The adoption of diesel LTC combustion concepts is widely recognised as a practical way to reduce simultaneously nitric oxides and particulate emission levels from diesel internal combustion engines. However, several challenges have to be faced up when implementing diesel LTC concepts in real application vehicles. In particular, achieving acceptable performance concerning the drivability comfort, in terms of output torque stability and combustion noise during engine dynamic transients, is generally a critical point. One of the most promising solutions to improve the LTC combustion operation lays in the exploitation of closed loop combustion control, based on in-cylinder pressure signals. In this work, the application of an in-cylinder pressure-based closed loop combustion control to a Euro 6-compliant demonstrator vehicle has been developed. The main challenges deriving from the control of the LTC combustion, directly affecting the engine/vehicle performance, have been analysed in detail. In order to overcome these drawbacks, a new control function, integrated into the base closed loop system, has been designed. The performance of the new function have been experimentally tested at the engine test bench. Results showed a significant enhancement of the LTC operation, in terms of both combustion stability and noise reduction during engine transients. The new function was also implemented on a real vehicle, thus proving the potential of the new control concept in realistic operating conditions.

This paper presents the potentialities of a new ignition system based on exposition of multi-walled carbon nanotubes containing 75% in weight of ferrocene to a low-consumption flash camera. The experiments were performed in a constant-volume chamber equipped with an optical access, to allow the acquisition of high-speed camera images, and with a piezoresistive pressure sensor. The chamber was filled with an air-methane gaseous mixture and its combustion was triggered by flashing the nanotubes. The resulting combustion process was compared with the one obtained triggering the mixture ignition with a traditional spark plug. The combustion process was characterized for different air-methane ratios. The results show that the ignition with nanotubes determines a higher combustion pressure gradient and a higher peak pressure than spark ignition for all the tested air-methane ratios. Furthermore, high-speed camera images show that the ignition with nanotubes leads to a more distributed homogeneous-like combustion and then a faster consumption of the air-methane mixture without the formation of a discernible flame front.

The possibility to ignite the single wall carbon nanotubes (SWCNTs) containing impurities of iron in atmosphere once exposed to the radiation of a flash camera was observed for the first time in 2002. Afterwards, it was proposed to exploit this property in order to use nanostructured materials as ignition agents for fuel mixtures. Finally, in 2011 it was shown that SWCNTs can be effectively used as ignition source for an air/ethylene mixture filling a constant volume combustion chamber; the observed combustion presented the characteristics of a homogeneous-like combustion. In this paper a system for the ignition of an air/methane mixture is proposed, based on the exposition of multi wall carbon nanotubes (MWCNTs) to a low consumption flash camera. Namely, several experiments have been run in which 20 mg of MWCNTs, containing 75% in weight of ferrocene, have been added to an air/methane fuel mixture inside a constant volume combustion chamber. The mixture has been heated up to 373 K and the onset pressure was set equal to 3 bar. The experiments have been run varying the equivalence ratio in the range 1 - 2. The combustion process so realized has been compared to that obtained igniting the mixture with a traditional spark as in spark ignition engines. The comparison has been based on chamber pressure measurement as well as combustion process images, both sampled at a frequency equal to 2,5 kHz for an overall duration of 1.8 s. Results confirm that the ignition triggered with MWCNTs leads to a homogeneous-like combustion, without observing a well-defined flame front propagation. The contrary is observed, as expected, with the spark assisted ignition. Moreover, dynamic pressure measurements show that, compared to spark assisted ignition, the MWCNTs photo-ignition determines a more rapid pressure gradient and a higher peak pressure which corresponds to a higher energy release rate.

This paper presents a new analytic model for the estimation of the trapping efficiency of two-stroke engines using an extremely reduced number of measured physical variables. Mainly, the model estimates the trapping efficiency according to the Ostwald diagram, to the molal concentration of carbon dioxide and oxygen at tailpipe and accordingto the mass flow of air and fuel. In order to provide a measure of effectiveness for the proposed model, a use case has been chosen. The model’s effectiveness has been evaluated comparing its outcomes with the results obtained by thermo-fluid dynamic simulation of the use case on a 0D-1D commercial code, whose scavenging model has been previously validated by an extensive experimental activity. The present study shows that, for all the cases considered, the model results differ no more than 11% in absolute value from the simulated ones. In brief, the accuracy of the model allows the estimation of the trapping efficiency for two-stroke engines with reasonable confidence, reduced computational effort and time and costs lower than the currently available techniques.

The process of conversion in Linz-Donawitz converters is a crucial stage in the production of steel: oxygen is blown on the surface of the melted bath in order to reduce the carbon concentration. At the same time, suitable amounts of coolants are added in order to govern the increase of the bath temperature and reduce the impurities (favoring the slag formation). The aim is to direct the bath of melted steel to the desired final condition, in terms of temperature and carbon content. At around 92-93% of the complete process of conversion, the oxygen blowing is suspended and the In-Blow is performed, i.e. a steel sample is collected by means of a lance introduced in the melted bath and its carbon percentage and temperature measured. A dynamic model, through two characteristic equations, describes the evolution of the carbon percentage and temperature of the melted steel during the final phase of the conversion process, i.e. from the In-Blow until the end. Based on this model, the volume of oxygen to be blown during this phase and the amount of coolant to be added in order to reach the required final (End-Point) conditions of carbon percentage and temperature can be calculated. The model is nonlinear and depends on four parameters to be estimated. Based on a dimensional analysis and on a large set of experimental data, the nominal model has been modified introducing the hypothesis that the parameters are not constant, but depend on the temperature. Within this framework the novel model is identified exploiting Least Squares (LS) methods and its output is compared with the existing practice.

The energy planning based on Mean - Variance theory, guides the investors in investment decisions, trying to maximize the return and minimize the risk of investment. However, this theory is based on strong hypotheses and, in addition, input data are often affected by estimation errors. Moreover, this theory determines poor diversification increasing return and risk of the portfolio, and strong variability of the outputs when inputs are varied. In the first part of the paper, the Mean - Variance theory was applied to the energy generation in Italy; in particular, the analysis was on the actual energy mix, but also assuming the use of nuclear technology and taking into account verisimilar improvement, of technologies in the future. On the other hand, in the second part of the paper, a methodology has been applied in order to limit the problems of Mean-Variance theory applied to the energy mix settlement. In particular, the input variables have been calculated using Monte Carlo simulation, in order to reduce the estimation error, and the Resampled Efficiency TM technique has been applied in order to calculate the resulting new "average" efficient frontier. This methodology has been applied either not limiting or limiting the minimum and maximum percentage for every energy generation technology, in order to simulate constraints due, for example, to the technological characteristics of the plant, the availability of the sources and eventually to norms, to the territorial characteristics and to the socio-political choices. The application of Mean - Variance theory allowed to obtain energy portfolio, alternative to the actual, characterized by higher values of expected returns an lower values of risk. It was also shown that the application of the Resampled Efficiency TM technique with data originated with the Monte Carlo simulation effectively tackles the problems of Mean - Variance theory; in this way, the decision maker is helped in making decisions in the energy system policy and development. Thanks to this approach, applied in particular to the Italian energy contest, it was also possible to evaluate the effectiveness of the introduced modifications to the Italian actual energy mix to achieve the 2020 European Energy Directive targets in particular concerning the reduction of CO2 levels.

