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Viewing 1 to 30 of 137
Technical Paper
2014-11-11
Silvana Di Iorio, Francesco Catapano, Paolo Sementa, Bianca Maria Vaglieco, Salvatore Florio, Elena Rebesco, Pietro Scorletti, Daniele Terna
The small gasoline engines are widely used as prime movers in the urban areas. For this reason great efforts have been paid to improve their efficiency as well as to reduce the pollutant emissions. The direct injection allows to improve the engine efficiency; on the other hand, the GDI combustion produces larger particle emissions because of the non-uniform mixture preparation and piston wetting. The properties of fuels play an important role both on engine performance and pollutant emissions. In particular, great attention was paid to the octane number. In this sense, ethanol is becoming even more attractive for spark ignition fuels as more resistant to knock phenomena due to its higher octane number. Moreover, ethanol is also expected to play an important role in PM emission reduction. In this study was analyzed the effect of fuels with different RON and with ethanol content. The analysis was performed on a small GDI engine. It was investigated two operating condition representative of the typical EUDC.
Technical Paper
2014-11-11
Luigi Allocca, Alessandro Montanaro, Rita Di Gioia, Giovanni Bonandrini
In the next future, improvements of direct injection systems for spark-ignited engines are necessary for the potential reductions in fuel consumptions and exhaust emissions. The admission and spread of the fuel in the combustion chamber is strictly related to the injector design and performances, such as to the fuel and environmental pressure and temperature conditions. In this paper the spray characterization of a GDI injector under normal and flash-boiling injection conditions has been investigated. A customized sensing of the injector nose permitted the temperature control of the nozzle up to 90 °C while a remote-controlled thermostatic device allowed the fuel heating from ambient to 120 °C. An axially-disposed, 0.200 mm in diameter, single-hole injector has been used with l/d ratio equal to 1 and static flow@100 bar: 2.45 g/s, using iso-octane as mono-component fluid. A 1.0 ms duration single pulse strategy has been adopted at the injection pressure of 10 MPa. The spray evolved in a quiescent optically-accessible vessel pressurize at 0.05, 0.1 and 0.3 MPa at ambient temperature of the gas (N2).
Technical Paper
2014-11-11
Daniela Siano, Fabio Bozza, Danilo D'Agostino, Maria Antonietta Panza
In the present work, an Auto Regressive (AR) model and a Discrete Wavelet Transform (DWT) are applied on vibrational signals, acquired by an accelerometer placed on the cylinder block of an internal combustion engine, for knock detection purposes. To this aim, vibrational signals are acquired on a four cylinder Spark Ignition engine for different engine speeds and spark advances. The same analysis is executed by also using the traditional MAPO (Maximum Amplitude of Pressure Oscillations) index, applied on the in-cylinder pressure waveforms. The results of the three methods are compared and in depth discussed to the aim of highlighting the pros and cons of each methodology. In particular, the problem of fixing a constant threshold level for each running condition is afforded and solved. The examples presented show the capability of the vibration based detection algorithms in accurately monitor the presence of heavy or soft knock phenomena, and to determine its intensity. Therefore, the possibility of implementation in modern on-board control units is foreseen, as well.
Technical Paper
2014-11-11
Francesco Catapano, Silvana Di Iorio, Paolo Sementa, Bianca Maria Vaglieco, Marcello Fiaccavento, Francesco Giari, Antonio Marchetti
This paper deals with the investigation of anomalous phenomena during the cranking phase of a spark ignition small engine, in particular backfire. The growing interest of this abnormal combustion is due to the use of fuels with different chemical-physical properties with respect to gasoline, that can affect especially the cranking phase of the engine. In this work the influence of the composition of the fuel on backfire was studied. In particular the investigation was focused on the presence of ethanol in the fuel. The experimental activity was carried out in an optically accessible engine derived from a 4-stroke spark ignition engine for two-wheel application. The test bench was instrumented and adapted in order to simulate the engine conditions similar to the ones that lead to the anomalous auto-ignition in the intake duct during the reverse rotation of the engine. Two different test procedures have been developed with the aim of promoting the auto-ignition at the intake. All the major engine parameters were measured, such as the in-cylinder pressure, the pressure at the exhaust and at the intake; in order to characterize the engine condition and to monitor the auto-ignition.
