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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 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 presents a description of the development phases of the new third generation of “green” fuel injectors. The development objective for the new PICO-ECOlogical injector was to define a layout, which enables an optimal parameter configuration for both the mixture preparation (high flexibility to adapt different atomizer plate structures) and the manufacturing processes. It is demonstrated in which way the use of high-level numerical simulation and visualization techniques have become an integrated part of the development process. A detailed description is given of the new layout with respect to earlier versions and the advantageous new features obtained are discussed. Test results obtained by the new 3rd-generation injector layout are presented. The impact of the improved dynamic response capability is explained and experimental data at both engine test rig and vehicle FTP-cycle conditions are reported and discussed.

The success obtained by use of Virtual Engine Modeling (VEM) in the design and development areas of fuel injectors generated a lot of interest from production and quality engineers to dispose of a similar tool related to spray vessel measurements. To respond to stringent PL6/EURO5 requirements it was decided to develop a Virtual Spray Vessel (VSV) tool capable of predicting spray patters and perform droplet diameter analysis comparable to Phase Doppler Analysis (PDA) results. The paper describes the analogies between VEM and VSV modeling, the specific new numerical approaches to obtain spatial spray data comparable to conventional mechanical measurement techniques and to perform droplet diameter analysis comparable to PDA data. The paper concludes with a series of comparisons of simulated and experimental data.

In the present paper the impact of three different geometrical layouts of the discharge nozzle of a high-pressure diesel injector designed is examined for a common rail second generation direct injection system. The paper presents a comparative study of the spray behavior of the three different nozzle layouts connected to a 150 MPa rail-pressure when mounted on a 1.6 liter European passenger car engine. To evaluate experimentally the differences in the fundamental physical spray parameters several specially developed optical visualization techniques are used, which enable phase-Doppler, Laser-sheet and high-speed recordings of dense high pressure sprays. The change in basic spray parameters (time-resolved droplet distribution and spray momentum) caused by the nozzle geometry variation is examined. The impact on the in-cylinder penetration and mixing characteristics is studied with a 3D-numerical simulation code 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.

In the present paper are examined the consequences of a substantial rise in the injection pressure for Gasoline Direct Injection (GDI) injector assemblies. The paper presents a comparative study of the spray behavior of two different injector nozzle layouts submitted to current 10 Mpa rail-pressure as well as to a 30 Mpa injection pressure. To evaluate the differences in the fundamental physical spray parameters are used several specially developed optical visualization techniques, which enable phase-Doppler, PIV, Laser-sheet and high-speed recordings of dense high pressure fuel sprays. A recently developed injector actuator and the necessary modifications to existing high-pressure pumps to reach a 30 MPa pressure level in the fuel system are presented. The change in basic spray parameters (time-resolved droplet distribution and spray momentum) caused by the rail-pressure rise is examined.

The paper presents a study of a key-element in the mixture preparation process. A typical common-rail (CR) high-pressure fuel injector was fitted with a prototype injector nozzle with atomizer bores of a particular conical layout. It is demonstrated within certain layout limits, that a considerable enhancement can be obtained for the secondary break-up of the hard-core fluid sprays produced by the nozzle. The impact on the combustion process is examined in terms of pressure and heat release as well as of the engine-out pollutant emission. The results are compared to those of an earlier developed CR high-pressure injector nozzle. The atomization behavior of the prototype nozzle is illustrated through experimental results in terms of engine-out emissions from a 1.3-liter turbo-charged passenger car diesel engine. The detailed spray behavior is visualized on a component test rig by use of specially developed optical visualization techniques.

In order to improve the atomization capability of a standard port fuel injector, an optimized suggestion for an air shrouded injector is presented. The fluid dynamic part of the retained solution is composed of a special flat seat design for the fuel metering function combined with a post atomization adapter enabling both mono- and multi-spray modes. The concept works equally well in natural manifold gradient mode and with an external pressure pump. The realized concept is tested in both free jet experiments and on two different 2 litre engines, one operated in stoechiometric conditions the other in lean-burn conditions. The experimental work confirms a potential of the concept to increase torque stability and thereby lean-burn limits, decrease required spark advance and enable open inlet valve injection and consequently decrease wall wetting phenomena.

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 outlines the main potential advantages of the direct fuel injection concept and describes the overall layout of a system in which the keystones are a piston rotary fuel delivery pump with integrated pressure regulation and electromechanical fast responding fuel injectors. Three different nozzle designs are discussed, a divergent pintle solid cone, a pintle hollow cone swirl layout and a closed cap multijet design. In the second part of the paper the used experimental high pressure dynamic test equipment is discussed. Then the results obtained by the use of phase illuminated visualisation techniques and phase Doppler analysis as well as by a 3D CFD approach are presented. The paper concludes by relating the spray patterns and the associated droplet penetration velocities, produced by the different nozzle types, to the combustion chamber layout and to the possible manufacturing precision requirements for each nozzle type.

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 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 first part of the present paper describes the means by which the spray momentum can be decreased. The objective can be obtained either by injector-internal geometrical design changes, which very often lead to a highly non-uniform spray density/droplet distribution or by a new injector-external process, called the colliding jet (CJ) approach. The paper continues with a detailed description of the physics of the controlled secondary breakup process provided by the CJ-approach, which enables a very uniform density/droplet distribution on the downstream side of the collision zone as well as an approximately 40 % decrease in spray penetration depth. The knowledge of the physics of the CJ-approach enables the introduction of a new spray model in the 3-D numerical simulation code NCF-3D.