di Stasio S.,CNR Istituto Motori
Journal of Aerosol Science | Year: 2016
SAXS experiments on a premixed ethylene-air flame burning at the so-called sooting threshold, i.e., a flame with Carbon-to-Oxygen molecular ratio between fuel C2H4 and air equal to [C]/[O] = 0.65 (ΦAir=25cm3/min, ΦC2H4=11.7cm3/min) is the object of this work. Measurements are performed at synchrotron SOLEIL / beamline SWING under the approved proposal #20130463. The height above burner considered for this case study is z=21mm (τres about 10ms). The background is made by considering an identical lean flame with [C]/[O]=0.19. The data processing approach consisting in subtracting to the signal S, the X-ray scattering from the air molecules surrounding the flame as background BCKG, is here revealed to be incorrect, owing to the fact that sometimes the S-BCKG evaluated as above is a negative quantity. This is caused by the much higher cool gas molecule number density at ambient conditions (300K) with respect to the lower gas molecule density inside the flame at hot temperatures (about 1800-2100K). Vice versa, by using a lean flame one obtains as BCKG the scattering contribute from the gas molecules alone in the absence of soot at about the identical premixed flame under test, which results in appreciating even the low signal from ultrafine incipient soot nanoparticles. The main results from the fit of SAXS data at larger q's are two: first, the demonstration of ultrafine nanoparticles, with gyration radius R g=25±10Å, as inferred by the Guinier regime fit, and overall size D=45±10Å, as evaluated through Kratky plots; second, the fact that these entities are present in the premixed flame with a huge concentration, about N=1013 cm-3. Such nanoparticles with D=45Å (Rg=25Å), do coexist contemporarily to isolated 20nm primaries and 160nm nanoparticle aggregates, which are observed with a number concentrations 6 and 8 order of magnitudes smaller with respect to the one of ultrafine nanoparticles.Our SAXS results do accord very well previous findings on size of premixed flame soot nanoparticles reported both by Wersborg et al. (1973) from molecular beam sampling and TEM analysis and, with concern to the number concentration, the results by Minutolo et al. (1998) and Sgro et al. (2009). © 2017 Elsevier Ltd.
Siano D.,CNR Istituto Motori |
Bozza F.,University of Naples Federico II
SAE Technical Papers | Year: 2013
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. Trains of consecutive experimental pressure cycles are acquired on a "downsized" turbocharged SI engine at full load and for different engine speeds. The above data are processed by the two techniques, and knock occurrence and intensity is estimated through suitably defined indices. The presented results demonstrate that the proposed methods give similar, although not coincident, results. While the kinetic procedure is able to furnish a more detailed insight of the thermo-kinetic conditions inside the cylinder, the ARMA technique is indeed characterized by a lower computational effort. In addition it may be applied to vibrational signals acquired by low-cost accelerometers, too. For this reason, it can be more easily implemented within a on board real time control system, aiming to adjust the spark advance and avoid abnormal combustion phenomena. Copyright © 2013 SAE International and Copyright © 2013 KSAE.
Di Bernardo M.,University of Naples Federico II |
Montanaro U.,CNR Istituto Motori |
Santini S.,University of Naples Federico II
IEEE Transactions on Automatic Control | Year: 2013
This paper is concerned with the derivation of a model reference adaptive control (MRAC) scheme for multimodal piecewise-affine (PWA) and piecewise-linear systems. The control allows the plant to track asymptotically the states of a multimodal piecewise affine (or smooth) reference model. The reference model can be characterized by a number and geometry of phase space regions that can be entirely different from those of the plant. Numerical simulations on a set of representative examples confirm the theoretical derivation and proof of stability. © 2012 IEEE.
