Comparative study of the internal flow in diesel injection nozzles at cavitating conditions at different needle lifts with steady and transient simulations approaches

[EN] The motion of the needle during the injection process of a diesel injector has a marked influence on the internal flow, the fuel characteristics at the nozzle exit, the spray pattern and the fuel-air mixing process. The current paper is focused on the computational study of the internal flow and cavitation phenomena during the injection process, with inclusion of the opening where the needle is working at partial lifts. This study has been performed with a homogeneous equilibrium model (OpenFOAM) customized by the authors to simulate the real motion of the needle. The first part of the study covers the analysis of the whole injection process with a moving mesh using the boundary conditions provided by a one-dimensional (1D) model of the injector created in AMESim. This 1D model has offered the possibility of reproducing the movement of the needle with real lift law and real injection pressure evolution during the injection. Thus, it has been possible to compare the injection rate profiles provided by OpenFOAM against those obtained both in AMESim and experimentally. The second part compares the differences in mass flow, momentum flux, effective velocity and cavitation appearance between steady (fixed lifts) and transient (moving mesh) simulations. The aim of this comparison is to establish the differences between these two approaches. On the one hand is a more realistic approach in its use of transient simulations of the injection process and where the needle movement is taken into account. On the other hand, is the use of steady simulations at partial needle lifts. This analysis could be of interest to researchers devoted to the study of the diesel injection process since it could help to delimit the uncertainties involved in using the second approach which is more easily carried out, versus the first which is supposed to provide more realistic results.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was partly sponsored by the 'Ministerio de Economa 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.; De La Morena, J.; Crialesi Esposito, M.; Martínez López, J. (2018). Comparative study of the internal flow in diesel injection nozzles at cavitating conditions at different needle lifts with steady and transient simulations approaches. Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering. 232(8):1060-1078. https://doi.org/10.1177/0954407017725672S10601078232

Study of the influence of the needle lift on the internal flow and cavitationphenomenon in diesel injector nozzles by CFD using RANS methods

It is well known that cavitation phenomenon in diesel injector nozzles has a strong influence on the internal flow during the injection process and spray development. However, its influence on the flow during needle opening and closing remains still unclear due to the huge difficulties related to performing experiments at partial needle lifts. In this paper, an extended computational study has been performed in a multi-hole nozzle modeling 10 different fixed needle lifts. The internal flow has been modeled with a continuum nozzle flow model that considers the cavitating flow as a homogeneous mixture of liquid and vapour. Due to high Reynolds numbers, turbulence effects have been taken into account by RANS methods using a RNG k e model. Firstly, the code has been validated against experimental data at full needle lift conditions in terms of mass flow, momentum flux and effective velocity, showing a fairly good agreement with experimental results. Once the code has been validated, it has been possible to study in depth the internal nozzle flow and its characteristics at the outlet at different partial needle lifts. Nevertheless, not only the main flow features have been explained, but also the cavitation appearance and the turbulence development, which present huge differences between the different needle lifts simulated.The authors wish to acknowledge the Generalitat Valenciana for the financial support through the project GVA PROMETEO CMT 2010 (reference code: GR001/2009/00167539).Salvador, FJ.; Martínez López, J.; Caballer Fernández, M.; Alfonso Laguna, CD. (2013). Study of the influence of the needle lift on the internal flow and cavitationphenomenon in diesel injector nozzles by CFD using RANS methods. Energy Conversion and Management. 66:246-256. https://doi.org/10.1016/j.enconman.2012.10.0112462566

Comparison of microsac and VCO diesel injector nozzles in terms of internal nozzle flow characteristics

