Internal Combustion Engines and Sprays

To request a copy of a publication send an email to antonio.ficarella02@gmail.com.

2016

"Experimental and Numerical Investigations on the Effect of Different Air-Fuel Mixing Strategies on the Performance of a Lean Liquid Fueled Swirled Combustor", Maria Grazia De Giorgi, Aldebara Sciolti, Stefano Capilongo, Antonio Ficarella, Energy Procedia Volume 101, November 2016, Pages 925-932

As regarding the experimental facilities, the combustor is equipped with four optical accesses for high speed flame imaging and with pressure and temperature sensors. Experimental data on flame characteristics and pollutant emissions are obtained. The characterization of the flame was realized using intensified high rate CCD camera for the acquisition in the ultraviolet spectral range. In front of the camera various combinations of optical filters were installed to selectively record the respective chemiluminescent species (OH* and CH*).

Computational fluid dynamic (CFD) simulations were also performed for a deeper understanding of the flame characteristics under the two injection strategies. The typical combustor operations were reproduced to more deeply understand the differences between the injection modes and the related flame patterns. The numerical results show different temperature and species fields predicted for the non-premixed and the partially premixed cases and furnish relevant information about the fluid dynamics in the combustion chamber in both the injection conditions.

“Effect of nozzle and combustion chamber geometry on the performance of a diesel engineoperated on dual fuel mode using renewable fuels”, VS Yaliwal, NR Banapurmath, NM Gireesh, RS Hosmath, T Donateo, P Tewari, Renewable Energy 93, 483-501, 2016

Renewable and alternative fuels have numerous advantages compared to fossil fuels as they are biodegradable, providing energy security and foreign exchange saving and addressing environmental concerns, and socio-economic issues as well. Therefore renewable fuels can be predominantly used as fuel for transportation and power generation applications. In view of this background, effect of nozzle and combustion chamber geometry on the performance, combustion and emission characteristics have been investigated in a single cylinder, four stroke water cooled direct injection (DI) compression ignition (CI) engine operated on dual fuel mode using Honge methyl ester (HOME) and producer gas induction. In the present experimental investigation, an effort has been made to enhance the performance of a dual fuel engine utilizing different nozzle orifice and combustion chamber configurations. In the first phase of the work, injector nozzle (3, 4 and 5 hole injector nozzle, each having 0.2, 0.25 and 0.3 mm hole diameter and injection pressure (varied from 210 to 240 bar in steps of 10 bar) was optimized. Subsequently in the next phase of the work, combustion chamber for optimum performance was investigated. In order to match proper combustion chamber for optimum nozzle geometry, two types of combustion chambers such as hemispherical and re-entrant configurations were used. Re-entrant type combustion chamber and 230 bar injection pressure, 4 hole and 0.25 mm nozzle orifice have shown maximum performance. Results of investigation on HOME-producer gas operation showed 4–5% increased brake thermal efficiency with reduced emission levels. However, more research and development of technology should be devoted to this field to further enhance the performance and feasibility of these fuels for dual fuel operation and future exploitations.

“Driving electronic board with adjustable piloting signal parameters for characterization of Common Rail diesel injectors with pure Biodiesel”, P. Visconti, V. Ventura, A.P. Carlucci and L. Strafella, Proceedings of 2016 IEEE 16th International Conference on Environment and Electrical Engineering (EEEIC), June 7-10, 2016 – Florence (Italy).

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 executionofwholeinjectionprocessis also composed of a National Instruments acquisition board, both units controlled from PC by means of an expressly implemented LabView Virtual Instrument.

"Experimental and Numerical Characterization of Single and Multipoint Injection Strategies in a Swirl Liquid Fueled Lean Combustor", Maria Grazia De Giorgi, Aldebara Sciolti, Stefano Capilongo, Antonio Ficarella, 71st Conference of the Italian Thermal Machines Engineering Association, ATI2016, Turin, Italy, 14-16 September 2016.

In the present work the performance of a multipoint lean direct injection strategy for low emission aero-propulsion systems has been experimentally and numerically investigated, and compared with the single point injection strategy. A swirler liquid fueled combustor was designed and used in experiments to investigate the flame behavior in lean and ultra-lean conditions for both the single-point and the multi-points injection strategies. Multipoint injection has been realized injecting an amount of fuel upstream the swirler inlet and using also the central injector as a “pilot” injection. As regarding the experimental facilities, the combustor is equipped with four optical accesses for high speed flame imaging and with pressure and temperature sensors. Experimental data on flame characteristics and pollutant emissions are obtained. The characterization of the flame was realized using intensified high rate CCD camera for the acquisition in the ultraviolet spectral range. In front of the camera various combinations of optical filters were installed to selectively record the respective chemiluminescent species (OH* an CH*). Computational fluid dynamic (CFD) simulations were also performed for a deeper understanding of the flame characteristics under the two injection strategies. The typical combustor operations were reproduced to more deeply understand the differences between the injection modes and the related flame patterns. The numerical results show different temperature and species fields predicted for the non-premixed and the partially premixed cases and furnish relevant information about the fluid dynamics in the combustion chamber in both the injection conditions.

"Detecting environmental features in an experimental combustion chamber of gas turbine: Advanced imaging process and accuracy", Lay-Ekuakille, A., De Giorgi, M.G., Ficarella, A., Urooj, S., Bhateja, V., 6th IMEKO TC19 Symposium on Environmental Instrumentation and Measurements 2016, pag. 56-59, 2016.

The quality of combustion process has an impact on combustion itself and mainly on emissions. This1 latter is one of the major concerns in an environmental viewpoint; for instance, the amount of oxygen is an indicator of bad and good combustion. It is also a constraint for regulating pollutant production, in particular dust that is also a vector transporting harmful micropollutants. The paper illustrates combustion quality detection by means of imaging. The work aims at retrieving possible precursors of combustion deterioration, and instability and allowing decision makers to provide accordingly. Images have been taken from an experimental setup.

"COMPARING SPRAY AND FLAME BEHAVIOR IN A SWIRL LIQUID FUELED LEAN BURNER WITH SINGLE AND MULTIPOINT INJECTIONS", M.G. De Giorgi, Aldebara Sciolti, S. Campilongo, A. Ficarella, GT2016-57353, Proceedings of ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition, GT2016, June 13 – 17, 2016, Seoul, South Korea, 2016.

Recent advances in gas turbine combustor design aimed at achieving low NOx emissions have focused on locally leaner combustion by rapid mixing of fuel and air. Multipoint injection leads to a fast and efficient mixing with the control of the spatial fuel distribution. In the present work, an experimental study on combustion phenomena in a liquid fuel burner, which operates in non-premixed (single point injection) and partially-premixed regimes (multipoint injections), was carried out in order to investigate the effect of the injection mode. In both the cases the lean combustion behavior was investigated in proximity of the blow-out limit. An intensified high rate CCD was used for flame imaging in the ultraviolet spectral range. It was equipped with different optical filters to selectively record single species chemiluminescence emissions (e.g. OH*, CH*). Analogous filters were also used in association with photomultiplier (PMT) tubes. Finally the NOx emissions were monitored. Furthermore, preliminary computational fluid dynamic (CFD) simulations were also performed under the typical combustor operation conditions to provide insight into the mixing of the air and the fuel under the different injection modes and the related flame pattern.

