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It is well known that ethanol can be used in spark-ignition (SI) engines as a pure fuel or blended with gasoline. High enthalpy of vaporization of alcohols can affect air-fuel mixture formation prior to ignition and may form thicker liquid films around the intake valves, on the cylinder wall and piston crown. These liquid films can result in mixture non-homogeneities inside the combustion chamber and hence strongly influence the cyclic variability of early combustion stages. Starting from these considerations, the paper reports an experimental study of the initial phases of the combustion process in a single cylinder SI engine fueled with commercial gasoline and anhydrous ethanol, as well as their blend (50%vol alcohol). The engine was optically accessible and equipped with the cylinder head of a commercial power unit for two-wheel applications, with the same geometrical specifications (bore, stroke, compression ratio).

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.

The role of Spark Ignition (SI) and Diesel engines as nanoparticles sources in urban area was investigated. Detection, sizing and counting of particles were realized at the exhaust of a Port Fuel Injection Spark Ignition (PFI SI) engine equipped with a Three-Way Catalyst (TWC) and a Unijet Common Rail (CR) Diesel engine equipped first with an Oxidation Catalyst (OC) and then with a Catalyzed Diesel Particulate Filter (CDPF). Engine operating conditions in high road traffic were considered. Electrical Low Pressure Impactor (ELPI) was used as real-time measurements device for particle size distribution in the range from 7 nm up to 10000 nm. Broadband UV-Visible Extinction and Scattering Spectroscopy (BUVESS) allowed investigating the chemical and physical nature of emitted particles. It was observed that the major contribution to particulate mass is due to Diesel engine equipped with the OC, the other engines contribute only in terms of number concentration.

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.

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.

Conventional methods for combustion gas concentration measurement are typically based on gas sampling, sample treatment and subsequent analysis. These procedures could affect the species concentrations in particular when temporal variations of process parameters are under study. Moreover, in these methods, the concentration measurements are usually performed at standard temperature and pressure. In order to overcome these limitations, in-situ and real-time concentration measurement techniques are needed. In this paper, an in-situ technique with high spatial and temporal resolution, based on ultraviolet-visible absorption spectroscopy, was proposed. This technique allowed the simultaneous determination of NO and OH absolute concentrations inside optically accessible diesel combustion chamber. Temporal and spatial distribution of OH and NO was evaluated.