In this paper, a detailed survey has been carried out in order to evaluate the performance of a micro combined heat and power system, based on internal combustion engine fed with natural gas as prime mover. In particular, several operating modes of the micro combined heat and power system are proposed to satisfy the electric load demand deriving from civil users. These operating modes consider a variable number of users and prime movers, as well as a variable strategy of load sharing among them. Moreover, the analysis takes into account the utilization of an electric energy storage system and a converter allowing the operation of the engine at variable speed as enabling technologies. The comparison has been done using as input a statistical profile of domestic electric load. The results, compared with the performance of the conventional systems, have highlighted a maximum natural gas saving up to 22% with consequent reduction of carbon dioxide emissions. Moreover, the results of simulations show that the number of engines and the engine operation at variable speed determines the greatest benefits on fuel consumption, followed by the utilization of an electric energy storage system. The load sharing strategy, among the operating engines, has, on the contrary, a secondary effect.

The development of energy crops can provide environmental benefits and may represent an opportunity to improve agriculture in areas considered at low productivity. In this work, we studied the energy potential of two species (Brassica carinata A. Braun and Cynara cardunculus L.) and their seed oil productivity under different growth conditions. Furthermore, the biodiesel from the oil extracted from the seeds of these species was produced and analysed in term of utilisation as fuels in compression ignition engines. In particular, the spray penetration and shape ratio were measured in a constant-volume chamber and compared with the results obtained with a standard diesel fuel. These results were obtained using a standard common rail injection system at different injection pressure, injection duration, and constant-volume chamber pressure.

In this paper, the results of an extensive experimental campaign about dual fuel combustion development and the related pollutant emissions are reported, paying particular attention to the effect of both the in-cylinder charge bulk motion and methane supply method. A diesel common rail research engine was converted to operate in dual fuel mode and, by activating/deactivating the two different inlet valves of the engine (i.e. swirl and tumble), three different bulk flow structures of the charge were induced inside the cylinder. A methane port injection method was proposed, in which the gaseous fuel was injected into the inlet duct very close to the intake valves, in order to obtain a stratified-like air–fuel mixture up to the end of the compression stroke. For comparison purposes, a homogeneous-like air–fuel mixture was obtained injecting methane more upstream the intake line. Combining the different positions of the methane injector and the three possible bulk flow structures, seven different engine inlet setup were tested. In this way, it was possible to evaluate the effects on dual fuel combustion due to the interaction between methane injector position and charge bulk motion. In addition, methane injection pressure and diesel pilot injection parameters were varied setting the engine at two operating conditions. For some interesting low load tests, the combustion development was studied more in detail by means of direct observation of the process, using an in-cylinder endoscope and a digital CCD camera. Each combustion image was post-processed by a dedicated software, in order to extract only those portions with flame presence and to calculate an average luminance value over the whole frame. These luminance values, chosen as indicators of the combustion intensity, were represented over crank angle position and, then, an analysis of the resulting curves was performed. Results showed that the charge bulk motion associated to the swirl port, improving the charge mixing of the diesel spray and the propagation of the turbulent flame fronts, is capable to enhance the oxidation of air–methane mixture, both at low and high engine loads. Furthermore, at low loads, the analysis of combustion images and luminance curves showed that methane port injection can significantly affect the intensity and the spreading of the flame during dual fuel combustion, especially when a suitable in-cylinder bulk motion is obtained. Concerning the engine emissions, some correlations with what observed during the analysis of the combustion development were found. Furthermore, it was revealed that, for several combinations of the engine operating parameters, methane port injection was always associated to the lowest emission levels, demonstrating that this methane supply method is a very effective strategy to reduce unburned hydrocarbons and nitric oxides concentrations, especially when implemented with variable intake geometry systems.

This work presents an experimental investigation to determine the performance and characteristics of the combustion process triggered by a new ignition system based on photo-thermal effect, observed when nano-Energetic Materials are exposed to a flash light. The resulting combustion process has been compared with the one obtained using the spark-plug traditionally used in spark ignition engines. Results showed that the photo-thermal ignition determines higher combustion pressure gradient, peak pressure, total heat released, fuel combustion efficiency, and a shorter ignition delay and combustion duration compared with the spark ignition, for all the tested fuels and air-fuel ratios.

The strategies adopted to control the combustion in Diesel applications play a key role when dealing with current and future requirements of automotive market for Diesel powertrain systems. The traditional “open loop” control approach aims to achieve a desired combustion behaviour by indirect manipulation of the system boundary conditions (e.g. fresh air mass, fuel injection). On the contrary, the direct measurement of the combustion process, e.g. by means of in-cylinder pressure sensor, offers the possibility to achieve the same target “quasi” automatically all over the vehicle lifetime in widely different operating conditions. Beside the traditional combustion control in closed loop (i.e. based on inner torque and/or combustion timing), the exploitation of incylinder pressure signal offers a variety of possible further applications, e.g. smart detection of Diesel fuel quality variation, control of combustion noise, modeling engine exhaust emission (e.g. NOx). Such advanced cylinder pressure-based control concepts can support the development of Diesel powertrain systems, taking into account recent trends characterized by an increasing system complexity, additional degrees of freedom related to e.g. real world driving emissions (RDE) procedure or penetration of opening markets, as well as an increasing attention paid by modern OEMs towards the development efficiency (time/costs optimization). In this contribution an overview about the on-going development activities is given and the deriving benefits are illustrated with the support of experimental results.

In this study, the effect of using two innovative biodiesels - derived respectively from coffee grounds and Cynara cardunculus - in blend with neat diesel fuel, on combustion and emissions in a compression ignition engine has been investigated. During tests, load and exhaust gas recirculation were varied and results compared with those obtained with neat diesel fuel and its blends with Brassica carinata or waste cooking oil derived biodiesels. Results show a reduction or a comparable NOx and CO emission levels using Cynara cardunculus and coffee ground compared to the other fuels tested, while PM and THC emissions are penalized. Fuel consumption, as expected, is slightly reduced. EGR reduces NOx levels, while CO, THC and PM are generally penalized.

