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Fuels are formulated by a variety of different components characterized by chemical and physical properties spanning a wide range of values. Changing the ratio between the mixture component molar fractions, it is possible to fulfill different requirements. One of the main properties that can be strongly affected by mixture composition is the volatility that represents the fuel tendency to vaporize. For example, changing the mixture ratio between alcohols and hydrocarbons, it is possible to vary the mixture saturation pressure, therefore the fuel vaporization ratio during the injection process. This paper presents a 1D numerical model to simulate the superheated injection process of a gasoline-ethanol mixture through real nozzle geometries. In order to test the influence of the mixture properties on flash atomization and flash evaporation, the simulation is repeated for different mixtures characterized by different gasoline-ethanol ratio.

The concept of Partially Premixed Combustion is known for reduced hazardous emissions and improved efficiency. Since a low-reactive fuel is required to extend the ignition delay at elevated loads, controllability and stability issues occur at the low-load end. In this investigation seven fuel blends are used, all having a Research Octane Number of around 70 and a distinct composition or boiling range. Four of them could be regarded as ‘viable refinery fuels’ since they are based on current refinery feedstocks. The latter three are based on primary reference fuels, being PRF70 and blends with ethanol and toluene respectively. Previous experiments revealed significant ignition differences, which asked for further understanding with an extended set of measurements. Experiments are conducted on a heavy duty diesel engine modified for single cylinder operation. In this investigation, emphasis is put on idling (600 rpm) and low load conditions.

In order to evaluate the potentialities of bioderived diesel fuels, the effect of fueling a 1.9 l displacement HSDI automotive Diesel engine with biodiesel and fossil/biodiesel blend on its emission and combustion characteristics has been investigated. The fuels tested were a typical European diesel, a 50% biodiesel blend in the reference diesel, and a 100% biodiesel, obtained by mixing rape seed methyl ester (RME) and recycled cooking oil (CME). Steady state tests were performed at two different engine speeds (2500 and 4000 rpm), and for a wide range of loads, in order to evaluate the behavior of the fuels under a large number of operating conditions. Engine performance and exhaust emissions were analyzed, along with the combustion process in terms of heat release analysis. Experimental evidences showed appreciably lower CO and HC specific emissions and a substantial increase in NOx levels. A significant reduction of smoke emissions was also obtained.

The paper presents a study made to define the optimal parameter configuration, which enables the mixture preparation, and ignition systems to perform a low-temperature engine start by pure ethanol fuelling without misfiring or failure. A numerical virtual engine, simulating the behavior of a real small displacement 8 valves passenger car engine, is set up to describe and understand the physical phenomena of mixture preparation, spatial and temporal in-cylinder mixture distribution and the ignition/combustion events. The complex phenomena, which govern the gas flow patterns and mixture formation in the intake port and the combustion chamber are particularly analyzed during low-temperature engine cranking. Furthermore is discussed the influence of open and closed valve injection modes.

The effects of using neat and blended (30% vol.) biodiesel, obtained from Rapeseed Methyl Ester (RME) and Jatropha Methyl Ester (JME), in a Euro 5 small displacement passenger car diesel engine have been evaluated in this paper. The impact of biodiesel usage on engine performance at full load was analyzed for a specifically adjusted ECU calibration: the same torque levels measured under diesel operation could be obtained, with lower smoke levels, thus highlighting the potential for maintaining the same level of performance while achieving substantial emissions benefits. In addition, the effects of biodiesel blends on brake-specific fuel consumption and on engine-out exhaust emissions (CO₂, CO, HC, NOx and smoke) were also evaluated at 6 different part load operating conditions, representative of the New European Driving Cycle. Emissions were also measured at the DPF outlet, thus providing information about after-treatment devices efficiencies with biodiesel.

In order to reduce both polluting emissions and fuel costs, many countries allow mixing ethanol to gasoline either in fixed percentages or in variable percentages. The resulting fuel is labeled E10 or E22, where the number specifies the ethanol percentage. This operation significantly changes way the stoichiometric value, which is the air-to-fuel mass ratio theoretically needed to completely burn the mixture. Ethanol concentration must be correctly estimated by the Engine Management System to optimally control exhaust emissions, fuel economy and engine performance. In fact, correct fuel quality recognition allows estimating the actual stoichiometric value, thus allowing the catalyst system to operate at maximum efficiency in any engine working point. Moreover, also other essential engine control functions should be adapted in real time by taking into account the quality of the fuel that is being used.

