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The efficiency of Hybrid Electric Vehicles (HEVs) may be substantially increased if the unexpanded exhaust gas energy is efficiently recovered and employed for vehicle propulsion. This can be accomplished employing a properly designed exhaust gas turbine connected to a suitable generator whose output electric energy is stored in the vehicle storage system; a new hybrid propulsion system is hence delineated, where the power delivered by the main engine is combined to the power produced by the exhaust gas turbogenerator: previous studies, carried out under some simplifying assumptions, showed potential vehicle efficiency increments up to 15% with respect to a traditional turbocharged engine. Given the power target of the required exhaust gas turbo-generator, no commercial or reference product could be considered: on account of this, in the preliminary evaluations, the turbine efficiency was assumed constant. In this paper instead the authors present the result of new evaluations performed by adequately considering the real efficiency of the exhaust gas turbine, which was designed and calculated by means of simple yet effective 1D approach, and validated by means of 3D CFD analysis. The 1D design and evaluation methodology, characterized by short calculation time, revealed sufficiently accurate compared to the result obtained by the time-consuming CFD simulations; the exhaust gas turbine efficiency was hence calculated for each required operating condition and used to compute the expected real efficiency of the compound engine; as a final result, it was found that, compared to a traditional turbocharged engine of the same rated power (73.5 kW), the realistic compound engine exhibit efficiency increments between 5% and 15%, depending on the output power.

The idea of investigating the fluid dynamic behavior of a ducted Savonius wind turbine derives from the research about the improvements of Oscillating Water Column Wave Energy Converters in which the air is forced to flow back and forth inside a duct. The Savonius rotors appeared to be very suitable for this kind of applications for many reasons. Indeed, these rotors are very simple to built, they are unidirectional respect to the incoming flow, they works well at low flow speed and they produce high torque which allow them to start at very low cut in velocities. By means of a CFD 2D numerical model, the present paper demonstrates the great potentialities offered by the use a Savonius wind turbine in Oscillating Water Column devices. The CFD model was developed and validated against experimental data, obtained in the subsonic wind tunnel owned by the University of Catania. The ducted rotor was simulated at different flow and rotational speed, in steady unidirectional condition which is of utmost importance as a first step in the more complex oscillating flow study.

In last decades environment has suffered strong and negative consequences resulted by a massive consuming fossil energy. As a result of this process, bioenergy has been intensively increased in recent years. Transportation sector has the largest impact in the use of bioenergy and bioethanol is a type of biofuel which can easily used for transports in place of traditional fossil fuels. Bioethanol production from 1st generation biomass such as corn, sugarcane, has been already commercialized but it is usually not sustainable because it could be seriously damage the food supply. For this reason scientific community has turned his interest to second generation bioethanol from specific energy crops or cultivation of biomass feedstock whose required land for cultivation cannot be used for food cultivations. The case arboreal lingo-cellulose Arundo donax is an example of the latter group. The present paper deals with a simulation method to optimize the performances of second generation bioethanol production by using Arundo donax as feedstock. The bioethanol production was analyzed by means of a life cycle assessment (LCA). The total energy consumption was calculated thanks to Monte Carlo method. The simulation of this second-generation biomass technology was optimized by considering the reuse of light components and of the energy recovery for the agriculture and industrial process. Thanks to these optimizations it was obtained an Energy Return On Investment (EROI) = 1,52 revealing that this technology may certainly be convenient from the energetic point of view.

The present study deals with a comparative evaluation of a single-zone (SZ) thermodynamic model and a 3D computational fluid dynamics (CFD) model for heat release calculation in internal combustion engines. The first law, SZ, model is based on the first law of thermodynamics. This model is characterized by a very simplified modeling of the combustion phenomenon allowing for a great simplicity in the mathematical formulation and very low computational time. The CFD 3D models, instead, are able to solve the chemistry of the combustion process, the interaction between turbulence and flame propagation, the heat exchange with walls and the dissociation and re-association of chemical species. They provide a high spatial resolution of the combustion chamber as well. Nevertheless, the computation requirements of CFD models are enormously larger than the SZ techniques. However, the SZ model needs accurate experimental in-cylinder pressure data for initializing the heat release calculation. Therefore, the main objective of an SZ model is to evaluate the heat release, which is very difficult to measure in experiments, starting from the knowledge of the in-cylinder pressure data. Nevertheless, the great simplicity of the SZ numerical formulation has a margin of uncertainty which cannot be known a priori. The objective of this paper was, therefore, to evaluate the level of accuracy and reliability of the SZ model comparing the results with those obtained with a CFD 3D model. The CFD model was developed and validated using cooperative fuel research (CFR) engine experimental in-cylinder pressure data. The CFR engine was fueled with 2,2,4-trimethylpentane, at a rotational speed of 600 r/min, an equivalence ratio equal to 1 and a volumetric compression ratio of 5.8. The analysis demonstrates that, considering the simplicity and speed of the SZ model, the heat release calculation is sufficiently accurate and thus can be used for a first investigation of the combustion process.

The aerodynamic characterization of airfoils is of crucial importance for the design and optimization of wind turbines. The present paper tries to provide an engineering methodology for the improvement of the accuracy and reliability of 2D airfoil computational fluid dynamics models, by coupling the ANSYS Fluent solver and a Micro-Genetic Algorithm. The modeling strategy provided includes meshing optimization, solver settings, comparison between different turbulence models and, mainly, the calibration of the local correlation parameters of the transition turbulence model by Menter, which was found to be the most accurate model for the simulation of transitional flows. Specifically, the Micro-Genetic Algorithm works by generating populations of the missing local correlation parameters. In doing so, it is possible to search for the minimization of the error in lift calculations. For each specific Reynolds number, the calibration was carried out only at the Angle of Attack where the lift drop occurs and the airfoil completely stalls. This new idea allowed for a relatively rapid and good calibration as demonstrated by the experimental–numerical comparisons presented in this paper. Only the experimental stall angle and the relative lift coefficient were, therefore, necessary for obtaining a good calibration. The calibration was made using the widely known S809 profile data. The correlation parameters, obtained as so, were subsequently used for testing on the NACA 0018 airfoil with satisfactory results. Therefore, the calibration obtained using the S809 airfoil data appeared to be reliable and may be used for the simulation of other airfoils. This can be done without the need for further wind tunnel experimental data or recalibrations. The proposed methodology will, therefore, be of essential help in obtaining accurate aerodynamic coefficients data. This will drastically improve the capabilities of the 1D design codes at low Reynolds numbers thanks to the possibility of generating accurate databases of 2D airfoil aerodynamic coefficients. The advantages of the proposed calibration will be helpful in the generation of more accurate 3D wind turbine models as well. The final objective of the paper was thus to obtain a fine and reliable calibration of the transition turbulence model by Menter. This was specifically made for an accurate prediction of the aerodynamic coefficients of any airfoil at low Reynolds numbers and for the improvements of 3D rotor models.