Technical Paper
2014-11-11
Silvana Di Iorio, Agnese Magno, Ezio Mancaruso, Bianca Maria Vaglieco, Luigi Arnone, Lorenzo Dal Bello
The present paper describes the results of an experimental activity performed on a small diesel engine for quadricycles, a category of vehicles that is widespreading in Europe and is recently spreading over Indian countries. The engine is a prototype three-cylinder with 1000 cc of displacement and it is equipped with a direct common-rail injection system that reaches a maximum pressure of 1400 bar. The engine was designed to comply with Euro 4 emission standard that is a future regulation for these vehicles. It is worth underline that the engine can meet emission limits just with EGR system and an oxidation catalyst, without DPF. Various blends of biodiesels, 50%volume with diesel fuel, were tested; pure biofuels were also used. The investigation was performed at several engine speeds, at medium and full load, respectively. Combustion characteristics of biofuels were analysed by means of in-cylinder pressure and rate of heat release. Gaseous emissions were measured at the exhaust. A smoke meter was used to measure the particulate matter concentration.
Technical Paper
2014-10-13
Simona Silvia Merola, Cinzia Tornatore, Luca Marchitto, Gerardo Valentino, Adrian Irimescu
Liquids with stable suspensions of nanoscale (typically 1−100 nm) materials are defined nanofluids. The nanomaterials can be metals, oxides, carbides, nitrides, or carbon-based nanostructures. These represent a tool if used as additives for traditional liquid fuels to enhance ignition and combustion. Because of their unique structures and unusual mechanical and electric properties, carbon nanotubes (CNTs) have been widely studied for applications in material, electrical, and biomedical sciences. They also have unique thermal properties; e.g., CNTs are reported to have unusually high thermal conductivity compared to the bulk material−graphene monolayer. Intensive investigation has been conducted into the thermal conductivity of nanofluids with CNTs. However, the optical and radiative properties of nanofluids with carbon-based nanostructures, as well as their impact on droplet evaporation and combustion, have not been deeply studied. The present paper examines the radiative properties of nanofluid fuels with suspensions of carbon nanotubes CNTs.
Technical Paper
2014-10-13
Francesco Catapano, Silvana Di Iorio, Paolo Sementa, Bianca Maria Vaglieco
The growing concerns over the pollutant emissions as well as the depletion of fossil fuel led to the research of advanced combustion mode and alternative fuels for the reduction both of fuel consumption and exhaust emissions. The dual-fuel injection system can be used to improve the engine performance and reduce the fossil fuel consumption performing simultaneously a direct-injection (DI) and a port-fuel-injection (PFI) of different fuels. Ethanol is one of the most promising alternative fuels for SI engines. It offers high anti-knock quality because of the high octane number; moreover, being an oxygenated fuel is very effective in particle emissions reduction. On the other hand, it is characterized by lower energy density mainly because of the low lower heating value (LHV). The aim of the paper is the investigation of the ethanol-gasoline dual fuel combustion on engine performance and emissions. The experimental activity was carried out in a single cylinder engine for two wheel vehicles with a displacement of 250 cc.
