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Nowadays, developing of effective camless engine systems, allowing Variable Valve Actuation (VVA), is one of the fundamental automotive challenge to increase engine power, reduce fuel consumption and pollutant emissions, as well as improve the engine efficiency significantly. Electromechanical devices based on double electromagnets have shown to be a promising solution to actuate engine valves during normal engine cycle due to their efficient working principle. Conversely, this solution requires special care at the key-on engine for the first valve lift, when the valve must be shifted from the middle equilibrium position to the closing one with limited coil currents and power requirements as well. Despite the central role of the first catching problem, few attempts have been done into the existing literature to tackle it systematically.

Modern VVA systems offer new potentialities in improving the fuel consumption for spark-ignition engines at low and medium load, meanwhile they grant a higher volumetric efficiency and performance at high load. Recently introduced systems enhance this concept through the possibility of concurrently modifying the intake valve opening, closing and lift leading to the development of almost "throttle-less" engines. However, at very low loads, the control of the air-flow motion and the turbulence intensity inside the cylinder may require to select a proper combination of the butterfly throttling and the intake valve control, to get the highest BSFC (Brake Specific Fuel Consumption) reduction. Moreover, a low throttling, while improving the fuel consumption, may also produce an increased gas-dynamic noise at the intake mouth. In highly "downsized" engines, the intake valve control is also linked to the turbocharger operating point, which may be changed by acting on the waste-gate valve.

High pressure diesel sprays were visualized under vaporizing and combusting conditions in a constant-volume combustion vessel. Near-simultaneous visualization of vapor and liquid phase fuel distribution were acquired using a hybrid shadowgraph/Mie-scattering imaging setup. This imaging technique used two pulsed LED's operating in an alternative manner to provide proper light sources for both shadowgraph and Mie scattering. In addition, combustion cases under the same ambient conditions were visualized through high-speed combustion luminosity measurement. Two single-hole diesel injectors with same nozzle diameters (100μm) but different k-factors (k0 and k1.5) were tested in this study. Detailed analysis based on spray penetration rate curves, rate of injection measurements, combustion indicators and 1D model comparison have been performed.

The present paper reassumes the results of an experimental study focused on the effects of the nozzle injector's coking varying the flow number (FN); the performance and emissions of an automotive Euro5 diesel engine have been analyzed using diesel fuel. As the improvement of the diesel engine performance requires a continuous development of the injection system and in particular of the nozzle design, in the last years the general trend among OEMs is lowering nozzle flow number and, as a consequence, nozzle holes size. The study carried out moves from the consideration that a reduction of the nozzle holes diameter could increase the impact of their coking process. For this purpose, an experimental campaign has been realized, testing the engine in steady state in three partial load operating points, representative of the European homologation driving cycle, and in full load conditions.

1D codes are nowadays commonly used to investigate a turbocharged ICE performance, turbo-matching and transient response. The turbocharger is usually described in terms of experimentally derived characteristic maps. The latter are commonly measured using the compressor as a brake for the turbine, under steady “hot gas” tests. This approach causes some drawbacks: each iso-speed is commonly limited to a narrow pressure ratio and mass flow rate range, while a wider operating domain is experienced on the engine; the turbine thermal conditions realized on the test rig may strongly differ from the coupled-to-engine operation; a “conventional” net turbine efficiency is really measured, since it includes the effects of the heat exchange on the compressor side, together with bearing friction and windage losses.

The paper describes the challenges and results achieved in developing a new high-speed Diesel combustion system capable of exceeding the imaginative threshold of 100 kW/l. High-performance, state-of-art prototype components from automotive diesel technology were provided in order to set-up a single-cylinder research engine demonstrator. Key design parameters were identified in terms boost, engine speed, fuel injection pressure and injector nozzle flow rates. In this regard, an advanced piezo injection system capable of 3000 bar of maximum injection pressure was selected, coupled to a robust base engine featuring ω-shaped combustion bowl and low swirl intake ports. The matching among the above-described elements has been thoroughly examined and experimentally parameterized.

One-dimensional (1D) models are commonly employed to study the performances of turbocharged engine. Manufacturers' provided steady turbomachinery maps are usually utilized, although they operate in unsteady conditions as a consequence of pressure pulses propagating into the intake and exhaust systems. This may lead to some inaccuracies in the engine-turbocharger matching calculations, which may be solved through the introduction of proper time-delays (virtual pipe corrections). These drawbacks, however, became more relevant when engine operates under low speed and high load conditions, or during a transient maneuver, because of possibilities of compressor surging.