"Performance optimization of a Two-Stroke supercharged diesel engine for aircraft propulsion", Carlucci A.P., Ficarella A., Trullo G. ENERGY CONVERSION AND MANAGEMENT, vol. 122, p. 279-289, ISSN: 0196-8904, doi: 10.1016/j.enconman.2016.05.077, 2016.

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.

"Biodiesel production from Cynara cardunculus L. and Brassica carinata A. Braun seeds and their suitability as fuels in compression ignition engines", De Domenico S., Strafella L., D’Amico L., Mastrorilli M., Ficarella A., Carlucci A.P., Santino A. ITALIAN JOURNAL OF AGRONOMY, vol. 11-1, p. 47-56, ISSN: 1125-4718, doi: 10.4081/ija.2016.685, 2016.

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.

"Image processing for the characterization of flame stability in a non-premixed liquid fuel burner near lean blowout", De Giorgi, Maria Grazia; Sciolti, Aldebara; Campilongo, Stefano; Ficarella, Antonio, AEROSPACE SCIENCE AND TECHNOLOGY, 49, 41-51, 2016.

In the present work, an experimental investigation was performed by varying the fuel/air ratio of a liquid-fuel gas turbine derived burner in the non-premixed mode, until an ultra-lean combustion condition was reached. In this condition, flame instabilities occur with negative impacts on combustion efficiency. Two high speed visualization systems in the visible range and in the infrared spectral region were used. Moreover, they were supported by an OH⁎ chemiluminescence measurement and by gas exhaust measurements. Different techniques were used starting from the luminosity signal of each pixel: the Wavelet Decomposition to calculate the wavelet energy, the frequency analysis of pixel intensities of the flame images to estimate the dominant frequency, finally the statistical analysis to calculate the pixel intensity variance. Both the statistical and frequency analyses were applied to the OH⁎ chemiluminescence data. One of the most important results of the present work regarded the capability of imaging techniques to individuate the instability insurgence and to be used as a predictive tool. Furthermore 2D maps of some parameters, extracted by the wavelet-based analysis of flame images, permitted to investigate local unsteadiness in the flame area.

2015

"Ultra Lean Combustion Characterization in a Pilot-Scale Gas Turbine Burner Using Image Processing Techniques", De Giorgi, Maria Grazia; Sciolti, Aldebara; Campilongo, Stefano; Ficarella, Antonio., Proceedings of ASME TURBO EXPO 2015 Turbine Technical Conference and Exposition GT2015 June 15-19, 2015, Montreal, Canada

The aim of the present investigation is the characterization of the behavior of a lean partially-premixed liquid fuel gas turbine near lean blowout limit. At this combustion regime the onset of instability will occur with negative impacts on combustion efficiency. The identification of the instability occurrence permits an efficient flame control adjusting the combustion parameters (as fuel or air mass flow, temperature, pressure, etc.) to stabilize the flame or designing opportunely flame control system. High-speed images of the flame under stable and near blowout condition were captured in conjunction with simultaneous optical data in order to better understand the phenomenology of the flame blowout process and the onset of instability. In particular the experimental characterization was performed through a High Speed Digital Camera, an Infrared camera and a Photomultiplier Tube (PMT) in association with the use of optical filter (OH*). The data collected with these instrumentations produce useful features for the development of an efficient tool for the flame control in industrial and aeronautical burners. The images acquired by the different cameras were processed considering the luminosity signal of each pixel and evaluating the frequency behavior, the variations of amplitude of the signals and some other descriptive parameters able to define the regime of the flame. Spectral analysis and Wavelet transform of pixel intensities of flame images were used and entropy and energy contents were evaluated. The spatial maps of the different spectral and statistical parameters were shown at different fuel/air equivalence ratio. The OH* emissions data measured by the PMT were processed and compared with the data obtained from the images processing.

“Cylinder Pressure-based Closed Loop Combustion Control: a Valid Support to Fulfill Current and Future Requirements of Diesel Powertrain Systems”, A.P. Carlucci, M. Benegiamo, M. R. Gaballo, S. Mannal, S. Motz, R. Saracino, ICE2015 - 12th International Conference on Engines & Vehicles, Capri, Napoli (Italy) September 13-17, 2015, ISBN 978-88-907870-4-1. SAE Technical Paper 2015-24-2423, 2015, doi:10.4271/2015-24-2423, ISSN: 0148-7191.

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 in-cylinder 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.

"FLAME IMAGE PROCESSING AND ANALYSIS IN AN ULTRA-LEAN LIQUID FUELED COMBUSTOR", Maria Grazia De Giorgi, Aldebara Sciolti, Stefano Campilongo, Antonio Ficarella, 23rd Conference of the Italian Association of Aeronautics and Astronautics, AIDAA2015, Politecnico di Torino, 17-19 November 2015.

The design of lean gas turbine combustion system requires a deep understanding of the instabilities that are evident at conditions close to the lean blowout limit. Furthermore the development of partially-premixed combustors, with multiple injection points, is particularly promising to reach the limitation of pollution. In the present work different experimental diagnostic techniques were used for characterizing unstable combustion in presence of non premixed and partially premixed flames. The applied techniques include OH* chemiluminescence acquisitions using a photomultiplier system, broadband visible and infrared optical emissions using two high rate CCD cameras and finally pollutant measurements using a multispecies exhaust gas measurements system. Several statistical and spectral post-processing methods were implemented to characterize the unstable combustion mechanisms and to permit the development of control strategies in lean premixed gas turbine combustors.

"Flame characterization in ultra-lean liquid fueled combustion regimes in the visible and UV spectra", Maria Grazia De Giorgi, Aldebara Sciolti, Stefano Campilongo, Antonio Ficarella, ISABE2015-22128, 2015.

An experimental investigation was performed by varying the fuel/air ratio in a liquid-fuel gas combustor operating in the nonpremixed and partially-premixed combustion modes, until ultra-lean conditions were reached. In these conditions, flame becomes unstable with negative impacts on combustion efficiency. A high speed visualization system was used and the acquisitions were supported by OH* measurements through a filtered photomultiplier tube (PMT) and the gas exhaust measurements. Different post-processing techniques were applied: the Wavelet Decomposition to calculate the wavelet energy, the frequency analysis of pixel intensities of the flame images to estimate the dominant frequency, and statistical analysis to calculate the pixel intensity variance. The spectral analysis was also applied to the PMT data. The most important results of the present work regard the capability of imaging techniques to individuate the instability insurgence and to be used as a predictive tool.

"Flame Instability in A Liquid Fuel Burner: Comparisons Between Single And Multipoint Injections", De Giorgi Maria Grazia, Ficarella Antonio, Sciolti Aldebara, Campilongo Stefano. In: PROCEEDINGS of XXXVIII Meeting of the Italian Section of the Combustion Institute, Lecce, Italy, September 20-23, 2015, ISBN: 978-88-88104-25-6. p. 1-6, Napoli:Italian Combustion Institute, ISBN: 978-88-88104-25-6, Lecce, 20-23 Settembre 2015, doi: 10.4405/38proci2015.X2, 2015.