Technical Paper
2014-10-13
Daniela Siano, Maria Antonietta Panza, Danilo D'Agostino
The easiest way to identify knock conditions during the operation of a SI engine is represented by the knowledge of the in-cylinder pressure. Traditional techniques like MAPO (Maximum Amplitude Pressure Oscillation) based method rely on the frequency domain processing of the pressure data. This technique may present uncertainties due to the correct specification of some model parameters, like the band-pass frequency range and the crank angle window of interest. In this paper two innovative techniques for knock detection, which make use of the in-cylinder pressure, are explained in detail, and the results are compared with those coming from the MAPO method. The first procedure is based on the use of statistical analysis by applying an Auto Regressive (AR) technique, whilst the second technique makes use of the Discrete Wavelet Transform (DWT). The data useful for the analysis have been acquired on a high compression ratio four cylinder, spark ignition engine. Results demonstrate that the analyzed methods give quite similar outcomes but they also highlight that AR and DWT techniques present an higher sensitivity for soft knock detection.
Technical Paper
2014-10-13
Daniela Siano, Fabio Bozza, Luigi Teodosio, Vincenzo De Bellis
This paper reports 1D and 3D CFD analyses aiming to improve the gas-dynamic noise emission of a downsized turbocharged VVA engine through the re-design of the intake air-box device, consisting in the introduction of external or internal resonators. Nowadays, modern SI ICEs show more and more complex architectures that, while improving the brake specific fuel consumption (BSFC), may be responsible for the increased noise radiation at the engine intake mouth. In particular VVA systems allow for the actuation of advanced valve strategies that provide a reduction in the BSFC at part load operations thanks to the intake line de-throttling. In these conditions, due to a less effective attenuation of the pressure waves that travel along the intake system, VVA engines produce higher gas-dynamic noise levels. The worsening of the engine gas-dynamic performance can be compensated with a partial re-design of the air-box device, without significantly penalizing the engine power output. In order to find new design configurations of the air-box device capable of improving the noise levels, different numerical models can be successfully employed.
Technical Paper
2014-10-13
Luca Marchitto, Simona Merola, Cinzia Tornatore, Gerardo Valentino
Alcohols are largely used in spark-ignition (SI) engines as alternative fuels to gasoline. Particularly, the use of n-butanol meets growing interest due to its properties that are similar to gasoline, if compared with other alcohols. This paper aims to make a comparative analysis on the atomization process of gasoline and n-butanol fuel injected by a multi-hole injector nozzle for spark ignition engines. Imaging and Phase Doppler Anemometry techniques were applied to investigate the behaviour of a spray emerging from a six-hole injector for spark ignition engine applications. Two different fuels were investigated: commercial gasoline and pure n-butanol. Fuels were injected at two pressures: namely at 5 and 10 MPa, in a test vessel at quiescent air conditions, ambient temperature and backpressure. Injection duration was set to deliver the same fuel mass for both fuels. Image sequences of the spray were collected by a high speed camera in order to characterize spatial-temporal evolution of the spray.
Technical Paper
2014-10-13
Fabio Bozza, Vincenzo De Bellis, Daniela Siano
Control of knock phenomenon is becoming more and more important in modern SI engine, due to the tendency to develop high boosted turbocharged engines (downsizing). To this aim, improved modeling and experimental techniques are required to precisely define the maximum allowable spark advance. On the experimental side, the knock limit is identified based on some indices derived by the analysis of the in-cylinder pressure traces or of the cylinder block vibrations. The threshold levels of the knock indices are usually defined following an heuristic approach. On the modeling side, in the 1D codes, the knock is usually described by simple correlation of the auto-ignition time of the unburned gas zone within the cylinders. In addition, the latter methodology commonly refers to ensemble-averaged pressure cycles and, for this reason, does not take into account the cycle-by-cycle variations. In this work, an experimental activity is carried out to characterize the effects of cyclic dispersion on knock phenomena for different engine speeds, at full load operations and referring to a spark advance of borderline knock.