A computational study focused on the inner nozzle flow and cavitation phenomena has been reported in this paper in order to investigate the two most common types of diesel injector nozzles at the present: microsac and valve covered orifice (VCO). The geometrical differences among both types of nozzles are mainly located at the needle seat, upstream of the discharge orifices. In the case of microsac nozzles there is a small volume upstream of the discharge orifices which is not present in VCO nozzles. Due to these geometrical differences among both type of nozzles, differences in the inner flow and the cavitation development have been found and analysed in this research. For the study, two cylindrical nozzles with six orifices and the same outlet diameter have been experimentally characterized in terms of mass flow rate. These measurements have been used to validate the CFD results obtained with the code OpenFOAM used for the analysis of the internal nozzle flow. For the simulations, two meshes that reproduce the microsac and VCO nozzles seat geometry while keeping the same geometry at the orifices have been built. The simulations have been carried out with a code previously validated and able to simulate cavitation phenomena using a homogeneous equilibrium model (HEM) and with RANS approach for the turbulence modelling (RNG k-epsilon). For the computational study, three injection pressures and different geometries simulating different needle lifts have been used. The comparison among nozzles has been made in terms of mass flow, momentum flux and effective velocity and in terms of other non-dimensional parameters which are useful for describing the inner nozzle flow: discharge coefficient (C-d), area coefficient (C-alpha) and velocity coefficient (C-v). The analysis performed by studying and comparing the particularities of the flow in each nozzle has been useful in order to explain the experimental differences found in terms of mass flow rate and critical cavitation conditions. One of the main conclusions of this study is the higher influence of the needle on the mass flow, momentum and injection velocity results for the VCO nozzle as compared to the microsac one. Hence, whereas in the first one these variables scale with the needle lift value, in the second one there is an intermediate needle lift from which they stop being influenced by the presence of the needle. Furthermore, the study has also revealed important differences in the proneness to produce cavitation and its morphology. For the VCO nozzle, cavitation phenomenon occurs only in the upper part of the orifice inlet. However, for the microsac nozzle cavitation appears both at the upper and the lower part of the nozzle orifice entrance.This work was partly sponsored by "Ministerio de Economia y Competitividad" in the frame of the project "Comprension de la influencia de combustibles no convencionales en el proceso de inyeccion y combustion tipo diesel", Reference TRA2012-36932. This support is gratefully acknowledged by the authors.Salvador Rubio, FJ.; Carreres Talens, M.; Jaramillo Císcar, D.; Martínez López, J. (2015). Comparison of microsac and VCO diesel injector nozzles in terms of internal nozzle flow characteristics. Energy Conversion and Management. 103:284-299. https://doi.org/10.1016/j.enconman.2015.05.062S28429910

Using one-dimensional modeling to analyse the influence of the use of biodiesels on the dynamic behavior of solenoid-operated injectors in common rail systems: Detailed injection system model

A combined experimental and computational investigation has been performed in order to evaluate the influence of physical properties of biodiesel on the injection process in a common-direct injection system with second generation solenoid injectors. For that purpose, after a complete characterization of the system, which involved mechanical and hydraulic characterization, a one-dimensional model has been obtained and extensively validated. Simulations have then been performed with a standard diesel and a 100% rape methyl ester (RME) biodiesel which allowed a comparison and analysis of the dynamic response of the injector to be done. Different injection strategies involving main injection and main plus post-injection have been used to explore the impact of the use of biodiesel on the performance and stability of solenoid injectors. As far as the dynamic response of the injector is concerned, the results obtained have clearly shown that the use of biodiesel affects the dynamic response of the needle, especially at low injection pressures. The behavior of the system under multi-injection strategies (main plus post-injection) has been also evaluated determining for different operating conditions (injection pressures and backpressures) the minimum dwell time between injections to assure a stable behavior in the injection process (mass flow rate). Important differences have been found between biodiesel and standard diesel in this critical parameter at low injection pressures, becoming less important at high injection pressure. Finally, a modification on the injector hardware has been proposed in order to compensate these differences.This research has been funded by "Ministerio de Ciencia e Innovacion" in the frame of the project "Estudio teorico experimental de la influencia del combustible sobre la cavitacion y el desarrollo del chorro evaporative (FlexiFuel)", Reference TRA2010-17564.Payri Marín, R.; Salvador Rubio, FJ.; Marti Aldaravi, P.; Martínez López, J. (2012). Using one-dimensional modeling to analyse the influence of the use of biodiesels on the dynamic behavior of solenoid-operated injectors in common rail systems: Detailed injection system model. Energy Conversion and Management. 54(1):90-99. https://doi.org/10.1016/j.enconman.2011.10.004S909954

Influence of diesel fuel viscosity on cavitating throttle flow simulations at erosive operation conditions