In the context of a transport sustainability, some solutions could be proposed from the integration of many disciplines, architects, environmentalists, policy makers, and consequently it may be addressed with different approaches. These solutions would be applied at different geographical levels, i.e. national, regional or urban scale. Moreover, the assessment of cars emissions in real use plays a fundamental role for their reductions. This is also the direction of the new harmonized test procedures (WLTP). Furthermore, it is fundamental to keep in mind that the new WLTC cycle will reproduce a situation closer to the reality comparing to the EUDC/NEDC driving cycle. In this paper, we will be focused on vehicle kinematic evaluation aimed at valuation of traffic situation and emissions.

Technologies for direct injection of fuel in compression ignition engines are in continuous development. One of the most investigated components of this system is the injector; in particular, main attention is given to the nozzle characteristics as hole diameter, number, internal shape, and opening angle. The reduction of nozzle hole diameter seems the simplest way to increase the average fuel velocity and to promote the atomization process. On the other hand, the number of holes must increase to keep the desired mass flow rate. On this basis, a new logic has been applied for the development of the next generation of injectors. The tendency to increase the nozzle number and to reduce the diameter has led to the replacement of the nozzle with a circular plate that moves vertically. The plate motion allows to obtain an annulus area for the delivery of the fuel on 360 degrees; while the plate lift permits to vary the atomization level of the spray.

The recent interest in alternative non-fossil fuels has led researchers to evaluate several alcohol-based formulations. However, one of the main requirements for innovative fuels is to be compatible with existing units’ hardware, so that full replacement or smart flexible-fuel strategies can be smoothly adopted. n-Butanol is considered as a promising candidate to replace commercial gasoline, given its ease of production from bio-mass and its main physical and chemical properties similar to those of Gasoline. The compared behavior of n-butanol and gasoline was analyzed in an optically-accessible DISI engine in a previous paper [1]. CFD simulations explained the main outcomes of the experimental campaign in terms of combustion behavior for two operating conditions. In particular, the first-order role of the slower evaporation rate of n-butanol compared to gasoline was highlighted when the two fuels were operated under the same injection phasing.

This paper is based on a Research Project of the Department of Mechanical Engineering (DiME) in collaboration with Aprilia, the Italian motorbike manufacturer. In an attempt to simulate the functioning of the cooling plant of the Aprilia RSV-4 motorbike a numerical model was constructed using mono-dimensional and three-dimensional simulation codes. Our ultimate aim was to create a simulation model which could be of assistance to engine designers to improve cooling plant performance, thereby reducing research and development costs. The model allows to simulate the running conditions of the whole cooling circuit upon variations in environmental and running conditions. In particular, the centrifugal pump of the cooling plant was simulated by a 3D commercial software, while the whole circuit was built by a 1D commercial code which allows simulation of all the thermal exchanges and pressure drops in the cooling circuit.

The present paper describes an experimental investigation over the impact of diesel injector nozzle flow number on spray formation and combustion evolution for a modern EURO5 light-duty diesel engine. The analysis has been carried out by coupling the investigations in non evaporative spray bomb to tests in optical single cylinder engine in firing conditions. The research activity, which is the result of a collaborative project between Istituto Motori Napoli - CNR and GM Powertrain Europe, is devoted to understanding the basic operating behaviour of low flow number nozzles which are showing promising improvements in diesel engine behaviour at partial load. In fact, because of the compelling need to push further emission, efficiency, combustion noise and power density capabilities of the last-generation diesel engines, the combination of high injection pressure fuel pumps and low flow number nozzles is general trend among major OEMs.

The present paper describes an experimental and numerical study on the effect of the nozzle flow number (FN) on the full load performance of a modern Euro5 diesel automotive engine, in terms of torque, efficiency and exhaust emissions. The improvement of the diesel engine performance requires a continuous development of the engine components, first of all the injection system and in particular the nozzle design. One of the most crucial factors affecting performance and emissions is the nozzle flow number and its influence becomes more and more important as high performance and low emissions are continuous requirements. Indeed, reducing the nozzle flow number, due to an increase of spray-air mixing, an improvement in PM-NOx trade-off is generally expectable. On the other hand, at full load, where peak firing pressure and exhaust valve temperature become the limiting factors, critical operating conditions can be easily reached reducing the nozzle hole diameter.

The present paper describes the results of a research project aimed at studying the impact of nozzle flow number on a Euro5 automotive diesel engine, featuring Closed-Loop Combustion Control. In order to optimize the trade-offs between fuel economy, combustion noise, emissions and power density for the next generation diesel engines, general trend among OEMs is lowering nozzle flow number and, as a consequence, nozzle hole size. In this context, three nozzle configurations have been characterized on a 2.0L Euro5 Common Rail Diesel engine, coupling experimental activities performed on multi-cylinder and optical single cylinder engines to analysis on spray bomb and injector test rigs. More in detail, this paper deeply describes the investigation carried out on the multi-cylinder engine, specifically devoted to the combustion evolution and engine performance analysis, varying the injector flow number.

