.1615/atomizspr.v17.i4.20Pandal, A., Pastor, J. M., Payri, R., Kastengren, A., Duke, D., Matusik, K., … Schmidt, D. (2017). Computational and Experimental Investigation of Interfacial Area in Near-Field Diesel Spray Simulation. SAE International Journal of Fuels and Lubricants, 10(2), 423-431. doi:10.4271/2017-01-0859Weller, H. G., Tabor, G., Jasak, H., & Fureby, C. (1998). A tensorial approach to computational continuum mechanics using object-oriented techniques. Computers in Physics, 12(6), 620. doi:10.1063/1.168744Faeth, G. M. (1983). Evaporation and combustion of sprays. Progress in Energy and Combustion Science, 9(1-2), 1-76. doi:10.1016/0360-1285(83)90005-9Pitzer, K. S., Lippmann, D. Z., Curl, R. F., Huggins, C. M., & Petersen, D. E. (1955). The Volumetric and Thermodynamic Properties of Fluids. II. Compressibility Factor, Vapor Pressure and Entropy of Vaporization1. Journal of the American Chemical Society, 77(13), 3433-3440. doi:10.1021/ja01618a002Lebas, R., Menard, T., Beau, P. A., Berlemont, A., & Demoulin, F. X. (2009). Numerical simulation of primary break-up and atomization: DNS and modelling study. International Journal of Multiphase Flow, 35(3), 247-260. doi:10.1016/j.ijmultiphaseflow.2008.11.005Duret, B., Reveillon, J., Menard, T., & Demoulin, F. X. (2013). Improving primary atomization modeling through DNS of two-phase flows. International Journal of Multiphase Flow, 55, 130-137. doi:10.1016/j.ijmultiphaseflow.2013.05.004Gimeno, J., Bracho, G., Martí-Aldaraví, P., & Peraza, J. E. (2016). Experimental study of the injection conditions influence over n-dodecane and diesel sprays with two ECN single-hole nozzles. Part I: Inert atmosphere. Energy Conversion and Management, 126, 1146-1156. doi:10.1016/j.enconman.2016.07.077Kastengren, A., Ilavsky, J., Viera, J. P., Payri, R., Duke, D. J., Swantek, A., … Powell, C. F. (2017). Measurements of droplet size in shear-driven atomization using ultra-small angle x-ray scattering. International Journal of Multiphase Flow, 92, 131-139. doi:10.1016/j.ijmultiphaseflow.2017.03.005Kastengren, A. L., Tilocco, F. Z., Powell, C. F., Manin, J., Pickett, L. M., Payri, R., & Bazyn, T. (2012). ENGINE COMBUSTION NETWORK (ECN): MEASUREMENTS OF NOZZLE GEOMETRY AND HYDRAULIC BEHAVIOR. Atomization and Sprays, 22(12), 1011-1052. doi:10.1615/atomizspr.2013006309Matusik, K. E., Duke, D. J., Kastengren, A. L., Sovis, N., Swantek, A. B., & Powell, C. F. (2017). High-resolution X-ray tomography of Engine Combustion Network diesel injectors. International Journal of Engine Research, 19(9), 963-976. doi:10.1177/1468087417736985Payri, R., Gimeno, J., Cuisano, J., & Arco, J. (2016). Hydraulic characterization of diesel engine single-hole injectors. Fuel, 180, 357-366. doi:10.1016/j.fuel.2016.03.083Naber, J., & Siebers, D. L. (1996). Effects of Gas Density and Vaporization on Penetration and Dispersion of Diesel Sprays. SAE Technical Paper Series. doi:10.4271/960034Pope, S. B. (1978). An explanation of the turbulent round-jet/plane-jet anomaly. AIAA Journal, 16(3), 279-281. doi:10.2514/3.7521Battistoni, M., Magnotti, G. M., Genzale, C. L., Arienti, M., Matusik, K. E., Duke, D. J., … Marti-Aldaravi, P. (2018). Experimental and Computational Investigation of Subcritical Near-Nozzle Spray Structure and Primary Atomization in the Engine Combustion Network Spray D. 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Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