The aim to photo-ignite Multi-wall carbon nanotubes (MWCNT) with added metal impurities (ferrocene), makers of photo-ignition process. The realized ac powered electronic boards present different features such as variable flash brightness, pulse duration and high flash rate as function of user-adjustable potentiometers or by PC provided command signals. By using the designed PC-configurable boards in the realized experimental setup, the lighting parameters (i.e. pulse energy/power and energy density) for different Xe lamps have been measured and optimized. Varying temporal/luminous parameters of used light sources by means of realized driving boards, different pulse energy and power values were obtained, in order to fully exploit and analyze MWCNTs/ferrocene photo-induced ignition. Finally, employing these boards, the ignition of MWCNT/Ferrocene mixtures has been triggered and investigated.

This paper describes the functioning of an electronic board for driving solenoid diesel injectors, designed and used in experimental setup based on Common Rail injection scheme, for injectors’ characterization with 100% biodiesel fuel through analysis of spray emitted in a quiescent velocimetric chamber. The board allows user to adjust electrical/temporal parameters of voltage signal applied to injector coil, determining its opening, by acting on six potentiometers. The electronic setup for control and execution of whole injection process is also composed of a National Instruments acquisition board, both units controlled from PC by means of an expressly implemented LabView Virtual Instrument.

The incoming RDE regulation and the on-board diagnostics -OBDpushes the research activity towards the set-up of a more and more efficient after treatment system. Nowadays, the most common after treatment system for NOx reduction is the selective catalytic reduction -SCR- . This system requires as an input the value of engine out NOx emission -raw- in order to control the Urea dosing strategy. In this work, an already existing grey box NOx raw emission model based on in-cylinder pressure signal (ICPS) is validated on two standard cycles: MNEDC and WLTC using an EU6 engine at the test bench. The overall results show a maximum relative error of the integrated cumulative value of 12.8% and 17.4% for MNEDC and WLTC respectively. In particular, the instantaneous value of relative error is included in the range of ± 10% in the steady state conditions while during transient conditions is less than 20% mainly. Finally, a sensitivity analysis is conducted in order to understand how the model “answers” to any air and fuel parameter deviation.

The paper presents the results of an extensive experimental activity aimed at exploring the potentialities of improvement of an ICE operation, working in dual fuel modality, through the gaseous charge stratification. In this early experimental campaign, the engine under analysis, a single cylinder equipped with a common rail Diesel fuel injection system, has been fed with two gaseous fuels, hydrogen and methane, through an injector positioned along the intake duct, thanks to the facilities available in Machinery Laboratory at University of Salento, with which it is possible to mix up to five gaseous species (CO2, CO, H2, N2, CH4) freely setting the mixture composition and pressure. The gaseous mixture air-fuel has been introduced into the combustion chamber inducing a swirl bulk motion; once trapped into the cylinder, the gaseous mixture has been ignited injecting a small quantity of Diesel fuel, while the injector used for supplying the gaseous fuel has been positioned either upstream the intake duct, in order to obtain a more homogeneous gaseous mixture before it enters the cylinder, or just before the intake valve, so trying to obtain a stratified-like distribution of the fuel into the cylinder before the combustion start. During the tests, the value of several factors affecting the process of charge preparation have been varied: injection pressure of the gaseous fuel, quantity of Diesel fuel, in addition to the variation of the gas injector position. The effect of these factors has been evaluated on the behavior of the pressure in the combustion chamber, on the related heat release rate and on the pollutant emission levels at the exhaust.

The use of carbon nanotubes (CNTs) in the combustion and propulsion sector, which is the object of this work, is due to the discovery of photo-ignition properties of such nano-material, when they are exposed to an intense luminous flash [1]. This phenomenon allows obtaining fuels combustion system more efficient and clean (HCCI engine) [2]. Most of the literature studies involve a Xe-lamp to ignite the CNTs mixed with metal catalyst; the use of this light source is not without criticism because it requires very high supply voltages, has an intrinsic mechanical instability, and it can’t work at frequencies required by an automotive engine running [3]. A LED-based ignition system can be considered the optimum solution, because LEDs have high luminous efficiency, higher mechanical stability and for the absence of frequency limitations. In this work, a LEDs-based experimental setup used to perform combustion tests of gaseous fuels, by means of photo-ignition of MWCNTs/FeCp2, has been proposed (Fig. 1). The setup uses a multi-LED ignition-system, placed outside the combustion chamber, convoying the light emitted by each LED source into the chamber by a fiber optic. The electronic section drives and controls the LED sources, synchronizing temporally them with the input of the enriched air-fuel mixture. Moreover, it will also handle and monitor all physical / environmental parameters involved in the combustion process, such as temperature and pressure inside the combustion chamber, etc. In order to obtain a light pulse of controlled duration, a driving and control electronic system was realized (Fig. 2). The white power LEDs (Cree XHP70) were driven by proper LED drivers; to generate a single light pulse, a pulsed signal is applied to the enable control input of each LED driver. This last signal is obtained on PC audio channel by proper LabVIEW application and after conditioning by an interface board. A four LEDs source was used to perform ignition tests on the dry mixtures MWCNTs/FeCp2 to obtain energy density comparable to which obtained with the Xe lamp. In the Figs. 3a and b, the setup used to perform ignition tests on dry mixtures MWCNTs/FeCp2, is shown; the driving and control unit is constituted by four LED drivers, the interface board and the PC with LabVIEW application (Fig. 3a), whereas tests area with the four LEDs source and the power/energy meter (Thorlabs PM100D) equipped with pyroelectric sensor (Thorlabs ES145C) are shown in Fig. 3b. The light source is placed at 1cm at least from the pyroelectric sensor and then from CNTs sample (Fig. 3b). Using this experimental setup, the minimum pulse durations needed to ignite the MWCNTs/FeCp2 samples for the different concentrations by weight, are determined. Known the light source intensity, the minimum ignition energy of the MWCNTs/FeCp2 samples for the considered concentrations, are calculated (Fig. 4).

The world natural gas reserve is plentiful. Instead of using gasoline to power ground vehicles, usage of Compressed Natural Gas (CNG) can improve the environment and reduce energy cost. However, most engines that runs on CNG are converted from gasoline based engine. Hence, the engines are not optimized for CNG. Other problems of converted engines are loss of power due to slower burn rate of CNG and gas displacement effect of CNG, hotter exhaust gas which degrade engine’s reliability, low mileage per tank and higher NOx. Since, converted engines are gasoline base engine, a dual fuel injection engine system can be developed to reduce the stated problems. Are activity controlled approach was incorporated where both gasoline and CNG are mixed before going into the combustion chamber. With this technique, when a blend of high reactive 35% gasoline and 65% CNG was used, the engine had its engine performance such torque, power and efficiency increasing by 10%. Also, the engine emissions such as hydrocarbon was reduced by 50% and carbon monoxide emission was reduced by 75% and NOx emission was reduced by 50% when compared with CNG baseline. Combustion of spark ignition engines converted to bi-fuel CNG is unstable and proper air and fuel mixing strategy is a concern here.