With the aim to characterize the flame behavior when ultra-lean combustion conditions are reached, an experimental investigation was performed on a liquidfuel gas turbine derived burner, at different fuel/air ratios and comparing different fuel injection modes. Ultra lean conditions have a negative impact on combustion efficiency for the instabilities insurgence. High speed acquisitions by a CCD camera were performed to investigate the behavior of the spray and the flame close to lean blowout. Statistical and spectral analyses were also applied to the flame acquisitions to extract suitable parameters for blowout recognition.

"Experimental characterization of near-blowout instabilities in a lean liquid-fuelled combustor", De Giorgi Maria Grazia, Sciolti Aldebara, Campilongo Stefano, Ficarella Antonio. In: Proceedings of the conference ASME-ATI-UIT 2015 Conference on Thermal Energy Systems: Production, Storage, Utilization and the Environment. p. 1-6, Napoli:asme-ati-uit, ISBN: 978-88-98273-17-1, Napoli (Italy), 17-20 May 2015.

In the present work, an experimental investigation was performed to characterize lean combustion flames in a liquid fuel burner. Two different regimes were investigated: non-premixed and partially-premixed combustion modes. The fuel mass flow rate was fixed and the air mass flow was reduced until the blow-out limit was reached. A high rate CCD and a PMT tube equipped wit1h an OH* filter were used for the acquisitions. Statistical and spectral post-processing methods were applied obtaining variance maps, trends of the averaged value of variance with respect to the equivalent fuel/air ratio and trends of the wavelets energy contents with respect to the frequency ranges. Results underline that the onset of flame instability occurs at higher fuel/air ratio in the non-premixed combustion regime compared to the partially premixed mode. Furthermore the rise of CO emissions starts at the leaner conditions in the case of partially premixed combustion. The present work also shows that imaging techniques are suitable to individuate this instability incipience using spectral and statistical parameters extracted by the temporal series of flame images, hence they might be implemented in online monitoring systems.

"Supercharging system behavior for high altitude operation of an aircraft 2-stroke Diesel engine", Carlucci, Antonio Paolo; Ficarella, Antonio; Laforgia, Domenico; Renna, Alessandro, ENERGY CONVERSION AND MANAGEMENT, 101, 470-480, 2015.

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.

"Sizing and Simulation of a Piston-Prop UAV", Donateo, T.; Spedicato, L.; Trullo, G.; Carlucci, A.P.; Ficarella, A., ATI 2015, Roma, 2015.

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.

"Multiobjective optimization of the breathing system of an aircraft two stroke supercharged Diesel engine", Carlucci, A.P.; Ficarella, A.; Laforgia, D.; Trullo, G., ATI 2015, Roma, 2015.

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).

"Ignition of a homogeneous gaseous air/methane mixture through a flash light", Carlucci, A.P.; Ficarella, A.; Laforgia, D.; Strafella, L., ASICI - Italian Section of the Combustion Institute, Lecce, 2015.

This paper proposes a new ignition system for air-methane mixtures, based on the exposition of Multi Wall Carbon NanoTubes (MWCNTs), containing 75% in weight of ferrocene, to a low-consumption flash camera. The experiments were performed in a constant-volume chamber filled with an air-methane mixture and its combustion was triggered by exposing the nanotubes to the flash of a camera. During the experimental activity, two types of tests have been carried out. The first, compares the results of the combustion process varying the amount of nanoparticles introduced into the combustion chamber at fixed air/methane ratio; the second compares the results of the combustion process varying the air/methane ratio at fixed amount of nanoparticles. Dynamic pressure measurements show that the photo-ignition phenomenon takes place when a minimum amount of nanoparticles, equal to 10 mg (for the first tests session) is provided, and when an air/methane ratio not exceeding 61.5, i.e. three times higher than the stoichiometric (for the second test session), is used. These results are considered to be of great scientific importance, since the combustion process has been obtained igniting a mixture extremely lean: the use of mixtures of this type would allow to reduce pollutant emissions, such as NOx and particulate.

"Definition and optimization of the supercharging architecture for an aircraft two stroke diesel engine", Carlucci, A. Paolo; Ficarella, Antonio; Laforgia, Domenico; Trullo, Gianluca, AIDAA 2015, Torino, 1-20, 2015.

One of the crucial points associated to the utilization of a piston internal combustion engine for aircraft propulsion is the performance decrease increasing the altitude of operation. This is due to the negative effect of air density reduction on cylinder filling. A solution to this problem is represented by the engine supercharging, consisting in the intake air compression. Unfortunately, in 2-stroke engines, the cylinder filling efficiency is antithetical to the cylinder scavenging efficiency. Moreover, due to the increasingly stringent request for higher performance and lower fuel consumption, the architecture of the supercharging system as well as its control has become more complex. In particular, different architectures integrating the classic positive displacement compressor or dynamic machineries to electric motors, generators and storage systems have been proposed and compared. Aim of the present work is to compare different architectures – single turbocharger, double turbocharger, single turbocharger combined with a mechanical compressor, electrically-assisted turbocharger, with intercooler or aftercooler – for supercharging an aircraft 2-stroke Diesel engine for general aviation and UAV (Unmanned Aerial Vehicles). This engine must be characterized by a very high altitude operation and long fuel distance. Therefore, a 1D model of the engine has been realized and the performance of the different supercharging architectures in terms of power and specific fuel consumption as well as their effect on trapping and scavenging efficiencies have been calculated and compared for different altitudes. The analysis showed that with the two turbochargers architecture it is possible to reach the target power with the lowest fuel consumption. The two turbochargers architecture was shown to be more effective even if compared with architectures in which a single turbocharger was used together with a mechanical compressor. The two turbochargers architecture performance was further improved making independent the low pressure compressor and turbine thanks to their electrical, and not mechanical, connection (electrically-assisted turbocharger). A detailed analysis of this architecture, named “hybrid”, at part loads and different altitudes allowed to study the energy fluxes of the hybrid turbocharger. In particular, based on this analysis, it was possible to determine the best control strategy leading to the lowest specific fuel consumption or the highest power surplus between electro-turbine and electro-compressor. It was shown that this supercharging system is particularly convenient, from an energetic point of view, especially at high engine speed and load, because it is possible to extract power from the electric turbocharger without a penalty on specific fuel consumption. Therefore, it was concluded that the architecture with the electrically-assisted turbocharger is characterized by a fuel consumption lower than two turbochargers architecture, although more complex and characterized by higher weight and bulk. The architecture with two turbochargers and one aftercooler per bank was further investigated seeking for the design trends for the breathing system maximizing the output power and minimizing the fuel consumption. The results of a multiobjective optimization are then discussed, finalized to the determination of the engine configurations better performing in terms of output power at sea level and fuel consumption at maximum operating altitude. During this optimization process, several parameters have been varied, like: exhaust valve opening angle, closing angle and maximum 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 pressure and high pressure compressor pressure ratios, air/fuel ratio. These parameters have been varied on discrete levels in acceptable range of values. Using an optimizing routine based on genetic algorithms, different configuration have been determined guarantying higher output power and/or lower fuel consumption. This algorithm has been run for two different engine working altitudes. At the end of this process and after the data analysis, it was revealed that at sea level, in order to maximize output power, the most influent design parameters are the air/fuel ratio, the two supercharging stages compression ratios and the distance between lower edge of the scavenging ports and bottom dead center. Considering the specific consumption minimization case at maximum design altitude, the results obtained at sea level are basically confirmed, but the effect of every design parameter is opposite compared to what observed at take-off conditions.

