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The paper aims at performing an environmental and energetic optimization of a naturally aspirated, light-duty direct injection (DI) diesel engine, equipped with a Common Rail injection system. Injection modulation into up to three pulses is considered starting from an experimental campaign conducted under non-evaporative conditions in a quiescent optically-accessible cylindrical vessel containing nitrogen at different densities. The engine performances in terms of power and emitted NOx and soot are reproduced by multidimensional modelling of the in-cylinder processes. The radiated noise is evaluated by resorting to a recently developed methodology, based on the decomposition of the CFD 3D computed in-cylinder pressure signal. Once validated, both the CFD and the acoustic procedures are applied to the simulation of the prototype engine and are coupled to an external optimizer with the aim of minimizing fuel consumption, pollutant emissions and radiated noise.

This paper reports the study of the effects of alternative diesel fuel and the impact for the air-fuel mixture preparation. The injection process characterization has been carried out in a non-evaporative high-density environment in order to measure the fuel injection rate and the spatial and temporal distribution of the fuel. The injection and vaporization processes have been characterized in an optically accessible single cylinder Common Rail diesel engine representing evaporative conditions similar to the real engine. The tests have been performed by means of a Bosch second generation common rail solenoid-driven fuel injection system with a 7-holes nozzle, flow number 440 cc/30s @100bar, 148deg cone opening angle (minisac type). Double injection strategy (pilot+main) has been implemented on the ECUs corresponding to operative running conditions of the commercial EURO 5 diesel engine.

GM Powertrain Europe and Istituto Motori CNR have undergone a research project aimed at studying the effects on engine performance, emissions and fuel consumption of alternative diesel fuels, from both first (FAME) and second (GTL) generation. The present paper reports some of the results achieved studying the impact on injection and spray behavior of rapeseed and soybean methyl-esters, as well as of GTL diesel blends. The test were performed on a Bosch second generation common rail solenoid-driven fuel injection system capable of 1600bar maximum injection pressure, fitted on GM 1.9L Euro4 diesel engine for passenger cars. The characterization of the injection process has been carried out in terms both of fuel injection rate, as well as of spatial and temporal fuel distribution in a quiescent non-evaporative optically accessible chamber.

Alternative diesel fuels from renewable sources (biodiesels) have increased significantly interest due to their potential CO₂ emission benefits, capability to reduce unburned hydrocarbons and particulate matter emissions, biodegradability and non-toxicity. Biodiesels undergo ageing effects due to autoxidation processes of their molecular chains. Ageing leads to a variety of decomposition products like peroxides, alcohols, aldehydes and carboxylic acids. They are detectable as alterations of chemical properties, odor and taste (rancidity). The characteristics of Rapeseed Methylester (RME), RME aged and diesel sprays have been analyzed for different injection strategies in engines. The tests have been performed on a Bosch second generation common rail solenoid-driven fuel injection system capable of 160 MPa maximum injection pressure, fitted on EURO5 diesel engine for passenger car applications.

This paper illustrates the results of an experimental characterization of a high pressure diesel spray injected by a common rail (CR) injection system both under non-evaporative and evaporative conditions. Tests have been made injecting the fuel with a single hole injector having a diameter of 0.18 mm with L/D=5.56. The fuel has been sprayed at 60, 90 and 120 MPa, with an ambient pressure ranging between 1.2 to 5.0 MPa. The spray evolution has been investigated, by the Mie scattering technique, illuminating the fuel jet and acquiring single shot images by a CCD camera. Tests under non-evaporative conditions have been carried out in an optically accessible high pressure vessel filled with inert gas (N2) at diesel-like density conditions. The instantaneous fuel injection rate, obtained with a time resolution of 10 microseconds, has been also evaluated by an AVL Fuel Meter working on the Bosch Tube principle.

This paper illustrates the results of an experimental investigation on the liquid fuel spray from a multi-jet common rail injection system both under non evaporative and evaporative conditions. Tests have been taken using a 5 hole, 0.13 mm diameter, 150° spray angle, micro-sac nozzle having a flow rate of 270 cm3/30 sec@10 MPa exploring different injection strategies. Experiments have been taken, under non evaporative conditions, injecting the fuel within stagnant inert gas, at different density, in a high-pressure optically-accessible cylindrical vessel with three large quartz windows. Under evaporative conditions, the experiments have been taken within a crank-case scavenged single-cylinder 2-stroke direct injection Diesel engine provided of optical accesses to the combustion chamber. It allows to study the fuel injection process under thermodynamic conditions similar to those currently reached in modern direct injection diesel engines.

One of the most important phases in the development of direct-injected diesel engines is the optimization of the fuel spray evolution within the combustion chamber, since it strongly influences both the engine performance and the pollutant emissions. Aim of the present paper is to provide information about mixture formation within the combustion chamber of a heavy-duty direct injection (HDDI) diesel engine for marine applications. Spray evolution, in terms of tip penetration, is at first investigated under quiescent conditions, both experimentally and numerically, injecting the fuel in a vessel under ambient temperature and controlled gas back-pressure. Results of penetration and images of the spray from the optically accessible high-pressure vessel are used to investigate the capabilities of some state-of-the-art spray models within the STAR-CD software in correctly capturing spray shape and propagation.

In the modern GDI systems, the optimization of the fuel injection process is essential to prepare an air-fuel mixture capable to promote efficient combustion and reduce fuel consumption and pollutant emissions. A key feature for a better atomization is the fuel injection pressure. The increasing of the injection pressure is considered a good way for particle number (PN) reduction due to improved spray atomization, faster evaporation and better mixture formation. In this paper, a multi-hole GDI injector was tested to investigate the effects of very high injection pressures (IVHP), in addition to different ambient densities and temperatures, on the fuel spray morphology, in a cycle-resolved images analysis. Commercial gasoline was injected at the pressures ranging between 40.0 to 70.0 MPa, at gas densities varying between 1.12 to 11.5 kg/m3, and gas temperature up to 200°C.