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Viewing 1 to 30 of 176
2016-04-05
Technical Paper
2016-01-0771
Silvana Di Iorio, Agnese Magno, Ezio Mancaruso, Bianca Maria Vaglieco
Methane is a promising fuel for internal combustion engine because of its environmental friendly characteristics and renewable nature. It can be used in existing compression ignition engine through dual fuel technology. This paper deals with the combustion characteristics and exhaust emissions of a small compression ignition engine modified to operate in diesel/methane dual fuel mode. The engine is a three-cylinder, 1028 cc of displacement, equipped with a common rail injection system and a diesel oxidation catalyst. A gas injector was set up in the intake manifold and it was managed by an external delay unit. Experiments were carried out at different engine speeds and loads. For each engine operating conditions, a part of the total load was supplied by the diesel combustion and the remaining by methane. Thermodynamics analysis of the combustion phase was performed by in-cylinder pressure signal.
2016-04-05
Technical Paper
2016-01-0697
Francesco Catapano, Silvana Di Iorio, Ludovica Luise, Paolo Sementa, Bianca Maria Vaglieco
Even more attention was paid to the direct injection (DI) system in spark ignition (SI) engines. DI allows to achieve improved efficiency. Nevertheless, the less time for fuel evaporation and mixing with respect to PFI engines as well as the larger fuel impingement, results in larger HC and CO emissions as well as particle emissions. PFI SI engine are characterized by low exhaust emissions but at the same time by lower engine performance. In this paper was investigated the effect of the O2 addition on engine performance and emissions. The experimental investigation was carried out in a small single-cylinder, PFI SI four-stroke engine. The engine emissions were characterized by means of gaseous analyzers and a smokemeter. Particle size distribution function was measured in the size range from 5.6 to 560 nm by means of an Engine Exhaust Particle Sizer (EEPS). The investigation was carried out at different engine speeds.
2016-04-05
Technical Paper
2016-01-0710
Adrian Irimescu, Simona Silvia Merola, Cinzia Tornatore, Gerardo Valentino, Alberto Grimaldi, Eugenio Carugati, Stefano Silva
Within the context of generalized diversification of the energy mix, the use of alcohols as gasoline replacement is proposed as a viable option. In the quest for improving fuel economy and reduce the environmental impact of automotive engines, alternative control strategies for spark ignition engines (SI) such as lean operation and exhaust gas recirculation (EGR) are used on an ever wider scale. In order to improve the stability of these operating points, alternative ignition systems are currently investigated. Another trend that is more and more present in engine development is the extensive use of simulation software; therefore, there is a continuous drive to improve the predictive capabilities of numerical codes. Within this context, the present work reports on the use of a plasma assisted ignition (PAI) system in a direct injection (DI) SI engine under lean conditions and cooled EGR with gasoline and n-butanol fueling.
2016-04-05
Technical Paper
2016-01-0738
Luca Marchitto, Simona Silvia Merola, Cinzia Tornatore, Gerardo Valentino
UV-visible digital imaging and 2D chemiluminescence were applied on a single cylinder optically accessible compression ignition engine to investigate the effect of different alcohol/diesel fuel blends on the combustion mechanism. The growing request for greenhouse gas emission reduction imposes to consider the use of alternative fuels with the aim of both partially replacing the diesel fuel and reducing the fuel consumption. To this purpose, the use of ABE (Acetone–Butanol–Ethanol) fermentation could represent an effective solution. Even if the different properties of alcohols compared to Diesel fuel limit the maximum blend concentration, low blend volume fractions can be employed for improving combustion efficiency and exhaust emissions.