The flow inside a purpose built enlarged single-orifice nozzle replica is quantified using time-averaged X-ray micro-computed tomography (micro-CT) and high-speed shadowgraphy. Results have been obtained at Reynolds and cavitation numbers similar to those of real-size injectors. Good agreement for the cavitation extent inside the orifice is found between the micro-CT and the corresponding temporal mean 2D cavitation image, as captured by the high-speed camera. However, the internal 3D structure of the developing cavitation cloud reveals a hollow vapour cloud ring formed at the hole entrance and extending only at the lower part of the hole due to the asymmetric flow entry. Moreover, the cavitation volume fraction exhibits a significant gradient along the orifice volume. The cavitation number and the needle valve lift seem to be the most influential operating parameters, while the Reynolds number seems to have only small effect for the range of values tested. Overall, the study demonstrates that use of micro-CT can be a reliable tool for cavitation in nozzle orifices operating under nominal steady-state conditions

Experimental and Computational Investigation of Subcritical Near-Nozzle Spray Structure and Primary Atomization in the Engine Combustion Network Spray D

[EN] In order to improve understanding of the primary atomization process for diesel-like sprays, a collaborative experimental and computational study was focused on the near-nozzle spray structure for the Engine Combustion Network (ECN) Spray D single-hole injector. These results were presented at the 5th Workshop of the ECN in Detroit, Michigan. Application of x-ray diagnostics to the Spray D standard cold condition enabled quantification of distributions of mass, phase interfacial area, and droplet size in the near-nozzle region from 0.1 to 14 mm from the nozzle exit. Using these data, several modeling frameworks, from Lagrangian-Eulerian to Eulerian-Eulerian and from Reynolds-Averaged Navier-Stokes (RANS) to Direct Numerical Simulation (DNS), were assessed in their ability to capture and explain experimentally observed spray details. Due to its computational efficiency, the Lagrangian-Eulerian approach was able to provide spray predictions across a broad range of conditions. In general, this "engineering-level" simulation was able to reproduce the details of the droplet size distribution throughout the spray after calibration of the spray breakup model constants against the experimental data. Complementary to this approach, higher-fidelity modeling techniques were able to provide detailed insight into the experimental trends. For example, interface-capturing multiphase simulations were able to capture the experimentally observed bimodal behavior in the transverse interfacial area distributions in the near-nozzle region. Further analysis of the spray predictions suggests that peaks in the interfacial area distribution may coincide with regions of finely atomized droplets, whereas local minima may coincide with regions of continuous liquid structures. The results from this study highlight the potential of x-ray diagnostics to reveal salient details of the near-nozzle spray structure and to guide improvements to existing primary atomization modeling approaches.Battistoni, M.; Magnotti, GM.; Genzale, CL.; Arienti, M.; Matusik, KE.; Duke, DJ.; Giraldo-Valderrama, JS.... (2018). Experimental and Computational Investigation of Subcritical Near-Nozzle Spray Structure and Primary Atomization in the Engine Combustion Network Spray D. SAE International Journal of Fuel and Lubricants. 11(4):337-352. https://doi.org/10.4271/2018-01-0277S33735211

Quantitative analysis of dribble volumes and rates using three-dimensional reconstruction of X-ray and diffused back-illumination images of diesel sprays