Technical Paper
2014-10-13
Alessandro Montanaro, Luigi Allocca, Ugo Sorge, Anqi Zhang, Michela Costa
Diesel sprays from an axial-disposed single-hole injector were studied under vaporizing conditions in a constant-volume combustion vessel. A hybrid Shadowgraph/Mie-scattering imaging setup was used to acquire the liquid and vapor phases of the fuel distribution in a near-simultaneous visualization mode by a high-speed camera (40,000 fps). Two geometries of the injector duct were used, identified with k-factors 0 and 1.5, having the exit-hole diameter of 0.1 mm and the ratio L/d =10. The studies were performed at 70, 120, and 180 MPa injection pressures, 25.37 kg/m3 ambient gas density, and the gas temperature in the vessel of 373/453 and 900 K for non-vaporizing and vaporizing conditions, respectively. The instantaneous positions of the front of the spray, extracted from the images and processed by an assessed software, defined the tip penetrations of the liquid and vapor phases at the various operating conditions. The FIRE-AVL provisional code was used to predict the jet behavior calibrating the sub-models with the experimental data.
Technical Paper
2014-10-13
Agnese Magno, Ezio Mancaruso, Bianca Maria Vaglieco
The aim of this study is to investigate the combustion process and pollutant formation in a small compression ignition engine. The engine is a prototype three-cylinder with 1000 cc of displacement and it is equipped with a direct common-rail injection system that reaches a maximum pressure of 1400 bar. The engine was designed to comply with Euro 4 emission standard that is a future regulation for this category of vehicles. Two optical accesses for endoscopes were realized in the first cylinder to investigate the combustion process. Two-color pyrometry method was applied to combustion images in order to detect both the flame temperature and soot concentration. The engine run with biofuels and conventional diesel fuel. Operating conditions at different engine speeds and loads were tested. Both in-cylinder pressure and rate of heat release traces were analysed. Gaseous emissions were measured at the exhaust. A smoke meter was used to measure the particulate matter concentration. A correlation between in-cylinder data of flame temperature and soot concentration with NOx and PM emissions, respectively, was found.
Technical Paper
2014-04-01
Gabriele Di Blasio, Mauro Viscardi, Michela Alfè, Valentina Gargiulo, Anna Ciajolo, Carlo Beatrice
Abstract Nowadays, alcohol fuels are of increasing interest as alternative transportation biofuels even in compression ignition engines because they are oxygenated and producible in a sustainable way. In this paper, the experimental research activity was conducted on a single cylinder research engine provided with a modern architecture and properly modified in a dual-fuel (DF) configuration. Looking at ethanol the as one of the future environmental friendly biofuels experimental campaign was aimed to evaluate in detail the effect of the use of the ethanol as port injected fuel in diesel engine on the size, morphology, reactivity and chemical features of the exhaust emitted soot particles. The engine tests were chosen properly in order to represent actual working conditions of an automotive light-duty diesel engine. A proper engine Dual-Fuel calibration was set-up respecting prefixed limits on in-cylinder peak firing pressure, cylinder pressure rise, fuel efficiency and gaseous emissions.
Technical Paper
2014-04-01
Daniela Siano, Luigi Teodosio, Vincenzo De Bellis, Fabio Bozza
Abstract The present paper reports 1D and 3D CFD analyses of the air-filter box of a turbocharged VVA engine, aiming to predict and improve the gas-dynamic noise emissions through a partial re-design of the device. First of all, the gas-dynamic noise at the intake mouth is measured during a dedicated experimental campaign. The developed 1D and 3D models are then validated at full load operation, based on experimental data. In particular, 1D model provides a preliminary evaluation of the radiated noise and simultaneously gives reliable boundary conditions for the unsteady 3D CFD simulations. The latter indeed allow to better take into account the geometrical details of the air-filter and guarantee a more accurate gas-dynamic noise prediction. 3D CFD analyses put in evidence that sound emission mainly occur within a frequency range of 350 to 450 Hz. Starting from the above result, the original air-box design is modified through the installation of a single Helmholtz resonator, taking into account layout constraints and the influence on engine performance, as well.