Energy procurement is a necessity which needs a deep study, of both the demand and the generation sources, referred to consumers localization. The study presented in the paper is an attempt to extend and consolidate the study of Shimon Awerbuch on Portfolio Theory applied to the energy planning, in order to define a broad-based generating mix which optimizes one or more objective functions defined by either the designer or the final user. For this purpose the computation model was specialized in energy procurement problem and extended with the addition of new cost-risk settings, like social-environmental assets and renewable energy availability, and Black-Litterman model, which extends Markovitz and Capital Asset Pricing Model (CAPM) theory. Energy planning was also contextualized to the territory: the introduction of geographic and climatic features, together with the respect of regulations on landscape-environment protection, allow to plan energy infrastructures on both global and local scale (regional, provincial, municipal). The result is an efficient decision making tool to drive the investment on typical energy policy assets. In general the tool allows to analyze several scenarios in support of renewable energy sources, environmental sustainability, costs and risks reduction.

Energy procurement is a necessity which needs a deep study of both the demand and the generation sources, referred to consumers territorial localization. The study presented in this paper extends and consolidate the Shimon Awerbuch’s study on portfolio theory applied to the energy planning, in order to define a broad generating mix which optimizes one or more objective functions defined for a determined contest. For this purpose the computation model was specialized in energy generation problem and extended with the addition of new cost-risk settings, like renewable energy availability, and Black–Litterman model, which extends Markowitz theory. Energy planning was then contextualized to the territory: the introduction of geographic and climatic features allows to plan energy infrastructures on both global and local (regional, provincial, municipal) scale. The result is an efficient decision making tool to drive the investment on typical energy policy assets. In general the tool allows to analyze several scenarios in support of renewable energy sources, environmental sustainability, costs and risks reduction. In this paper the model was applied to the energy generation in Italy, and the analysis was done: on the actual energy mix; assuming the use of nuclear technology; assuming the verisimilar improvement of several technologies in the future.

The aim of this work is to investigate and characterize the photo-ignition process of dry multi-walled carbon nanotubes (MWCNTs) mixed with ferrocene (FeCp2) powder, using an LED (light-emitting diode) as the light source, a combination that has never been used, to the best of our knowledge. The ignition process was improved by adding a lipophilic porphyrin (H2Pp) in powder to the MWCNTs/FeCp2 mixtures—thus, a lower ignition threshold was obtained. The ignition tests were carried out by employing a continuous emission and a pulsed white LED in two test campaigns. In the first, two MWCNT typologies, high purity (HP) and industrial grade (IG), were used without porphyrin, obtaining, for both, similar ignition thresholds. Furthermore, comparing ignition thresholds obtained with the LED source with those previously obtained with a Xenon (Xe) lamp, a significant reduction was observed. In the second test campaign, ignition tests were carried out by means of a properly driven and controlled pulsed XHP70 LED source. The minimum ignition energy (MIE) of IG-MWCNTs/FeCp2 samples was determined by varying the duration of the light pulse. Experimental results show that ignition is obtained with a pulse duration of 110 ms and a MIE density of 266 mJ/cm2. The significant reduction of the MIE value (10–40%), observed when H2Pp in powder form was added to the MWCNTs/FeCp2 mixtures, was ascribed to the improved photoexcitation and charge transfer properties of the lipophilic porphyrin molecules.

Nowadays, In-Cylinder Pressure Sensors (ICPS) have become a mainstream technology that promises to change the way the enginecontrol is performed. Among all the possible applications, the prediction of raw (engine-out) NOX emissions would allow to eliminate the NOX sensor currently used to manage the aftertreatment systems. In the current study, a semi-physical model already existing in literature for the prediction of engine-out nitric oxide emissions based on in-cylinder pressure measurement has been improved; in particular, the main focus has been to improve nitric oxide prediction accuracy when injection timing is varied. The main modification introduced in the model lies in taking into account the turbulence induced by fuel spray and enhanced by in-cylinder bulk motion. The effectiveness of the new model has been tested with data acquired during an extensive experimental campaign during which a 2.0l 4 cylinders Diesel engine, whose after-treatment system allows to fulfil the EU6 legislation limits, has been operated on the overall engine map. It is shown that, comparing measured and estimated NOX on a wide range of engine settings, the improved model is quite effective in capturing the effect of injection timing on engine-out NOX emissions: the average error between measured and estimated NOX is reduced of about 10% while the correlation coefficient is increased from 0.86 to 0.97.

Dual-fuel biodiesel-producer gas combustion has shown potential in reducing nitric oxides and particulate emission levels compared to only diesel operation; however, engine overall efficiency is slightly penalized, while the main drawbacks are represented by the higher levels of total hydrocarbons and carbon monoxide emissions. In this work, the improvements in the combustion development deriving from the splitting of the liquid fuel injection at low loads have been assessed using a 0.51 L single-cylinder research diesel engine equipped with a high pressure common rail injection system and operated in dual-fuel mode. In this case, a synthetic producer gas was used as inducted gaseous fuel, while biodiesel was used as pilot fuel. Initially, the spray morphology was characterized in a constant-volume vessel for different values of injection duration and pressure, as well as vessel backpressure. Then, the experimental campaign, run on the engine at 1500 rpm, was divided in two sessions. During the former, only one pilot injection of constant fuel amount (11 mm3/cycle) was performed, the rail pressure was set equal to 500 or 1000 bar, the injection timing was varied in the range −50 ÷ 5 degrees crank angle after top dead center while the amount of gaseous fuel inducted in the cylinder was varied on three levels. During the latter, the pilot fuel amount, kept equal to the one pilot injection tests, was split in two smaller injections and the effect of the dwell between them – varied in the range 5 ÷50 degrees crank angle – was investigated as well. The results of the first set of experiments revealed that pilot injection timing and pressure both affect the combustion development. This resulted in sensible variations on thermal and combustion efficiencies, and therefore on fuel conversion efficiency, the last one exhibiting higher values with pilot injection timing slightly advanced respect to top dead center and lower injection pressure. In these conditions, total hydrocarbons and carbon monoxide are lowered, while nitric oxides are increased. The amount of gas demonstrated to have asecondary effect on combustion development and emissions levels at the exhaust. Splitting pilot injection, demonstrated to be an effective way to increase fuel conversion efficiency and to reduce the levels of all the pollutant species compared to the single pilot injection strategy. Based on the extensive experimental activity described in this paper, a dwell ranging between 10 and 30 degrees of crank angle, combined with a first injection timing ranging between 35 and 20 degrees of crank angle before top dead center guarantee the highest fuel conversion efficiency and the lowest pollutants emission levels. Injection pressure confirmed to be a significant factor in affecting the combustion development, while a secondary effect was determined by the gaseous mass inducted in the cylinder.Ultimately, pilot injection splitting demonstrated to be an effective way for improving gaseous fuel combustion in dual-fuel mode at low load (lean mixture) conditions.