The performance and emission characteristics of the compression ignition engines are largely governed by the fuel atomization and air mixing, processes which in turn are strongly influenced by the flow dynamics inside the injector nozzle. This is controlled by dynamic (injection pressure, needle lift, etc.) and geometrical factors (orifice conicity, hydro grinding, etc.). Moreover, the modern diesel fuel injection systems are susceptible of deposits formation that can occur in different locations, e.g. in nozzle spray-holes and inside the injector body. The present paper describes the results of a research project aimed at studying the impact of injector coking on diesel spray formation for three injectors with different flow numbers. The characterization of the injection process has been carried out in terms of fuel injection rate as well as spatial and temporal fuel distribution in a quiescent chamber in non evaporative conditions.

A set of additives was selected to improve the durability of the physical-chemical and biological characteristics of mineral diesel and its blend with biodiesel. Two biodiesels were used: soybean (SME) and rapeseed (RME). Both physical-chemical properties and fuel dispersion of fuel blends and their mixtures with additives were measured that could have effects on the combustion process in diesel engines. The dispersion of the fuel is affected by the injection nozzle integrity, influencing the capacity of the fuel to vaporize, while the modification of the fuel molecular structure can cause changes in combustion reaction. A 7 hole Common Rail (CR) 2nd generation injector, 136 μm in diameter, was used at 80 MPa and 1.0 ms injection pressure and duration, respectively. The injection rate was determined using the Bosch's Method, while the fuel dispersion was measured by analyzing the images of spray evolving in an optical accessible quiescent vessel.

In this paper the investigation with X-ray Tomography on the structure of a gasoline spray from a GDI injector for automotive applications based on polycapillary optics is reported. Table-top experiment using a microfocus Cu Kα X-ray source for radiography and tomography has been used in combination with a polycapillary halflens and a CCD detector. The GDI injector is inserted in a high-pressure rotating device actuated with angular steps Δθ = 1° at the injection pressure of 8.0 MPa. The sinogram reconstruction of the jets by slices permits a 360° spray access to the fuel downstream the nozzle tip. A spatial distribution of the fuel is reported along the direction of six jets giving a measure of the droplet concentration in a circle of 16 mm2 below the nozzle tip at atmospheric backpressure and ambient temperature.

The combustion quality in modern diesel engines depends strictly on the quality of the air-fuel mixing and, in turn, from the quality of spray atomization process. So air-fuel mixing is strongly influenced by the injection pressure, geometry of the nozzle duct and the hydraulic characteristics of the injector. In this context, spray concepts alternative to the conventional multi-hole nozzles could be considered as solutions to the extremely high injection pressure increase to assure a higher and faster fuel-air mixing in the piston bowl, with the final target of increasing the fuel efficiency and reducing the engine emissions. The study concerns an experimental depiction of a spray generated through a prototype high-pressure hollow-cone nozzle, under evaporative and non-evaporative conditions, injecting the fuel in a constant-volume combustion vessel controlled in pressure and temperature up to engine-like gas densities in order to measure the spatial and temporal fuel patterns.

The application of more efficient compression ignition combustion concepts requires advancement in terms of fuel injection technologies. The injector nozzle is the most critical component of the whole injection system for its impact on the combustion process. It is characterized by the number of holes, diameter, internal shape, and opening angle. The reduction of the nozzle hole diameter seems the simplest way to promote the atomization process but the number of holes must be increased to keep constant the injected fuel mass. This logic has been applied to the development of a new generation of injectors. First, the tendency to increase the nozzle number and to reduce the diameter has led to the replacement of the nozzle with a circular plate. The vertical movement of the needle generates an annulus area for the fuel delivery on 360 degrees, so controlling the atomization as a function of the vertical plate position.

In recent years, in order to optimize performance and exhaust emissions of internal combustion engines, the design of auxiliary systems assumed a particular importance especially due to the need to obtain higher efficiency and reduce power losses required by these components. In this sense, looking at the lubrication circuit, it appears important to use solutions that allow to optimize the fluid dynamics of both the ducts and the pump. In this paper a tridimensional CFD analysis of a lubrication circuit oil pump of a modern high-performance engine will be shown. In this particular application there is a variable displacement pump used to optimize the operative conditions of the lubricant circuit in all engine running conditions. This variable displacement pump changes the positions of the ring as a function of the boundary conditions.