2016-04-05
Technical Paper
2016-01-0810
Massimo Cardone, Ezio Mancaruso, Renato Marialto, Luigi Sequino, Bianca Maria Vaglieco
The interest of the vehicle producers in fulfill the emission legislations without adopting after treatment systems is driving to the use of non-conventional energy sources for modern engines. A previous test campaign on the use of blends of diesel and propane in a CI engine has pointed out the potential of this non-conventional fuel for diesel engines. The soft adaptation of the common rail injection system and the potential benefits, in terms of engine consumption and pollutant emissions, encourage the use of propane/diesel blends if an optimization of the injection strategies is performed. In this work, the performances of a propane/diesel preformed mixture in a research diesel engine have been investigated. The injection strategies of Euro 5 calibration have been used as reference for the develop of optimized strategies. The aim of the optimization process was to gather the same engine power output and reduce the pollutant emissions.
2016-04-05
Technical Paper
2016-01-0874
Giuseppe Quaremba, Luigi Allocca, Amedeo Amoresano, Vincenzo Niola, Alessandro Montanaro, Giuseppe Langella
The characterization of a stationary spray, such as gas turbine, or of an unsteady one, such that in i.c. engines, is mainly based on the study of fluid dynamic parameters such as the average velocity, both radial and axial, the droplet diameters distribution, etc. These data are mostly recovered by using optical diagnostic systems such as LDV, PDPA, PIV. Furthermore, it is necessary to associate to these data other geometric and morphologic parameters, giving information about the length of the spray, the jet penetration and the cone angle. Finally, a time-analysis of the jet behavior is necessary to understand its evolution within the combustion chamber. This information is retrieved by means of optical measurement techniques such as Schlieren imaging and light scattering, by using sensors to be connected to cameras and therefore subject to the laws of the geometrical optics. In fact, the images thus recorded are real matrices and can be processed by advanced digital techniques.
2016-04-05
Technical Paper
2016-01-0853
Francesco Catapano, Michela Costa, Guido Marseglia, Paolo Sementa, Ugo Sorge, Bianca Maria Vaglieco
Performance of internal combustion engines is well known being greatly affected by the air-fuel mixture formation process. In GDI engines, the impact of the gasoline spray on the piston or cylinder walls is a key factor, especially under the so-called wall-guided mixture formation mode, but not only. The impact causes droplets rebound and/or the deposition of a liquid film (wallfilm). After being rebounded, droplets undergo what is called secondary atomization. The wallfilm, on the other hand, may remain of no negligible size and evaporate slowly. This leads to increased unburned hydrocarbons and particulate matter emissions. In the present paper, the experimental characterization of a multi-hole spray in its impact over the piston shaped is carried out through optical diagnostic developed under different injection strategies to investigate the effect of the wall temperature distribution on the phenomenon.
2016-04-05
Journal Article
2016-01-0601
Sebastiano Breda, Alessandro D'Adamo, Stefano Fontanesi, Nicola Giovannoni, Francesco Testa, Adrian Irimescu, Simona Merola, Cinzia Tornatore, Gerardo Valentino
The occurrence of knock is the most limiting hindrance for modern Spark-Ignition (SI) engines. In order to understand its origin and move the operating condition as close as possible to originate this potentially harmful phenomenon, a joint experimental and numerical investigation is the most recommended approach. A preliminary experimental activity was carried out at IM-CNR on a 0.4 liter GDI unit, equipped with a flat transparent piston. The analysis of flame front morphology allowed to correlate high levels of flame front wrinkling and negative curvature to knock prone operating conditions, such as increased spark timings or high levels of exhaust back-pressure. In this study a detailed CFD analysis is carried out for the same engine and operating point as the experiments. The aim of this activity is to deeper investigate the reasons behind the main outcomes of the experimental campaign.
2015-09-06
Technical Paper
2015-24-2405
Michela Costa, Daniele Piazzullo, Ugo Sorge, Simona Merola, Adrian Irimescu, Vittorio Rocco
Abstract Ignition and flame inception are well recognised as affecting performance and stable operation of spark ignition engines. The very early stage of combustion is indeed the main source of cycle-to-cycle variability, in particular in gasoline direct injection (GDI) engines, where mixture formation may lead to non-homogenous air-to-fuel distributions, especially under some speed and load conditions. From a numerical perspective, 3D modelling of combustion within Reynolds Averaged Navier Stokes (RANS) approaches is not sufficient to provide reliable information about cyclic variability, unless proper changes in the initial conditions of the flow transport equations are considered. Combustion models based on the flamelet concept prove being particularly suitable for the simulation of the energy conversion process in internal combustion engines, due to their low computational cost.