The uncertainty about the world energy production, the lack of crude oil reserves, the environmental problems caused by a massive use of fossil fuels and their increased prices, are the main reasons inducing modern society to find alternative solutions for fuels production. According to this point of view, a great attention is addressed to the biodiesel production as substitute of diesel derived by fossil hydrocarbons. The use of biomasses from different sources for the energy production constitutes one of the main objects thanks to which European Community intends to reduce its dependence from oil importations and derived products over the medium to longer term. Several sources can be used for biodiesel production, among these Brassica carinata and Brassica napus are considered as possible dedicated energy crops. The present work is based on the implementation of a model that allows to analyze the insertion of agro-energetic farms, identifying and evaluating the crops previously mentioned, economically suitable to enter in rotation with cereals and legumes. Through the analysis of official statistical data and cereals and legumes production, an estimation of potential biodiesel production in relation with the considered territory chosen as case study. It was implemented a model based on a procedure of logistics and distribution management in Matlab and in a Gis environment in order to find the best location for a potential production plant. The model considered some collection points of crops according the administrative units of the territory of reference. Moreover, for the same territory, thanks to some simulations it was calculated how the potential biodiesel production could affect fuels consumption and the potential reduction of the amount of CO2 in the environment.

Wind power generation differs from other energy sources, such as thermal, solar or hydro, due to the inherent stochastic nature of wind. For this reason wind power forecasting, especially for wind farms, is a complex task that cannot be accurately solved with traditional statistical methods or needs large computational systems if physical models are used. Recently, the so-called learning approaches are considered a good compromise among the previous methods since they are able to integrate physical phenomena such as wake effects without presenting heavy computational loads. The present work deals with an innovative method to forecast wind power generation in a wind farm with a combination of GISbased methods, neural network approach and a wake physical model. This innovative method was tested with a wind farm located in Sicily (Italy), used as a case study. It consists of 30 identical wind turbines (850 kW each one), located at different heights, for an overall Power peak of 25 MW. The time series dataset consists of one year with a sampling time of 10 minutes considering wind speeds and wind directions. The output of this innovative model leaded to good results, especially for medium-term overall energy production forecast for the case study.

In this work, the authors evaluate the energetic and economic advantages connected to the implementation of an electric Kinetic Energy Recovery System (e-KERS) on an internal combustion engine vehicle (ICEV). The e-KERS proposed is based on the use of a supercapacitor (SC) as energy storage element, a brushless motor generator unit (MGU) for the conversion of the vehicle kinetic energy into electric energy (and vice versa), and a power converter properly designed to manage the power transfer between SC and MGU. The low complexity of the system proposed, the moderate volume and weight of the components selected for its assembly, together with their immediate availability on the market, make the solution presented ready for the introduction in current vehicle production. A widely diffused passenger car, endowed of a gasoline fuelled spark ignition engines, was selected for the evaluation of the advantage connected to the implementation of the e-KERS. The attainable energy saving, together with the related fuel economy, were evaluated on the basis of standard driving cycles by means of simulation performed using MatLab Simulink employing a model properly developed by the authors. It was found that the proposed KERS could allow substantial energy savings, to which correspond important fuel economy improvement together with a reduction of CO2 emissions. The achievable fuel economy and the cost of the KERS components allowed also to estimate the economic advantage of its implementation.

Atmospheric dispersion pollution modelling is of great and actual concern in the scientific international community. Many dispersion models have been developed and used to estimate the downwind ambient concentration of air pollutants from sources such as industrial plants, vehicular traffic or accidental chemical release. Among them, Gaussian model is perhaps the most commonly used model type. It is often used to predict the dispersion of air pollution plumes originated from ground-level or elevated sources. In this research an experimental campaign was carried out in the wind tunnel of the Industrial Engineering Department of University of Catania. It was tested an emission plume of particulate matters and the concentrations of PM 10 were evaluated in several points downwind beyond the emitter. Both the wind velocity and PM 10 mass flow were varied in order to test the differences in terms of PM10 concentrations in the sampling points. A Gaussian plume mathematical model was developed according the boundaries conditions of the experimental campaign. The results of the model were compared with experimental ones in order to identify the limits and the advantages of this model in such a small scale system.

In this paper the authors describe a design and optimization process of micro HAWTs using a numerical and experimental approach. An in-house 1D BEM model was used to obtain a first geometrical draft. It allowed to quickly optimize blade geometry to maximize energy production as well. As these models are quite sensitive to airfoil coefficients, above all at low Reynolds numbers, an accurate 3D CFD model was developed to support and validate the 1D BEM design, analyzing and fixing the discrepancies between model output. The 3D CFD model was developed and optimized using ANSYS Fluent solver and a RANS transition turbulence model. This allowed to correctly reproduce the transition and stall phenomena that characterize the aerodynamic behavior of micro wind turbines, solving the issues related to low Reynolds flows. The procedure was completed, thus building two micro HAWTs with different scales, testing them in the subsonic wind tunnel of the University of Catania. Wind tunnel features, experimental set-up and testing procedures are presented in the paper. Through the comparison of numerical CFD and experimental test results, a good compatibility was found. This allowed the authors to analyze and compare numerical calculation results and verify blockage effects on the prototypes as well.

