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The paper presents a study of the influence of fuel pressure supply fluctuations on the upstream side of the fuel injector atomizer. The study is performed over a wide range of pressures (70 to 130 Mpa) with two different common-rail (CR) high-pressure fuel injectors. The common atomizer is a VCO-type equipped with conically shaped atomizer bores. With the injector tip (nozzle) mounted in a counter-pressure vessel the pressure fluctuations in the fuel-rail and in the injector body are recorded simultaneously with stroboscopic Schlieren-visualization of the time-resolved spray behavior. It is demonstrated that not only the instantaneous mass flow is affected. As a function of rail-pressure, pulse-width and injection strategy the pressure fluctuations change the spray hard-core structure and its break-up behavior.

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.

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.

The paper presents the background physics of droplet coalescence phenomena and the basic research carried on the topic by interactive use 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 gives a short introduction to the notion of flex fuel approach for diesel engines. The paper continues with a description of a basic study of the diesel combustion process to allow the design of a strategy for recognition of a random bio-diesel fraction, Bx, by a purely software-based sensing technique, which creates an image of the temporal combustion behavior and uses only sensors already in service for current common rail mixture preparation systems. A description is made of two different approaches to software- based sensing techniques, one based on the presence of a crank angle speed sensor and the other on the presence of a lambda sensor in the exhaust system. The principles of the associated software flow diagrams embedded in the engine control unit are also explained. The paper concludes presenting a series of experimental verification data obtained on a large-scale series produced 1.3 liter turbo-charged common rail passenger car engine.

In a torch ignition engine system the combustion starts in a prechamber, where the pressure increase pushes the combustion jet flames through calibrated nozzles to be precisely targeted into the main combustion chamber. The paper presents the layout of the prototype engine and the developed fuel injection system. It continues with a detailed description of the performance of the torch ignition engine running on a gasoline/ethanol blend for different mixture stratification levels as well as engine speeds and loads. Also detailed analyses of specific fuel consumption, thermal and combustion efficiency, specific emissions of CO2 and the main combustion parameters are carried out. A supplementary decrease in NOX emissions was obtained by use of Brazilian pure hydrated fuel. The paper concludes presenting the main results obtained in this work, which show significant increase of the torch ignition engine performance in comparison with the commercial baseline engine.

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 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 present paper describes a study of the basic parameters, which govern particulate (soot) formation within the combustion chamber of a small displacement (1.3 liter) turbocharged European CR-diesel engine. The main tools used for the study are a real fired engine, a numerical virtual engine and a special high ambient pressure vessel for injector spray visualization. The paper describes an improved soot formation model implemented in the virtual engine setup. A comparison is presented between measured and computed combustion data at 8 different load points. The paper concludes with a discussion of the means, which can be used to minimize the particulate matter formation in the design phase of both the combustion layout and the fuel injector atomizer as well as in the design of the injection control strategies.

The present paper describes in detail the development of such a combustion process, starting from the initial design, referring to the simulation of the entire system with the description of the injection, vaporisation and combustion, through to the test bench experiments. The particular focus of the presentation lies on the application of 3D-CFD simulation technologies for modelling the entire system, including the high-pressure direct injection. This paper looks into the analysis and validation of the simulation data, as well as into the thermodynamic analysis and evaluation of the data measured in the tests. The results regarding the performance, emissions and other parameters are represented in comparison with other combustion processes, thus showing the potential of the newly designed combustion process.

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 paper gives a short introduction to the bio-diesel mixture approach for diesel engines. The paper continues with a description of the design of a strategy for recognition of a random bio-diesel fraction, Bx, by a purely software-based sensing technique, which creates an image of the temporal combustion behavior and uses only sensors already in service for current common rail mixture preparation systems. A short description is made of a baseline approach of a sensing technique using a crank angle speed sensor. Hereafter the paper continues by the introduction of several integral or Upper Level (UL) key-parameters applied to enhance the precision of the Bx-detection or completely replace the original lower level combustion key-parameter set, which relates the instantaneous fraction of bio-diesel, Bx, to the engine torque. The paper concludes presenting a series of experimental verification data obtained on a large-scale series produced 1.3 liter Turbo CR-rail passenger car engine.

In a torch ignition engine system the combustion starts in a prechamber, where the pressure increase pushes the combustion jet flames through calibrated nozzles to be precisely targeted into the main combustion chamber. The paper presents the layout of the prototype engine and the developed fuel injection system. It continues with a detailed description of the performance of the torch ignition engine running on a gasoline/ethanol blend for different mixture stratification levels as well as engine speeds and loads. Also detailed analyses of specific fuel consumption, thermal and combustion efficiency, specific emissions of CO2 and the main combustion parameters are carried out. A supplementary decrease in NOX emissions was obtained by use of Brazilian pure hydrated fuel. The paper concludes presenting the main results obtained in this work, which show significant increase of the torch ignition engine performance in comparison with the commercial baseline engine.

In a torch ignition engine system the combustion starts in a prechamber, where the pressure increase pushes the combustion jet flames through calibrated nozzles to be precisely targeted into the main combustion chamber. The paper presents the layout of the prototype engine and the developed fuel injection system. It continues with a detailed description of the performance of the torch ignition engine running on a gasoline/ethanol blend for different mixture stratification levels as well as engine speeds and loads. Also detailed analyses of specific fuel consumption, thermal and combustion efficiency, specific emissions of CO2 and the main combustion parameters are carried out. A supplementary decrease in NOX emissions was obtained by use of Brazilian pure hydrated fuel. The paper concludes presenting the main results obtained in this work, which show significant increase of the torch ignition engine performance in comparison with the commercial baseline engine.