In dual-fuel engines, a combustible mixture of air and generally a gaseous fuel is ignited, thanks to the injection and autoignition 6 of a small amount of liquid fuel. It is well-known that dual-fuel engines suffer from poor combustion when operated at low loads. This 7 behavior, due mainly to the presence of an overlean mixture into the combustion chamber, leads to unacceptably high levels of carbon 8 monoxide and unburned hydrocarbons emitted at the exhaust. In order to solve this problem a possible solution could be to split the pilot 9 injection of liquid fuel into two split injections, the second having the function of boosting the combustion of gaseous fuel also during the late 10 combustion phase. In this paper this solution has been implemented on a diesel common rail single cylinder research engine converted to 11 operate in dual-fuel mode. The composition of the gaseous fuel, indirectly injected, simulated a typical producer gas. The liquid fuel used 12 during the experiments was biodiesel, injected by means of a common rail injection system. The first section of results describes the tests run 13 for comparison purposes, performing only one pilot biodiesel injection and varying its timing on a wide range. The second section of results 14 then presents the tests run for different timings, varied on a wide range, of the first split injection, and different dwells between the first and the 15 second injections. The engine behavior has been discussed in terms of heat release rate, fuel conversion efficiency, and nitric oxides, total 16 hydrocarbons, and carbon monoxide emission levels at the exhaust. The results demonstrate that splitting the pilot injection leads to an 17 increase of fuel conversion efficiency and a reduction of both total hydrocarbons and carbon monoxide. This final result allows to state 18 that splitting the pilot injection is an effective way for sustaining the gaseous fuel combustion in dual-fuel engine late during the combustion 19 phase.

Biodiesel fuels are increasingly attracting interest in the scientific community and in the world motor industry. The morphological analysis of injected sprays is a key factor to increase engine performances using new biodiesel fuels and to compare them with those related to the use of conventional fuels. In this paper, an experimental setup is realised to carry out test campaigns, in order to analyse and compare the spray injections of different fuel typologies. A PC-interfaced electronic system was realised for driving BOSCH injectors and for varying the injection pressure and opening time. Hence, the morphological analysis was performed for each tested fuel by characterising the shaperatio and penetration depth inside the velocimetric chamber. The results show higher penetration values for biodiesel fuels due to their viscosity and drops in superficial tension, which facilitate a deeper penetration compared to those obtained with conventional diesel fuels. Although used biodiesels contain only 20% of renewable vegetable-origin diesel fuels, the viscosity and superficial tension are slightly higher than those of petroleum diesel, thus determining a weak vaporisation and formation of larger drops. By knowing the morphological behaviour of sprays using biofuels and conventional fuel, it is possible, by using programmable electronic systems, to adjust and improve the spray parameters in order to obtain better engine performances. The results reported in this instance could be utilised by future research works for choosing the most suitable biofuel based on the desired morphological behaviour of the injected sprays.

The possibility to ignite the Single Wall Carbon Nanotubes (SWCNTs) once exposed to the radiation of a flash camera, was observed for the first time in 2002. Subsequently, it was proposed to exploit this property in order to use nanostructured materials as ignition agents for fuel mixtures. Lastly, in 2011, it was shown that SWCNTs can be effectively used as ignition source for an air/ethylene mixture filling a constant volume combustion chamber; the observed combustion presented the characteristics of a homogeneous-like combustion. In the presented experimental activity, the potentiality of igniting an air/methane mixture by flashing Multi Wall Carbon Nanotubes (MWCNTs) has been exploited, and the results compared with those obtained igniting the mixture with a traditional spark plug. In detail, two types of tests have been carried out: the first, aiming at comparing the combustion process flashing a variable amount of nanoparticles introduced into the combustion chamber at fixed air/methane ratio; the second, at comparing the combustion process with the one obtained using a traditional engine spark plug, varying the air/methane ratio and at fixed amount of MWCNTs. During tests, the combustion process has been characterized measuring the pressure into the combustion chamber as well as acquiring images with a high-speed camera. The results confirm that the ignition triggered with MWCNTs leads to a faster combustion, without observing a well-defined flame front propagation, observed, as expected, with the spark assisted ignition. Moreover, dynamic pressure measurements show that the MWCNTs photo-ignition determines a more rapid pressure gradient and a higher heat release rate compared to spark assisted ignition.

The potentials and characteristics of a new ignition system for air-fuel mixtures are discussed. This ignition method (referred to as photo-thermal ignition) is based on light exposure of Multi-Walled Carbon Nanotubes (MWCNTs), bonded with other nano-Structured Materials (nSMs), (collectively referred here as ‘‘nanoignition agent”), using a low-consumption camera flash. Here, Ferrocene, an organometallic compound, was used as the nSMs. Results from, and benefits of, this new ignition method are compared with a conventional spark-plug initiated ignition used in automotive engines. The main objective of this research is to demonstrate ignition feasibility of mixtures of both gaseous and liquid fuels with air under high pressures using the photo-thermal ignition (PTI) phenomenon. Specifically, the ignition and subsequent combustion characteristics of gaseous air-fuel mixtures at different air-fuel ratios were investigated by means of light exposures of nano-ignition agents (nIAs) after they are mixed with air-fuel mixtures. Analysis of the acquired data showed that for the range of air-fuel ratios tested, the photo-thermal ignition with a flash lamp resulted in a higher peak chamber pressure when compared to those obtained with a conventional spark ignition system. Heat release rate analysis showed that shorter ignition delays and total combustion durations for the Photo-thermal ignition are achieved. Comparative percent reduction of these values for photo-ignition ranges from 20% to 50% for LPG and methane, whereas values up to 70% were observed for the hydrogen. The positive impact of the photo-thermal ignition appears to be primarily at the ignition delay period of the combustion. With liquid fuels, photo-thermal ignition was capable to ignite mixtures as lean as a relative air-fuel ratio of 2.7 while the spark ignition was incapable to initiate combustion. Additionally, tests with the liquid gasoline injection highlighted that the combustion process with a higher ‘‘residence mixing time” exhibited higher peak pressures and shorter ignition delay times. High-speed camera images were used to capture images of the light emission during the combustion process in visible range, allowing investigation of the ignition processes. In particular, the results showed that the photo-thermal ignition process of the air-fuel mixtures with nano-ignition agents led to a spatially-distributed ignition followed by a faster consumption of the air-fuel mixture with no evidence of any discernible flame front formation or propagation.

