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Diesel engine exhausts from a common rail 3.0 L F1C diesel engine were analyzed at two different load conditions of the WLTC testing cycle downstream of both the diesel particulate filter (DPF) and selective catalytic reactor (SCR) to verify their effect on the characteristics of carbon particulate matter. An array of chemical, physical and spectroscopic techniques (gas chromatography coupled with mass spectrometry (GC-MS), mobility analyzer, UV-Visible absorption and fluorescence spectroscopy) was applied for characterizing polycyclic aromatic hydrocarbons (PAH), heavy aromatic compounds and soot, constituting the particulate matter (PM) sampled from the exhaust. The engine was operated in half load (HL) (188 Nm, representing the more common condition for engine in urban traffic) and full load (FL) (452 Nm, representing the best performance of the engine operation) conditions, at the same engine speed (2000 rpm). Soot formation was enhanced in HL condition, with respect to FL, but, just because of the much lower soot amount, the after-treatment systems in this last condition resulted to be less efficient in the soot abatement. Indeed, the abatement through DPF was about 40% lower in the FL condition with respect to HL condition, and any significant further concentration decrease was found after SCR, in both conditions. By contrast, PAH concentration after DPF abatement was found to be higher in the HL with respect to FL condition. A further PAH concentration decrease of about 30% was found after the SCR in the HL condition whereas in FL the reduction was only about 5-6%. Also the heavy aromatic compounds having molecular weight above the GC-MS detection limit (300 u), were mitigated by SCR. Therefore, SCR did not cause a further soot reduction, whereas it was effective in largely reducing PAH and heavy aromatics emissions, especially in the lower temperature condition featuring the half-load condition, when combustion efficiency is worse. Moreover, SCR system reduced the emission of small particles probably due to an enhanced agglomeration of particles, with beneficial effect on the harmfulness to human health.

The modern Common Rail Diesel engine are, normally, optimised for being fuelled with the commercial Diesel fuel. The ECU calibrations are, consequently, defined to obtain the correct compromise between performances and emissions. It is, so, clear that if the engine is fuelled with an alternative bio-fuel with different characteristics (net heating value, stoichiometric A/F ratio, density, viscosity, etc.) the calibration must be modify. Interest in fuels from renewable sources and their use in transport has grown over the last decade. This is because of their biodegradability, potential improvements in exhaust emissions and benefits on the virtuous CO2 cycle of the earth. This paper demonstrates that it is possible to optimise the emissions and the performances of a light duty diesel C.R. engine fuelled with a vegetable derived fuel (Rapeseed Methyl-Ester) pure or blended with commercial Diesel fuel. Particularly in this paper the experimental results and the ECU control solutions referring to different fuel compositions are shown.

In this paper some preliminary experimental results on a Zebra battery based propulsion system for urban bus applications are presented. The tests were carried out using a laboratory 1:1 scale test bench, composed by a 65 kW electric drive, specifically designed for urban bus applications, supplied by two 20 kWh Zebra batteries connected in parallel. The electric power train was tested on a laboratory bench, connected through a fixed ratio gear box to a 100 kW regenerative electric brake provided with speed and torque controls, in order to evaluate the propulsion system performance in steady state operative conditions. The obtained preliminary experimental results were utilized to implement a Matlab-Simulink model of urban bus, which might be powered by the same electric propulsion system studied. Thanks to this model it was possible to evaluate the dynamic behavior of the urban bus, working on standard driving cycles, taking into account the resistant forces represented by proper vehicle/road/aerodynamic parameters. An evaluation of the expected real vehicle driving range was also estimated in different road conditions.