Capasso C.,CNR Istituto Motori |
Veneri O.,CNR Istituto Motori
Applied Energy | Year: 2015
This paper is aimed to analyze design criteria, setting up, control strategies and experimental tests related to a power configuration of DC micro-grid for fast charging of full electric and plug in hybrid vehicles. The proposed DC fast charging architecture is derived by an analysis comparing the main characteristics of well known architectures, mainly based on AC and DC bus, taking also into account the integration of renewable energy sources (RESs) with stationary energy storage systems and fleets of road electric/hybrid vehicles. On the base of the proposed architecture a laboratory prototype of charging station has been realized by means of a 20. kW AC/DC bidirectional grid tie converter interconnected with two different power DC/DC converters of similar rated power. In this micro-grid architecture the AC/DC converter realizes a conversion stage at 790. V DC, whereas other two converters allow either the electric vehicle battery packs to be charged or an energy storage buffer to save electric energy and support the main grid during the fast charging operations. The laboratory tests described in this paper are mainly devoted to characterize the laboratory demonstrator, in different operative conditions, such as vehicle-to-grid (V2G), charging/discharging operations of different types of storage systems and fast charging operations of road electric vehicles. Then the study of the proposed power conversion architecture is focused on the evaluation of charging/discharging power, efficiency, energy flux management and its impact on the main grid. In addition proper control strategies are evaluated and implemented, allowing the proposed architecture to follow the required operations. The obtained experimental results demonstrate real advantages in terms of charging times and power requirements from the main grid, when adopting DC buffer architecture for fast charging operations. Finally, these results support the identification of a knowledge base, useful to evaluate energy management and control strategies to be adopted for DC charging stations and each one of their power converters in a smart grid scenario with distributed generation systems. © 2015 Elsevier Ltd.
Costagliola M.A.,CNR Istituto Motori |
De Simio L.,CNR Istituto Motori |
Iannaccone S.,CNR Istituto Motori |
Prati M.V.,CNR Istituto Motori
Applied Energy | Year: 2013
In this experimental work, the influence of some bio-fuels on the spark-ignition engine combustion efficiency and engine-out emissions was investigated. A conventional 1.6. l port injection engine was tested over steady-states, with some bio-ethanol/gasoline blends (0, 10, 20, 30, and 85. vol% of ethanol in gasoline) and with a 10. vol% of n-butanol in gasoline. Study of combustion development was made through the heat release analysis of pressure cycles measured in combustion chamber. Regulated emissions, unregulated organics (Polycyclic Aromatic Hydrocarbons, carbonyl compounds and Volatile Organic Compounds) and particulate were measured. Particulate was characterized in terms of total particle number (PN) and size distribution between 7. nm up to 10. μm. The tests were carried out at stoichiometric conditions in closed loop and spark advance was optimized with a calibration tool software in order to have the same peak pressure position. By fueling the alcohol blends, the engine-out particulate emissions are strongly reduced compared to gasoline. The PN reduction percentage ranges between 60% and 90%. The benefits also concern some gaseous unregulated species very harmful for humans, such as benzene and benzo(a)pyrene (reduction of almost 50% and 70% respectively). The highest oxygen content of alcohol blends, instead, provides an increasing of the total carbonylic emissions. © 2012 Elsevier Ltd.
Siano D.,CNR Istituto Motori
Simulation Modelling Practice and Theory | Year: 2011
Automotive exhaust systems give a major contribution to the sound quality of a vehicle and must be properly designed in order to produce acceptable acoustic performances. Obviously, noise attenuation is strictly related to the internal gas-dynamic field that, on the other hand, needs to be optimised also in terms of pressure losses. In this work, the noise attenuation characteristics of a typical perforated muffler for automotive applications are investigated. Acoustic performances are quantified by the Transmission Loss (TL) parameter, which only depends on the geometrical characteristics of the device. Different numerical analyses are employed. At first, a one-dimensional (1D) simulation code (GT Power™) is used to predict the TL profile in a low frequency range. 1D simulation, in fact, may be only applied under the hypothesis of a planar wave propagation. A more complex 3D FEM/BEM approach is also realised using the VNOISE™ code, , specifically designed for acoustic applications. Obviously, such analysis allows to obtain more accurate results at high frequency, depending on the mesh size. Different flow velocities and gas temperatures are investigated in both 1D and 3D models. The predicted TL profiles are compared and discussed in order to assess the potentiality and limitations of the employed numerical approaches. © 2010 Elsevier B.V. All rights reserved.