2015-09-06
Technical Paper
2015-24-2413
Michela Costa, Francesco Catapano, Guido Marseglia, Ugo Sorge, Paolo Sementa, Bianca Maria Vaglieco
Abstract Gasoline direct injection (GDI) allows flexible operation of spark ignition engines for reduced fuel consumption and low pollutants emissions. The choice of the best combination of the different parameters that affect the energy conversion process and the environmental impact of a given engine may either resort to experimental characterizations or to computational fluid dynamics (CFD). Under this perspective, present work is aimed at discussing the assessment of a CFD-optimization (CFD-O) procedure for the highest performance of a GDI engine operated lean under both single and double injection strategies realized during compression. An experimental characterization of a 4-stroke 4-cylinder optically accessible engine, working stratified lean under single injection, is first carried out to collect a set of data necessary for the validation of a properly developed 3D engine model.
2015-09-06
Technical Paper
2015-24-2411
Carmelina Abagnale, Maria Cristina Cameretti, Umberto Ciaravola, Raffaele Tuccillo, Sabato Iannaccone
The dual-fuel (diesel/natural gas, NG) concept represents a solution to reduce emissions from diesel engines by using natural gas as an alternative fuel. As well known, the dual-fuel technology has the potential to offer significant improvements in the emissions of carbon dioxide from light-duty compression ignition engines. A further important requirement of the DF operation in automotive engines is a satisfactory response in a wide range of load levels. In particular, the part-load levels could present more challenging conditions for an efficient combustion development, due to the poor fuel/air ratio. Basing on the above assumptions, the authors discuss in this article the results of a combined numerical and experimental study on the effect of different injection timings on performance and pollutant fractions of a common rail diesel engine supplied with natural gas and diesel oil.
2015-09-06
Technical Paper
2015-24-2432
Michela Costa, Paolo Sementa, Ugo Sorge, Francesco Catapano, Guido Marseglia, Bianca Maria Vaglieco
Abstract Present work investigates both experimentally and numerically the benefits deriving from the use of split injections in increasing the engine power output and reducing the tendency to knock of a gasoline direct injection (GDI) engine. The here considered system is characterized by an optical access to the combustion chamber. Imaging in the UV-visible range is carried out by means of a high spatial and temporal resolution camera through an endoscopic system and a transparent window placed in the piston head. This last is modified to allow the view of the whole combustion chamber almost until the cylinder walls, to include the so-called eng-gas zones of the mixture, where undesired self-ignition may occur under some circumstances. Optical data are correlated to in-cylinder pressure oscillations on a cycle resolved basis.
2015-09-06
Technical Paper
2015-24-2428
Ferdinando Taglialatela Scafati, Francesco Pirozzi, Salvatore Cannavacciuolo, Luigi Allocca, Alessandro Montanaro
Gasoline direct injection (GDI) combustion with un-throttled lean stratified operation allows to reduce engine toxic emissions and achieve significant benefits in terms of fuel consumption. However, use of gasoline stratified charges can lead to several problems, such as a high cycle-to-cycle variability and increased particle emissions. Use of multiple injection strategies allows to mitigate these problems, but it requires the injection of small fuel amounts forcing the traditional solenoid injectors to work in their “ballistic” region, where the correlation between coil energizing time and injected fuel amount becomes highly not linear. In the present work a closed-loop control system able to manage the delivery of small quantities of fuel has been introduced. The control system is based on a particular feature found on the coil voltage command signal during the de-energizing phase.
