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The paper presents the main reasons for the increasing market share of vehicles with the capacity to run on random bio fuel blends. It describes the philosophy and basic layout of current integral flex mixture preparation systems. The paper demonstrates the necessity to introduce a series of new high-performance analysis tools for further improvement of the mixture preparation system and in particular the fuel injector performance. The paper continues with a discussion of the basic structure of the interactive Virtual Engine Model approach applied to fuel injector atomizer optimization. Test results obtained by application of the new tools to two different series production flex engines are presented. The impact of the improved spray formation capability of the optimized fuel injector atomizers is explained and experimental vehicle FTP-cycle data are reported and discussed.

The paper describes the application of laser sheet flow visualisation with numerical image analysis as a useful complementary tool to numerical simulation techniques for the optimisation of fluid dynamics within SI-engine in-take systems. The lay-out of the laser sheet visualisation system and the applied numerical image analysis are discussed in detail. Two applicative examples are given, one of smoke induced visualisation of the internal gas flow of an intake manifold, the other of natural visualisation of fuel injector wall film deposit in the intake runner. Finally is concluded that the addition of visualisation techniques to the development strategy allows a time gain, because it contributes to a rapid understanding of complex flow phenomena.

The paper describes the setup of a 4-cylinder 1.4-liter prototype Spark Ignited (SI)-engine, which is highly boosted, extremely downsized and port fuel injected. During experimental data gathering with the engine it was discovered that the originally mounted fuel injectors were non-optimized an unable to produce an expected low fuel consumption performance at low speed, low load engine working conditions. To solve this problem by finding an optimized alternative solution for the mixture preparation process it was decided to use a high-performance numerical simulation tool. The paper presents the overall layout of the prototype engine as well as the structure of the 3-D dynamic optimization tool used to address the mixture preparation problem. The paper continues with a detailed description of the different steps used to reach the complete optimization of the mixture preparation system (both the fuel injectors and the intake manifold).

The present paper is a contribution in which is used a numerical simulation approach, the Virtual Engine Model, to study the combination of the Compression Ignition process with a Gasoline Direct Injection mixture preparation in a limited number of load-points. The first part of the paper describes the reasons for which current Gasoline Direct Injection engine technology must be combined with other technologies related to the in-cylinder mixture preparation control to further increase their potential for decreased fuel consumption. The paper continues with a description of the physics of spark and compression ignited processes as well as of the involved mixture preparation hardware components. The setup and the practical use of the Virtual Engine Model are discussed for both spark and compression ignited approaches.

The paper presents the background research on the physics of the droplet coalescence phenomena carried out by an interactive usage of high-level 3-D numerical simulation tools and high-level optical visualization and measurement techniques. The presentation continues with the description of a new injector atomizer plate layout, which enables a physical coalescence control of the droplet population within the entire fuel spray. Finally are presented examples of the impact on exhaust emissions of the introduction the new atomizer plate with coalescence control by engine test bed experiments (steady state low load conditions) and vehicle tests (first cold part of the FTP-cycle).

The paper describes the optimization to match the Brazilian market requirements for a Flex-Vehicle of the intake system and in particular the fuel injectors of a small displacement (1.6 l) 8 valves passenger car engine. The imposed target was to find a compromise for the hardware components related to the mixture preparation process, which optimize their performance with respect to a gasoline with a random content (from 0 to 100 %) of ethanol. The analytical optimization process is performed by use of a 3-D numerical virtual engine in which can be studied the physical phenomena of spray atomization, vaporization and momentum fluctuations from different injector atomizer layouts. The different atomizer layouts as well as several vaporization enhancement approaches are rated with respect to a baseline configuration on the virtual engine. The paper presents the results obtained by highest rated solutions, which were manufactured as prototypes and tested on the real engine.

The suggestions for upcoming Euro 2000 clean air act puts an increasing legislative pressure for lower specific fuel consumption in order to reduce the emission of CO2 and thereby decrease the impact of the “green house” effect. One of the possible suggestions to meet these requirements for SI-engines is the gasoline direct injected (GDI) power unit. One of the key points of the success of a layout of a GDI system is the optimization of the fuel injector and combustion chamber charge formation parameters. A brief description of the basic GDI-system used during the study is given. Hereafter are outlined the computational and experimental optimization tools which have been used to produce, on a reasonable industrial time scale, the main indications to optimize the design of a given injector/chamber configuration. The paper discusses in detail the results produced by the latest enhancements introduced into the 3D multi-phase computational approach, NCF-3D.

Experimental measurements and numerical computations were made to characterize a spray generated by a high-pressure swirl injector. The Phase Doppler technique was applied to get information on droplet sizes (d10) and axial velocities at defined distances from the injector tip. Global spray visualization was also made. Computations were carried out using a modified version of KIVA 3V. In particular, the break-up length of the sheet and its dimension were computed from a semi-empirical correlation related to the wave instability theory suggested by Dombrowski, including the modifications introduced by Han and Reitz. Two different approaches were used to describe the initial spray conditions. According to the first, discrete particles with a characteristic size equal to the thickness of the sheet are injected. The second approach assumes, that the particles having a SMD computed by a semi-empirical correlation are injected according to a statistical distribution.