One of the factors limiting the utilization of piston internal combustion engines for aircraft propulsion is the performance decrease increasing the altitude of operation. This is due to the negative effect of air density reduction increasing the altitude on cylinder filling. A solution to this problem is represented by the engine supercharging. Unfortunately, in two stroke engines, the cylinder filling efficiency is antithetical to the cylinder scavenging efficiency. With the aim of guaranteeing an optimal balance between engine performance and specific consumption, an engine breathing system optimization is needed. In this work, the results obtained running a multi-objective optimization procedure aiming at performance increase and fuel consumption reduction of an aircraft two stroke supercharged diesel engine at various altitudes are analyzed. During the optimization procedure, several geometric parameters of the intake and exhaust systems as well as geometric and operating engine parameters have been varied. Then, a multi-objective optimization algorithm based on genetic algorithms has been run to obtain the configurations optimizing the engine performance at Sea Level (take-off conditions) and fuel consumption at 10680 m (cruise conditions).

The performance and the exhaust emissions of a diesel engine operating on nano-diesel-biodiesel blended fuels has been investigated. Multi wall carbon nano tubes (CNT) (40, 80 and 120 ppm) and nano silver particles (40, 80 and 120 ppm) were produced and added as additive to the biodiesel-diesel blended fuel. Six cylinders, four-stroke diesel engine was fuelled with these new blended fuels and operated at different engine speeds. Experimental test results indicated the fact that adding nano particles to diesel and biodiesel fuels, increased diesel engine performance variables including engine power and torque output up to 2% and brake specific fuel consumption (bsfc) was decreased 7.08% compared to the net diesel fuel. CO2 emission increased maximum 17.03% and CO emission in a biodiesel-diesel fuel with nano-particles was lower significantly (25.17%) compared to pure diesel fuel. UHC emission with silver nano-diesel-biodiesel blended fuel decreased (28.56%) while with fuels that contains CNT nano particles increased maximum 14.21%. With adding nano particles to the blended fuels, NOx increased 25.32% compared to the net diesel fuel. This study also presents genetic programming (GP) based model to predict the performance and emission parameters of a CI engine in terms of nano-fuels and engine speed. Experimental studies were completed to obtain training and testing data. The optimum models were selected according to statistical criteria of root mean square error (RMSE) and coefficient of determination (R2). It was observed that the GP model can predict engine performance and emission parameters with correlation coefficient (R2) in the range of 0.93–1 and RMSE was found to be near zero. The simulation results demonstrated that GP model is a good tool to predict the CI engine performance and emission parameters.

Since more than one century, energy procurement worldwide has been based on liquid products obtained from refining of crude oil, a not-renewable energy source destined to the exhaustion. It is well known, however, that emissions produced by combustion of fossil fuels, containing CO2, CO, nitrogen and sulphur oxides, Volatile Organic Compounds and particulate, are harmful and cause environmental problems as well. A characterization of performance and pollutant emission levels was then conducted on a compression ignition engine fed with a diesel fuel-biodiesel mixture. In particular, five different blends of the two fuels were studied, and, for each of them, the EGR valve was set on four different opening values. For each of these operating conditions, cylinder pressure fluctuations were measured and heat release rate calculated; moreover, fuel consumption, together with NOx, CO2, HC and particulate matter (PM) levels have been measured. Data obtained from the experimental campaign indicate the biodiesel as an excellent substitute of the diesel fuel from the point of view of energy sources diversification, since its utilization leads to a reduction of HC emission levels equal to about 25% and of PM of about 20%. On the other hand, fuel consumption is increased of about 15% and NOx emission levels of about 30%.

In Two-Stroke engines, the cylinder filling efficiency is antithetical to the cylinder scavenging efficiency; moreover, both of them are influenced by geometric and thermodynamic parameters characterizing the design and operation of both the engine and the related supercharging system. Aim of this work is to provide several guidelines about the definition of design and operation parameters for a Two-Stroke two banks Uniflow diesel engine, supercharged with two sequential turbochargers and an aftercooler per bank, with the goal of either increasing the engine brake power at take-off or decreasing the engine fuel consumption in cruise conditions. The engine has been modeled with a 0D/1D modeling approach. Then, the model capability in describing the effect of several parameters on engine performance has been assessed comparing the results of 3D simulations with those of 0D/1D model. The validated 0D/1D model has been used to simulate the engine behavior varying several design and operation engine parameters (exhaust valves opening and closing angles and maximum valve lift, scavenging ports opening angle, distance between bottom edge of the scavenging ports and bottom dead center, area of the single scavenging port and number of ports, engine volumetric compression ratio, low and high pressure compressor pressure ratios, air/fuel ratio) on a wide range of possible values. The parameters most influencing the engine performance are then recognized and their effect on engine thermodynamic behavior is discussed. Finally, the system configurations leading to best engine power at sea level and lowest fuel consumption in cruise conditions - respectively +42% and -7% with respect to baseline - have been determined implementing a multicriteria optimization procedure.

This work aims to investigate and characterize the photo-ignition phenomenon of MWCNT/ferrocene mixtures by using a continuous wave (CW) xenon (Xe) light source, in order to find the power ignition threshold by employing a different type of light source as was used in previous research (i.e., pulsed Xe lamp). The experimental photo-ignition tests were carried out by varying the weight ratio of the used mixtures, luminous power, and wavelength range of the incident Xe light by using selective optical filters. For a better explanation of the photo-induced ignition process, the absorption spectra of MWCNT/ferrocene mixtures and ferrocene only were obtained. The experimental results show that the luminous power (related to the entire spectrum of the Xe lamp) needed to trigger the ignition of MWCNT/ferrocene mixtures decreases with increasing metal nanoparticles content according to previously published results when using a different type of light source (i.e., pulsed vs CW Xe light source). Furthermore, less light power is required to trigger photo-ignition when moving towards the ultraviolet (UV) region. This is in agreement with the measured absorption spectra, which present higher absorption values in the UV–vis region for both MWCNT/ferrocene mixtures and ferrocene only diluted in toluene. Finally, a chemo-physical interpretation of the ignition phenomenon is proposed whereby ferrocene photo-excitation, due to photon absorption, produces ferrocene itself in its excited form and is thus capable of promoting electron transfer to MWCNTs. In this way, the resulting radical species, FeCp2+∙ and MWCNT−, easily react with oxygen giving rise to the ignition of MWCNT/ferrocene samples.