"Behaviour of a compression ignition engine fed with biodiesel derived from cynara cardunculus and coffee grounds", Carlucci, A.P.; Ficarella, A.; Strafella, L.; Tricarico, A.; Domenico, S. De; D’Amico, L.; Santino, A., ASICI - Italian Section of the Combustion Institute, Lecce, 2015.

Biodiesel is one of the most tested and efficient amongst alternative fuels on the market and a considerable number of scientific papers show that its performance is similar to that of petroleum diesel. Moreover, it can work with existing engines and injection systems with negligible impact on the operating performance. Aim of this work is to assess the performance of biodiesel derived from Cynara cardunculus and coffee grounds as fuels, in blend with standard diesel fuel, for feeding a compression ignition engine. The combustion behavior and its effect on engine performance and exhaust emission levels have been quantified during an extensive experimental activity and compared with the results obtained feeding the engine with standard diesel fuel, alone or in blend with biodiesel derived from Brassica carinata. Results show that an overall conversion efficiency comparable or only slightly lower compared to that obtained with standard diesel fuel is observed using the biodiesel blends, mainly due to the lower heating value, lower for biodiesel than for standard diesel fuel. Moreover, total hydrocarbons (THC), carbon monoxide (CO) an particulate matter (PM) are all lowered with biodiesel, mainly due to the oxygen present in the biodiesel molecule. For the same reason, on the other hand, nitrogen oxides (NOx) increase. Thanks to these results, it can be concluded that biodiesels derived from Cynara cardunculus and coffee grounds are good candidates for feeding, alone or in blend with standard diesel fuel, compression ignition engines.

"An easy and inexpensive way to estimate the trapping efficiency of a two stroke engine", Carlucci, A.P.; Ficarella, A.; Laforgia, D.; Longo, M.P., ATI 2015, Roma, 2015.

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 according to 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.

"Air/methane mixture ignition with Multi-Walled Carbon Nanotubes (MWCNTs) and comparison with spark ignition", Carlucci, A.P.; Carnevale, F.; Ciccarella, G.; Ficarella, A.; Filippo, E.; Laforgia, D.; Mussardo, F.; Strafella, L., Nanofim 2015, Lecce, 101-106, 2015.

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.

2014

“An Inter-disciplinary Approach to theDevelopment of a Low-consumption Prototype for the European ShellEco-marathon”, T. Donateo, F. Ingrosso, A. Nicolì, A. Taurino, Advanced Materials Research Vols. 875-877, pp. 977-982, ISSN: 1022-6680, 1662-8985, 2014

The paper describes the design, the test and the optimization of a prototype for the European Shell Eco-Marathon (SEM) competition. The design step includes the definition of vehicle shape, materials, structure, tires, power-train and control with an inter-disciplinary approach. The test phase was performed both numerically and experimentally. The vehicle, named Carla 2012 has been build at the DII (Department of Innovation Engineering) at Università Del Salento and tested on the facilities available at the Nardò Technical Center and was able to satisfy all the specifics of SEM regulation in 2012 edition. The optimization step is aimed at defining an innovative powertrain and an high-efficiency race strategy in order to achieve 3000 km with the equivalent of 1 liter of gasoline.

“ExperimentalValidation of a CFD Model and an Optimization Procedure for Dual Fuel Engines”, Teresa Donateo, Antonio Paolo Carlucci, Luciano Strafella, Domenico Laforgia, SAE Technical Paper 2014-01-1314, ISSN 0148-7191, 2014

An analytical methodology to efficiently evaluate design alternatives in the conversion of a Common Rail Diesel engine to either CNG dedicated or dual fuel engine has been presented in a previous investigation. The simulation of the dual fuel combustion was performed with a modified version of the KIVA3V code including a modified version of the Shell model and a modified Characteristic Time Combustion model. In the present investigation, this methodology has been validated at two levels. The capability of the simulation code in predicting the emissions trends when changing pilot specification, like injected amount, injection pressure and start of injection, and engine configuration parameters, like compression ratio and axial position of the diesel injector has been verified. The second validation was related to the capability of the proposed computer-aided procedure in finding optimal solutions in a reduced computational time. Therefore, a multi-objective genetic algorithm was run for 100 generations with a population of 50 individuals including the same geometric and control variables taken into account in the first validation. The optimization was aimed at minimizing HC and NOx emissions. Three Pareto solutions selected from the results of the optimization were tested experimentally as a final validation. The potential improvement of the combustion process that can be obtained by optimizing the shape of the bowl is finally addressed in the paper.

"Experimental Validation of a CFD Model and an Optimization Procedure for Dual Fuel Engines", Donateo, T., Carlucci, A., Strafella, L., and Laforgia, D., SAE World Congress & Exhibition 2014, Detroit (Michigan), April 8-10, 2014. SAE Technical Paper 2014-01-1314, 2014, doi:10.4271/2014-01-1314, ISSN: 0148-7191.

“Advanced closed loop combustion control of a LTC diesel engine based on in-cylinder pressure signals”, A.P. Carlucci, D. Laforgia, S. Motz, R. Saracino, S. P. Wenzel, Energy Conversion and Management 77 (2014) 193-207 (DOI: 10.1016/j.enconman.2013.08.054) ISSN: 0196-8904.

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.

“Potentialities of common rail injection system for the control of dual fuel biodiesel-producer gas combustion and emissions”, A.P. Carlucci, A. Ficarella, D. Laforgia, Journal of Energy Engineering Volume 140, Number 3 (2014) A4014011-1 — A4014011-8 (DOI: 10.1061/(ASCE)EY.1943-7897.0000150) ISSN: 0733-9402.

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 (H-2), and nitrogen (N-2) 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. (C) 2014 American Society of Civil Engineers.

"Improvements in Dual-Fuel Biodiesel-Producer Gas Combustion at Low Loads through Pilot Injection Splitting", A. P. Carlucci; G. Colangelo; A. Ficarella; D. Laforgia; L. Strafella, JOURNAL OF ENERGY ENGINEERING, 141, C4014006-C4014006, 2014.

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

"Assessment of the combustion behavior of a pilot-scale gas turbine burner using image processing", A. Sciolti, S. Campilongo, M.G. De Giorgi, A. Ficarella. Proceedings of the ASME 2014 Power Conference Power 2014, July 28-31, Baltimore, Maryland, USA. Power2014-32022, 2014.

