Antonio Ficarella

Automotive application of sol–gel TiO2 thin film-based sensor for lambda measurement

We report on the preparation and characterization of titanium dioxide thin film gas sensor devices for application in lambda measurement. The sensor responses to different oxygen concentrations have been analyzed. Moreover, according to a computing software that simulates the composition of exhaust gases for different λ values, we exposed the sensors to different complex mixtures of exhaust gases, calibrating in such a way the sensor for the measurement of lambda.

Effects of Pilot Injection Parameters on Combustion for Common Rail Diesel Engines

The aim of the present work is to evaluate the influence of the pilot injection on combustion of a TDI Diesel engine for different engine torque and speed conditions. For this investigation, pilot injection timing and duration were varied on a wide range of values, and their effects on combustion pressure, rate of heat release, pilot and main combustion delay, combustion process and exhaust emissions in terms of NO x and smoke were analyzed. An in-line, four-cylinder, turbocharged FIAT 1930 cm 3 TDI Diesel engine, equipped with Common Rail injection system, was tested. A piezoelectric sensor was located in the combustion chamber in order to acquire combustion pressure; from these signals, gross heat release rate was,derived in order to analyze the combustion behavior. Pollutant emission levels have been measured by means of a gas analyzer, while for smoke an opacimeter was used. It was found that both timing and duration of pilot injection strongly influence its autoignition tendency; in particular, pilot injection autoignition mainly occurs with low values of timing and high durations. Moreover, pilot injection timing effect is more evident on pilot ignition delay than pilot duration, whereas the effect of both variables on the main ignition delay depends on the engine operating conditions. The effect of pilot injection parameters is evident on engine emission behavior too; in particular, NO x emissions levels are mainly influenced by the pilot duration, whereas pilot timing effect is more evident at lower engine load and speed. Smoke emission seems to be influenced by both variables, but their effect is stronger especially at medium and high load.

EFFECTS ON COMBUSTION AND EMISSIONS OF EARLY AND PILOT FUEL INJECTIONS IN DIESEL ENGINES

Abstract Different injection strategies applied to a common rail direct injection diesel engine were tested for different engine torque and speed conditions. The injection strategies differ for the use of early and pilot injections; during the tests the injection parameters were varied, in terms of duration and timing of early, pilot, and main injections. The combustion behaviour and the engine performances, in terms of brake specific fuel consumption, were analysed. In addition, data on nitrogen oxides (NOx), total unburned hydrocarbons, and particulate emissions were collected. The injection strategy based on both early and pilot injections has been compared with the techniques using either pilot or early injections. Results show that, particularly at lower values of engine torque and speed, the small fuel quantity injected during early injection, coupled with the pilot injection, leads to comparable levels or even to a sensible reduction in fuel consumption compared with the only-pilot or only-early injection cases. Furthermore, a reduction in NOx and particulate is generally observed, while the level of unburned hydrocarbons usually increases. Experimental tests have shown that, using the early injection, a very lean premixed charge is obtained, both globally and locally, inside the combustion chamber, thus avoiding diesel problems (in particular, high NOx and soot production), mainly caused by the locally rich mixture. On the other hand, by using the pilot injection the ignition delay of the main injection is reduced, contributing to the NOx reduction.

Numerical simulation of flow-field and dioxins chemistry for incineration plants and experimental investigation

The development of incineration units (kiln and afterburner) for hazardous wastes in terms of design and fluid-dynamic optimization has been carried out together with definition of a new design methodology. An extensive theoretical and experimental analysis has been carried out on a hazardous waste incineration pilot plant to test the methodologies and to optimize the entire system in terms of reduction of the polluting emissions and higher combustion eAciency. In particular, the combustion chamber and the afterburner have been thoroughly studied. A computer code for multiple chemical reactions occurring in an afterburner chamber of an incineration system was developed, based on the equations presented herein, to evaluate the decomposition rate of dioxins for diAerent chamber geometries. The results of these analysis are presented herein. # 2000 Elsevier Science Ltd. All rights reserved.

Energy conservation in alcohol distillery with the application of pinch technology

Abstract The energy audit of an operating distillery producing ethyl alcohol from low quality wine and wine dregs is presented. Three different processes were analyzed: the production of raw (unrefined) alcohol using stripping columns working at pressure lower than atmospheric, the same production using columns at higher pressure and the production of neutral (refined) alcohol. The operational and design data of these three processes were used to compute mass and energy balances. The liquid streams in a distillery are multicomponent nonideal solutions. The data reported in the literature for ethyl and methyl alcohol–water mixtures were utilized, together with purposely developed correlations for density, specific heat and vapor–liquid equilibrium and simplified exergy formulas. The methodologies used to study the alcohol production are based on the pinch technology approach: the detailed energy balances of the three industrial processes are presented. The main step was to present the heat sources and sinks of the production processes in the grand composite curve, laying out all the thermodynamic opportunities of any heat recovery. Thermodynamic analysis methods were used to minimize the heating energy needed by the production processes when using heat pump systems. The use of heat pump systems, mainly based on mechanical vapor re-compression, has proven to be effective in energy saving and profitable in other applications, as the concentration of gelatine, distillation of organic vapors, pulp drying and beer production. Different heat pump systems were investigated and compared with respect to fuel utilization and capital expenditures: electrical engine driven compressors, gas engine driven compressors, steam turbine driven compressors, gas absorption chillers, steam absorption chillers and thermo-vapor re-compression. It showed that the cogeneration of mechanical energy and heat to drive vapor compression (the so-called thermodynamic heating method of Frutschi et al.) is superior to other types of systems. Then, for mechanical vapor compression systems, two different applications to different production processes were analyzed: (a) a system using commercially available refrigerants and (b) a heat pump cycle using water from the bottom of the distillation columns or steam condensate as working fluid. The thermodynamic analysis, based on performance coefficients and fuel utilization, as well as the economic profitability in terms of costs, benefits and payback period, were discussed in detail.