2015-09-06
Technical Paper
2015-24-2445
Carlo Beatrice, Gabriele Di Blasio, Ezio Mancaruso, Luigi Sequino, Bianca Maria Vaglieco
Abstract In this paper, a detailed analysis of combustion and emissions is carried out on both metal and optical light duty diesel engines equipped with up-to-date combustion architecture. Both engines were fed with glycerol ethers mixture (GEM) in blend (10% and 20% v/v) within a commercial diesel fuel. The engines ran in significant operating points in the NEDC (New European Driving Cycle) emission homologation area. The results of the experimental campaign on the metal engine show comparable performances between the diesel/GEM blends and the diesel fuel and demonstrate benefits mainly in terms of soot production. The exhaust particles diameters of diesel/GEM blends shift toward smaller dimensions and the total number decreases. Moreover, at lower load conditions, the outputs show a worsening of the unburnt mainly ascribable to the fuel characteristics.
2015-09-06
Technical Paper
2015-24-2459
Francesco Catapano, Silvana Di Iorio, Paolo Sementa, Bianca Maria Vaglieco
Abstract The use of direct injection (DI) engines allows a more precise control of the air-fuel ratio, an improvement of fuel economy, and a reduction of exhaust emissions thanks to the ultra-lean combustion due to the charge stratification. These effects can be partially obtained also with an optimized Air Direct Injection that permits to increase the turbulence at low speed and load increasing the combustion stability especially in lean condition. In this paper, a gasoline PFI (named G-PFI), gasoline PFI-methane DI dual fuel (named G-MDF) lean combustion were analyzed. The G-MDF configuration was also compared with a gasoline PFI - air DI (named G-A) configuration in order to distinguish the chemical effect of methane from the direct injection physical effect. The tests were carried out in a small displacement PFI/DI SI engine. The experimental investigation was carried out in a transparent small single-cylinder, spark ignition four-stroke engine.
2015-09-06
Technical Paper
2015-24-2461
Agnese Magno, Ezio Mancaruso, Bianca Maria Vaglieco
Abstract In the present activity, dual fuel operation was investigated in a single cylinder research engine. Methane was injected in the intake manifold while the diesel was delivered via the standard injector directly into the engine. The aim is to study the effect of increasing methane concentration at constant injected diesel amount on both pollutant emissions and combustion evolution in an optically accessible engine. Emissions are in line with those previously published by other authors, it is noted no PM and constant NOx emissions. Moreover, a decrease of the brake specific CO emissions and an increase of the brake specific THC for the operating condition with the highest premixed ratio was detected. THC was mainly constituted by methane unburned hydrocarbons. Combustion resulted more or less stable. Moreover, via both UV-VIS spectroscopy and digital imaging, the spatial distribution of several species involved in the combustion process was analyzed.
2015-09-06
Technical Paper
2015-24-2473
Alessandro Montanaro, Luigi Allocca, Giovanni Meccariello, Maurizio Lazzaro
Abstract In internal combustion engines, the direct injection at high pressures produces a strong impact of the fuel on the combustion chamber wall, especially in small-bore sizes used for passenger cars. This effect is relevant for the combustion process resulting in an increase of the pollutant emissions and in a reduction of the engine performances. This paper aims to report the effects of the injection pressure and wall temperature on the macroscopic behavior and atomization of the impinging sprays on the wall. The gasoline spray-wall interaction was characterized inside an optically accessible quiescent chamber using a novel make ready Z-shaped schlieren-Mie scattering set-up using a high-speed C-Mos camera as imaging system. The arrangement was capable to acquire alternatively the schlieren and Mie-scattering images in a quasi-simultaneous fashion using the same line-of-sight.