Experimental investigations were performed on a nonpremixed liquid fuel-lean burner. The present work aims to the development of a methodology for the recognition of flame instability regimes in industrial and aeronautical burners. Instability, in fact, is an unpleasant aspect of combustive system that negatively impacts on combustion efficiency. The online monitoring of the occurrence of instability conditions, permits to adjust combustion parameters (as fuel or air mass flow, temperature, pressure, etc.) and to stabilize again the flame. High speed visualization systems are promising methods for on-line combustion monitoring. In this study two high speed visualization systems in the visible range and in the infrared spectral region were applied to characterize combustion efficiency and flame stability. Different processing techniques were used to extract representative data from flame images. Wavelet Decomposition and Spectral analysis of pixel intensities of flame images were used for feature extraction. Finally a statistical analysis was performed to identify the most unstable regions of the flame by the pixel intensity variance.

"Frequency Analysis And Predictive Identification Of Flame Stability By Image Processing", M.G. De Giorgi, A. Sciolti, E. Pescini, A. Ficarella. Proceedings of the ASME 2014 8th International Conference on Energy Sustainability & 12th Fuel Cell Science, Engineering and Technology Conference ESFuelCell2014; June 30-July2, Boston, Massachusetts ES-FuelCell2014-6599, 2014.

Monitoring and characterization of combustion flames by digital image processing is an active research topic. This study experimentally investigates the feasibility of high speed visualization techniques for combustion instability monitoring in a swirl liquid-fueled lean combustor for different air/fuel ratios. Instability, in fact, is an unpleasant aspect in the combustive system that negatively impacts on combustion efficiency. This work investigates methods for extracting significant parameters using the geometrical and luminous data of the flame images; some flame features are related to the combustion regimes. The stability of the flame is identified using spectral and wavelet-based analysis of the pixel intensities of the flame images. In particular the most flame unstable regions were identified by analyzing the two dimensional maps of different physical quantities. The impact of the fuel/air ratio on the stability of the flame is investigated also by a Monochromator/Photomultiplier system (PMT). The results support the potential of the methods described for flame monitoring.

2013

“Effect of the Shape of the Combustion Chamberon Dual Fuel Combustion”, T. Donateo, L. Strafella, D. Laforgia, SAE Technical Paper 2013-24-0115, ISSN 0148-7191, 2013

The effect of the geometry of the bowl on the combustion process and emissions of a NG-Diesel dual fuel engine is analyzed as a result of a multi-objective optimization performed with CFD simulations and genetic algorithms. The simulation of the dual fuel combustion is performed with a modified version of the KIVA3V code where diesel is treated as the main fuel and a further reacting species is introduced as CH4. The auto-ignition of the pilot is simulated with the modified Shell model and the first stage of the combustion, related to the pilot burning process, is simulated with the Characteristic Time Combustion model. When the temperature of the mixture reaches a certain threshold, a kernel of combustion is initialized. Until the kernel reaches a nominal radius the combustion of CH4 is prevented. The combustion of CH4 is simulated with a turbulent characteristic time too. The model has been validated with comparison with experimental data including in-cylinder pressure traces and tailpipe emissions. The numerical analysis has been performed with respect to a single cylinder diesel engine converted to dual fuel combustion. The results of the investigation showed that the conversion rate of CH4 can be increased by optimizing the bowl profile and particularly by allowing the combustion to spread both in the bowl and in the squish region.

“Computer-aided conversion of an engine from diesel to methane”, T. Donateo, F. Tornese, D. Laforgia, Applied Energy, Volume 108, Pages 8–23, ISSN: 0306-2619, August 2013.

The paper proposes an analytical methodology that uses empirical based models and CFD simulations to efficiently evaluate design alternatives in the conversion of a diesel engine to either CNG dedicated or dual fuel engines. The procedure is performed in five steps. Firstly, a database of different combustion chambers that can be obtained from the original piston is obtained. The chambers in the database differ for the shape of the bowl, the value of the compression ratio, the offset of the bowl and the size of the squish region. The second step of the procedure is the selection, from the first database, of the combustion chambers able to resist to the mechanical stresses due to the pressure and temperature distribution at full load. For each combination of suitable combustion chamber shape and engine control parameters (ignition/injection crank angle, EGR, etc.), a CFD simulation is used to evaluate the combustion performance of the engine. Then, a post-processing procedure is used to evaluate the detonation tendency and intensity of each combination. All the tools developed for the application of the method have been linked in the ModeFrontier optimization environment in order to perform the final choice of the combustion chamber.The overall process requires not more of a week of computation on the four processor servers considered for the optimization. Moreover, the selected chambers can be obtained from the original piston of the engine. Therefore, the conversion cost of the engine is quite small compared with the case of a completely new piston. The paper also describes the application of the procedure to two different engines.

2012

“On the Computer-Aided Conversion of a Diesel Engine to CNG-Dedicated or DualFuel Combustion Regime”, T. Donateo, A. de Risi, D. Laforgia, 2012 Proceedings of the ASME Internal Combustion Engine Division Spring Technical Conference (ICES2012), ISBN number: 9780791844663, May 6-9, 2012

The paper proposes a cost-saving analytical methodology using empirical based models to efficiently evaluate design alternatives in the optimization of a CNG converted diesel engine. The procedure is performed in five steps. Firstly, a database of different combustion chambers that can be obtained from the original piston is obtained. The chambers in the database differ for the shape of the bowl, the value of the compression ratio, the offset of the bowl and the size of the squish region. The second step of the procedure is the selection, from the first database, of the combustion chambers able to resist to the mechanical stresses due to the pressure and temperature distribution at full load. For each combination of suitable combustion chamber shape and ignition timing, a CFD simulation is used to evaluate the combustion performance of the engine. Then, a post-processing procedure is used to evaluate the detonation tendency and intensity of each combination. All the tools developed for the application of the method have been linked in the ModeFrontier optimization environment in order to perform the final choice of the combustion chamber. The overall process requires not more of a week of computation on the 4 processor servers considered for the optimization. Moreover, the selected chambers can be obtained from the original piston of the engine. Therefore, the conversion cost of the engine is quite small compared with the case of a completely new piston. The procedure can be applied to diesel engines to be converted to either CNG dedicated or dual fuel combustion. The main aspects and challenges to be taken into account in both cases are also analyzed.

"EFFECT OF THE CHARGE PREPARATION IN A COMPRESSION IGNITION DUAL FUEL ENGINE - COMPARISON BETWEEN METHANE AND HYDROGEN", A.P. Carlucci, A. Coricciati, A. Ficarella, D. Laforgia, D. Mauro, A. Orlando, G. Spedicato, L. Strafella, 67° Congresso Annuale ATI, Trieste (Italy), Sept. 11-14, 2012.

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.