Capaldi P.,CNR Istituto Motori
Applied Thermal Engineering | Year: 2016
The paper deals with the design and the overall performance of 20 kWe cogeneration plant, suitable for local energy conversion and based on a wide-spread automotive internal combustion engine. The manuscript starts by defining the state of art of commercial cogenerators of the same power, underlining that a higher electric efficiency, which leads to a lower heat to electricity ratio, can elevate the annual service factor and the economic effectiveness while reducing CO2 emission. Then is reported the concept which leaded to the specific choice of a small displacement, high boosted engine (in terms of brake mean effective pressure) made to obtain a significant improvement of the engine global efficiency especially at partial load (if compared to most of the best competitors) and consequently a higher electric efficiency. The unit has been derived from a turbocharged Diesel engine, then converted into a spark ignition methane/natural gas system and finally coupled with an asynchronous liquid cooled generator together with high efficiency heat exchangers and some unconventional heat recovery devices in order to maximize thermal efficiency. The whole system, after being placed into a sealed capsule expressly designed to reduce heat losses and noise emission, has been tested as an electricity/heat generation plant to know its running global behavior. © 2016 The Author
Capasso C.,CNR Istituto Motori |
Veneri O.,CNR Istituto Motori
Applied Energy | Year: 2014
This paper deals with an experimental evaluation regarding the real performance of lithium based energy storage systems for automotive applications. In particular real working operations of different lithium based storage system technologies, such as Li[NiCoMn]O2 and LiFePO4 batteries, are compared in this work from the point of view of their application in supplying full electric and hybrid vehicles, taking as a reference the well-known behavior of lead acid batteries. For this purpose, the experimental tests carried out in laboratory are firstly performed on single storage modules in stationary conditions. In this case the related results are obtained by means of a bidirectional cycle tester based on the IGBT technology, and consent to evaluate, compare and contrast charge/discharge characteristics and efficiency at constant values of current/voltage/power for each storage technology analyzed. Then, lithium battery packs are tested in supplying a 1.8kW electric power train using a laboratory test bench, based on a 48V DC bus and specifically configured to simulate working operations of electric vehicles on the road. For this other experimentation the test bench is equipped with an electric brake and acquisition/control system, able to represent in laboratory the real vehicle conditions and road characteristics on predefined driving cycles at different slopes. The obtained experimental results on both charge/discharge tests and driving cycles demonstrate the advantages of using lithium technologies, mainly in terms of their high efficiency, particularly at high current values. That represents a feasible solution to offer vehicle designers and users extended driving ranges and reduced recharging times. © 2014 Elsevier Ltd.
Capaldi P.,CNR Istituto Motori
Applied Thermal Engineering | Year: 2014
The paper focuses on the design and the overall performance of a 10 kW electric power microcogeneration plant suitable for local energy production, based on an Atkinson-cycle internal combustion engine prototype and entirely set by Istituto Motori of the Italian National Research Council. The engine was originally a wide-spread Diesel automotive unit, then converted into a methane spark ignition system and finally modified to perform an Atkinson/Miller cycle with an extended expansion, capable of a higher global efficiency and low gaseous emissions. The paper starts by defining the ratio which leaded to this specific choice among many other automotive and industrial engines, in order to obtain a reliable, long endurance, cost effective, high efficiency base, suitable for microcogeneration in residential or commercial applications. The new engine has been coupled with a liquid cooled induction generator, a set of heat exchangers and finally placed in a sealed containing case, to reduce both noise emission and heat losses. Then the plant has been tested as an electricity and heat production system, ready for grid connection thanks to a new designed management/control system. During endurance test a complete description of its functioning behaviour has been given. © 2014 The Author.
Mancaruso E.,CNR Istituto Motori |
Vaglieco B.M.,CNR Istituto Motori
Applied Energy | Year: 2012
In this paper we report the use of the optical technique applied in the cylinder of an optically accessible engine equipped with the latest-generation diesel engine head of a European passenger car. The injection strategy with high percentage of EGR, characteristic of real engine operating point, was adopted. Alternative diesel fuels were used. In particular, rapeseed methyl ester (RME) and gas to liquid (GTL) were selected as representative of 1st and 2nd generation alternative diesel fuels, respectively. Combustion analysis was carried out in the engine combustion chamber by means of 2D spectroscopic measurements from UV to visible. These measurements helped to analyze the chemical and physical events occurring during the mixture preparation and the combustion development. Ultraviolet (UV) digital imaging was also performed and the presence of characteristic radical, like OH, in the various phases of combustion was detected as well. OH spatial distribution and temporal evolution were measured. Two color pyrometry technique was applied in order to measure the soot volume fraction within the combustion chamber. The GTL fuel showed better performance in terms of indicated mean effective pressure (IMEP) with respect to the diesel reference fuel with different effects on particulate matter (PM) and gaseous emissions. It showed the highest in cylinder soot production, while the OH radical had maximum intensity value close to the reference diesel (REF) one. On the other hand, the RME fuel showed a decrease in IMEP that can be adjusted with a little increase of fuel injected quantity, and very low production of soot in the cylinder and PM at the exhaust compared to the diesel reference fuel. Finally, the OH radical had the lowest intensity value. © 2011 Elsevier Ltd.