Aim of this work is to describe the electronic driving system and the entire experimental setup realized in order to photo-ignite a gaseous fuel/air mixture enriched with Multi-wall carbon nanotubes (MWCNTs) with added metal impurities, makers of photo-ignition process. The realized electronic boards present different features such as variable flash brightness, pulse duration and high flash rate, allowing to fully characterize the combustion process under investigation. Varying the Xenon light source’s parameters, the needed light energy/power to ignite MWCNT/Fe mixtures with different weight ratio was found. Experimental results show that lower energy thresholds are required with increasing MWCNTs amount respect to ferrocene. Then, the photo-induced ignition of CNTs mixed with nanoparticles was used in a properly realized experimental setup for triggering the combustion of different CNT-enriched air/fuel mixtures (CH4, Liquid Propane and H2). The combustion tests triggered by MWCNTs/ferrocene photo-ignition show better performances (shorter ignition delays, higher peak pressure values and a higher fuel burning rate), for all used gaseous fuels and all tested air / fuel ratios, compared with those obtained by using a traditional spark plug.

The possibility to use carbon nanotubes (CNTs) enriched with a certain amount of metal nanoparticles for photo-inducing the combustion of liquid fuel sprays, gaseous and solid fuels was investigated in different research works. CNTs photo-ignition phenomenon has been used to trigger the combustion of different fuel typologies, demonstrating better features compared with those obtained by employing a traditional spark-plug.These improvements are due to the presence of distributed ignition nuclei inside the combustion chamber, so obtaining better values of the peak pressure, ignition delay and combustion duration. In this work, the CNTs photo-ignition phenomenon has been analyzed in order to find the minimum energy values needed to trigger the ignition, by varying the light pulse parameters and the nanoparticles concentration, Multi Wall CNTs (MWCNTs) – ferrocene, by weight. Afterwards, the results of combustion processes, triggered by using the nanoparticles, are shown comparing them with those obtained by means the spark plug and with results already published related to other fuel typologies. Hence, an overview of the possible applications of this photo-ignition phenomenon, beside that of the automotive field, is presented, also considering the disadvantages ofthe Xe-lamp based triggering system. Therefore, after a critical discussion on the light source typology until now used (Xenon lamp), by reporting the possible contra-indications deriving from the use of this light source in most of the applicative fields, a solution is here proposed. It involves the substitution of the Xe lamp with LED sources, showing also the related experimental setup. This solution is also strengthened by the our experimental observations of CNTs photo-ignition by using high-power white LEDs as light source, never reported up to now in the literature, and by better characteristics of adaptability, robustness, easy driving and benefits provided by the LEDs rather than the Xenon lamp.

This article describes the photo-induced ignition process of multi-walled carbon nano-tubes (MWCNTs)/ferrocene mixtures by pulsed Xe lamps using programmable driving boards with adjustable parameters, such as variable flash rate and pulse’s energy/intensity. Varying the energy of incident light pulse, minimum ignition energy values were found as a function ofmixture weight ratio, observing that a higherMWCNT amount with respect to metal nano-particles leads to lower ignition energy. The photo-induced ignition of CNTsmixed with nano-particles was then used iin a properly realized experimental setup for triggering the combustion of CNT-enriched fuel mixtures. Different types of gaseous fuels mixed with air (CH4, liquid propane, and H2) were tested. The combustion process triggered by MWCNTs/ferrocene photo-ignition shows better performances, for all used gaseous fuels and for all tested air/fuel ratios, compared with those obtained by using a traditional spark plug. In particular, CNT-based photo-induced combustion evolves more rapidly with shorter ignition delays, higher peak pressure values, and a higher fuel burning rate as observed by reported experimental tests.

In internal combustion engines, an ignition source is required to initiate the combustion process. This is commonly obtained either through an electric spark generation or by physical art of compression-ignition. In order to improve performance and lower pollutants levels, researchers have proposed alternatives to conventional ignition or combustion processes, such as Homogeneously-Charge Compression-Ignition (HCCI) combustion, whose critical operational requirement is precise control of the autoignition timing within the engine operating cycle. In this work, an innovative volumetrically-distributed ignition approach is proposed to control the onset of the autoignition process, by taking advantage of the optical ignition properties of carbon nanotubes when exposed to a low-consumption light source. It is shown that this ignition method enhanced the combustion of methane, hydrogen, LPG and gasoline (injected to chamber in liquid phase). Results for this new ignition method show that pressure gradient and combustion efficiency are increased, while combustion duration and ignition delay time are decreased. A direct observation of the combustion process indicates that these benefits are due to the spatially-distributed ignition followed by a faster initial consumption of the air/fuel mixture. The use of this ignition system is therefore proposed as a promising technology for the combustion management in internal combustion engines, specifically for HCCI engines.

This paper conducts an extensive experimental campaign for dual fuel biodiesel-producer gas combustion development and the related pollutant emissions and reports the results with the aim of highlighting the effect of biodiesel pilot injection parameters. For this purpose, a common rail diesel research engine was converted to operate in dual fuel mode; the gaseous fuel was introduced into the engine through an indirect injector housed well upstream of the engine intake duct; and the composition of the gaseous fuel simulating the producer gas was obtained using a mixing system able to generate a gaseous mixture of carbon monoxide (CO), hydrogen (H2), and nitrogen (N2) with the desired amount for each of them. The biodiesel pilot injection required to ignite the gaseous fuel was instead sprayed into the cylinder using a common rail high-pressure injection system. During tests, the biodiesel injection amount, pressure, and advance were varied on several levels, together with the composition and amount of gaseous fuel. The cylinder pressure was sampled and, from it, heat release rate and indicated mean effective pressure were estimated. Moreover, gaseous pollutant emissions at the exhaust were measured. The results demonstrate that biodiesel pilot injection parameters are crucial to control the development of combustion and emission levels when the engine is operated in dual fuel biodiesel-producer gas mode. Therefore, the potentialities of the common-rail high-pressure injection system may be developed to optimize as much as possible the operation of such engines in terms of power output, increase in combustion efficiency, and reduction of environmental impact.

This paper describes the design and testing of programmable driving boards for turning on Xenon flash lamps, with the aim to photo-ignite a gaseous fuel/air mixture enriched with Multi-walled carbon nanotubes with added metal impurities, makers of photo-ignition process. The key factor of realized electronic boards is the availability to adjust the triggering parameters of pulsed Xe lamps, allowing to fully characterize the combustion process under investigation. By using the designed PC-configurable boards in the realized experimental setups, the effects of Xenon light source’s parameters such as pulse luminous intensity, flash-rate and time duration have been investigated in order to find the needed light energy/power to ignite MWCNT/Fe mixtures with different weight ratio (from 1:4 to 4:1). Experimental results show that lower energy thresholds are required with increasing MWCNTs amount respect to ferrocene.