2011

“Gestioneintelligente del motore termico in veicoli ibridi plug-in” , T. Donateo, D. Pacella , F. Greco, Atti del 66° Congresso Nazionale Ati, Rende (Cosenza), 5-9 Settembre 2011

Negli ultimi anni particolare attenzione è stata data, da parte della comunità scientifica, allo sviluppo di soluzioni tecnologiche per veicoli ibridi plug-in e in particolare per l’ottimizzazione della gestione dei flussi energetici al fine di minimizzare consumi ed emissioni. In questa memoria si presenta una strategia auto-adattativa di gestione dell'energia per i veicoli ibridi elettrici in configurazione serie basata su mappe ottimizzate per i diversi componenti e su predizioni di profili di velocità effettuate da SUMO (Simulation of Urban MObility). Il primo passo della ricerca è stato quello di eseguire l'ottimizzazione off-line dei parametri della strategia di controllo basata su una serie di mini cicli di guida, ottenuta da cicli di guida standard (UDDS, NEDC, ecc.) e cicli di guida reale acquisiti dal veicolo ITAN500 (prototipo realizzato dall’Università del Salento). Le variabili ottimizzate ottenute per ogni mini ciclo di guida vengono memorizzate in mappe che saranno implementate sull'ITAN500. Il sistema proposto prevede uno scambio di informazioni con i veicoli circostanti e le infrastrutture. Tali informazioni sono utilizzate da un simulatore di traffico locale eseguito a bordo, per predire le condizioni di guida dell'HEV in un periodo di tempo futuro (T=60s). Il ciclo di guida predetto viene confrontato con i mini cicli di guida di riferimento per trovare quello più simile e per selezionare i relativi parametri ottimi. I risultati presentati dimostrano che la procedura sviluppata è in grado di gestire in modo ottimale il funzionamento del motore termico consentendo di farlo funzionare per gran parte della missione solo quando si trova in condizioni di massimo rendimento.

“Combustion and emissions control in diesel-methane dual fuel engines: the effects of methane supply method combined with variable in-cylinder charge bulk motion”, A.P. Carlucci, D. Laforgia, R. Saracino, G. Toto, Energy Conversion and Management 52 (2011) 3004–3017 ISSN: 0196-8904.

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.

2010 and before

“Optimal Design of a Common Rail Diesel Engine Piston”, T. Donateo, in “Computational Intelligence in Expensive Optimization Problems” by TENNE Yoel and GOH Chi-Keong, Springer Verlag, ISBN 978-3-642-10700-9, 2010

This chapter analyzes the main challenges in the application of “simulation optimization” to the design of engine components, with particular reference to the combustion chamber of a Direct Injection Diesel engine evaluated via Computational Fluid Dynamic (CFD) codes.

“Performance and environmental impact of a compression ignition engine fed with biodiesel and gasoil blends”, A. P. Carlucci, D. Laforgia, A. Vergari, SEEP2010 Conference Proceedings, June 29th – July 2nd, Bari, ITALY ISBN: 9788890518522

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 CO 2 , 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 NO x , CO 2 , 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 NO x emission levels of about 30%.

“Study of combustion development in methane-diesel dual fuel engines, based on the analysis of in cylinder luminance”, P. Carlucci, D. Laforgia, R. Saracino, G. Toto, SAE World Congress & Exhibition 2010, Detroit (Michigan), April 13-15, 2010. SAE Technical Paper 2010-01-1297, 2010, doi:10.4271/2010-01-1297, ISSN: 0148-7191. Also in “Emissions Measurement and Testing, 2010 – Special Publication SP-2289.

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.

"Study of the Delivery Behaviour of a Pump for Common Rail Fuel Injection Equipments", A. Ficarella, A. Giuffrida, D. Laforgia, Proc. IMechE, Vol. 223 Part I: J. Systems and Control Engineering, pp. 521-535, IMechE 2009.

This work deals with the delivery flowrate of a radial piston pump for common rail fuel injection equipment. At first, attention is paid to the volumetric efficiency of the pump, presenting basic formulas and reviewing common theory. A new efficiency model is proposed and considerations regarding the pump running under large pressure differences between suction and delivery and variable driving speeds are formulated in order to realize difficulties in pump filling. Later, a numerical model simulating the working behaviour of the pump is used to investigate the effects of variable inlet pressures under high delivery pressure and different

driving speeds. Comparisons between numerical results and experimental data referring to the delivery behaviour of the pump are reported, as well as in-cylinder pressure diagrams, necessary to realize filling deficiencies quickly.

The flowrate delivered by the investigated pump depends on both the inlet and outlet pressures. Increasing the driving speed beyond certain values does not result in proportional flowrate at pump delivery.

"Performance and exhaust emissions of a di diesel engine fueled with a blend of biodiesel and diesel fuel", A. CARLUCCI; FICARELLA A; FIORILLO R; LAFORGIA D, 63° Congresso Nazionale ATI, Palermo (Italy), Sept. 23-26, 2008.

The oscillating increase in the oil price per barrel and the changes in petroleum distillate demand, together with the necessity to face the environmental pollution problems, lead to the need to improve diesel-fuel quality and open the way for the commercialization of biodiesel, which is a useful tool to deal with the effects of emissions on climate change. The substitution of diesel with renewable fuels is of particular

interest and biodiesel is an easily prepared substitute for diesel fuel that does not contain sulphur and does not require significant modifications of the conventional diesel engine.

The objective of the work is to investigate the performance and exhaust emission levels of a stationary, direct injection, turbocharged, 4-cylinder diesel engine when it is fuelled by petroleum diesel fuel or by a volume blend of petroleum diesel and biodiesel SME and, then, by Low-Sulphur diesel fuel.

The present work tests the possibility to use biodiesel blend as fuel for compression ignition internal combustion engine in order to diversify energy sources. However, biodiesel causes a small decrease of BSEC and, at the exhaust, an increase of NOx emissions, as it is reported by previous research works, with also a reduction of THC and TPM sampled using a dilution tunnel. Furthermore, Low-Sulphur diesel fuel causes a small reduction of BSEC, THC and TPM without increasing NOx at the exhaust.

"Investigation of Short Injections Using Standard and Modified Common Rail Injectors", A. Ficarella, A. Giuffrida, R. Lanzafame, International Journal of Automotive Technology, Vol. 8, No 2, pp. 155-263, 2007.

The control of the fuel to be introduced into the combustion chamber under idling and low-load conditions is known to be a problem in Diesel engines, owing to the relatively small fraction of the full-load fuel needed under light loads. Thus, particular attention should be paid to the behavior of the injector with reference to short injection events. This work presents the results of an experimental campaign carried out with two different types of common rail injectors, a standard injector and a modified one. The latter, coming from a simple modification realized in a standard injector, exhibits linear behavior between injected fuel and solenoid energizing time in the field of short injections. A direct comparison of the two injection behaviors suggests a possible way to better control short or pilot injections.

“Control of the Combustion Behaviour in a Diesel Engine Using Early Injection and Gas Addition”, P. Carlucci, A. Ficarella, D. Laforgia, “4th Workshop – Fuel Injection – Spray – Combustion: Experimental and Modelling, Modena, 27-28 maggio, 2004. Journal of Applied Thermal Engineering, Vol. 26, pp. 2279-2286, 2006.

Multiple injections and natural gas addition were investigated as ways to modify combustion behaviour, and therefore pollutant emissions and specific fuel consumptions, inside a direct injection Diesel engine equipped with a common rail injection system. During the experimental tests, engine efficiency, in terms of fuel consumption, and pollutant emissions, in terms of nitric oxides, opacity, carbon monoxide and total hydrocarbons, have been measured.