This work investigates the effect of liquid fuel viscosity, as specific by the European Committee for Standardization 2009 (European Norm) for all automotive fuels, on the predicted cavitating flow in micro-orifice flows. The wide range of viscosities allowed, leads to a significant variation of orifice nominal Reynolds numbers for the same pressure drop across the orifice. This in turn, is found to affect flow detachment, formation of large-scale vortices and micro-scale turbulence. A pressure-based compressible solver is used on the filtered Navier-Stokes equations using the multi-fluid approach; separate velocity fields are solved for each phase that share a common pressure. The rates of evaporation and condensation are evaluated with a simplified model based on the Rayleigh-Plesset equation; the Coherent Structure Model is adopted for the sub-grid scales modeling in the momentum conservation equation. The test case simulated is a well reported benchmark throttled flow channel geometry, referred to as ’I-channel’; this has allowed for easy optical access for which flow visualization and LIF measurements allowed for validation of the developed methodology. Despite its simplicity, the Ichannel geometry is found to reproduce the most characteristic flow features prevailing in high-speed flows realized in cavitating fuel injectors. Following, the effect of liquid viscosity on integral mass flow, velocity profiles, vapor cavities distribution and pressure peaks indicating locations prone to cavitation erosion are reported

Large-eddy simulation analysis of the influence of the needle lift on the cavitation in diesel injector nozzles