2015-09-06
Technical Paper
2015-24-2477
Ezio Mancaruso, Renato Marialto, Luigi Sequino, Bianca Maria Vaglieco, Massimo Cardone
Abstract Blends of propane-diesel fuel can be used in direct injection diesel engines to improve the air-fuel mixing and the premixed combustion phase, and to reduce pollutant emissions. The potential benefits of usinf propane in diesel engines are both environmental and economic; furthermore, its use does not require changes to the compression ratio of conventional diesel engines. The present paper describes an experimental investigation of the injection process for different liquid preformed blends of propane-diesel fuel in an optically accessible Common Rail diesel engine. Slight modifications of the injection system were required in order to operate with a blend of propane-diesel fuel. Pure diesel fuel and two propane-diesel mixtures at different mass ratios were tested (20% and 40% in mass of propane named P20 and P40). First, injection in air at ambient temperature and atmospheric pressure were performed to verify the functionality of the modified Common Rail injection system.
2015-09-06
Technical Paper
2015-24-2490
Francesco Catapano, Silvana Di Iorio, Paolo Sementa, Bianca Maria Vaglieco
Abstract Ethanol is the most promising alternative fuel for spark ignition (SI) engines, that is blended with gasoline, typically. Moreover, in the last years great attention is paid to the dual fueling, ethanol and gasoline are injected simultaneously. This paper aims to analyze the better methods, blending or dual fueling in order to best exploit the potential of ethanol in improving engine performance and reducing pollutant emissions. The experimental activity was carried out in a small displacement single cylinder engine, representative of 2-3 wheel vehicle engines or of 3-4 cylinder small displacement automotive engines. It was equipped with a prototype gasoline direct injection (GDI) head. The tests were carried out at 3000, 4000, and 5000 rpm full load. The investigated engine operating conditions are representative of the European homologation urban driving cycle.
2015-09-06
Technical Paper
2015-24-2497
Pierpaolo Napolitano, Carlo Beatrice, Chiara Guido, Nicola Del Giacomo, Leonardo Pellegrini, Pietro Scorletti
Abstract The present paper describes the results of a research activity aimed at studying the potential offered by the use of Hydrocracked fossil oil (HCK) and Hydrotreated Vegetable Oil (HVO) blends as premium fuels for next generation diesel engines. Five fuels have been tested in a light duty four cylinder diesel engine, Euro 5 version, equipped with closed loop control of the combustion. The set of fuels comprises four experimental fuels specifically formulated by blending high cetane HVO and HCK streams and oneEN590-compliant commercial diesel fuel representative of the current market fuel quality. A well consolidated procedure has been carried out to estimate, for the tested fuels, the New European Driving Cycle (NEDC) vehicle performance by means of the specific emissions at steady-state engine operating points.
2015-09-06
Technical Paper
2015-24-2525
Luigi De Simio, Sabato Iannaccone, Michele Gambino, Veniero Giglio, Natale Rispoli, Gianluca Barbolini, Dario Catanese, Marco Ferrari, Walter Lo Casale
This paper presents an experimental study on a 2-stroke SI engine, used on small portable tools for gardening or agriculture, aimed to identify possible correlations between parameters related to ionization current and air/fuel mixture richness, considering different fuels and spark plug wear. This, to realize a simple system to control the engine parameters and adapt them to engine aging and fuel type changing. The engine was fed with commercial gasoline, low octane number gasoline, alkylate gasoline and a blend of 80% gasoline and 20% ethanol. In all tests carried out with varying engine speed and spark advance the ionization signal was characterized by a single peak, resulting in the impossibility of distinguishing chemical and thermal ionization. All data collected were analyzed looking for correlations between all the available data of CO emissions and several characteristic parameters obtained from the ionization signal.
2015-09-06
Technical Paper
2015-24-2509
Maria Vittoria Prati, Giovanni Meccariello, Livia Della Ragione, Maria Antonietta Costagliola
The aim of this study is to investigate the parameters influencing the real driving emission monitoring with particular attention towards the influence of road gradient. For this purpose, an experimental activity was carried out with a Euro 5 Diesel light-duty vehicle, driven along two tracks of Naples characterized by a different road gradient: the first pattern is quite flat, the second includes positive (+2.9%) and negative (−3.6%) road gradient. Exhaust emissions of CO, THC, NOx, CO2 were acquired on road by using a portable emission measuring system (PEMS) connected also to the Engine Control Unit for saving the main engine parameters and to the GPS for the geographical coordinates and altitude. The acquired speed profiles were repeated on the chassis-dynamometer without simulating the road gradient.
