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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, [17], 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. Source

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. Source

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. Source

Guida M.,University of Salerno | Pulcini G.,CNR Istituto Motori
Structural Safety | Year: 2011

In order to approximate the unknown transition probability densities of a state-dependent, possibly inhomogeneous, Markov degradation model, a continuous-state discrete-time Markov model is proposed, which is based on the use of the Pearson's family of distributions for approximating the true transition density. Unlike the alternative approach based on Markov chain approximation, the proposed one has the decisive advantage of dramatically reducing the computing time of the estimation procedure, thus allowing a age- and state-dependent model to be potentially applied also in more complex experimental frameworks, e.g., in presence of random effects. Hence, the proposed model is used to analyse, on the basis of real data from the literature, two different degradation phenomena, namely: the wear of some cutting tools and the crack growth of metallic specimens. © 2011 Elsevier Ltd. Source

Mancaruso E.,CNR Istituto Motori | Vaglieco B.M.,CNR Istituto Motori
Experimental Thermal and Fluid Science | Year: 2010

In order to understand the effect of both the new homogeneous charge compression ignition (HCCI) combustion process and the use of biofuel, optical measurements were carried out into a transparent CR diesel engine. Rape seed methyl ester was used and tests with several injection pressures were performed. OH and HCO radical were detected and their evolutions were analyzed during the whole combustion. Moreover, soot concentration was measured by means the two colour pyrometry method. The reduction of particulate emission with biodiesel as compared to the diesel fuel was noted. Moreover, this effect resulted higher increasing the injection pressure. In the case of RME the oxidation of soot depends mainly from O2 content of fuel and OH is responsible of the NO formation in the chamber as it was observed for NOx exhaust emission. Moreover, it was investigated the evolution of HCO and CO into the cylinder. HCO was detected at the start of combustion. During the combustion, HCO oxidizes due to the increasing temperature and it produces CO. Both fuels have similar trend, the highest concentrations are detected for low injection pressure. This effect is more evident for the RME fuel. © 2009 Elsevier Inc. All rights reserved. Source

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