Nowadays wind power forecasting research is becoming more and more important in economic operation and safety management of power systems. Moreover, with a huge increase of data availability, data-driven models, especially for short-term forecast, represent a good compromise between precision and computational loads. This paper deals with a data-driven algorithm consisting of a combination of three main steps: gis-based data collection and pre-treatment, classification wind turbines step (Twostep cluster analysis) and short-term wind power forecast with artificial neural networks (ANN). The wind turbines were geo-referenced, the initial variables (single turbines power output, wind direction and speed) were pre-processed, a recursive optimized cluster analysis (CA) was performed to obtain a simplified mathematical structure for an artificial neural network. A windfarm (48 MW) placed in the eastern part of Sicily (Italy), was tested as case study. It consists of two different sites each one with 28 wind turbines at different rotor heights and different orography. The time series dataset consists of almost four years data (sampling time of 10 minutes). The consequent simplified mathematical structure leaded to perform good results in in a short-term wind power output forecast for both sites of the case study.Nowadays wind power forecasting research is becoming more and more important in economic operation and safety management of power systems. Moreover, with a huge increase of data availability, data-driven models, especially for short-term forecast, represent a good compromise between precision and computational loads. This paper deals with a data-driven algorithm consisting of a combination of three main steps: gis-based data collection and pre-treatment, classification wind turbines step (Twostep cluster analysis) and short-term wind power forecast with artificial neural networks (ANN). The wind turbines were geo-referenced, the initial variables (single turbines power output, wind direction and speed) were pre-processed, a recursive optimized cluster analysis (CA) was performed to obtain a simplified mathematical structure for an artificial neural network. A windfarm (48 MW) placed in the eastern part of Sicily (Italy), was tested as case study. It consists of two different sites each one with 28 wind tu...

The scientific interest toward micro wind turbine power generation is growing thanks to the fact that these systems appear to be very suitable for small stand-alone devices such as controllers, actuators, sensors, small lightning systems which cannot be easily powered through electricity grids. Furthermore, micro wind turbines are widely used for wind tunnel testing as the wind tunnel dimensions are usually quite limited. The present paper deals with the CFD modeling of a micro H-Darrieus wind turbine, designed and tested in the subsonic wind tunnel, owned by the University of Catania. Such small rotors are usually very difficult to simulate accurately due to the very low Reynolds number effects and the strong unsteadiness related to their operation. Through the use of an accurate unsteady Delayed Detached Eddy Simulation approach for turbulence modeling, the authors demonstrated the possibility to obtain reliable CFD 2D model of such micro rotors. The modeling methodology was developed by means of an accurate grid and time step sensitivity study and by comparing different approaches for turbulence closure. The model was validated using data obtained from experiments carried out in the wind tunnel, which showed a rather satisfactory predictive capability of the model. Therefore, the proposed numerical model allowed for a better comprehension of the fluid dynamic behavior of such micro rotors. Furthermore, the model will be used for trying to optimize micro H-Darrieus turbines which usually show poor efficiency compared to micro horizontal axis wind turbines.

The centrifugal pumping, also known as rotational augmentation, is a 3D phenomenon which is of utmost importance in the aerodynamics of HAWTs. A clear physical explanation about the rise and development of this phenomenon is still missing in the scientific literature. Indeed, several empirical approaches have been proposed for taking into account the rotational effects inside 1D design codes. However, at the state, these approaches lead to results, which are quite different amongst each other. In the present paper the authors propose a thorough analysis of the rotational augmentation in an experimental micro HAWT. For this purpose, previously validated CFD 3D models were used. These models were developed using ANSYS Fluent solver with a calibrated RANS transition turbulence model. The post-processing analysis, presented in this paper, demonstrates that the strong increase of the aerodynamic forces is mainly due to the presence of a strong helical vortex which develops in the inner part of the blade. This vortex depressurizes the entire separated layer and it is found to be due to the combined effect of Coriolis and centrifugal forces along with the span-wise pressure gradient. Moreover, the essential contribution of the radial component of the Coriolis force was evidenced in contrast with the fact that this component is usually neglected.

The hydraulic storage plants play a strategic role in the management of large electrical networks. Besides the widely known capability to store and provide great amount of energy, in a green and efficient way, these plants are of utmost importance to guarantee the perfect balance of the Italian electricity grid. For this reason the reversible turbomachineries, used in these plants, are subjected to a particularly intensive use which strongly affects their reliability. The present work deals with a real issue of the ENEL Green Power "Anapo" storage hydro plant, located in Sicily (Italy). In this plant strong and increasing vibrations were detected in the Fink's guide vane, particularly during the pumping operating conditions. In order to find the sources of these vibrations and for a quantitative evaluation of the structural loads on the Fink's guide vane blades, an unsteady CFD 3D model of the reversible turbine was implemented and validated using data provided by ENEL. The model accurately reproduced the hydrodynamic behavior of the water flow within the entire machinery, between the Kaplan's diffuser and the spiral case. This allowed for the calculation of the time dependent trend of the structural loads over the Fink's vane blades. The frequencies and the amplitudes of the loads were analyzed through the use of a Fast Fourier Transformation. Moreover, the CFD model allowed for a sensitivity study of the guide vane opening angle effects. This study provides an interesting insight into the hydrodynamic behavior of the machine.

The present paper deals with a study of an air turbine as power take-off in Oscillating Water Column systems. In Particular, the focus of the study is on the analysis of the air turbine performance in ducted configuration. Savonius type turbines were tested as a function of air flux oscillation frequency. In more details, a turbine with an overlap ratio of 1/6 was used, while three air flux oscillating frequencies are imposed: 0.1, 0.5, 1 and 1.5 Hz. In order to measure turbine performance, a specific experimental setup was built, based on an OWC simulator. The testing tube (operating as power take-off simulator) was built using transparent materials to allow Particle Image Velocimetry measurement. A simple band brake system was used to apply load to turbine shaft and to measure turbine torque. Therefore, turbine torque, rotational speed, pressure drop and input air velocity were registered and turbine power and power coefficient as a function of tip speed ratio were calculated.