[EN] Post-injection fuel dribble is known to lead to incomplete atomisation and combustion due to the release of slow-moving, and often surface-bound, liquid fuel after the end of injection. This can have a negative effect on engine emissions, performance and injector durability. To better quantify this phenomenon, we developed an image-processing approach to measure the volume of ligaments produced during the end of injection. We applied our processing approach to an Engine Combustion Network 'Spray B' 3-hole injector, using datasets from 220 injections generated by different research groups, to decouple the effect of gas temperature and pressure on the fuel dribble process. High-speed X-ray phase-contrast images obtained at room temperature conditions (297 K) at the Advanced Photon Source at Argonne National Laboratory, together with diffused back-illumination images captured at a wide range of temperature conditions (293-900 K) by CMT Motores Termicos were analysed and compared quantitatively. We found a good agreement between image sets obtained by Argonne National Laboratory and CMT Motores Termicos using different imaging techniques. The maximum dribble volume within the field of view of the imaging system and the mean rate of fuel dribble were considered as characteristic parameters of the fuel dribble process. Analysis showed that the absolute mean dribble rate increases with temperature when injection pressure is higher than 1000 bar and slightly decreases at high injection pressures (>500 bar) when temperature is close to 293 K. Larger maximum volumes of the fuel dribble were observed at lower gas temperatures (similar to 473 K) and low gas pressures (<30 bar), with a slight dependence on injection pressure.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The image processing research was supported by the United Kingdom's Engineering and Physical Science Research Council (Grants EP/K020528/1 and EP/M009424/1) and BP Formulated Products Technology. The X-ray measurements were performed at the Advanced Photon Source at Argonne National Laboratory. Use of the Advanced Photon Source (APS) is supported by the U.S. Department of Energy (DOE) under Contract No. DEAC02-06CH11357. The X-ray component of this research was partially funded by DOE's Vehicle Technologies Program, Office of Energy Efficiency and Renewable Energy.Sechenyh, V.; Duke, DJ.; Swantek, AB.; Matusik, KE.; Kastengren, AL.; Powell, CF.; Viera, A.... (2020). Quantitative analysis of dribble volumes and rates using three-dimensional reconstruction of X-ray and diffused back-illumination images of diesel sprays. International Journal of Engine Research. 21(1):43-54. https://doi.org/10.1177/1468087419860955S4354211Örley, F., Hickel, S., Schmidt, S. J., & Adams, N. A. (2016). Large-Eddy Simulation of turbulent, cavitating fuel flow inside a 9-hole Diesel injector including needle movement. International Journal of Engine Research, 18(3), 195-211. doi:10.1177/1468087416643901Benajes, J., Novella, R., De Lima, D., & Tribotté, P. (2014). Analysis of combustion concepts in a newly designed two-stroke high-speed direct injection compression ignition engine. International Journal of Engine Research, 16(1), 52-67. doi:10.1177/1468087414562867Moon, S., Huang, W., Li, Z., & Wang, J. (2016). End-of-injection fuel dribble of multi-hole diesel injector: Comprehensive investigation of phenomenon and discussion on control strategy. Applied Energy, 179, 7-16. doi:10.1016/j.apenergy.2016.06.116Kook, S., Pickett, L. M., & Musculus, M. P. B. (2009). Influence of Diesel Injection Parameters on End-of-Injection Liquid Length Recession. SAE International Journal of Engines, 2(1), 1194-1210. doi:10.4271/2009-01-1356Kastengren, A., Powell, C. F., Tilocco, F. Z., Liu, Z., Moon, S., Zhang, X., & Gao, J. (2012). End-of-Injection Behavior of Diesel Sprays Measured With X-Ray Radiography. Journal of Engineering for Gas Turbines and Power, 134(9). doi:10.1115/1.4006981Manin, J., Bardi, M., Pickett, L. M., & Payri, R. (2016). Boundary condition and fuel composition effects on injection processes of high-pressure sprays at the microscopic level. International Journal of Multiphase Flow, 83, 267-278. doi:10.1016/j.ijmultiphaseflow.2015.12.001Payri, R., Bracho, G., Marti-Aldaravi, P., & Viera, A. (2017). NEAR FIELD VISUALIZATION OF DIESEL SPRAY FOR DIFFERENT NOZZLE INCLINATION ANGLES IN NON-VAPORIZING CONDITIONS. Atomization and Sprays, 27(3), 251-267. doi:10.1615/atomizspr.2017017949Gimeno, J., Martí-Aldaraví, P., Carreres, M., & Peraza, J. E. (2018). Effect of the nozzle holder on injected fuel temperature for experimental test rigs and its influence on diesel sprays. International Journal of Engine Research, 19(3), 374-389. doi:10.1177/1468087417751531Payri, R., Salvador, F. J., Manin, J., & Viera, A. (2016). Diesel ignition delay and lift-off length through different methodologies using a multi-hole injector. Applied Energy, 162, 541-550. doi:10.1016/j.apenergy.2015.10.118Duke, D. J., Matusik, K. E., Kastengren, A. L., Swantek, A. B., Sovis, N., Payri, R., … Powell, C. F. (2017). X-ray radiography of cavitation in a beryllium alloy nozzle. International Journal of Engine Research, 18(1-2), 39-50. doi:10.1177/1468087416685965Duke, D., Swantek, A., Kastengren, A., Fezzaa, K., & Powell, C. (2015). Recent Developments in X-ray Diagnostics for Cavitation. 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Comparison of different techniques for characterizing the diesel injector internal dimensions