Technical Paper
2014-04-01
Silvana Di Iorio, Paolo Sementa, Bianca Maria Vaglieco, Francesco Catapano
Abstract The use of methane as supplement to liquid fuel is one of the solution proposed for the reduction of the internal combustion engine pollutant emissions. Its intrinsic properties as the high knocking resistance and the low carbon content makes methane the most promising clean fuel. The dual fuel combustion mode allows improving the methane combustion acting mainly on the methane slow burning velocity and allowing lean burn combustion mode. An experimental investigation was carried out to study the methane-gasoline dual fuel combustion. Methane was injected in combustion chamber (DI fuel) while gasoline was injected in the intake manifold (PFI fuel). The measurements were carried out in an optically accessible small single-cylinder four-stroke engine. It was equipped with the cylinder head of a commercial 250 cc motorcycles engine representative of the most popular two-wheel vehicles in Europe. UV-visible spectroscopy measurements were performed to analyze the combustion process with high spatial and temporal resolution.
Technical Paper
2014-04-01
Alessandro Montanaro, Marianna Migliaccio, Luigi Allocca, Valentina Fraioli, Seong-Young Lee, Anqi Zhang, Jeffrey Naber
Abstract This paper reports an experimental and numerical investigation on the spatial and temporal liquid- and vapor-phase distributions of diesel fuel spray under engine-like conditions. The high pressure diesel spray was investigated in an optically-accessible constant volume combustion vessel for studying the influence of the k-factor (0 and 1.5) of a single-hole axial-disposed injector (0.100 mm diameter and 10 L/d ratio). Measurements were carried out by a high-speed imaging system capable of acquiring Mie-scattering and schlieren in a nearly simultaneous fashion mode using a high-speed camera and a pulsed-wave LED system. The time resolved pair of schlieren and Mie-scattering images identifies the instantaneous position of both the vapor and liquid phases of the fuel spray, respectively. The studies were performed at three injection pressures (70, 120, and 180 MPa), 23.9 kg/m3 ambient gas density, and 900 K gas temperature in the vessel. The predictive capabilities of the Lib-ICE code, which is a set of applications and libraries for IC engine simulations developed using the OpenFOAM® technology, were evaluated in describing fuel sprays.
Technical Paper
2014-04-01
Pierpaolo Napolitano, Valentina Fraioli, Carlo Beatrice, Marianna Migliaccio, Chiara Guido
Abstract An increasing interest in the use of natural gas in CI engines is currently taking place, due to several reasons: it is cheaper than conventional Diesel fuel, permits a significant reduction in the amount of emitted carbon dioxide and is intrinsically cleaner, being much less prone to soot formation. In this respect, the Dual Fuel (DF) concept has already proven to be a viable solution, industrially implemented for several applications in the high duty engines category. Despite this, some issues still require a technological solution, preventing the commercialization of DF engines in wider automotive fields: the release of high amounts of unburned fuel, the risk of engine knock, the possible thermal efficiency reduction are some factors regarding the fuel combustion aspect. DF configuration examined in the present paper corresponds to Port Fuel Injection of natural gas and direct injection of the Diesel Fuel. The paper reports a theoretical study on the adoption of natural gas for the specific application of the DF concept to Light Duty Diesel Engines for automotive applications.
Technical Paper
2014-04-01
Francesco Catapano, Silvana Di Iorio, Paolo Sementa, Bianca Maria Vaglieco
Abstract The objective of this paper is the evaluation of the effect of the fuel properties and the comparison of a PFI and GDI injection system on the performances and on particle emission in a Spark Ignition engine. Experimental investigation was carried out in a small single cylinder engine for two wheel vehicles. The engine displacement was 250 cc. It was equipped with a prototype GDI head and also with an injector in the intake manifold. This makes it possible to run the engine both in GDI and PFI configurations. The engine was fuelled with neat gasoline and ethanol, and ethanol/gasoline blends at 10% v/v, 50% v/v and 85% v/v. The engine was equipped of a quartz pressure transducer that was flush-mounted in the region between intake and exhaust valves. Tests were carried out at 3000 rpm and 4000 rpm full load and two different lambda conditions. These engine points were chosen as representative of urban driving conditions. The gaseous emissions and particle concentration were measured at the exhaust by means of conventional instruments.