The present paper deals with the study of water effect on the combustion of fuels with low Octane Number in Internal Combustion Engines. In particular, this study was carried out using a variable volumetric compression ratio CFR fuel engine. ASTM Standards for Motor and Research methods were followed to determine fuels and fuel-water mixture Octane Number. CFR fuel engine intake manifold was modified to install water injection. Different water/fuel mass ratios were used and Research and Motor Methods Octane Number and pollutant emissions were measured. In particular, water to fuel mass flow ratio was imposed from 0 to 1.5. Increasing the water/fuel mass ratio an increment in octane number was registered and this behaviour is evident for each base octane number studied. At the same time a reduction in the NOx emissions was registered due to both in-cylinder temperature reduction and water chemical interaction with NOx. Analysing in-cylinder pressure traces highlighted that water presence reduces pressure oscillation within the cylinder engine. On the basis of the results it is possible to state that water is able to control detonation in the fuel combustion and an increment of the octane number is registered.

This paper focuses on the comparison between two different Photovoltaic systems. Both of them are located in the same place in the south part of Italy - Sicily. The first system is a photovoltaic system (PV) with a fixed tilt angle of 30° and an azimuth orientation of 0° South; its peak power is about 1.63 kWp and its 10 modules are made up of polycrystalline silicon for a total area of 13.13 m 2 . The second system is a low concentration photovoltaic system (LCPV) with a biaxial suntracker and a concentration of 25 suns; its peak power is about 4.65 kWp and its modules are made up of monocrystalline Silicon for a total area of 44.6 m 2 . In order to analyse the behaviour of these two different systems the most common Performance Indexes (YR, Yf, PR and η) has been used for the comparison, starting from the measured radiation data for both systems. The experimental data were treated for almost one year. Moreover it was analysed the thread of these indexes for two typical days in different seasons. Analysis results showed that LCPV has better performances (according the PR index) during the summer months thanks to a greater percentage of direct irradiation, while the efficiency of the fixed angle PV system is higher during the other months.

Information on air quality in urban areas represents an important objective to raise awareness and participation of citizens towards those measures aimed at containing and reducing vehicular traffic. For several years at the international level, evaluation procedures have been adopted by indices. One of the first synthetic indices, adopted by the United States Environmental Protection Agency (US-EPA), was the Pollution Standard Index (PSI). In 1999, the EPA replaced the PSI index with Air Quality Index (AQI), which includes two new sub-indices, the ozone at ground level and fine particulate. Despite the European Decisions 97/101/EC and 2001/752/EC, have established an exchange of information from networks and individual stations measuring ambient air pollution in Member States, the use of a single index has not yet been defined that allows you to compare different realities. This heterogeneity emerges in Italy as well, where only a few Environmental Protection Agencies disclose indexes to inform citizens. In this article, the Air Quality Index (AQI) currently used by the United States Environmental Protection Agency has been applied to the metropolitan city of Catania, in order to analyze the level of pollution daily from 2010 to 2014. Through the use of the AQI it was possible to synthesize in a single daily value, concentrations of major pollutants in urban areas (NO2, O3, CO, SO2, PM10) for the entire period. For the calculation procedure of the AQI, the data concentrations were provided by Municipal Ecology and Environment Office. The data relates to three monitoring stations, whose locations have not changed over the years. This also made it possible to evaluate the change in frequency of AQI agglomerations where the monitoring units have been positioned. The value obtained by the AQI for each station has been ranked in six levels of pollution; each level has been associated with a particular coloring allowing this information to be more intuitive. Lastly, it was possible to reach the air quality assessment in urban environment from the frequency variations of each level derived from the year 2010 until 2014.

Fuel laminar burning velocity is an important parameter in internal combustion engine modeling and combustion analysis. The present paper deals with the development of a mathematical correlation able to provide laminar burning velocity for fuels/air mixture at different thermodynamic conditions. Therefore, a mathematical investigation of laminar burning velocity for most significant and used fuels was carried out. Fifth order logarithmic polynomial functions were implemented to predict the propagating laminar burning velocity of combusting fuels as a function of equivalent ratio at different conditions of temperature and pressure. On the basis of results obtained, the mathematical model proposed in this paper showed a higher precision in experimental data fitting and the possibility to interpolate and use a single mathematical function for a wider operation field.

In the European scene a breakthrough in the field of environmental sustainability is represented by the innovative model of multi-level governance, introduced by European Community in 2008, well known as the “Covenant of Mayors”. It is an initiative that involves countries, cities and regions that voluntarily commit to reducing their emissions of greenhouse gases, through the so-called “20-20-20”, that is to reduce by 2020 the 20% of CO2, generating 20% of energy from renewable sources with a reduction of the 20% of energy consumption. The aim of the initiative is to provide a practical tool in order to guide municipalities in the process of drafting a SEAP (Sustainable Energy Action Plan) according to the European Guidelines drawn up by the Covenant of Mayors Office (Co.MO). Since 2012 the new regional government of Sicily has followed carefully the initiative “Covenant of Mayors” by establishing a technical, scientific and organizational structure called “Control room for the Covenant of Mayors”. The Control room has been as promoter of cultural activities with information and educational purpose, organizing and following meetings with many delegates of all municipalities in Sicily. This path led to a full participation of many Sicilian municipalities, recovering the previous gap during the early years of the initiative. In this analysis, a general overview about the participation of all regions of Italy is exposed, focusing the attention on on the virtuous path undertaken by the Region of Sicily. A more accurate statistical analysis by using several indexes has been conducted to better understand the strengths and weakness of this initiative.

This paper presents an improved numerical code based on BEM theory, implemented to evaluate the performance of a HAWT (Horizontal Axis Wind Turbines). This numerical code is a 1-D code characterized by fast processing times and reliable results. The critical aspects of the codes based on the BEM theory are widely known in scientific literature. In this paper, the authors explain how to resolve these aspects. One of these is represented by the radial flow along the blades. Radial flow is a 3-D flow, but can be dealt with inside a 1-D code only using a mathematical expedient. This expedient was tested and validated for the Riso test turbine LM 8.2 (with the NACA 63 x -2xx airfoil series along the blades). Radial flow along the blades is taken into account, thus increasing the experimental C L distribution in the stalled aerodynamic region, based on CFD 3D results. The mathematical equation adopted to describe the C L distribution of the NACA 63 x -2xx airfoil is a fifth order logarithmic polynomial. With this numerical code, the mechanical power curve of the Riso test turbine has been calculated, and then compared with the experimental curve found in scientific literature.