The tested multiple injection strategy consisted of the simultaneous use of early and pilot injections. This strategy has been compared with the more traditional techniques based on the use of either pilot or early injections. During the tests, the effects of several injection parameters were analysed, like duration and timing of early, pilot and main injections. Results show that, mainly for medium values of engine torque and speed, the injection of a small fuel quantity during the early stage of the compression stroke, coupled with the pilot injection, may be effective in reducing specific fuel consumption if compared to the only pilot or only early injection strategies. Furthermore, this result is obtained whit a simultaneous reduction in nitric oxides and particulate. However, unburned hydrocarbons levels remain constant or usually increase. Early injection is in effect a way to obtain a very lean premixed charge, both globally and locally, inside the combustion chamber. Therefore, it has been shown that nitric oxides and soot, deriving respectively from an inhomogeneous distribution of temperatures and a locally rich mixture, both decrease performing the early and pilot before the main injection.

Concerning the natural gas addition, it has been premixed with the engine intake air before the turbocharger and used in small percentages, in order to improve the engine combustion and to reduce pollutant emissions, in particular the soot produced during the mixing-controlled combustion phase. Experiments underlined that, using the natural gas as an additive fuel, while performing the Diesel fuel main injection, leads to keep practically unchanged engine efficiency with respect to the traditional Diesel fuel operation mode.

Concerning the emission levels at the exhaust, the use of small quantities of gas (10–30% respect to the total fuel energy) improves the oxides – soot trade-off; however, at the same time, total hydrocarbons and carbon monoxide emissions are characterized by higher values.

“Common Rail Injector Modified to Achieve a Modulation of the Injection Rate”, A. Ficarella, A. Giuffrida, R. Lanzafame, Intl. J. of Automotive Technology, Vol. 6, Issue 4, August 2005, pagg. 305-314.

“Neural network for modeling and optimization of internal combustion engines”, P. Carlucci, A. Ficarella, D. Laforgia, Proceedings of TNC CAE 2005 International Conference on CAE and Computational Technologies for Industry, Lecce, October 4-6, 2005.

In this work, the possibility of modeling the engine emissions has been analyzed in terms of NOx, CO, unburned hydrocarbons and brake specific fuel consumption as a function of injection parameters and EGR levels. The results showed that the neural network technique was capable of analyzing the influence of any single input parameter on any output variable and allowed the formulation of an efficient simple mathematical model of the engine that was able to predict the output of interest.

“Combined Effectof Exhaust Gas Recirculation and Partially Premixed Charge onPerformance and Emissions of a Direct Injection Diesel Engine”, P. Carlucci, F. F. Chiara, A. Ficarella, T. Giuranna, D. Laforgia, Proceedings of 7th International Conference on Engines for Automobile, Capri (Napoli), September 11-16, 2005.

The influence, on the combustion of a Common-Rail Diesel engine of the exhaust gas recirculation, with and without cooling, in combination with a partially-premixed charge, obtained with different injection strategies characterized by a very advanced fuel injection (early injection), have been experimentally investigated. Engine performances, in terms of brake specific fuel consumption and gaseous emissions, together with the combustion behaviour, have been analysed.

Experimental tests have been carried out on a direct injection Fiat 1929 cm3 Common Rail Diesel engine. Three different injection strategies have been investigated: the first one was obtained performing an early, a pilot and a main injection, the second one coupling an early and a main injections and the third one with a pilot and a main injections. The effects on engine combustion of hot and water cooled EGR have been compared with combustion behaviour obtained without EGR, also showing the effect produced by different pilot injection timings and quantities, and different early injection quantities. Results show that, fixing the early injection quantity to low levels, both the triple injection strategy, with low quantity of pilot injection, and the early-main strategy, improve performance and emissions, particularly at high levels of both hot and cooled EGR, showing in the same time the benefits of a partially premixed charge produced by the earlyinjection.

“Diesel Combustion Enhancement through an Early Injection-Based Injection Strategy”, P. Carlucci, A. Ficarella, D. Laforgia, Beograd 2005 EAEC Congress, May 30 – June 1, 2005.

A new multiple injection strategy was tested, obtained performing an early, a pilot and a main injection. The aim of this strategy is in fact to obtain the benefits of both the premixed lean diesel combustion and the

multiple injection systems already on the market. Tests were carried out for different engine torque and speed conditions, and the effect of the injection parameters, like duration and timing of early and pilot injections was investigated. The combustion quality, in terms of nitric oxides, total unburned hydrocarbons and particulate emissions, and the engine performances, in terms of fuel consumption and combustion stability, were analysed.

The performance of the aforementioned injection strategy have been compared with the results obtained using either pilot or early injections. Results show that the fuel quantity injected during the early injection, coupled with the pilot injection, leads to comparable levels or even to a sensible reduction of fuel consumption compared to the only pilot or only early injection cases. Furthermore, a reduction in both NOx and particulate is always obtained, while the level of unburned hydrocarbons usually increases.

ratio and consequently temperature, leading to high NOx and soot production. On the other hand, by using the pilot injection, the ignition delay of the main injection was stabilized, thus leading to a regular engine

operation.

"Effects on Combustion and Emissions of Early and Pilot Fuel Injections in Diesel Engines", P. Carlucci, A. Ficarella, D. Laforgia, International Journal of Engine Research, Vol. 6, No. 1, pp. 43-60, 2005.

Different injection strategies applied to a common rail direct-injection diesel engine were tested for different engine torque and speed conditions. The injection strategies differ for the use of early and pilot injections; during the tests the injection parameters were varied, in terms of duration and timing of early, pilot and main injections. The combustion behaviour and the engine performances, in terms of brake specific fuel consumption, were analysed. In addition, data on nitrogen oxides (NOx), total unburned hydrocarbons and particulate emissions were collected.

The injection strategy based on both early and pilot injections has been compared with the techniques using either pilot or early injections. Results show that, particularly at lower values of engine torque and speed, the small fuel quantity injected during early injection, coupled with the pilot injection, leads to comparable levels or even to a sensible reduction in fuel consumption compared with the only-pilot or only-early injection cases. Furthermore, a reduction in NOx and particulate is generally observed, while the level of unburned hydrocarbons usually increases.

Experimental tests have shown that, using the early injection, a very lean premixed charge is obtained, both globally and locally, inside the combustion chamber, thus avoiding diesel problems (in particular, high NOx and soot production), mainly caused by the locally rich mixture. On the other hand, by using the pilot injection the ignition delay of the main injection is reduced, contributing to the NOx reduction.

"Preliminary Studies on the Effects of Injection Rate Modulation on the Combustion Noise of a Common Rail Diesel Engine", P. Carlucci, A. Ficarella, F. Chiara, A. Giuffrida, R. Lanzafame, SAE Fuel and Lubricant 2004, Tolosa (Francia), 8-10 giugno 2004, SAE Paper 2004-01-1848. - pubblicato in New Combustion Systems in SI & Diesel Engines, and Combustion & Emission Formation Processes in Diesel Engines, SP-1890, ISBN 0-7680-1484-0 (pagg. 129-141).