Technical Paper
2014-04-01
Silvana Di Iorio, Agnese Magno, Ezio Mancaruso, Bianca Maria Vaglieco
Abstract This paper deals with the combustion characteristics and exhaust emissions of a diesel engine fuelled with conventional diesel fuel and a biodiesel blend, in particular a 20% v/v concentration of rapeseed methyl ester (RME) mixed with diesel fuel. The investigation was carried out on a prototype three-cylinder engine with 1000 cc of displacement for quadricycle applications. The engine is equipped with a direct common-rail injection system that reaches a maximum pressure of 1400 bar. The engine was designed to comply with Euro 4 and BS IV exhaust emission regulations without a diesel particulate filter. Both in-cylinder pressure and rate of heat release traces were analyzed at different engine speeds and loads. Gaseous emissions were measured at the exhaust. A smoke meter was used to measure the particulate matter concentration. The sizing and the counting of the particles were performed by means of an engine exhaust particle sizer spectrometer. It was found that the number-size distribution of particles is strongly dependent on the engine operating conditions.
Technical Paper
2014-04-01
Ezio Mancaruso, Renato Marialto, Luigi Sequino, Bianca Maria Vaglieco
Abstract In recent years, several studies on the efficiency of modern diesel engines have focused on the modeling of combustion process in its different phases. Here, analytical equations are used to describe the physical phenomena that occur in the cylinder. The good agreement between the experimental and simulated data could improve the predictive capabilities of the computational code and reduce the cost of experimental activities. For the modeling of a diesel spray, the first step has been to investigate its behavior in a non-combusting environment; in particular, Musculus and Kattke proposed a model for the simulation of the injection of fuel in non-reacting still environment. Starting from that knowledge, the authors apply the injection model to a compression ignition research engine. By means of an optical engine, injection phase has been investigated via 2D digital imaging. The main jet characteristics like penetration and dispersion angle have been measured. The penetration data were compared with those provided by the 1D model with the same in-cylinder conditions.
Technical Paper
2014-04-01
Stefano Fontanesi, Elena Severi, Daniela Siano, Fabio Bozza, Vincenzo De Bellis
In the present paper, two different methodologies are adopted and critically integrated to analyze the knock behavior of a last generation small size spark ignition (SI) turbocharged VVA engine. Particularly, two full load operating points are selected, exhibiting relevant differences in terms of knock proximity. On one side, a knock investigation is carried out by means of an Auto-Regressive technique (AR model) to process experimental in-cylinder pressure signals. This mathematical procedure is used to estimate the statistical distribution of knocking cycles and provide a validation of the following 1D-3D knock investigations. On the other side, an integrated numerical approach is set up, based on the synergic use of 1D and 3D simulation tools. The 1D engine model is developed within the commercial software GT-Power™. It is used to provide time-varying boundary conditions (BCs) for the 3D code, Star-CD™. Particularly, information between the two simulation tools are at first exchanged under motored conditions to tune an “in-house developed” turbulence sub-model included in the 1D software. 1D results are then validated against the experimental data under fired full load operations, by employing a further “in-house developed” combustion sub-model.