Nowadays, transport and deposition of aerosol particles (PM2.5, PM10, TSP) caused by industrial plants, environmental applications and transports, are of great concern to public health. Despite the establishment by the European Union of emission standards (European directive 2008/50/CE e.g) to control the limits of particulates in the air, the emissions by industrial plants are still not accurately monitored. In particular, the interaction between plume dispersion and obstacles, such as buildings, is not currently well studied. A lot of theoretical researches were carried out in this field with a lack of experimental data comparison. This paper focuses on a laboratory work made to better explain the interaction of a continuous plume released from a point source and various obstacles. First of all a vertical pipe was reproduced, a continuous aerosol emitter was characterized in terms of a specified and controlled mass flow and the ratio between smoke emission and the total suspended particulates thanks to use of the certified gravimetric calculation of PM10. The experimental campaigns were conducted by means of a wind tunnel all the data collected were validated. The characterization of plume was made by the use of several sensors and calculation of velocity in several points of the field. Moreover, the plume dispersion was studied also by using digital image analysis. It was then investigated downwind the influence of obstacles of various shapes and distances from source in terms of aerosol concentration in several points.

The present paper deals with a study on the wind turbine wake mathematical modelling as well as experimental validation by means of wind tunnel experiments. In particular, different wind turbine wake’s equations were implemented and results compared with experimental data. Therefore, an experimental setup was implemented in the wind tunnel test section with a small-scale wind turbine, while velocity deficit was measured. A design of experiment based on three parameters variation was defined: wind velocity, turbine rotational speed and distance from the wind turbine rotor. In the same experimental conditions simulations were carried out by means of three 1D equations. In particular, Jensen, Larsen and Frandsen equations were studied. Comparing theoretical and experimental results, it is evident that Larsen mathematical model is in good agreement with experimental data, while Jensen and Frandsen mathematical models are able to identify only mean and peak velocity deficit, respectively.

Nowadays various technical solutions have been proposed in order to improve the performance of spark-ignition internal combustion engines both at part and full load operations, especially in terms of Brake Specific Fuel Consumption (BSFC). Among the most advanced technical solutions, a fully flexible valve control system (VVA – Variable Valve Actuation) appears a very robust and reliable approach to attain the above aim. In fact advanced valve strategies, such as Early Intake Valve Closure (EIVC) and Late Intake Valve Closure (LIVC), proved to be an effective way to decrease the fuel consumption: at part load through a reduction of the pumping work and, at high load, through a knock mitigation and an over-fueling reduction. In this paper, a comparative numerical study is realized to evaluate the influence of the intake valve strategy on the performance of a small-size turbocharged spark-ignition engine. The analyzed engine is equipped with a fully flexible VVA on the intake side, based on the “lost motion” principle and able to realize both EIVC and Full Lift strategies, while the virtual modification of the intake cam profile allows for the actuation of LIVC profiles. First, a 1D model of the tested engine is developed in GT-Power™ framework. It is integrated with in-house developed sub-models for the description of in-cylinder phenomena, including turbulence, combustion, knock and heat transfer. The adopted approach is validated against 3D turbulence results, measured global performance parameters and in-cylinder pressure cycles. The consistency of the proposed approach, without requiring any case-dependent tuning, is demonstrated at various speeds, loads and intake valve strategies. The validated engine model is used to perform a parametric analysis for different intake valve closure angles in two representative operating points at full and part load. The results point out that both EIVC and LIVC induce an improved fuel consumption with respect to a conventional Full Lift valve strategy. EIVC proves to be more effective at part load than LIVC, while similar BSFC advantages are obtained at high load. The proposed approach, based on refined sub-models for in-cylinder phenomena description, shows the capability to predict the effects of advanced valve strategies, making the implementation of a “virtual” calibration of a VVA engine possible.

In the last decades, the public opinion has paid great attention to environmental pollution and global warming. Energy sector has a strong impact on environment. Thus, the use of renewable energies is becoming mandatory. The present paper deals with a study of ducted Savonius turbine performance as a function of geometric and operating parameters. Ducted turbines could be used as power take-off in multiple applications. In this paper, two main applications were studied. The first application is related to the possibility to install the turbine inside building with the purpose of architectonic integration of the system. The second one is related to wave energy harvesting. In both cases the same type of turbine was used to convert input energy (wind or wave energy) into electricity. Turbine performance were studied as a function of turbine overlap ratio, as well as air flux oscillating frequencies. On the basis of the obtained results, turbine performance increase in ducted configuration and a change in best overlap ratio was registered.

This paper describes the development of a Horizontal Axis Wind Turbine 3D CFD model using the Ansys Fluent solver. The model was developed to predict wind turbine performance and evaluate the capabilities of the 1D model (based on BEM Theory) developed by the authors. The two models were compared in terms of accuracy, predictability and calculation time. The strategy of generating a high quality mesh and optimizing the turbulence models (two equations SST k–ω fully turbulent and four equations Transitional SST models) is presented. In particular, a high quality unstructured 3D grid was generated to optimize spatial discretization and meet turbulence model requirements. The mesh was subsequently converted from a tetrahedral into a polyhedral geometry to considerably reduce the number of cells and better align the cell faces and flow. Polyhedral cells also reduce interpolation errors and false numerical diffusion. The empirical correlations of the Transitional SST turbulence model were modified to improve it for wind turbine applications. A significant number of numerical 2D airfoil tests were implemented to calibrate the turbulence model. The results of these tests were applied to the turbulence model by modifying the local correlation parameters. The same parameters were used in the 3D wind turbine model. A Moving Reference Frame model was used to simulate rotation and evaluate 3D flow along the rotor blades. The numerical results were compared to the fully turbulent SST k–ω simulation data to demonstrate the superior capabilities of the modified Transitional model. The 3D CFD model was validated using NREL PHASE VI experimental data available from scientific literature. An application of the 3D model to a new micro wind turbine is presented at the end of this paper. The micro rotor was designed and optimized using the 1D code and actually built.