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.

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.

In the future generation of low consumption SI-engine layouts, it has become necessary to reduce costs as well as the complexity level and, increase the system reliability by the latter. To avoid driving the GDI-system in the critical, very lean stratified operation mode without losing the fuel consumption benefit, a solution is suggested, which combines a fully variable valve control system with a low level, robust GDI combustion layout. The first part of the present paper presents the latest development in the field of high precision multi-hole GDI injector spray nozzles. The basic aspects of mixture preparation with multi-hole gasoline atomizers are highlighted and their spray behavior compared to that of the current swirl atomizer nozzle. The second part of the paper presents primary optimization of a largely homogeneous GDI combustion layout combined with a fully variable valve timing control system including complete cylinder de-activation.

The first part of the paper gives an overview of the current results obtained with the first-generation of GDI-powered vehicles launched on the European market. In view of the rather limited success in fuel consumption gain the second-generation of very lean stratified layouts has begun, but this process requires the development and application of new high-level analysis tools. A possible high performance approach is the multi-purpose use of 3-D numerical simulation both in the development and the engine control strategy calibration phases. The development of a small 1.6 liter lean stratified engine project was chosen to demonstrate the dual application capability of the NCF-3D simulation tool. The paper continues with a description of the engine application frame, the basic features of the NCF-3D simulation tool and the latest enhancements made to combustion and fuel composition models within the software frame.

On the basis of the large amount of know-how accumulated in the field of automotive ethanol SI-engine fuelling in Brazil, it seemed appropriate to continue and set a new milestone in the usage of ethanol fuel. The paper presents the preliminary study made to enable the transfer of the ethanol technology to a 5.9-liter 4-cylinder boxer aircraft engine. The study describes the steps made to define the optimal parameter configuration for the transfer of the fuel system packaging, the fuel injector layout, the engine control unit (ECU) and the legislative redundancy requirements for aviation applications. The paper illustrates the use of numerical simulation techniques and special visualization approaches necessary to understand the physical phenomena of mixture preparation (spray atomization and momentum). Two different layouts are presented and discussed and a certain number of experimental results obtained with the retained solution are presented and discussed.

The first part of the paper gives an overview of the results obtained with European GDI-powered vehicles launched on the market. Thereafter, a discussion of in-vehicle limitations due to the exhaust gas after-treatment system requirements is given. The paper continues with a description of the current development status of European lean stratified direct injection system layouts. A detailed presentation is made of the mixture preparation system key components, basic control algorithms and the necessary new high-level experimental and analytical development tools. Particularly the topic of the multi-purpose use of 3-D numerical simulation is addressed both in the development and the engine control strategy calibration phases. The development of a small 1.6 liter lean stratified engine project is taken as example to demonstrate the dual application capability of the 3D simulation tool.

The new European legislation on two-wheeler pollutant emissions has forced two stroke engine manufacturers to study the direct fuel injection (DI) technology. The Piaggio “ET2 Injection” was the first DI engine in production, using the FAST system (Fully Atomized Stratified Turbulence) applied on a 50 cm3 engine. Within the framework of the DOLCE project (Development Of innovative Low pollutant, noise and fuel Consumption two stroke spark ignition Engines for future vehicles for individual urban mobility) coordinated by Piaggio and supported by the European Commission, a 125 cm3 direct injection 2-stroke engine was developed. This paper presents the engine-related part of this work, which was concluded in March 2000. The engine is equipped with the FAST system and the fuel metering is performed by means of a low-pressure electronic fuel injection system integrated in an Engine Management System (EMS) specially developed for this type of application.

The paper presents the basic scientific analytical approach to identify the main physical parameters, which enable an optimization of several layouts for an Ethanol Cold Start (ECS) device. The main optimization criteria for the system layout are a single mixture preparation system for both cold start and hot engine handling, a short energy release time, a short start time and a possible high-precision ethanol metering system capability after start. The paper describes 3 suggested solutions. Two of the solutions are prototyped and tested on several vehicles. The paper concludes with a series of experimental data obtained on different flex engines with the new ECS-system variants. The obtained test results show good pure ethanol cold start capability for temperatures above 263 K and an excellent system temperature control of the fuel in the fuel-rail and in the injectors, which prevents the occurrence of any cavitations phenomenon.

The paper presents the main reasons for the increasing market share of vehicles with the capacity to run on random bio fuel blends. It explains the reason for which a single fuel supply system is mandatory in modern flex vehicles, even for cold start by pure ethanol fuelling The paper continues with an analytic research for the most appropriate device location and a detailed description of 3 suggested device layouts. The paper concludes by a presentation of a series of data obtained by real-time vehicle experiments at low ambient temperature conditions.