Technical Paper
2014-04-01
Anqi Zhang, Alessandro Montanaro, Luigi Allocca, Jeffrey Naber, Seong-Young Lee
High pressure diesel sprays were visualized under vaporizing and combusting conditions in a constant-volume combustion vessel. Near-simultaneous visualization of vapor and liquid phase fuel distribution were acquired using a hybrid shadowgraph/Mie-scattering imaging setup. This imaging technique used two pulsed LED's operating in an alternative manner to provide proper light sources for both shadowgraph and Mie scattering. In addition, combustion cases under the same ambient conditions were visualized through high-speed combustion luminosity measurement. Two single-hole diesel injectors with same nozzle diameters (100μm) but different k-factors (k0 and k1.5) were tested in this study. Detailed analysis based on spray penetration rate curves, rate of injection measurements, combustion indicators and 1D model comparison have been performed. It is concluded that the nozzle geometry is causing the velocity and liquid flow area to vary at the nozzle outlet, which has an impact on air entrainment into the spray and results different combustion behavior.
Technical Paper
2013-10-14
Simona Silvia Merola, Stefano Iannuzzi, Luca Marchitto, Cinzia Tornatore, Gerardo Valentino
Optical diagnostic was applied to undiluted engine exhaust to supply a low cost and real time evaluation of the oil dilution tendency of selected fuels. Specifically, UV-visible-near IR extinction spectroscopy was applied in the exhaust line of a Euro 5 turbocharged, water cooled, DI diesel engine, equipped with a common rail injection system. The engine was fuelled with commercial B5 fuel and a B30 v/v blend of RME and ultra low sulfur diesel. The proposed experimental methodology allowed to identify the contribution to the multi-wavelength extinction of soot, fuel vapor, hydrocarbons and nitrogen oxide. Further, the evolution of each species for different post-injection interval settings was followed. On-line optical results were correlated with off-line liquid fuel absorption values. Moreover, spectroscopic measurements were linked to in-cylinder pressure related data and with HC and smoke exhaust emissions. The late post injection activation and fuel amount increase did not affect the energy release within the cylinder for either fuels.
Technical Paper
2013-10-14
Daniela Siano, Fabio Bozza
During the last years, a number of techniques aimed at the experimental identification of the knocking onset in Spark-Ignition (SI) Internal Combustion Engines have been proposed. Besides the traditional procedures based on the processing of in-cylinder pressure data in the frequency domain, in the present paper two innovative methods are developed and compared. The first one is based on the use of statistical analysis by applying an Auto Regressive Moving Average (ARMA) technique, coupled to a prediction algorithm. It is shown that such parametric model, applied to the instantaneous in-cylinder pressure measurements, is highly sensitive to knock occurrence and is able to identify soft or heavy knock presence in different engine operating conditions. An alternative, more expensive procedure is developed and compared to the previous one. The latter is based on the solution of a kinetic scheme in the end-gas zone, whose thermodynamic conditions are reconstructed by means of a two-zone inverse heat release analysis.
Technical Paper
2013-10-14
Simona Silvia Merola, Luca Marchitto, Cinzia Tornatore, Gerardo Valentino, Adrian Irimescu
Detailed experimental information on the early stages of spark ignition process represent a substantial part for guiding the development of engines with higher efficiencies and reduced pollutant emissions. Flame kernel formation influences strongly combustion development inside the cylinder, especially for a direct injection spark ignition engine. This study presents the analysis of the evolution of spark-ignited flame kernels with detailed view upon cycle-to-cycle variations. Experiments are performed in a SI optical engine equipped with the cylinder head and injection system of a commercial turbocharged engine. Blend of commercial gasoline and butanol (40% by volume) is tested at stoichiometric and lean mixture conditions. Experiments are carried out at 2000 rpm through conventional tests (based on in-cylinder pressure measurements and exhaust emission analysis) and through optical diagnostics. In particular, UV-visible digital imaging and natural emission spectroscopy are applied. A post-detection procedure is used to evaluate flame kernel areas evolution and its correlation to the MFB.
