Proceedings of VAFSEP2004, 6-9 July 2004, Dublin, Ireland MODELLING OF COMMON RAIL FUEL INJECTION SYSTEM AND INFLUENCE OF FLUID PROPERTIES ON INJECTION PROCESS X.L.J. Seykens 1 , L.M.T. Somers 2 and R.S.G. Baert 3 1. Faculty of Mechanical Engineering, Division Thermo Fluids Engineering (TFE), Eindhoven University of Technology, The Netherlands, email: X.L.J.Seykens@tue.nl. 2. Faculty of Mechanical Engineering, Division Thermo Fluids Engineering (TFE), Eindhoven University of Technology, The Netherlands. 3. Faculty of Mechanical Engineering, Division Thermo Fluids Engineering (TFE), Eindhoven University of Technology, The Netherlands. ABSTRACT This paper focuses on the modelling of a research type Heavy Duty Common Rail (CR) fuel injection system. More specifically it reports on the observed interaction between fuel properties and injection and on the capability to model this. For that reason a hydraulic model of the fuel injection system has been developed using the AMESim code (Imagine S.A., 2003). The reliability of the numerical results is tested through a comparison between numerical and experimental results when using regular diesel fuel. Basis for this detailed comparison are measurements of injected mass flow rate, needle lift and pressure oscillations in the injection duct for a single injection. Simulation results for regular diesel show good agreement with measured data for pressure oscillations in the injection duct, needle lift and injected fuel mass flow rate. A comparison of experimental and simulated results for Rapeseed oil Methyl Ester (RME) also shows good correspondence, which proves the capability of the model to capture the influence of different fuel properties. Keywords: Fuel injection, Modelling, Fluid properties 1 INTRODUCTION With modern diesel engines the injection process (i.e. the injection rate and injection pressure) has a major impact on noise production, exhaust gas emissions and fuel consumption. In view of the ever-increasing demands on these engines, modelling of the fuel injection system has become an essential step in the fuel injection equipment design and optimisation process. As part of the move towards greenhouse gas reduction and diversification of energy supply there is a growing interest to test and enhance the ability of diesel engines to run on alternative fuels. Because fuel properties such as density, bulk modulus of elasticity and viscosity influence the injection behaviour, the use of an alternative fuel will affect the injection process. Szybist et al. [1] found that injection timing advanced and injection duration shortened with increased biodiesel content. The higher viscosity of biodiesel is believed to be responsible for the change in injection timing by Choi et al. [2], but no mechanism is offered for this conclusion. Arcoumanis et al. conclude that only fluid bulk modulus of elasticity is responsible for a change in injection timing. Rapokoulos and Hountalas [5] state that the only fluid properties that are of importance for modeling of fuel line pressure are fluid density and fluid bulk modulus of elasticity. Again, fuel viscosity was not found to affect injection timing. All of the above analyzed pump-in-line fuel injection systems. Ziejewski et al. [6] studied the discharge coefficient of a diesel injector nozzle for laminar and turbulent flows and for different (alternative) fuels. He found that for a specific injector nozzle geometry a relation between Reynolds number and discharge coefficient could be established that was valid irrespective of fuel properties. The goal of the present study is to validate our hydraulic, one-dimensional, model of a Common Rail (CR) type injection system using both standard diesel and RME and to analyze differences in the fuel injection behaviour related to the difference in fluid properties. The capability of the model to capture these differences is tested. 2 COMMON RAIL INJECTION SYSTEM The studied fuel injection system is of the Common Rail (CR) type and is designed for the fuel delivery to a one-cylinder 2.1-litres Heavy Duty (HD) research diesel engine. In figure 1, this injection system is shown schematically. The system comprises a 2 nd generation light-duty CR high-pressure pump with an electronically controlled throttling valve to adjust the delivered