[EN] In this paper, a one-dimensional computational model of the flow in a common-rail injector is used to compute local variations of fuel temperature (including the temperature change produced upon expansion across the nozzle) and analyse their effect on injector dynamics. These variations are accounted through the adiabatic flow hypothesis, assessed in a first part of the paper where the model features are also described. They imply variations in the fuel properties and the flow regime established across the injector internal restrictions driving the solenoid valve. An extensive validation of the model against experimental results is presented for a wide range of conditions. Multiple injection strategies are also explored, analysing the influence of the inlet fuel temperature and its variations on the mass injected by successive injections and the critical dwell time below which they cannot be separated. Results show significant changes in fuel temperature across some injector restrictions. These changes are greater the higher the rail pressure and lower the fuel temperature at the injector inlet. In the case of the flow across nozzle orifices, the fuel can be either heated or subcooled depending on the operating conditions, the heating being especially relevant for cold-start-like fuel temperatures at the inlet. Thermal effects also influence the injection rate and duration. This influence on injector dynamics is particularly accused in the injector of study due to its ballistic nature. In this regard, the time needed to effectively separate two successive injections is greater the higher the fuel temperature and the injection pressure. This work was partly sponsored by FEDER and the Spanish "Ministerio de Economia y Competitividad" in the frame of the project "Desarrollo de modelos de combustion y emisiones HPC para el analisis de plantas propulsivas de transporte sostenible (CHEST)", reference TRA2017-89139-C2-1-R-AR. On the other hand, the support given to Mr Mario Belmar by "Universitat Politecnica de Valencia" through the "FPI-Subprograma 2" grant within the "Programa de Apoyo para la Investigacion y Desarrollo (PAID-01-18)" is gratefully acknowledged by the authors. Payri, R.; Salvador, FJ.; Carreres, M.; Belmar-Gil, M. (2020). Thermal effects on the diesel injector performance through adiabatic 1D modelling. Part II: Model validation, results of the simulations and discussion. Fuel. 260:1-17. https://doi.org/10.1016/j.fuel.2019.115663 Gumus, M., Sayin, C., & Canakci, M. (2012). The impact of fuel injection pressure on the exhaust emissions of a direct injection diesel engine fueled with biodiesel–diesel fuel blends. Fuel, 95, 486-494. doi:10.1016/j.fuel.2011.11.020 Agarwal, A. K., Dhar, A., Gupta, J. G., Kim, W. I., Choi, K., Lee, C. S., & Park, S. (2015). Effect of fuel injection pressure and injection timing of Karanja biodiesel blends on fuel spray, engine performance, emissions and combustion characteristics. Energy Conversion and Management, 91, 302-314. doi:10.1016/j.enconman.2014.12.004 Zecca, A., & Chiari, L. (2010). Fossil-fuel constraints on global warming. Energy Policy, 38(1), 1-3. doi:10.1016/j.enpol.2009.06.068 Wang, J., Feng, L., Tang, X., Bentley, Y., & Höök, M. (2017). The implications of fossil fuel supply constraints on climate change projections: A supply-side analysis. Futures, 86, 58-72. doi:10.1016/j.futures.2016.04.007 Wang, X., Huang, Z., Zhang, W., Kuti, O. A., & Nishida, K. (2011). Effects of ultra-high injection pressure and micro-hole nozzle on flame structure and soot formation of impinging diesel spray. Applied Energy, 88(5), 1620-1628. doi:10.1016/j.apenergy.2010.11.035 