The present work deals with tests on a DI Diesel engine equipped with two different types of Common Rail injectors, the second one allowing a “smoother” fuel rate in the first stage of injection. The work aims at

understanding how injection parameters and different injection rates may affect the combustion process in terms of in-cylinder pressure, noise and vibrations of the engine block. The tests performed for the same engine torque generally showed that engine speed, injection pressure and pilot injection duration are the most significant parameters that affect engine noise emissions. As regards the effect of the injection rate

modulation, experiments showed that it is possible to reduce combustion noise at low engine speeds.

"Experimental Comparisons of Different Strategies for Natural Gas Addition in a Common Rail Diesel Engine", P. Carlucci, A. Ficarella, D. Laforgia, Proceeding of the FISITA 2004 Congress, Barcelona (Spain), 23-27 maggio 2004, paper F2004V136.

"Improvementsin Diesel Engine Combustion by Using both Early and Pilot Injection", P. Carlucci, A. Ficarella, D. Laforgia, Proceedings of the 6th International Conference on Engines for Automobile ICE03, Capri, Sept. 14-19, 2003. SAE-NA Paper 2003-01-72.

"Study of the modulation of the Fuel Rate of a Common Rail Injector", P. Carlucci, A. Ficarella, A. Giuffrida, R. Lanzafame, Proceedings of the 6th International Conference on Engines for Automobile ICE03, Capri, Sept. 14-19, 2003. SAE-NA Paper 2003-01-78.

“Investigation on Realizing Fuel Rate Shaping Using a Common Rail Injector ”, P. Carlucci, A. Ficarella, A. Giuffrida, R. Lanzafame, ASME Internal Combustion Engine Division, 2003 Spring Technical Conference, Salzburg, Austria, 11-14 maggio 2003. ASME Paper ICES 2003-599.

“Effectsof Pilot Injection Parameters on Combustion for Common Rail DieselEngines”, P. Carlucci, A. Ficarella, D. Laforgia, The SAE 2003 World Congress, Cobo Center in Detroit, MI-USA, 3-6 marzo 2003. SAE Paper 2003-01-0700. Published on SAE 2003 Transactions, Journal of Engines, vol. 6, pp. 722-735, September 2004.

“Measurements of opacity at exaust of Diesel engine using extinction laser thecnique”, A. Lay-Ekuakille, P. Carlucci, A. Ficarella, D. Laforgia, A. Pascali, Photonics Asia, Shangai (China), Oct. 14-18, 2002.

“A CombinedOptimization Method for Common Rail Diesel Engines”, P. Carlucci, A. De Risi, T. Donateo, A. Ficarella, 2002 Spring ASME ICE Conference, Rockford (Illinois-USA), April 14-17, 2002.

“Pilot Injection Behavior and Its Effects on Combustion in a Common Rail Diesel Engine”, in collaborazione con P. Carlucci, D. Laforgia, International Workshop on Modeling, Emissions and Control in Automotive Engines MECA'01, Fisciano, Salerno (Italy), 9-10 settembre 2001.

“Influence of the Injection Parameters on Combustion Pressure and Noise in a Common Rail Diesel Engine”, in collaborazioen con P. Carlucci, D. Laforgia, Paper 01A3015, 3rd International Conference on Control and Diagnostics in Automotive Application CD AUTO 01, Sestri Levante, Genova (Italy), 4 – 6 luglio 2001.

“Studyof the Influence of the Injection Parameters on Combustion Noise in aCommon Rail Diesel Engine Using ANOVA and Neural Networks”, P. Carlucci, A. Ficarella, D. Laforgia, SAE Paper 2001-01-2011, International Spring Fuels & Lubricants, Orlando, Florida (USA), May 7-9, 2001.

“Evaluation of Instability Phenomena in a Common Rail Injection System for High Speed Diesel Engines”, A. Ficarella, D. Laforgia, V. Landriscina. 1999 SAE International Congress and Exposition, Detroit (USA), 01-04 marzo 1999. SAE Paper 1999-01-0192; SAE 1999 Transactions - Journal of Engines, pp. 322-336, 1999.

"A Theoretical Code to Simulate the Behaviour of an Electro-Injector for Diesel Engines and Parametric Analysis", in collaborazione con V. Amoia, D. Laforgia, S. De Matthaeis, C. Genco, SAE Paper 970055, SAE International Congress and Exposition, Detroit (USA), 24-27 febbraio 1997.

"Experimental Investigation of the Spray of an Axi-Symmetric Nozzle of a Common-Rail High Pressure Electro-Injector", in collaborazione con D. Laforgia, G. Starace e V. Damiani, SAE Paper 970054, SAE International Congress and Exposition, Detroit (USA), 24-27 febbraio 1997.

“Diesel Electro-Injector: A Numerical Simulation Code”, in collaborazione con G. Bruni, P. DiGesù, D. Laforgia e M. Ricco, SAE Paper No. 940193, 1994. SAE 1994 Transactions - Journal of Engines, vol. 103/3, pp. 100-119, 1994.

"Spray Characteristics of Five-Hole V.C.O. Nozzles of a Diesel Electro-Injector", in collaborazione con R. Campanella, V. Damiani e D. Laforgia, SAE Paper No. 940192, SAE 1994 Transactions - Journal of Engines, vol. 103/3, pp. 120-133, 1994.

"Injection Characteristics Simulation and Analysis in Diesel Engines", in collaborazione con D. Laforgia, International Journal of Meccanica, vol. 28, pp. 239-248, 1993.

"Spray Analysis Using the Phase Doppler System", in collaborazione con J. M. Buchlin, Proceedings del Workshop and Exposition on Fluidmechanics, Combustion and Emissions in Reciprocating Engines, Napoli, 1-5 aprile 1990.

"Investigation and Computer Simulation of Diesel Injection System with Rotative Pump", in collaborazione con D. Laforgia e G. Cipolla, ASME Journal of Engineering for Gas Turbine and Power, vol. 112, pag. 317-323, luglio 1990. Presentato all' ASME Conference on Engine Design, Operation and Control Using Computer Systems, Dearborn (USA), (ASME ICE vol. 9, pp. 87-96), 16-18 ottobre 1989.

"Poppet Valve Flow Characteristics in Internal Combustion Engines", in collaborazione con D. Laforgia, ASME ICE, Basic Process in Internal Combustion Engines, vol. 6, pp. 33-42, 1989. Presentato anche alla XII Annual Energy Sources Conference, Houston (USA), 22-25 gennaio 1989.

"Contribution to the Simulation of Injection Systems for Reciprocating Internal Combustion Engines", in collaborazione con D. Laforgia, SAE Paper No. 885016, 1988. Presentato al 22nd Congress FISITA 1988, Dearborn-Washington (USA), 25-30 settembre 1988.

"Fluiddynamische Erscheinungen in Einspritzanlagen", in collaborazione con D. Laforgia, MTZ Motortechnische Zeitschrift, vol. 52/1, pp. 28-34, gennaio 1991.

"Fluid Dynamic Phenomena in Fuel-Injection Systems", in collaborazione con D. Laforgia, Proceedings della II International Conference, Titograd (Yugoslavia), 19-21 maggio 1988.