A sizing and simulation platform has been developed for the optimization of advanced configurations for aircrafts including, but not limited to, more electric, hybrid-electric, turbo-compound piston engines and fuel cell systems. In the present investigation the software has been applied to the simulation of a medium-altitude, medium-endurance unmanned aerial vehicle (UAV) equipped with a two-stroke diesel engine with a single stage turbo-compressor. The engine was simulated with a 1D code (AVL-Boost) taking into account several values of speed, air-fuel ratio and flight altitude. The behavior of the waste-gate valve at the different flight levels was also accounted for. The Willans line method is used to obtain the seal level and in flight performance map of scaled engines with the same configuration. The power requests of a reference 128 kW engine and two scaled engines along the mission have been compared with the available power to discuss the potentiality of hybrid electric and turbo-compound configurations.

The effects of several operating parameters on dual fuel combustion at light load were investigated by means of direct endoscopic observation of the process. Therefore, an intense experimental campaign was performed on a single cylinder diesel common rail research engine, converted to operate in dual fuel mode and equipped with optical accesses and variable intake configuration. Three bulk flow structures of the charge were induced inside the cylinder by activating/deactivating the two different inlet valves of the engine (i.e. swirl and tumble). Methane was injected into the inlet manifold at different pressure levels and varying the injector position. In order to obtain a stratified-like air-methane mixture, the injector was mounted very close to the inlet valve, while, to obtain a homogeneous-like one, methane was injected more upstream. By combining the different positions of the methane injector and the three possible bulk flow structures, seven different engine inlet setup were tested. Moreover, pressure and quantity of the diesel pilot injection were varied. For each acquired combustion image, the luminance plane was extracted and a luminance value, averaged over the whole frame, was calculated in order to obtain an indicator of the combustion intensity. These crank angle-based luminance curves were compared while the total integral and the peak values were calculated. From the analysis of the luminance curves it can be observed that the in-cylinder bulk flow associated with the swirl port is characterized by a more rapid development of the combustion. Especially for certain combinations of the engine operating parameters, higher peaks of luminance values can be noticed while the luminance curves fall to zero earlier with respect to the other inlet configurations. Concerning the methane injector position, some noticeable effects on the intensity and distribution of the flame during dual fuel combustion were observed. Depending on the bulk flow structure induced inside the cylinder, methane injector position can induce a certain degree of stratification of the in-cylinder charge, capable to enhance dual fuel combustion at low loads.

Different studies on both 2- and 4-stroke engines have shown how the choice of different supercharging architectures can influence engine performance. Among them, architectures coupling one turbocharger with a mechanical compressor or two turbochargers are found to be the most performing in terms of engine output power and efficiency. However, defining the best supercharging architecture for aircraft 2-stroke engines is a quite complex task because the supercharging system as well as the ambient conditions influence the engine performance/efficiency. This is due to the close interaction between supercharging, trapping, scavenging and combustion processes. The aim of the present work is the comparison between different architectures (single turbocharger, double turbocharger, single turbocharger combined with a mechanical compressor, single turbocharger with an electrically-assisted turbocharger, with intercooler or aftercooler) designed to supercharge an aircraft 2-stroke Diesel engine for general aviation and unmanned aerial vehicles characterized by a very high altitude operation and long fuel distance. A 1D model of the engine purposely designed has been used to compare the performance of the different supercharging systems in terms of power, fuel consumption, and their effect on trapping and scavenging efficiency at different altitudes. The analysis shows that the engine target power is reached by a 2 turbochargers architecture; in this way, in fact, the cylinder filling, and consequently the engine performance, are maximized. Moreover, it is shown that the performance of a 2 turbochargers architecture performance can be further improved connecting electrically and not mechanically the low pressure compressor and turbine (electrically-assisted turbocharger). From an energetic point of view, this system has also proved to be particularly convenient at high engine speed and load, because it is possible to extract power from the electric turbocharger without a penalty on specific fuel consumption.

This chapter illustrates a procedure having as a goal the definition of the supercharging architecture of a 2-Stroke diesel engine for general aviation and Unmanned Aerial Vehicles (UAV) propulsion. At the beginning, the engine platform (a six-cylinder uniflow engine) is modeled coupled with different supercharging solutions – single turbocharger, double turbocharger, single turbocharger combined with a mechanical compressor, with intercooler or aftercooler. A comparison of fuel consumption under different configuration is provided after the ability in reaching the target power was assessed. Afterwards, the potential of increasing the engine output power at take-off or decreasing the fuel consumption at highest operating altitude has been explored running a multivariable optimization process on the engine supercharged by two sequential turbochargers and an aftercooler per bank. In order to make a comprehensive analysis, many design and operation parameters have been selected as input parameters for the optmization procedure, i.e. exhaust valves opening and closing angles and maximum valve lift, scavenging ports opening angle, distance between bottom edge of the scavenging ports and bottom dead center, area of the single scavenging port and number of ports, engine volumetric compression ratio, low and high pressure compressor pressure ratios, air/fuel ratio. These parameters have been varied on a wide range of values. It is demonstrated that, with a proper design and control of the engine, it is possible either to increase the output power at sea level of about 42% or to save about 7% fuel with the engine operating at highest altitude. Finally, the benefits in engine performance have been assessed deriving from the utilization of: an electrically assisted turbocharger on the low pressure side; thermoelectric generators. Results show that the former technology is more effective at low operating altitudes and high engine speed, basically due to the higher availability of energy at the engine exhaust, exceeding that required by the compressors to compress the air and reach the target values of power. A fuel saving up to 3.6% could be achieved at sea level and rated engine speed.

La valutazione dell’impatto acustico generato da una installazione eolica richiede la conoscenza delle caratteristiche del suono emesso e le modalità con cui questo si propaga in campo aperto. Gli strumenti attualmente disponibili per tale analisi previsionale fanno riferimento, per la maggior parte, al modello standard proposto dalla ISO9613-2, e partono dall’assunto che una turbina eolica sia rappresentabile da una sorgente di rumore puntuale, la cui direttività è tenuta in considerazione solo in modo approssimato. Per valutare le caratteristiche della direttività, infatti, non vi sono in letteratura sufficienti riscontri sperimentali che consentano di apprezzarne la reale efficacia e/o i limiti dei modelli che si stanno adoperando. Lo scopo del presente lavoro, quindi, è validare, attraverso rilievi fonometrici eseguiti presso installazioni eoliche esistenti, un modello semplice che permetta di valutare ante operam il campo acustico prodotto da una installazione eolica tenendo in conto le caratteristiche di direttività del rumore emesso dalle turbine.