Boccardo, G., Millo, F., Piano, A., Arnone, L., Manelli, S., Fagg, S., … Weber, J. (2019). Experimental investigation on a 3000 bar fuel injection system for a SCR-free non-road diesel engine. Fuel, 243, 342-351. doi:10.1016/j.fuel.2019.01.122 Mancaruso, E., Sequino, L., & Vaglieco, B. M. (2016). Analysis of the pilot injection running Common Rail strategies in a research diesel engine by means of infrared diagnostics and 1d model. Fuel, 178, 188-201. doi:10.1016/j.fuel.2016.03.066 Breda, S., D’Orrico, F., Berni, F., d’ Adamo, A., Fontanesi, S., Irimescu, A., & Merola, S. S. (2019). Experimental and numerical study on the adoption of split injection strategies to improve air-butanol mixture formation in a DISI optical engine. Fuel, 243, 104-124. doi:10.1016/j.fuel.2019.01.111 Wang, B., Pamminger, M., Vojtech, R., & Wallner, T. (2018). Impact of injection strategies on combustion characteristics, efficiency and emissions of gasoline compression ignition operation in a heavy-duty multi-cylinder engine. International Journal of Engine Research, 21(8), 1426-1440. doi:10.1177/1468087418801660 Sun, Z.-Y., Li, G.-X., Chen, C., Yu, Y.-S., & Gao, G.-X. (2015). Numerical investigation on effects of nozzle’s geometric parameters on the flow and the cavitation characteristics within injector’s nozzle for a high-pressure common-rail DI diesel engine. Energy Conversion and Management, 89, 843-861. doi:10.1016/j.enconman.2014.10.047 Torelli, R., Som, S., Pei, Y., Zhang, Y., & Traver, M. (2017). Influence of fuel properties on internal nozzle flow development in a multi-hole diesel injector. Fuel, 204, 171-184. doi:10.1016/j.fuel.2017.04.123 Salvador, F., De la Morena, J., Crialesi-Esposito, M., & Martínez-López, J. (2017). 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. doi:10.1177/0954407017725672 Ihme, M., Ma, P. C., & Bravo, L. (2018). Large eddy simulations of diesel-fuel injection and auto-ignition at transcritical conditions. International Journal of Engine Research, 20(1), 58-68. doi:10.1177/1468087418819546 Desantes, J. M., Salvador, F. J., Carreres, M., & Martínez-López, J. (2014). 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:10.1177/0954407014542627 Payri, R., Salvador, F. J., Carreres, M., & De la Morena, J. (2016). Fuel temperature influence on the performance of a last generation common-rail diesel ballistic injector. Part II: 1D model development, validation and analysis. Energy Conversion and Management, 114, 376-391. doi:10.1016/j.enconman.2016.02.043 Salvador, F. J., Carreres, M., Crialesi-Esposito, M., & Plazas, A. H. (2017). Determination of critical operating and geometrical parameters in diesel injectors through one dimensional modelling, design of experiments and an analysis of variance. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 232(13), 1762-1781. doi:10.1177/0954407017735262 Desantes, J., Salvador, F., Carreres, M., & Jaramillo, D. (2015). Experimental Characterization of the Thermodynamic Properties of Diesel Fuels Over a Wide Range of Pressures and Temperatures. SAE International Journal of Fuels and Lubricants, 8(1), 190-199. doi:10.4271/2015-01-0951 Dernotte, J., Hespel, C., Houille, S., Foucher, F., & Mounaim-Rousselle, C. (2012). INFLUENCE OF FUEL PROPERTIES ON THE DIESEL INJECTION PROCESS IN NONVAPORIZING CONDITIONS. Atomization and Sprays, 22(6), 461-492. doi:10.1615/atomizspr.2012004401 Park, Y., Hwang, J., Bae, C., Kim, K., Lee, J., & Pyo, S. (2015). Effects of diesel fuel temperature on fuel flow and spray characteristics. Fuel, 162, 1-7. doi:10.1016/j.fuel.2015.09.008 Wang, Z., Ding, H., Wyszynski, M. L., Tian, J., & Xu, H. (2015). Experimental study on diesel