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The efficiency of engine operations, i.e. cold start, transient response and operating at idle, depends on the capability of the injection fuel system to promote a homogeneous mixture formation through an efficient interaction with engine fluid dynamics and geometry. The paper presents the development and the application of a methodology for running a CFD PFI engine simulation. A preliminary assessment of the wall-film and droplet-wall interaction sub models has been carried out in order to validate the methodology. Then a three-step numerical procedure has been adopted. The first two steps are aimed to properly initialize the secondary breakup model depending on the type of injector installed on board in order to achieve accurate predictions of spray characteristics.

This paper presents a complete numerical and experimental characterisation of the transient diesel spray of a modern 5-holes high pressure electronic controlled injector performed in a constant volume pressurised vessel. The experimental analysis has been carried out using a self-developed injection rate measuring device, a visualisation rig based on a Nd-Yag pulsed laser and a synchronized CCD camera to measure spray penetration and spray cone angles and a PDA equipment to measure droplets size and velocity. The numerical analysis has been carried out by statically coupling a 1D model of the common rail injection system to a full 3D computation of both gas and fuel spray dynamics. The 1D injection system model has been developed in the AVL HYDSIM environment and the reliability of the model is demonstrated by comparing the numerical results with the experimental data. The multidimensional numerical simulation tool is a modified version of the KIVA-3V code.

The interest towards hydrogen fueling in internal combustion engines (ICEs) is rapidly growing, due to its potential impact on the reduction of the carbon footprint of the road transportation sector in a short-term scenario. While the conversion of the existing fleet to a battery-electric counterpart is highly debated in terms of both technical feasibility and life-cycle-based environmental impact, automotive researchers and technicians are exploring other solutions to reduce, if not to nullify, the carbon footprint of the existing ICE fleet. Indeed, ICE conversion to “green” fuels is seen as a promising short-term solution which does not require massive changes in powertrain production and end-of-life waste management. To better evaluate potentials and challenges of hydrogen fueling, a clear understanding of fuel injection and mixture formation prior to combustion is mandatory.

Diesel engine technology is continuously focused on higher performances and lower emission levels. Reduced costs and lower fuel consumption are key factors in engine development too, in particular for small diesel engine, both for on-road and non-road application. In order to fulfill emission legislation requirements, improve engine performance and reduce fuel consumption, nowadays the common rail injection system with electronic actuation is widely used in diesel engines. Nevertheless, conventional common rail system cost is quite high, mainly due to the complex indirect actuation of the injector, and the injector backflow leads to inefficiencies in the injection system. In this work an analysis of a medium pressure injection system for small diesel engines is presented, focusing on the achievable engine performances and emissions.