The effects of using blended renewable diesel fuel (30% vol.), obtained from Rapeseed Methyl Ester (RME) and Hydrotreated Vegetable Oil (HVO), in a Euro 5 small displacement passenger car diesel engine have been evaluated in this paper. The hydraulic behavior of the common rail injection system was verified in terms of injected volume and injection rate with both RME and HVO blends fuelling in comparison with commercial diesel. Further, the spray obtained with RME B30 was analyzed and compared with diesel in terms of global shape and penetration, to investigate the potential differences in the air-fuel mixing process. Then, the impact of a biofuel blend usage on engine performance at full load was first analyzed, adopting the same reference calibration for all the tested fuels.

The potentialities in terms of engine performance and emissions reduction of pure biodiesel were examined on a Common Rail HSDI Diesel engine, trying to define a proper tuning of the injection strategies to bio-fuel characteristics. An experimental investigation was therefore carried out on a typical European passenger car Diesel engine, fuelled with a soybean oil derived biodiesel. A standard European diesel fuel was also used as a reference. In particular, the effects of an equal relative air/fuel ratio at full load condition were analysed; further, a sensitivity study on the outcome of the pilot injection timing and duration at part load on engine emissions was performed. Potentialities in recovering the performance gap between fossil fuel and biodiesel and in reducing NOx specific emissions, affecting only to a limited extent the biodiesel emission benefit in terms of CO, HC and FSN, were highlighted.

An experimental investigation on a group of unleaded gasolines of different chemical composition has been carried out, in order to analyze their knock behaviour in a mass-produced engine at high revolution speed, to highlight possible inconsistencies with their standard Research and Motor octane numbers and to try to discover explanations for the abovementioned inconsistencies. The investigation has been focused on fuels containing oxygenated compounds, such as alcohols (methanol and ethanol) and ethers (MTBE), with the aim of pointing out the influence of the fuel composition on the octane rating, especially as far as the variation in the stoichiometric air/fuel ratio (due to oxygenated compounds blending) is concerned. In particular, the rating of all the fuels under the same relative air/fuel ratio has shown to be a mandatory condition in order to obtain a proper estimate of antiknock performances. The evaluations obtained are consistent with the standard Motor octane numbers.

Experimental work was carried out on a small displacement Euro 5 automotive diesel engine alternatively fuelled with ultra low sulphur diesel (ULSD) and with two blends (30% vol.) of ULSD and of two different fatty acid methyl esters (FAME) obtained from both rapeseed methyl ester (RME) and jatropha methyl ester (JME) in order to evaluate the effects of different fuel compositions on particle number (PN) emissions. Particulate matter (PM) emissions for each fuel were characterized in terms of number and mass size distributions by means of two stage dilutions system coupled with a scanning mobility particle sizer (SMPS). Measurements were performed at three different sampling points along the exhaust system: at engine-out, downstream of the diesel oxidation catalyst (DOC) and downstream of the diesel particulate filter (DPF). Thus, it was possible to evaluate both the effects of combustion and after-treatment efficiencies on each of the tested fuels.

Alternative and oxygenated fuels are nowadays being studied in order to increase engine efficiency and reduce exhaust emissions and also to limit the automotive industry's economical dependency from crude oil. These fuels are considered more ecological compared to hydrocarbons because they are obtained using renewable sources. Fuels like anhydrous/hydrous ethanol, methanol or alcohol/gasoline blends which are injected in liquid form must vaporize quickly, especially in direct injection engines, therefore their volatility is a very important factor and strongly depends on thermodynamic conditions and chemical properties. When a multi-component fuel blend is injected into a low pressure environment below its saturation pressure, a rapid boiling of the most volatile component triggers a thermodynamic atomization mechanism. These kinds of sprays show smaller droplets and lower penetration compared to mechanical break up.

The effects of using neat FAME (Fatty Acid Methyl Ester) in a modern small displacement passenger car diesel engine have been evaluated in this paper. In particular the effects on engine performance at full load with standard (i.e., without any special tuning) ECU calibration were analyzed, highlighting some issues in the low end torque due to the lower exhaust gas temperatures at the turbine inlet, which caused a remarkable decrease of the available boost, with a substantial decrease of the engine torque output, far beyond the expected engine derating due to the lower LHV of the fuel. However, further tests carried out after ECU recalibration, showed that the same torque levels measured under diesel operation can be obtained with neat biodiesel too, thus highlighting the potential for maintaining the same level of performance.