fuel injection characteristics under cold start conditions with single and split injection strategies. Fuel Processing Technology, 131, 213-222. doi:10.1016/j.fuproc.2014.10.003 Salvador, F. J., Gimeno, J., Carreres, M., & Crialesi-Esposito, M. (2017). Experimental assessment of the fuel heating and the validity of the assumption of adiabatic flow through the internal orifices of a diesel injector. Fuel, 188, 442-451. doi:10.1016/j.fuel.2016.10.061 Nurick, W. H. (1976). Orifice Cavitation and Its Effect on Spray Mixing. Journal of Fluids Engineering, 98(4), 681-687. doi:10.1115/1.3448452 Soteriou C, Andrews R, Smith M. Direct injection diesel sprays and the effect of cavitation and hydraulic flip on atomization. SAE Pap 950080 1995. doi: 10.4271/950080. Lichtarowicz, A., Duggins, R. K., & Markland, E. (1965). Discharge Coefficients for Incompressible Non-Cavitating Flow through Long Orifices. Journal of Mechanical Engineering Science, 7(2), 210-219. doi:10.1243/jmes_jour_1965_007_029_02 Franc J-P. The Rayleigh-Plesset equation: a simple and powerful tool to understand various aspects of cavitation. Fluid Dyn. Cavitation Cavitating Turbopumps, vol. 496, Vienna: Springer; 2007, p. 1–41. doi: 10.1007/978-3-211-76669-9_1. PAYRI, 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.2004.10.009 Salvador, F. J., Gimeno, J., Carreres, M., & Crialesi-Esposito, M. (2016). Fuel temperature influence on the performance of a last generation common-rail diesel ballistic injector. Part I: Experimental mass flow rate measurements and discussion. Energy Conversion and Management, 114, 364-375. doi:10.1016/j.enconman.2016.02.042 Payri, R., Salvador, F. J., Gimeno, J., & Bracho, G. (2008). A NEW METHODOLOGY FOR CORRECTING THE SIGNAL CUMULATIVE PHENOMENON ON INJECTION RATE MEASUREMENTS. Experimental Techniques, 32(1), 46-49. doi:10.1111/j.1747-1567.2007.00188.x Theodorakakos, A., Strotos, G., Mitroglou, N., Atkin, C., & Gavaises, M. (2014). Friction-induced heating in nozzle hole micro-channels under extreme fuel pressurisation. Fuel, 123, 143-150. doi:10.1016/j.fuel.2014.01.050 Strotos, G., Koukouvinis, P., Theodorakakos, A., Gavaises, M., & Bergeles, G. (2015). Transient heating effects in high pressure Diesel injector nozzles. International Journal of Heat and Fluid Flow, 51, 257-267. doi:10.1016/j.ijheatfluidflow.2014.10.010 Salvador, F. J., Carreres, M., De la Morena, J., & Martínez-Miracle, E. (2018). Computational assessment of temperature variations through calibrated orifices subjected to high pressure drops: Application to diesel injection nozzles. Energy Conversion and Management, 171, 438-451. doi:10.1016/j.enconman.2018.05.102 Payri, R., Salvador, F. J., Gimeno, J., & Bracho, G. (2008). Effect of fuel properties on diesel spray development in extreme cold conditions. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 222(9), 1743-1753. doi:10.1243/09544070jauto844 Salvador, F. J., Gimeno, J., De la Morena, J., & Carreres, M. (2012). Using one-dimensional modeling to analyze the influence of the use of biodiesels on the dynamic behavior of solenoid-operated injectors in common rail systems: Results of the simulations and discussion. Energy Conversion and Management, 54(1), 122-132. doi:10.1016/j.enconman.2011.10.007 Moon, S., Gao, Y., Park, S., Wang, J., Kurimoto, N., & Nishijima, Y. (2015). Effect of the number and position of nozzle holes on in- and near-nozzle dynamic characteristics of diesel injection. Fuel, 150, 112-122. doi:10.1016/j.fuel.2015.01.097

Thermal effects on the diesel injector performance through adiabatic 1D modelling. Part II: Model validation, results of the simulations and discussion

Abstract