The cavitation phenomenon has a strong influence on the internal flow and spray development in diesel injector nozzles. Despite its importance, there are many aspects which still remain unclear, especially for partial needle lifts when the injector is in the opening and closing phases. For that reason, the current paper is focused on the influence of the needle lift on the internal flow in a diesel nozzle. This study was carried out with three-dimensional simulations at a high injection pressure (160 MPa) using a homogeneous equilibrium model implemented in OpenFOAM to model the cavitation phenomenon. The nozzle was simulated with large-eddy simulation methods at six different needle lifts (10 mm, 30 mm, 50 mm, 75 mm, 100 mm and 250 mm), providing relevant information about the evolution of the internal flow, the turbulence development (the vorticity, the turbulence–cavitation interaction and the turbulent structures) and the flow characteristics in the nozzle outlet (the mass flow, the momentum flux and the effective velocity) with the needle position.Desantes Fernández, JM.; Salvador Rubio, FJ.; Carreres Talens, M.; Martínez López, J. (2015). Large-eddy simulation analysis of the influence of the needle lift on the cavitation in diesel injector nozzles. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering. 229(4):407-423. doi:10.1177/0954407014542627S4074232294Faeth, G. ., Hsiang, L.-P., & Wu, P.-K. (1995). Structure and breakup properties of sprays. International Journal of Multiphase Flow, 21, 99-127. doi:10.1016/0301-9322(95)00059-7Park, S. H., Suh, H. K., & Lee, C. S. (2009). Effect of Bioethanol−Biodiesel Blending Ratio on Fuel Spray Behavior and Atomization Characteristics. Energy & Fuels, 23(8), 4092-4098. doi:10.1021/ef900068aPAYRI, 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.2004.10.009Suh, H. K., & Lee, C. S. (2008). Effect of cavitation in nozzle orifice on the diesel fuel atomization characteristics. International Journal of Heat and Fluid Flow, 29(4), 1001-1009. doi:10.1016/j.ijheatfluidflow.2008.03.014Payri, 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.2008.10.009Park, S. H., Kim, S. H., & Lee, C. S. (2009). Mixing Stability and Spray Behavior Characteristics of Diesel−Ethanol−Methyl Ester Blended Fuels in a Common-Rail Diesel Injection System. Energy & Fuels, 23(10), 5228-5235. doi:10.1021/ef9004847Desantes, J. M., Payri, R., Salvador, F. J., & Gil, A. (2006). Development and validation of a theoretical model for diesel spray penetration. Fuel, 85(7-8), 910-917. doi:10.1016/j.fuel.2005.10.023Desantes, J. M., Payri, R., Garcia, J. M., & Salvador, F. J. (2007). A contribution to the understanding of isothermal diesel spray dynamics. Fuel, 86(7-8), 1093-1101. doi:10.1016/j.fuel.2006.10.011Badock, C., Wirth, R., Fath, A., & Leipertz, A. (1999). Investigation of cavitation in real size diesel injection nozzles. International Journal of Heat and Fluid Flow, 20(5), 538-544. doi:10.1016/s0142-727x(99)00043-0Som, S., Aggarwal, S. K., El-Hannouny, E. M., & Longman, D. E. (2010). Investigation of Nozzle Flow and Cavitation Characteristics in a Diesel Injector. Journal of Engineering for Gas Turbines and Power, 132(4). doi:10.1115/1.3203146Macian, V., Payri, R., Margot, X., & Salvador, F. J. (2003). A CFD ANALYSIS OF THE INFLUENCE OF DIESEL NOZZLE GEOMETRY ON THE INCEPTION OF CAVITATION. Atomization and Sprays, 13(5-6), 579-604. doi:10.1615/atomizspr.v13.i56.80Alajbegovic, A., Meister, G., Greif, D., & Basara, B. (2002). Three phase cavitating flows in high-pressure swirl injectors. Experimental Thermal and Fluid Science, 26(6-7), 677-681. doi:10.1016/s0894-1777(02)00179-6Unverdi, S. O., & Tryggvason, G. (1992). A front-tracking method for viscous, incompressible, multi-fluid flows. Journal of Computational Physics, 100(1), 25-37. doi:10.1016/0021-9991(92)90307-kBrackbill, J. ., Kothe, D. ., & Zemach, C. (1992). A continuum method for modeling surface tension. Journal of Computational Physics, 100(2), 335-354. doi:10.1016/0021-9991(92)90240-yPlesset M, Devine R. Effect of exposure time on cavitation damage. Report (Office of Naval Research Contract Nonr-220(28)), California Institute of Technology, Pasadena, California, USA, 1965.Chen, Y., & Heister, S. D. (1996). MODELING CAVITATING FLOWS IN DIESEL INJECTORS. Atomization and Sprays, 6(6), 709-726. doi:10.1615/atomizspr.v6.i6.50Vortmann, C., Schnerr, G. H., & Seelecke, S. (2003). Thermodynamic modeling and simulation of cavitating nozzle flow. International Journal of Heat and Fluid Flow, 24(5), 774-783. doi:10.1016/s0142-727x(03)00003-1Echouchene, F., Belmabrouk, H., Le Penven, L., & Buffat, M. (2011). Numerical simulation of wall roughness effects in cavitating flow. International Journal of Heat and Fluid Flow, 32(5), 1068-1075. doi:10.1016/j.ijheatfluidflow.2011.05.010Salvador, F. J., Romero, J.-V., Roselló, M.-D., & Martínez-López, J. (2010). Validation of a code for modeling cavitation phenomena in Diesel injector nozzles. Mathematical and Computer Modelling, 52(7-8), 1123-1132. doi:10.1016/j.mcm.2010.02.027Salvador, F. J., Hoyas, S., Novella, R., & Martínez-López, J. (2011). Numerical simulation and extended validation of two-phase compressible flow in diesel injector nozzles. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 225(4), 545-563. doi:10.1177/09544070jauto1569Payri, 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.2012.01.005Salvador, F. J., Martínez-López, J., Caballer, M., & De Alfonso, C. (2013). Study of the influence of the needle lift on the internal flow and cavitation phenomenon in diesel injector nozzles by CFD using RANS methods. Energy Conversion and Management, 66, 246-256. doi:10.1016/j.enconman.2012.10.011Salvador, F. J., Martínez-López, J., Romero, J.-V., & Roselló, M.-D. (2013). Computational study of the cavitation phenomenon and its interaction with the turbulence developed in diesel injector nozzles by Large Eddy Simulation (LES). Mathematical and Computer Modelling, 57(7-8), 1656-1662. doi:10.1016/j.mcm.2011.10.050Piomelli, U. (1999). Large-eddy simulation: achievements and challenges. Progress in Aerospace Sciences, 35(4), 335-362. doi:10.1016/s0376-0421(98)00014-1Launder, B. E., & Spalding, D. B. (1974). The numerical computation of turbulent flows. Computer Methods in Applied Mechanics and Engineering, 3(2), 269-289. doi:10.1016/0045-7825(74)90029-2Payri, F., Bermúdez, V., Payri, R., & Salvador, F. J. (2004). The influence of cavitation on the internal flow and the spray characteristics in diesel injection nozzles. Fuel, 83(4-5), 419-431. doi:10.1016/j.fuel.2003.09.010Payri, R., Salvador, F. J., Gimeno, J., & de la Morena, J. (2009). Study of cavitation phenomena based on a technique for visualizing bubbles in a liquid pressurized chamber. International Journal of Heat and Fluid Flow, 30(4), 768-777. doi:10.1016/j.ijheatfluidflow.2009.03.011Martínez López, J. (s. f.). Estudio computacional de la influencia del levantamiento de aguja sobre el flujo interno y el fenómeno de la cavitación en toberas de inyección diésel. doi:10.4995/thesis/10251/29291Tabor, G. R., & Baba-Ahmadi, M. H. (2010). Inlet conditions for large eddy simulation: A review. Computers & Fluids, 39(4), 553-567. doi:10.1016/j.compfluid.2009.10.007Payri, R., Gimeno, J., Marti-Aldaravi, P., & Bracho, G. (2013). Study of the influence of the inlet boundary conditions in a LES simulation of internal flow in a diesel injector. Mathematical and Computer Modelling, 57(7-8), 1709-1715. doi:10.1016/j.mcm.2011.11.019de Villiers E. The potential of large eddy simulation for the modeling of wall bounded flows. PhD Thesis, Imperial College of Science, Technology and Medicine, London, UK, 2006.Lee, J. W., Min, K. D., Kang, K. Y., Bae, C. S., Giannadakis, E., Gavaises, M., & Arcoumanis, C. (2006). Effect of piezo-driven and solenoid-driven needle opening of common-rail diesel injectors on internal nozzle flow and spray development. International Journal of Engine Research, 7(6), 489-502. doi:10.1243/14680874jer00806Desantes, J. M., Payri, R., Salvador, F. J., & De la Morena, J. (2010). Influence of cavitation phenomenon on primary break-up and spray behavior at stationary conditions. Fuel, 89(10), 3033-3041. doi:10.1016/j.fuel.2010.06.004Lesieur, M., Métais, O., & Comte, P. (2005). Large-Eddy Simulations of Turbulence. doi:10.1017/cbo9780511755507Sagaut, P. (2001). Large Eddy Simulation for Incompressible Flows. Scientific Computation. doi:10.1007/978-3-662-04416-

