The study presents a one-dimensional, transient and compressible flow models of a commercial Common Rail Injector (CRI) and a prototype of a single-fuel Hydraulically actuated Electrically controlled Unit Injector (HEUI) developed at the University of New South Wales (UNSW) in conjunction with local industry. The unique feature of the UNSW HEUI is the fact that it uses diesel fuel as the driver for pressure amplification within the unit injector. The work undertaken is part of a wider study aimed at optimization of the design of diesel injectors for dual-fuel systems to reduce green house gas emissions. The contribution of this thesis is the development of the model of the UNSW HEUI injector, which can be used to investigate possible modifications of the injector for its use in dual-fuel injection systems. The developed models include electrical, mechanical and hydraulic subsystems present in the injectors. They are based on Kirchhoff??s laws, on the mass and momentum conservation equations and on the equilibrium of forces. The models were implemented in MATLAB/SIMULINK graphical software environment, which provides a high degree of flexibility and allows simulation of both linear and nonlinear elements. The models were used to perform sensitivity analysis of both injectors. The sensitivity analysis has revealed that the temperature of the solenoid coil is one of the critical parameters affecting the timing and the quantity of the fuel injection of both injectors. Additional critical parameters were found to be the dimensions of the piston of the CRI, the stiffness of the needle spring of the HEUI and the dimensions of the intensifier of the HEUI. The models also revealed that in the case of pilot injections the speed of the solenoid is the major limiting factor of the performance. The developed models provide better understanding of the issues and limitations of the injectors. They give detailed insight into their working principles. The investigations of the models permit making quantitative analysis of the timing of the HEUI solenoid and to evaluate the proposed change of the direction of the pressure acting on the HEUI solenoid plunger.

This work focuses on the cooling of diesel engines. Facing heavy constraints such<p>as emissions control or fossil energy management, political leaders are forcing car<p>manufacturers to drastically reduce the fuel consumption of passenger vehicles. For<p>instance, in Europe, this fuel consumption has to reach 120 g CO2 km by 2012, namely 25 % reduction from today's level.<p>Such objectives can only be reached with an optimization of all engines components<p>from injection strategies to power steering. A classical energy balance of an internal<p>combustion engine shows four main losses: enthalpy losses at the exhaust, heat<p>transfer to the cylinder walls, friction losses and external devices driving. An<p>optimized cooling will improve three of them: the heat transfer losses by increasing<p>the cylinder walls temperature, the friction losses by reducing the oil viscosity and<p>the coolant pump power consumption.<p>A model is first built to simulate the engine thermal behavior from the combustion<p>itself to the temperatures of the different engine components. It is composed by two<p>models with different time scales. First, a thermodynamic model computes the in cylinder<p>pressure and temperature as well as the heat flows for each crank angle.<p>These heat flows are the main input parameters for the second model: the nodal<p>one. This last model computes all the engine components temperatures according<p>to the nodal model theory. The cylinder walls temperature is then given back to<p>the thermodynamic model to compute the heat flows.<p>The models are then validated through test bench measurements giving excellent<p>results for both Mean Effective Pressure and fluids (coolant and oil) temperatures.<p>The used engine is a 1.9l displacement turbocharged piston engine equipped with<p>an in-cylinder pressure sensor for the thermodynamic model validation and thermocouples<p>for the nodal model validation.<p>The model is then used to optimize the coolant mass flow rate as a function of<p>the engine temperature level. Simulations have been done for both stationary<p>conditions with effciency improvement up to 7% for specific points (low load, high<p>engine speed) and transient ones with a heating time improvement of about 2000s.<p>This gains are then validated on the test bench showing again good agreement. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished