Fulvio Palmieri

Diesel Nozzle Flow Investigation in Non-Radial Multi Hole Geometry

Flow features at hole inlet traditionally depend both on injector tip type (Minisac, VCO, Microsac), and on hole drilling & finishing technology (hydro grinding, paste honing); such a topic is going to be faced by researchers for many years, due to the importance of high pressure injection process in current and upcoming diesel engine.In the present paper, investigations have been extended to an unconventional diesel nozzle layout, highlighting its capability on altering the flow structure at hole inlet, and thus influencing the flow development within the nozzle holes. As described in the article, the investigated nozzle is based on a multihole layout but, referring to the injector axis, nozzle holes have a non-radial arrangement.The investigations on nozzle hole flow development have been based on modeling. Moving from the standard nozzle configuration towards non-radial arranged holes, 3D-CFD campaigns have been devoted to highlight the influence of such unusual nozzle layout on diesel nozzle flow.In the modeling process, data concerning spatial distribution of velocity and cavitation behavior at hole exit have been computed; the effect of non-radial multi hole geometry has been investigated both on MicroSac and VCO layouts. Specific attention has been focused on the fuel flow distribution among the holes; the computations have evidenced how the unconventional layout is capable to improve the behavior of VCO geometries when needle eccentric displacement is considered. Results have been synthetized indicating how flow pattern properties are reflected at hole exit, quantitatively.Copyright

Modeling the Effect of Nozzle Hole Geometry on Diesel Injection and Combustion

The performance of the ensemble diesel engine-injection system has been investigated by modeling; different approaches have been combined and integrated in a multi step procedure. In a preliminary phase, the nozzle flow features have been investigated by means of 3D CFD simulation (FIRE), allowing for the evaluation of nozzle hole discharge coefficients. Such values have been used in the subsequent phase, based on a 0/1D approach, in which the complete model of the fuel injection system has been realized and the injected fuel amounts have been evaluated. On the basis of these indications, a further simulation phase has been included and a packet model for the modeling of fuel jet formation, evaporation and combustion has been built and used. In-cylinder pressure trends have been obtained and the effects of different nozzle hole geometries have been investigated.Copyright

Inline Pump Internal Flow Characterization for Optimized Diesel Injection

The injection process optimization plays a key role in diesel engine development activities, both for pollutant formation control and performance improvement. The present paper focuses on relatively small diesel units, equipped with fully mechanical injection systems; in detail, the considered system layout is based on the use of spring injectors; the amount of delivered fuel is controlled by the positioning of the pump plunger groove. The paper highlights the role of the inline pump and the influence of fuel characteristics on the system operation. By means of a three-dimensional numerical flow study, the behavior of pump fuel passages and delivery valve is simulated. Then, on the basis of the system features, a complete lumped/one-dimensional numerical model is realized, in which the discharge coefficients evaluated through the three-dimensional simulation are employed. Fuel injection rate and local pressure time histories are investigated, paying specific attention to the occurrence of the relevant phenomena in the system components. Obtained results are compared with experimental data.Copyright

Coupling Codes for Nozzle Flow Modelling in Diesel Injection System

This paper deals with a numerical investigation of a single cylinder diesel engine equipped with mechanical fuel direct injection system and focuses on the fuel injection system modelling with the aim of predicting the performance of the entire injection system, the spray characteristics, the interaction among spray-cones, combustion chamber flows and geometry. In the simulations, two different codes have been used. With the former one, AMESim code, the complete injection system has been analysed and the single components have been selected and modelled. The results obtained from the injection system simulation, in terms of injection needle lift, injection flow rate, pressure time evolution, have been used to initialize the latter computation tool, FIRE code, in which 3D flow numerical investigation of the internal injector flow has been performed. Since such a flow is directly linked to the spray modelling, the primary break-up effects have been taken into account. The details of the adopted modelling strategy have been shown and the results of each simulation step have been presented. In order to highlight the relationship among the nozzle flow condition and the spray formation-vaporization characteristics, a comparison between two different calculation setups has been shown. Moreover, a qualitative comparison among predictions and experimental data has been discussed.© 2006 ASME

Investigating the influence of highway traffic flow condition on pollutant emissions using driving simulators