Numerical Simulation of Diesel Injector Internal Flow Field

AbstractIn Diesel engines, fuel-air mixing process and spray evolution drastically affect combustion efficiency and pollutant formation. Within this context, a detailed study of the effects of injector geometry and internal flow is of great importance to understand the effects of turbulence and cavitation on the liquid jet atomization process. To this end, both numerical and experimental tools are widely employed.Objective of this work is to simulate the complex flow behavior inside the injector nozzle taking the most relevant physical phenomena into account. CFD simulations were carried out using a compressible solver with phase change modeling available in the OpenFOAM framework. In particular, cavitation was modeled by using an homogeneous equilibrium model based on a barotropic equation of state while the RANS k-ω SST model was used for turbulence. Experiments performed at Kobe University (Japan) on simplified nozzle geometries were used to validate the proposed approach in terms of velocity and vapor distributions. A rather good agreement between computed and experimental data was achieved in terms cavitation length, mass flow, momentum flux making possible to apply the proposed methodology also to real injector configurations in the near future

Computational study of the cavitation phenomenon and its interaction with the turbulence developed in diesel injector nozzles by Large Eddy Simulation (LES)

Firstly, the code has been validated at real operating diesel engine conditions with experimental data in terms of mass flow, momentum flux and effective velocity, showing that the model is able to predict with a high level of confidence the behavior of the internal flow at cavitating conditions. Once validated, the code has allowed to study in depth the turbulence developed in the discharge orifices and its interaction with cavitation phenomenon. (C) 2011 Elsevier Ltd. All rights reserved.This work was partly sponsored by "Vicerrectorado de Investigacion, Desarrollo e Innovacion'' of the "Universitat Politecnica de Valencia'' in the frame of the project "Estudio numerico de la cavitacion en toberas de inyeccion Diesel mediante Grid Computing (Cavigrid)'', reference No. 2597 and by "Ministerio de Ciencia e Innovacion'' in the frame of the project "Estudio teorico-experimental sobre la influencia del tipo de combustible en los procesos de atomizacion y evaporacion del chorro Diesel (PROFUEL)'', reference TRA2011-26293. This support is gratefully acknowledged by the authors.Salvador Rubio, FJ.; Martínez López, J.; Romero Bauset, JV.; Roselló Ferragud, MD. (2013). Computational study of the cavitation phenomenon and its interaction with the turbulence developed in diesel injector nozzles by Large Eddy Simulation (LES). Mathematical and Computer Modelling. 57(7-8):1656-1662. https://doi.org/10.1016/j.mcm.2011.10.050S16561662577-