Investigation of a Micro Dielectric Barrier Discharge Plasma Actuator for Regional Aircraft Active Flow Control

This paper reports a multitechnique investigation of a micro dielectric barrier discharge plasma actuator (DBDPA) as a promising system to control separated flows. The device was manufactured through a photolithographic technique and its performances and capabilities were compared with the ones of conventional macro DBDPAs. Alternate current operation under sinusoidal voltage excitation was studied in the absence of external flow by means of many experimental techniques like discharge imaging, flow visualizations, particle image velocimetry, infrared thermography, and electrical characterization. The influence of the operating parameters was investigated. The main results underlined that an increase in the voltage amplitude or frequency brought to a rise in the maximum induced velocity, electrical power dissipation, and actuator surface temperature. Moreover, it was assessed that the small heating of the micro DBDPA did not affect the actuated flow. A jet velocity up to 1.36 m/s was obtained at a 9.01 W/m electrical power dissipation per unit electrode length. The device realized by microelectronic fabrication technology allowed reaching a flow velocity magnitude comparable with the one of conventional macro DBDPAs, with a reduction in applied voltage, power dissipation, and actuator size. Furthermore, the induced wall jet was more confined in the area in proximity of the device, because of the limited plasma discharge extension.

A COMBINED OPTIMIZATION METHOD FOR COMMON RAIL DIESEL ENGINES

The optimization method proposed in the present study consists of a multi-objective genetic algorithm combined with an experimental investigation carried out on a test bench, by using a DI Diesel engine. The genetic algorithm selects the injection parameters for each operating condition whereas the output measured by the experimental apparatus determines the fitness in the optimization process. The genetic algorithm creates a random population, which evolves combining the genetic code of the most capable individuals of the previous generation. Each individual of the population is represented by a set of parameters codified with a binary string. The evolution is performed using the operators of crossover, mutation and elitist reproduction. This genetic algorithm allows competitive fitness functions to be optimized with a single optimization process. For the determination of the overall fitness function the concept of Pareto optimality has been implemented. In this work, the input variables used for the optimization method are injection parameters like start of pilot and main injection, injection pressure and duration. The engine used is a FIAT 1929 cc DI diesel engine, in which the traditional injection system has been replaced by a common rail high pressure injection system.The competitive fitness functions were determined based on the measured values of fuel consumption, emissions levels (i.e. NOx, soot, CO, CO2, HC); combustion noise and overall engine noise, for each operating conditions. The optimization was performed for different engine speed and torque conditions typical of the EC driving cycles.

Experimental and Numerical Investigations of Cavitating Flows

Cavitating flows have been investigated using both numerical and experimental methods. Three different cavitation models, based on mechanical or thermal equilibrium hypotesis, have been implemented in a general-purpose CFD code. As an external flows example, the behavior of a NACA 0015 hydrofoil was investigated. The cavitating flow field over the hydrofoil was predicted, and the results compared with experimental data, reported in literature. The general characteristics of the cavitating flow were well predicted. Especially, the cavity length was calculated with reasonable accuracy. Further, the cavitation models were applied to flows through an orifice, and the computed results were compared with the experimental observations, obtained with a CCD camera. The cavitation originates at the inlet of the flow constriction area. It grows intensively and transforms into a dense cloud. Shedding is observed in this stage. As flow rate was increased, it was observed that the cloud travels downstream of the hole oscillating about the exit position and it is connected to the hole inlet through a sheet having a complex turbulent structures.

Cavitation Regime Detection by LS-SVM and ANN With Wavelet Decomposition Based on Pressure Sensor Signals

A cavitating two-phase flow of water in a pipe with area shrinkage was experimentally investigated, acquiring at high sampling rate pressure signals and images of the cavitating flow field. The time series of the pressure fluctuations was analyzed in terms of power spectral density and related to the cavitation regimes. Furthermore, the fluctuations of the pressure measurements were also decomposed using the wavelet transform to analyze the frequency distribution of the signals energy with respect to the flow behavior. The energy content at each frequency band of the acquire signals is well related to cavitation flow-field behavior. Moreover, the artificial neural network and the least squares support vector machine (LS-SVM) were implemented to identify the cavitation regime, using, as inputs, the power spectral density distributions of the pressure fluctuations, and some features of the decomposed signals, as the wavelet energy for each decomposition level and wavelet entropy. Results indicate the most accurate model to be used in the cavitation regime identification, underlining the enhanced capability of LS-SVM trained with the input data set based on the wavelet decomposition features.

Aircraft Distributed Flow Turbulence Sensor Network with Embedded Flow Control Actuators

Several active and passive flow control systems are studied to improve the performances of fluid machineries and to increase aerodynamic efficiency of propulsion systems. Among all the well-known active flow control devices, the dielectric barrier discharge plasma actuator (PA) is in full expansion and of great interest in the scientific community. A PA modifies the following behaviour of a fluid by providing an electronically controllable disturbance that brings to drag reduction, flow separation control, enhanced mixing, and noise suppression. PA is potentially easy to construct, has no moving parts and has low power requirements. This leads to its possible applications for separation control in low pressure turbine blade and compressor cascade, tip clearance flow control and compressor stability range extension. The present work reports the design and fabrication of cheap Kapton-based flow turbulence capacitive sensors able to be embedded into aircraft wing profiles and airfoil structures for critical turbulence conditions detection and early-detected separated flows control. The embedded system will provide a Kapton-foil based pressure detection and linear/synthetic jet plasma actuators working in feedback, for prevention and active reduction of separated flow for regional aircraft applications.