2015-09-06
Journal Article
2015-24-2416
Roberto Finesso, Ezio Spessa, Ezio Mancaruso, Luigi Sequino, Bianca Maria Vaglieco
Abstract An investigation has been carried out on the spray penetration and soot formation processes in a research diesel engine by means of a quasi-dimensional multizone combustion model. The model integrates a predictive non stationary 1D spray model developed by the Sandia National Laboratory, with a diagnostic multizone thermodynamic model, and is capable of predicting the spray formation, combustion and soot formation processes in the combustion chamber. The multizone model was used to analyze three operating conditions, i.e., a zero load point (BMEP = 0 bar at 1000 rpm), a medium load point (BMEP = 5 bar at 2000 rpm) and a medium-high load point (BMEP = 10 bar at 2000 rpm). These conditions were experimentally tested in an optical single cylinder engine with the combustion system configuration of a 2.0L Euro4 GM diesel engine for passenger car applications.
2015-09-06
Journal Article
2015-24-2415
Katarzyna Danuta Bizon, Simone Lombardi, Gaetano Continillo, Paolo Sementa, Bianca Maria Vaglieco
Abstract Data decomposition techniques have become a standard approach for the analysis of 2D imaging data originating from optically accessible internal combustion engines. In particular, the method of Proper Orthogonal Decomposition (POD) has proven to be a valuable tool for the evaluation of cycle-to-cycle variability based on luminous combustion imaging and particle image velocimetry (PIV) measurements. POD basically permits to characterize the dominant structures of the process under consideration. Recently, an alternative procedure based on Independent Component Analysis (ICA) has been introduced in the engine field. Unlike POD, the method of ICA identifies the patterns corresponding to physical processes that are statistically independent. In this work, a Group-ICA approach is applied to 2D cycle-resolved images of the luminosity emitted by the combustion process. The analysis is meant to characterize cyclic variability of a port fuel injection spark ignition (PFI SI) engine.
2015-09-06
Journal Article
2015-24-2435
Gerardo Valentino, Simona Merola, Luca Marchitto, Cinzia Tornatore
Abstract The paper reports the results of an experimental investigation carried out in a prototype optically accessible compression ignition engine fuelled with different blends of commercial diesel and n-butanol. Thermodynamic analysis and exhaust gas measurements were supported by optical investigations performed through a wide optical access to the combustion chamber. UV-visible digital imaging and 2D chemiluminescence were applied to characterize the combustion process in terms of spatial and temporal occurrence of auto-ignition, flame propagation, soot and OH evolution. The paper illustrates the results of the spray combustion for diesel and n-butanol-diesel blends at 20% and 40% volume fraction, exploring a single and double injection strategy (pilot+main) from a common rail multi-jet injection system. Tests were performed setting a pilot+main strategy with a fixed dwell time and different starts of injection.
2015-09-06
Journal Article
2015-24-2520
Simona Silvia Merola, Adrian Irimescu, Gerardo Valentino, Cinzia Tornatore, Stefano Silva, Alberto Grimaldi, Eugenio Carugati
Abstract A plasma ignition system was tested in a GDI engine with the target of combustion efficiency improvement without modifying engine configuration. The plasma was generated by spark discharge and successively sustained to enhance its duration up to 4 ms. The innovative ignition system was tested in an optically accessible single-cylinder DISI engine to investigate the effects of plasma on kernel stability and flame front propagation under low loads and lean mixture (λ≅1.3). The engine was equipped with the head of a commercial turbocharged engine with similar geometrical specifications (bore, stroke, compression ratio). All experiments were performed at 2000 rpm and 100 bar injection pressure. UV-visible 2D chemiluminescence was applied in order to study the flame front inception and propagation with particular interest in the early combustion stages. A bandpass filter allowed selecting luminous signal due to OH radicals.