This paper aims to correlate the in-cylinder soot formation and the exhaust particle emissions for different methods of gasoline/ethanol fueling in spark ignition engine. In particular, the engine was fueled with gasoline and ethanol separately and not, in this latter case both blended (E30) and dual fueled (EDF). For E30 the bend was direct injected and for EDF, the ethanol was injected in the combustion chamber and the gasoline into the intake duct. For both the injection configurations, the same percentage of ethanol in gasoline was supplied: 30%v/v. The measurements were carried out at 2000 and 4000 rpm, under full load, and stoichiometric condition, in small single cylinder optical engine. 2D-digital imaging was performed to follow the combustion process with a high spatial and temporal resolution through a full-bore optical piston. The two-color pyrometry was applied for the analysis of the in cylinder soot formation in the combustion chamber. Particle mass concentration was evaluated at the exhaust by means of a smoke meter. The particle size distribution function was measured in the range from 5.6 to 560 nm by an Engine Exhaust Particle Sizer (EEPS). It was observed that the use of ethanol allows the reduction of soot formation and particles emission in DI configuration. However, for E30 the in-cylinder soot formation and emissions are larger than EDF. This result is mainly due to the different contribution of gasoline. Optical analysis shows that in E30 the direct injected gasoline causes wide diffusive flames where soot formation is promoted; whereas for EDF the better evaporation and mixing of gasoline, typical of PFI configuration, results in few, small, and localized diffusive flames producing smaller particle emissions.

The use of methane as supplement to liquid fuel is one of the solution proposed for the reduction of the internal combustion engine pollutant emissions. Its intrinsic properties as the high knocking resistance and the low carbon content makes methane the most promising clean fuel. The dual fuel combustion mode allows improving the methane combustion acting mainly on the methane slow burning velocity and allowing lean burn combustion mode. An experimental investigation was carried out to study the methane-gasoline dual fuel combustion. Methane was injected in combustion chamber (DI fuel) while gasoline was injected in the intake manifold (PFI fuel). The measurements were carried out in an optically accessible small single-cylinder four-stroke engine. It was equipped with the cylinder head of a commercial 250 cc motorcycles engine representative of the most popular two-wheel vehicles in Europe. UV-visible spectroscopy measurements were performed to analyze the combustion process with high spatial and temporal resolution. In particular, UV-visible spectroscopy allows detecting the chemical markers of combustion process such as the radicals OH* and CH*. The in-cylinder lambda spatial and temporal evolution was evaluated. The combustion evolution is characterized by means of a high speed cycle resolved camera. The exhaust emissions were characterized by means of gaseous analyzers. The measurements were performed under steady state conditions at different engine operating conditions.

In the last years, even more attention was paid to the alternative fuels that allow both reducing the fossil fuel consumption and the pollutant emissions. Gaseous fuels like methane and hydrogen are the most interesting in terms of engine application. This paper reports a comparison between methane and different methane/hydrogen mixtures in a single-cylinder Port Fuel/Direct Injection spark ignition (PFI/DI SI) engine operating under steady state conditions. It is representative of the gasoline engine for automotive application. Engine performance and exhaust emissions were evaluated. Moreover, 2D-digital cycle resolved imaging was performed with high spatial and temporal resolution in the combustion chamber. In particular, it allows characterizing the combustion by means of the flame propagation in terms of mean radius and velocity. Moreover, the interaction of turbulence with the local flame was evaluated. For both the engine configurations, it was observed that the addition of hydrogen results in a more efficient combustion, even though the engine configuration plays an important role. In PFI mode, the lower density of hydrogen causes a lower energy input. In DI mode, instead, the larger hydrogen diffusivity counteracts the charge stratification especially for larger hydrogen content. © 2016 Elsevier Ltd. All