Technical Paper
2013-10-14
Alessandro Montanaro, Luigi Allocca
The performance and emission characteristics of the compression ignition engines are largely governed by the fuel atomization and air mixing, processes which in turn are strongly influenced by the flow dynamics inside the injector nozzle. This is controlled by dynamic (injection pressure, needle lift, etc.) and geometrical factors (orifice conicity, hydro grinding, etc.). Moreover, the modern diesel fuel injection systems are susceptible of deposits formation that can occur in different locations, e.g. in nozzle spray-holes and inside the injector body. The present paper describes the results of a research project aimed at studying the impact of injector coking on diesel spray formation for three injectors with different flow numbers. The characterization of the injection process has been carried out in terms of fuel injection rate as well as spatial and temporal fuel distribution in a quiescent chamber in non evaporative conditions. Three different injection pressures have been adopted namely 40, 80, and 160 MPa with 1.0, 0.6, and 0.3 ms solenoid energizing time.
Technical Paper
2013-09-08
Katarzyna Bizon, Gaetano Continillo, Ezio Mancaruso, Bianca Maria Vaglieco
This study aims at building efficient and robust artificial neural networks (ANN) able to reconstruct the in-cylinder pressure of Diesel engines and to identify engine conditions starting from the signal of a low-cost accelerometer placed on the engine block. The accelerometer is a perfect non-intrusive replacement for expensive probes and is prospectively suitable for production vehicles. In this view, the artificial neural network is meant to be efficient in terms of response time, i.e. fast enough for on-line use. In addition, robustness is sought in order to provide flexibility in terms of operation parameters. Here we consider a feed-forward neural network based on radial basis functions (RBF) for signal reconstruction, and a feed-forward multi-layer perceptron network with tan-sigmoid transfer function for signal classification. The networks are trained using measurements from a three-cylinder real engine for various operating conditions. The RBF neural network is trained with time series from in-cylinder pressure signals and vibration signals measured on a cylinder which is distant from the one in which the pressure signal is measured.
Technical Paper
2013-09-08
Francesco Catapano, Luigi De Simio, Michele Gambino, Sabato Iannaccone, Paolo Sementa, Bianca Maria Vaglieco, Stefano Bernardi, Dario Catanese, Marco Ferrari
The improvement in engines efficiency and reduction of emissions is the permanent aim of engine industry in order to meet European standards regulation. To optimize small internal combustion engines it is necessary to improve the basic knowledge of thermo-fluid dynamic phenomena occurring during the combustion. This paper describes the combustion process in an optically accessible two-stroke spark-ignition engine used in a commercial 43 cm3 chainsaw. Two different feeding systems were tested: standard and CWI one. The engine head was modified in order to allow the visualization of the combustion using endoscopic system coupled with a high spatial resolution ICCD camera. Flame front propagation was evaluated through an image processing procedure. The image visualization and chemiluminence allowed to follow the combustion process from the spark ignition to the exhaust phase at high engine speed. All the optical data were correlated with engine parameters and exhaust emissions. The effect of the injection system on deposits formed by fuel accumulation and on the flame front propagation and unburned hydrocarbons emission was investigated.
Technical Paper
2013-09-08
Simone Malaguti, Giuseppe Bagli, Alessandro Montanaro, Stefano Piccinini, Luigi Allocca
This paper reports an experimental and numerical investigation of the spray structure development for pure gasoline fuel and two different ethanol-gasoline blends (10% and 85% ethanol). A numerical methodology has been developed to improve the prediction of the pure and blends fuel spray. The fuel sprays have been simulated by means of a 3D-CFD code, adopting a multi-component approach for the fuel simulations. The vaporization behavior of the real fuel has been improved testing blends of 7 hydrocarbons and a reduced multi-component model has been defined in order to reduce the computational cost of the CFD simulations. Particular care has been also dedicated to the modeling of the atomization and secondary breakup processes occurring to the GDI sprays. The multi-hole jets have been simulated by means of a new atomization approach combined with the Kelvin-Helmholtz/Rayleigh-Taylor hybrid model. At the nozzle hole exit an initial distribution of atomized droplets has been predicted by the numerical approach taking into account cavitation phenomena and turbulent effects.
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