2015-09-06
Journal Article
2015-24-2460
Gabriele Di Blasio, Giacomo Belgiorno, Carlo Beatrice, Valentina Fraioli, Marianna Migliaccio
Abstract The paper reports an experimental study on the effect of compression ratio variation on the performance and pollutant emissions of a single-cylinder light-duty research diesel engine operating in DF mode. The architecture of the combustion system as well as the injection system represents the state-of-the-art of the automotive diesel technology. Two pistons with different bowl volume were selected for the experimental campaign, corresponding to two CR values: 16.5 and 14.5. The designs of the piston bowls were carefully performed with the 3D simulation in order to maintain the same air flow structure at the piston top dead center, thus keeping the same in-cylinder flow characteristics versus CR. The engine tests choice was performed to be representative of actual working conditions of an automotive light-duty diesel engine.
2015-09-06
Journal Article
2015-24-2527
Daniela Siano, Giovanni Ferrara, Giulio Lenzi, Danilo D'Agostino, Andrea Fioravanti
In an Internal Combustion Engine, the design of the intake system is a very critical aspect since it affects both the engine power output and noise emissions at the intake side. In particular, downsized VVA engines typically produce higher gas-dynamic noise levels since, due to the intake line de-throttling at part-load, a less effective attenuation of the pressure waves is realized. In this work, the acoustic performance of the intake air filter of a commercial VVA engine is numerically and experimentally analyzed. In particular, a FEM model of the system is realized in order to compute the Transmission Loss (TL) parameter of the base device. The numerical analysis accounts of fluid-structure interaction, which gives the possibility to determine the effect of structure participation on the TL profile. Contemporarily, the experimental tests are performed on an acoustic test bench based on the multi-microphone technique for the evaluation of the acoustic parameters.
2015-09-06
Journal Article
2015-24-2392
Vincenzo De Bellis, Luigi Teodosio, Daniela Siano, Fabrizio Minarelli, Diego Cacciatore
In this paper, a high performance V12 spark-ignition engine is experimentally investigated at test-bench in order to fully characterize its behavior in terms of both average parameters, cycle-by-cycle variations and knock tendency, for different operating conditions. In particular, for each considered operating point, a spark advance sweep is actuated, starting from a knock-free calibration, up to intense knock operation. Sequences of 300 consecutive pressure cycles are measured for each cylinder, together with the main overall engine performance, including fuel flow, torque, and fuel consumption. Acquired data are statistically analyzed to derive the distributions of main indicated parameters, in order to find proper correlations with ensemble-averaged quantities. In particular, the Coefficient of Variation (CoV) of IMEP and of the in-cylinder peak pressure (pmax) are correlated to the average combustion phasing and duration (MFB50 and Δθb), with a good coefficient of determination.
2015-09-01
Technical Paper
2015-01-1945
Alessandro Montanaro, Luigi Allocca
During an injection process, a fluid undergoes a sudden pressure drop across the nozzle. If the pressure downstream the injector is below the saturation value of the fluid, superheated conditions are reached and thermodynamic instabilities realized. In internal combustion engines, flashing conditions greatly influence atomization and vaporization processes of a fuel as well as the mixture formation and combustion. This paper reports imaging behavior of a fuel under both flash boiling and non-flash boiling conditions. A GDI injector, eight-hole, 15.0 cc/s @ 10 MPa static flow, injected a single-component fluid (iso-octane), generating the spray. Experiments were carried out in an optically-accessible constant-volume quiescent vessel by Mie-scattering technique. A C-Mos high-speed camera was used to acquire cycle-resolved images of the spray evolving in the chamber filled with N2 which pressure ranged between 0.05 and 0.3 MPa.
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