[EN] The geometry of certain parts of diesel injectors is key to the injection, atomization and fuel-air mixing phenomena. Small variations on the geometrical parameters may have a strong influence on the aforementioned processes. Thus, OEMs need to assess their manufacturing tolerances, whereas researchers in the field (both experimentalists and modelers) rely on the accuracy of a certain metrology technique for their studies. In the current paper, an investigation of the capability of different experimental techniques to determine the geometry of a modern diesel fuel injector has been performed. For this purpose, three main elements of the injector have been evaluated: the control volume inlet and outlet orifices, together with the nozzle orifices. While the direct observation of the samples through an optical microscope is only possible for the simplest pieces, both Computed Tomography Scanning and the visualization of silicone molds technique have proven their ability to characterize the most complex internal shapes corresponding to the internal injector elements. Indeed, results indicate that the differences observed among these methodologies for the determination of the control volume inlet orifice diameter and the nozzle orifice dimensions are smaller than the uncertainties related to the experimental techniques, showing that they are both equally accurate. This implies that the choice of a given technique for the particular application of determining the geometry of diesel injectors can be done on the basis of availability, intrusion and costs, rather than on its accuracy.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.Salvador, FJ.; Gimeno, J.; De La Morena, J.; Carreres, M. (2018). Comparison of different techniques for characterizing the diesel injector internal dimensions. Experimental Techniques. 42(5):467-472. https://doi.org/10.1007/s40799-018-0246-1S467472425Mobasheri R, Peng Z, Mostafa S (2012) Analysis the effect of advanced injection strategies on engine performance and pollutant emissions in a heavy duty DI-diesel engine by CFD modeling. 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Illustrating the effect of viscoelastic additives on cavitation and turbulence with X-ray imaging

The effect of viscoelastic additives on the topology and dynamics of the two-phase flow arising within an axisymmetric orifice with a flow path constriction along its main axis has been investigated employing high-flux synchrotron radiation. X-ray Phase Contrast Imaging (XPCI) has been conducted to visualise the cavitating flow of different types of diesel fuel within the orifice. An additised blend containing Quaternary Ammonium Salt (QAS) additives with a concentration of 500 ppm has been comparatively examined against a pure (base) diesel compound. A high-flux, 12 keV X-ray beam has been utilised to obtain time resolved radiographs depicting the vapour extent within the orifice from two views (side and top) with reference to its main axis. Different test cases have been examined for both fuel types and for a range of flow conditions characterised by Reynolds number of 35500 and cavitation numbers (CN) lying in the range 3.0–7.7. It has been established that the behaviour of viscoelastic micelles in the regions of shear flow is not consistent depending on the cavitation regimes encountered. Namely, viscoelastic effects enhance vortical (string) cavitation, whereas hinder cloud cavitation. Furthermore, the use of additised fuel has been demonstrated to suppress the level of turbulence within the orifice