The present paper deals with a study of the damping induced by a turbine in the power take off of an small scale Oscillating Water Column Wave Energy Converter. In order to study the turbine-induced damping, an experimental setup was built. The experimental setup consists of a wave flume 2000 mm long, 190 mm high and 96 mm wide with an impermeable beach as a dissipative system at the end to avoid wave reflections. The system is all built in Plexiglas to allow optical real-time observation. An Oscillating Water Column chamber model was placed in the measurement area between the wave-maker and the dissipative beach. The chamber was 37 mm long, 200 mm high and 96 mm wide also built in Plexiglas. In order to study the effect of turbine-induced damping on the system, a calibrated and variable hole was used to simulate the turbine presence, while outflow and inflow air velocity were measured by means of Particle Image Velocimetry (PIV) method. Pressures and velocities of air and water as well as the free water surfaces evolution were measured at different wave frequencies and heights.

The present paper deals with a real issue of the Exxon-Mobil refinery in Augusta (Sicily). The crude oil, which is transported by oil tankers, is transferred through a submarine pipeline where it remains for a long time. In order to predict the transient temperature of the pipe, two numerical approaches were developed. The simplest one was a conductive model, based on the Finite Element Method, implemented by using the ANSYS Thermal FEM software for a first approximation solution. After having carried out an accurate grid resolution study and having evaluated the thermal error, a prediction of thermal profiles and heat fluxes was obtained. Thanks to the axisymmetrics of the physical problem, only a limited portion of the 3D pipe was modelled. The second approach was instead based on the use of a more accurate CFD Finite Volume Model, developed in ANSYS Fluent. In this case, in order to have reasonable calculation time and thanks to the aforementioned axisymetrics, the problem was carried out in 2D. Moreover, both grid and time step sensitivity was evaluated. Accurate buoyancy and turbulence models as well as viscosity and density temperature dependence models were used in order to obtain the most accurate physical modelling. The CFD model was developed basing on codes validated in the scientific literature. The comparison between FEM conductive and CFD results demonstrated the superior accuracy of the CFD, thanks to an accurate modelling of the internal convective motions.

The aim of this work is to exploit the potential of residual biomass, different from the traditional wood feedstock, by using the thermochemical gasification process. In particular, citrus peels, residues of the juice extraction process, was selected since it is a typical local Sicilian residue. The citrus peel conversion performances in an air-steam gasification process were evaluated and compared with those obtained with pinewood as feedstock. Experimental activities of air-steam gasification were carried out in a bench-scale fluidized bed reactor at 1023 K, for both citrus peel and pinewood, varying the steam to biomass ratio (S/B). A simulation model of the experimental facility was developed in order to find a useful tool to realize the virtual scale-up of the system with downstream syngas utilization. The cold gas efficiency (CGE) and the net cold gas efficiency (CGEnet) were calculated to define the best gasification conditions. Results showed that using pinewood a very low reactivity can be observed, showing a very low net CGE. The highest net CGE for citrus peel was observed at S/B = 0.5, while for pinewood the addition of water did not improve the net CGE. Finally, an integration of the citrus peel gasification system with a commercial CHP unit was proposed and the efficiencies were evaluated

In this paper, the electrical and thermal performances of a single-crystalline submerged photovoltaic (PV) solar panel (SP2) is investigated. In particular, due to the presence of water, several phenomena occur such as the modification of solar-radiation spectrum and the reduction of the module operating temperature. These phenomena have different impacts on the global energy performance of the PV module, which depends on the environmental conditions, on the PV technology, and on the water depth. Energy performances of an SP2 module are measured using two different experimental setups in different environmental conditions, with an increase in power ranging from 10% to 15%.

This research deals with the analysis of the dispersion of PM10 by using fluid-dynamic simulation framework. Firstly, an experimental campaign was made in a wind tunnel. A cylindrical emitter of PM10 was characterized in terms of PM10 mass flow rate and outlet velocity. It was positioned in the wind tunnel chamber where several sensors were also placed downwind. The use of different sensor configurations allowed the evaluation of the PM10 concentrations in several locations. The experimental campaign was reproduced in ANSYS-Fluent, by recreating in Design-Model, a 3D geometries of the test case. Different calculation grids were tested in order to find the proper balance between computing time and accuracy. The CFD 3D model was based on the Eulerian approach for the continuous phase and Lagrangian approach for the dispersion phase setting the DPM for the evaluation and dispersion of particulate matters. The turbulence was solved by using a k-ɛ RANS approach and a quite advanced unsteady DES model. Several simulations were carried out by varying the flow inlet velocities in configurations with and without obstacles. The results obtained from the post-processing phase were then compared with the experimental campaign. With obstacles a PM concentration increment is observed at all imposed air velocity because of recirculation phenomena generated around the obstacles.

A mathematical model for fluid dynamics wind turbine design (based on the blade element momentum theory) has been implemented and improved. The mathematical simulations have been compared with experimental data found in the literature. The simulation was performed for the whole wind velocity range, in on-design and off-design conditions. Several simulations were performed in order to maximize the agreement between the simulated and experimental data. Particular attention was paid to the tangential induction factor and to the models for the representation of the lift and drag coefficients. A comparison was also made between the mathematical model presented in the paper and those considered in the literature. Finally, the model was implemented to optimize rotor performance, especially at low wind velocities, which is crucial to produce power during the machine start-up phase.