Analysis of the combined effect of hydrogrinding process and inclination angle on hydraulic performance of diesel injection nozzles

A computational study to investigate the influence of the orifices inclination and the rounding radius at the orifice inlet (consequence of the hydro-erosive grinding process applied after the orifices machining) over the internal nozzle flow is performed in this paper. The study starts with the analysis of experimental results where the mass flow and momentum flux of two nozzles with very different values of these two variables are compared. This analysis shows relatively small differences in terms of mass flow and momentum flux, since the higher losses associated to the higher deflection of the streamlines with a higher inclination of the orifices are counteracted by the higher rounding radius, which favors the flow entrance to the orifice. To explain this experimental outcome, an extensive computational study involving nine geometries that combine different inclination angles and rounding radius is conducted, in order to quantify the influence of both parameters on the flow separately, as well as to assess the potential of their combination. These geometries are compared in terms of discharge coefficient, critical cavitation conditions and effective injection velocity, among others. Results show differences up to 15% in terms of mass flow rate and 8% for the effective injection velocity among the two extreme cases (lowest inclination and highest hydro-erosion level versus the nozzle with the highest inclination and lowest hydro-erosion level). Given the importance of these phenomena on the subsequent mixing and combustion processes, the results hereby presented are of interest for Diesel engines injectors and combustion chambers designers.This work was partly sponsored by "Ministerio de Economia y Competitividad" in the frame of the project "Comprension de la influencia de combustibles no convencionales en el proceso de inyeccion y combustion tipo diesel", Reference TRA2012-36932. The equipment used in this work has been partially supported by FEDER project funds "Dotacion de infraestructuras cientifico tecnicas para el Centro Integral de Mejora Energetica y Medioambiental de Sistemas de Transporte (CiMeT), (FEDER-ICTS-2012-06)", in the frame of the operation program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain. This support is gratefully acknowledged by the authors.Salvador Rubio, FJ.; Carreres Talens, M.; Jaramillo Císcar, D.; Martínez López, J. (2015). Analysis of the combined effect of hydrogrinding process and inclination angle on hydraulic performance of diesel injection nozzles. Energy Conversion and Management. 105:1352-1365. https://doi.org/10.1016/j.enconman.2015.08.035S1352136510

A CFD STUDY OF CAVITATION IN REAL SIZE DIESEL INJECTORS

In Diesel engines, the internal flow characteristics in the fuel injection nozzles, such as the turbulence level and distribution, the cavitation pattern and the velocity profile affect significantly the air-fuel mixture in the spray and subsequently the combustion process. Since the possibility to observe experimentally and measure the flow inside real size Diesel injectors is very limited, Computational Fluid Dynamics (CFD) calculations are generally used to obtain the relevant information. The work presented within this thesis is focused on the study of cavitation in real size automotive injectors by using a commercial CFD code. It is divided in three major phases, each corresponding to a different complementary objective. The first objective of the current work is to assess the ability of the cavitation model included in the CFD code to predict cavitating flow conditions. For this, the model is validated for an injector-like study case defined in the literature, and for which experimental data is available in different operating conditions, before and after the start of cavitation. Preliminary studies are performed to analyze the effects on the solution obtained of various numerical parameters of the cavitation model itself and of the solver, and to determine the adequate setup of the model. It may be concluded that overall the cavitation model is able to predict the onset and development of cavitation accurately. Indeed, there is satisfactory agreement between the experimental data of injection rate and choked flow conditions and the corresponding numerical solution.This study serves as the basis for the physical and numerical understanding of the problem. Next, using the model configuration obtained from the previous study, unsteady flow calculations are performed for real-size single and multi-hole sac type Diesel injectors, each one with two types of nozzles, tapered and cylindrical. The objective is to validate the model with real automotive cases and to ununderstand in what way some physical factors, such as geometry, operating conditions and needle position affect the inception of cavitation and its development in the nozzle holes. These calculations are made at full needle lift and for various values of injection pressure and back-pressure. The results obtained for injection rate, momentum flux and effective injection velocity at the exit of the nozzles are compared with available CMT-Motores Térmicos in-house experimental data. Also, the cavitation pattern inside the nozzle and its effect on the internal nozzle flow is analyzed. The model predicts with reasonable accuracy the effects of geometry and operating conditions.Patouna, S. (2012). A CFD STUDY OF CAVITATION IN REAL SIZE DIESEL INJECTORS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14723Palanci