Alternative fuels and energy vectors are becoming increasingly important in terms of technical, geopolitical, economic, and environmental aspects. In particular, gaseous fuels and vectors, such as fossil or synthetic natural gas (NG) blended with hydrogen, commonly help provide optimal strategies to reduce global and toxic emissions of internal combustion engines, owing to their adaptability, anti-knock capacity, lower toxicity of pollutants, reduced CO2 emissions, and costeffectiveness. However, diesel engines still represent the reference category among internal combustion engines in terms of maximum thermodynamic efficiency. The possibility offered by dual-fuel (DF) systems to combine the efficiency and performance of diesel engines with the environmental advantages of gaseous fuels has been the subject of extensive investigations. However, the simple replacement of diesel fuel with gaseous fuel does not allow for optimising the engine performance, owing to the high percentage of unburned gaseous fuel, which compromises the potential reduction of CO2; therefore, more complex combustion strategies should be realised. In this study, with the aim of improving the DF combustion process, an experimental investigation was performed to analyse low-temperature combustion (LTC), using NG and two enriched hydrogen-compressed NG blends as primary fuels. The LTC mode was activated by means of a very early advanced pilot injection and carried out in two close steps. The double pilot injection was used to control the energy release rate in the first combustion stage, thereby minimizing the increase of the rate of pressure and allowing the extension of the operation range under LTC. The experimental activity was also focused on analysing the particle emissions, as it is well known that these emissions, together with those of nitrogen oxide, constitute the main pollutants resulting from diesel fuel combustion. The results demonstrated the potential to reduce the unburned fuel, NOx, and particle emissions simultaneously, while maintaining equivalent CO2 emissions to a diesel-only engine. Both the timing and pressure of the pilot injection proved to be critical parameters for optimising the emissions and performance

Internal combustion engines are still the energy conversion units of choice in transport and distributed energy generation. Due to the fuel mix, spark ignition (SI) engines represent a viable solution that features improved fuel flexibility with respect to their compression ignition counterparts. Therefore, manufacturers are continuously trying to increase their performance and reduce emissions through experimental and numerical investigations. A growing trend in engine improvement is the application of simulations on a wider scale in order to contain development costs. Combustion is the most complex part of the working cycle and for SI power units, modeling flame propagation represents an essential feature of predictive numerical investigations. Within this context, the present study was aimed at better understanding the mass transfer between unburned and reacting gas, as well as characteristic reaction time scales within the reaction zone. A OD model with three zones was applied for different engine speed, load, air-fuel ratio and spark timing settings, chosen as representative for mid-road load automotive use. Combined in-cylinder pressure measurements and flame imaging were used for validating the essential concept of fresh charge entrainment and burn-up process. One major conclusion of the work was that there is a definite stratification of chemical species within the burned-reacting gas that can be well captured by the entrainment model. The fact that the calibration coefficients require different values for accurate prediction of the pressure traces during flame propagation, emphasizes the complexity of the combustion process, as well as the limitations of considering flames as laminar even at local scale. The study also identified the scale at which mass transfer takes place as an essential factor for correct turbulent combustion modeling. (C) 2015 Elsevier Ltd. All rights reserved.

In themediumtolongterm,lowfossilfuelavailabilitywillmakeitnecessarytofindalternatives.Mass productionofbiofuelswillnotbeapracticalsolutionbecauseitrequiresstrongcompetitionforland that isusedforgrowingfood.Therefore,itwillbenecessarytorevisetheframeoftransportation energy sources.Thenumberofpurelight-andheavy-dutyelectricvehiclescouldincreaseinurban areas.Instead,itwillbehardtofindaviablealternativetotheinternalcombustionengineforextra- urban transportvehicles,thereforealternativesyntheticfuelscouldbeusedtocompensateforfossil fuel depletion.Asidefromasmallshareobtainablefrombiomass,mostsyntheticfuelsareexpectedto be obtainedfromcoal.Amongthese,syntheticnaturalgasrepresentsaverygoodsolution.Infact, syntheticnaturalgaswillbeadvantageouswithrespecttohydrogen,whoseon-boardstoragewillbean unsolvedprobleminthemediumterm,andwithrespecttosyntheticliquidfuels,whichrequiremore energy intheproductionphase.Moreover,thecarboncontentofliquidfuels,whichishigherthanthat of gaseousfuels,willberesponsibleforhigherCO2 emissionsfromvehicles.Currently,naturalgashas poor diffusioninthetransportsector,andthispaperhighlightsthemotivationsforfavouringapolicy aimedatincreasingtheshareofgaseousfuel-poweredvehicles.Inadditiontothelowenvironmental impact,syntheticnaturalgasalsooffersthepossibilityofoptimisingtheutilisationoffutureresources