The present paper deals with the study of the performance of a heavy-duty gas turbine running on biofuels. In particular, synthesis gas from glycerol steam reforming was used to feed the combustion turbine. Engine performances were compared with methane fed ones. Therefore, a mathematical model of the gas turbine was implemented using GateCycle software. Model calibration was made using gas turbine on-design parameters, while performance test results were compared with experimental running data. The resulting analysis highlighted that the mathematical model is able to correctly simulate engine behaviour in different combustion turbine running conditions thus validating the mathematical model. The combustion turbine studied was integrated with a syngas generator plant and overall efficiency was evaluated. The analysis of the results confirms that using biofuels a reduction in engine performance occurs. On the contrary, integrating the gas turbine and syngas generator plant an overall efficiency increase was registered.

This paper focuses on the analysis of the energy production of building integrated photovoltaic systems. All the PV systems are located in the south part of Italy - Sicily. A comparison has been made between two different conversion technologies: string-inverter versus micro-inverter. The two string-inverter systems analyzed have different azimuth angle, no shadowing, different peak power and different types of photovoltaic modules (monocrystalline and polycrystalline silicon). The four micro-inverter systems have different shadowing percentage, different azimuth. All systems have fixed tilt angle and fixed azimuth angle. The experimental data were treated for almost one year. In order to analyze the performance of the systems, the most common Indexes (the Energy Yield Y f , the Reference Yield Y R , the Performance Ratio PR and Efficiency η) have been used. This allowed to obtain a correct comparison even with different Irradiance values and different Peak Powers. The main goal of the analysis has been to evaluate the performances of the micro-inverter systems at different shadowing conditions. The results of the comparison have confirmed that micro-inverter systems present better performances both at shadowed and “not-shadowed” conditions. By comparing not-shadowed systems with the two different conversion technologies and similar azimuth and tilt angle it has been shown how, with almost the same values of Irradiance, micro-inverter systems maximize the energy production. Furthermore, the highest percentage of produced energy could justify the more expensive cost of this new conversion technology.

The importance and the complexity of the phenomena related to the development of radial flows is demonstrated in the first part of this paper. In order to further study the radial flow effects and to extend the analysis to laminar and transitional flows, the authors used a CFD 3D model, validated in the wind tunnel owned by the University of Catania. In the second part of this paper, the authors describe the strategy which was used to post-process the simulation results. Furthermore, a comparison of the results was made. Several simulations were first carried out at various wind and rotational speeds. Angles of Attack and aerodynamic coefficients were evaluated on cylindrical surfaces at different radial stations using the ANSYS Fluent Solver and ANSYS Post. Local velocities and forces, related to the sectional airfoil, were obtained in each cylindrical surface along with pressure coefficient distributions. In this way, it was possible to demonstrate the close relationship between radial flows and the strong depressurization of the suction side of the blade. Moreover, the results proved that the increase of lift and drag coefficients is linked to rotational speed and Angle of Attack as well. The radial effects were found to be enforced by laminar and transitional flows related to low Reynolds numbers. This will affect both design and analysis of wind rotor performance, more so than that which was originally suggested by empirical stall delay models.

During last decades the aerosol concentrations have increased causing a further restriction of current regulations. The World Health Organization (WHO) has estimated that the impact of aerosol air pollution to health, especially for PM10 and PM2.5, constitutes one of the main preoccupations in terms of the interaction health-environment. Since last report about air quality in Europe, published by European Environment Agency (EEA), it is evident that the 90% of citizens of European citiesis exposed to very dangerous pollution levels and, furthermore, it has been estimated that between 2009 and 2011 the 96% of population of main European cities was subjected to aerosol levels greater than the limits imposed by WHO. One of the main tasks of UE, within 2020, is aiming at reducing the pollution with a consequent improvement of its effects to health. In this work it was analyzed experimentally the distribution of aerosol particles in function of the sampling height and the aerodynamic diameters of particles. There were used portable samplers. The experimental campaign was conduced during rush hours in a high congested road of Catania at three different heights. Thanks to analysis of variance (ANOVA) it was possible to verify the interaction between the aerodynamic diameter of particles and the considered sampling heights.

The present paper deals with a preliminary study on an Oscillating Water Column Wave Energy Converter (OWCWEC). The energy conversion is based on a straight-bladed Darrieus type wind turbine. The design of the turbine for maximum power coefficient is discussed. A physical laboratory scale OWC wave energy converter model was built to measure velocity field in the column. The air column was built using transparent materials to allow Particle Image Velocimetry measurements. Velocity field around air turbine rotor was measured by means of PIV. The measured velocities with and without the air turbine are used as inputs in the design procedure and to calibrate and test mathematical models. Moreover, design criteria were obtained using experimental and mathematical results.

This paper focuses on the principal atmospheric pollutants monitored in Catania (Italy) according to European Directive 50/2008. A couple of years, 2012 and 2013 have been considered as a study period. The monitoring system of Catania is made up of five stations that control the presence of the air pollutants in the most important anthropic areas of the urban territory. First of all the mechanisms of formation of the main pollutants have been summarized in order to identify the main causes and effects in urban environment. The raw data have been collected and validated according the UNI CEI EN ISO/IEC 17025:2005 by the Ecologic and Environmental research unit of the municipality of Catania. The trend of all pollutants during the two cited years have been investigated and the results highlight that the most principal polluting gas is NO2 confirming the trend of the previous years. A further analysis of what the principal causes of pollution in Catania could be,has been conducted in order to evaluate possible actions to reduce the atmospheric pollution. As a result it has been demonstrated that the principal cause of the atmospheric pollutant emissions is connected to private urban mobility. The experimental results demostrated that the principal cause of the atmospheric pollutant emissions is connected to private urban mobility. A development of realistic mathematical model will be the object of future research works.

The aim of this paper is to propose a new strategy to optimize the performance and to reduce the emission levels of Internal Combustion Engines by varying intake valve lift profile and timing. The object of the study was an ICE – SI, GDI, 1.4 l, four cylinders, 16 V, turbocharged. It was equipped with an electrohydraulic VVA system which allows the intake valves to vary, at the same time, lift and timing in order to realize early IVC and/or late IVO. Thanks to this, the engine can always operate in the optimal fluid dynamics conditions in order to achieve the best performance and emission levels. A model of the engine was implemented in GT-Power™ for several operating conditions (partial load, full load, low and high engine speed), and then coupled with a single-objective genetic algorithm, evolved subsequently into a multi-objective genetic algorithm. Two different analysis were carried out: the first one for reducing CO2 emissions at partial load and low engine speed (single-objective optimization), and the second one for increasing the brake torque at full load (multi-objective optimization). The proposed model shows the possibility to quickly find optimal solutions for the test cases considered, and it let the opportunity to be further developed and improved in order to optimize many other parameters of the ICE.