In the last 20 years the attention of international organizations towards air pollution has been improved, leading to definition of laws and regulations. In order to evaluate strategies and policies, forecasting tools have been adopted by institutions. Currently, the estimation of traffic emissions is based on static models, in which the amount of pollutant is computed as a function of average parameters obtained on a single road stretch. The well-known traffic increase of recent years has significantly changed the actual flow conditions, producing a strong rise of interferences. As this facet affects the operating condition of each vehicle, the use of a standard emission model at high traffic interference can lead to some inaccuracies. In such cases, instantaneous emission models introduce deeper capabilities; essentially, the pollutant prediction is directly tied to the engine vehicle operation point in reallike traffic condition. This second modelling approach has been adopted in the current work. A complete lumped parameter vehicle model has been built to be used as a virtual on-road emission/fuel consumption test unit. Investigations have highlighted the dependence of emission level and fuel consumption on drivers’ behaviour; indeed, the analysis took advantage of the experiments carried out in the virtual reality laboratory: on a typical highway geometry, characterized by a dual lane carriageway with three lanes each, three different flow conditions have been simulated. Once the relationship between highway interference level and drivers’ behaviour has been evidenced (in terms of emissions and fuel consumption), a relation between highway interference level and emissions/fuel consumption has been highlighted. Finally, in order to assess the differences

On the Influence of the Slot Orifice in Diesel Common Rail Nozzle

Methods: In the research, a solenoid injector for light duty diesel engines is equipped with the novel nozzle prototype and tested. The prototype layout is described, pointing out the features of the nozzle orifices, in which a Slot cross-section is adopted; the investigation is accomplished extending the hydraulic tests and the spray visualizations to a reference nozzle with standard holes. The influence of the hole layout on the mechanical-hydraulic behavior of the nozzle is assessed by experimental analysis based on the rate of injection measurement, in comparison with the reference nozzle. Once the hydraulic behavior of the novel nozzle has been characterized in terms of mass flow rate, the slot influence on the spray shape is assessed analyzing the macroscopic features such as the penetration distance and the spray angle, in non evaporative conditions. The study is carried out under transient injection conditions, for different injection pressures, up to 1400 bar.

The Effects of Traffic Flow Conditions on the Pollutants Emissions: A Driving Simulator Study

In the last 20 years the attention of international organizations towards air pollution has been improved, leading to definition of laws and regulations. In order to evaluate strategies and policies, forecasting tools have been adopted by institutions. Mainly, two groups of emission models are available: the former is represented by the static or “standard” models, in which the amount of pollutant is computed as a function of average parameters; the latter is represented by the dynamic models, where the amount of pollutant is computed as a function of instantaneous parameter, such as instantaneous speed or acceleration. The well-known traffic increase of the recent years has significantly changed the actual flow conditions, producing a strong rise of interferences. As this facet affects the operating condition of each vehicle, the use of a standard emission models at high traffic interference can lead to some inaccuracies. In such cases, instantaneous emission models introduce deeper capabilities; essentially, the pollutant prediction is directly tied to the engine vehicle operation point in real-like traffic condition. However, this approach requires a large amount of input data (i.e. video recordings or remote sensing analysis), which are not always available. In order to overtake such a difficulty, the present study is based on an integrated simulation tool. Emissions from road traffic are simulated through a dynamic model, whose input data are obtained by the output of virtual reality simulation. Indeed, the analysis took advantage of the experiments carried out in the vehicle virtual reality laboratory: on typical highway geometry, three different flow conditions have been simulated. Investigations have highlighted the dependence of emission level and fuel consumption on drivers’ behavior. The comparison between a gasoline and a diesel compact passenger car in terms of pollutant emissions and fuel consumption has been also reported. In order to assess the differences between static and instantaneous emission models, a comparative analysis has been carried out.

Integrated Modelling of Fuel Influence on Common Rail Injection System Performance

A model for the analysis of diesel engine common rail injection system has been developed and the influence that different fuels have on the injection performances has been investigated. Diesel fuel, biodiesel and kerosene have been used and the differences of injection flow rate, injection pressure time trace, nozzle flow features and break up mechanism have been highlighted. The coupling of two different codes has been used in the simulations: the former one, AMESim code, has been adopted to model the common rail system and to investigate the fuel flow rate and the injection pressure dependence on the fuel type. The latter computational tool, FIRE code, has been initialized by means of the results obtained from the injection system simulation and has been used to perform the 3D investigation of the internal nozzle flow and of the spray formation phenomena, aimed at evaluating the effect of physical fuel features on local flow characteristics and their influence on the system performances. Details of the adopted modeling strategy are described and results of each simulation step are presented.Copyright