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A computational model and an experimental analysis have been performed to study the atomisation processes of hollow cone fuel sprays from a high pressure swirl injector for gasoline direct injection (GDI) engines. The objective has been to obtain reliable simulations and better understood structure and evolution of the spray and its interaction with air the flow field. The 3D computations are based on the KIVA 3 code in which basic spray sub models have been modified to simulate break-up phenomena and evaporation process. Spray characteristics have been measured using a system, able to gather and to process spray images, including a CCD camera, a frame grabber and a pulsed sheet obtained by the second harmonic of Nd-YAG laser (wavelength 532 nm, width 12 ns, thickness 80 μm). The readout system has been triggered by a TTL signal synchronized with the start of injection. A digital image processing software has been used to analyse the collected pictures.

The performances increasing of internal combustion engines for race car has driven to develop special systems in order to improve the volumetric efficiency. To this aim, in the last years, a great effort has been done especially in studying geometries for airbox, turbo-compressors, special exhaust systems, etc. In this paper, the project of a “high-performance” airbox for a naturally aspirated internal combustion engine (ICE) of a car racing in prototype sport competitions is described. In order to optimize the airbox geometry under extremely complex operative conditions, the fluid dynamic phenomena inside the airbox have been studied by means of a three dimensional computational code (3D CFD). This approach has allowed to study different airbox geometry and to define the one to be realized and tested on race track. The new airbox geometry, defined in this way, has brought to good results.

An extensive experimental work has been made in order to analyze the structure of the spray of a large-angle single-hole high-pressure swirl injector for direct-injection spark-ignited (DISI) gasoline engines. Spatial and temporal evolution measurements of the spray have been carried out in an optically accessible vessel. The spray has been lighted by an 80 mm thickness and 12 ns duration pulsed laser sheet, generated by a 532 nm Nd-YAG laser, both along the spray axis and in cross sections perpendicularly to it. The scattered light has been collected at 90° from the laser sheet direction by a digital CCD camera with a frame grabber synchronized to the single-shot injection command and the laser start pulse. A digital image processing system has allowed analyzing the images collected by the CCD camera. It has been possible to visualize the formation and the spatial and temporal evolution of the initial liquid slug (pre-spray) and of the hollow-cone and solid-cone stray structure.

The first part of the paper gives an overview of the current status in fuel consumption gain of the GDI-vehicles previously launched on the European market. In order to increase the potential for a further gain in specific fuel consumption the behaviour of 3 different combustion chamber layouts are studied. The chamber layouts are aimed to adapt as well as possible to the particular requirements for application to a small displacement/small bore engine working in stratified lean conditions. The paper continues with a description of the application that shows the different steps of a structured optimisation methodology for a 1.2 litre, small bore 4-cylinder engine. The applications of an air-motion-guided and a wall-guided layout with a mechanically actuated valve train to the same combustion chamber are discussed. The potential of the air-motion-guided concept is enhanced through the introduction of an electromagnetic fully variable valve train.

The first part of the paper gives an overview of the environmental conditions with which a future two stroke powered vehicle must comply and explains the reasons for which a direct gasoline injection into the combustion chamber offers a potential solution. The paper continues with a description of the fuel/air mixture injection used in the F.A.S.T. concept and gives a detailed overview of the layout of the 125 cc engine to which it is applied. The structure of its electronic engine management system, mandatory for the necessary control precision, is presented. Hereafter is made a short introduction to the visualization and numerical computation tools used for the engine design optimization. The paper concludes with a detailed presentation and discussion of the experimental results obtained with the engine operated, either in steady state and transient conditions on an engine test rig, and mounted in a classic small dimension two-wheel vehicle submitted to road tests.

The first part of the paper gives an overview of the current development status of the GDI system layout for the middle displacement engine, typically 2 liter, using the stoichiometric or weak lean concept. Hereafter are discussed the particular requirements for the transition to a small displacement/small bore engine working in stratified lean conditions. The paper continues with a description of the application of the different steps of the optimization methodology for a 1.2 liter, small bore 4 cylinder engine from its original base line MPI version towards the lean stratified operation mode. The latest changes in the combustion model, used in the numerical simulation software applied to the combustion chamber design, are discussed and comparison made with the previous model. The redesign of the combustion chamber geometry, the proper choice of injector atomizer type and location and the use of two-stage injection and multi-spark strategies are discussed in detail.

For compliance with future LEV/ULEV emission standards in United States and Euro 2000/Euro 2005 standards in European Community, catalytic converter performance has to be remarkably improved. The development of simulation codes allows to investigate a high range of possible exhaust system configurations and engine operating parameters. In the present study an hybrid Lattice BGK-finite volume technique will be described, able to determine the mass transfer rates of the chemical species to the catalyzed wall of the monolith channels. The BGK code solves the fluid motion governing equations in a reduced form obtained by discretizing the continuum in a fixed number of particles. Each of them will be moved by a set of discrete velocities and collide with the neighbour particles according to a fixed pattern of particle-interaction.

Pollutant emissions from D.I. Diesel engines strongly depend on injection system characteristics and mainly on injection pressure and timing. In the latest years some solutions have been proposed based on very high fuel pressure values (up to 150 MPa). Among them, the so called “Common rail” system configuration, being able to electronically control needle lift and injection pressure, seems to be particularly promising. Much experimental and theoretical work has been done to improve system performance for automotive applications. With the aim of investigating the influence of some details of geometrical configuration on the injector operating mode, a mathematical model able to describe the pressure-time history in any section of the delivery pipe and the fuel injection rate through the nozzle has been developed, based on a semi-implicit finite volumes approach. The computed results have been compared with experimental data provided by the Institut Français du Pétrole.

The performance of a small cross-scavenged two stroke spark ingition engines have been analysed by means of a displacement-mixing model for the intake gases, a two-zones combustion model, and one-dimensional numerical technique for the gas flow in the exhaust system. Numerical studies have shown that two stroke engine performance can be optimized by using a resonant chamber connected by means of a valve to the exhaust manifold. The configuration of the exhaust system C the resonant chamber's volume, the geometry of the pipe) may be determined as function of the required engine applications by the implemented code.