This work analyses the link between the aspect ratio of a vertical-axis straight-bladed (H-Rotor) wind turbine and its performance (power coefficient). The aspect ratio of this particular wind turbine is defined as the ratio between blade length and rotor radius. Since the aspect ratio variations of a vertical-axis wind turbine cause Reynolds number variations, any changes in the power coefficient can also be studied to derive how aspect ratio variations affect turbine performance. Using a calculation code based on the Multiple Stream Tube Model, symmetrical straight-bladed wind turbine performance was evaluated as aspect ratio varied. This numerical analysis highlighted how turbine performance is strongly influenced by the Reynolds number of the rotor blade. From a geometrical point of view, as aspect ratio falls, the Reynolds number rises which improves wind turbine performance.

In the present paper, the authors describe the strategy to develop a 2D CFD model of H-Darrieus Wind Turbines. The model was implemented in ANSYS Fluent solver to predict wind turbines performance and optimize its geometry. As the RANS Turbulence Modeling plays a strategic role for the prediction of the flowfield around wind turbines, different Turbulence Models were tested. The results demonstrate the good capabilities of the Transition SST turbulence model compared to the classical fully turbulent models. The SST Transition model was calibrated modifying the local correlation parameters through a series of CFD tests on aerodynamic coefficients of wind turbines airfoils. The results of the tests were implemented in the 2D model of the wind turbine. The computational domain was structured with a rotating ring mesh and the unsteady solver was used to capture the dynamic stall phenomena and unsteady rotational effects. Both grid and time step were optimized to reach independent solutions. Particularly a high quality 2D mesh was obtained using the ANSYS Meshing tool while a Sliding Mesh Model was used to simulate rotation. Spatial discretization algorithm, interpolation scheme, pressure - velocity coupling and turbulence boundary condition were optimized also. The 2D CFD model was calibrated and validated comparing the numerical results with two different type of H-Darrieus experimental data, available in scientific literature. A good agreement between numerical and experimental data was found. The present work represents the basis to develop an accurate 3D CFD unsteady model and may be used to validate the simplest 1D models and support wind tunnel experiments.

This paper defines a new procedure for optimising wind farm turbine placement by means of Monte Carlo simulation method. To verify the algorithm’s accuracy, an experimental wind farm was tested in a wind tunnel. On the basis of experimental measurements, the error on wind farm power output was less than 4%. The optimization maximises the energy production criterion; wind turbines’ ground positions were used as independent variables. Moreover, the mathematical model takes into account annual wind intensities and directions and wind turbine interaction. The optimization of a wind farm on a real site was carried out using measured wind data, dominant wind direction, and intensity data as inputs to run the Monte Carlo simulations. There were 30 turbines in the wind park, each rated at 20 kW. This choice was based on wind farm economics. The site was proportionally divided into 100 square cells, taking into account a minimum windward and crosswind distance between the turbines. The results highlight that the dominant wind intensity factor tends to overestimate the annual energy production by about 8%. Thus, the proposed method leads to a more precise annual energy evaluation and to a more optimal placement of the wind turbines.

It is well known that acetylene is a high flammable and explosive compound. In comparison with commercial liquid fuels, very wide flammability limits and a low Octane Number have relegated the acetylene into the “iperdetonat” fuels category. Thus, it is impossible to run an internal combustion engine on acetylene without a detonation phenomena control system. The current paper deals with a theoretical and experimental analysis of an internal combustion engine running on acetylene and alcohol. A standard 8 kW spark ignition engine with carburettor was modified with electronic injection control system (ECU) and two standard commercial injectors: one for the acetylene and one for the alcohol. The two injectors were installed using a modified engine intake system. The ECU is able to manage two fuels: acetylene and alcohol. Moreover, an optimization method base on Genetic Algorithms and Neural Networks was used to cerate engine parameters map. Thus, Running an ICE on acetylene and alcohol it is possible to achieve acceptable engine performance and very low pollutant emissions.

The present paper deals with the study of the combustion of reforming gas in a small size Internal Combustion Engine. Therefore, mathematical models of both reforming process and internal combustion engine were implemented. In particular, steams reforming of glycerol to produce synthesis gas and spark ignition four strokes ICE were studied. The reforming process mathematical model was verified using experimental data. Synthesis gas was used to feed the ICE with different syngas and engine configuration. On the basis of the comparison with the experimental results, it is possible to state that the mathematical model is validated. Engine performance and pollutant emission evaluation was carried out using the integrated mathematical models with reference to the engine running on standard commercial fuel. The results highlight a reduction in engine performance and, at the same time a reduction of pollutant emissions in terms of CO and CO 2 .

In scientific literature, when the aerodynamic design of a horizontal axis wind turbine is discussed, different brake state models are presented. The brake state models are implemented within a BEM code which is a 1-D numerical code, based on Glauert propeller theory, and able to predict HAWT performance. This code provides reliable results only if a proper brake state model and aerodynamic post-stall model are implemented. In this research, the authors have produced a numerical code based on BEM theory in conjunction with an aerodynamic post-stall model, indispensable for taking into account radial flow along the wind turbine blades (Himmelskamp Effect), and the brake state models by Buhl, combined with the calculation of Jonkman's tangential induction factor. In scientific literature, Shen's brake state model is commonly implemented within 1-D numerical codes, based on BEM theory. Subsequently, a comparison with Shen's brake state models was carried out. With the numerical code presented in this work, the power for an NREL wind rotor was predicted. With the numerical simulation, it was possible to notice when these different brake state model furnish results close to experimental data.

Blade Element Momentum (BEM) theory based numerical codes are employed, both in the scientific and industrial field, for designing wind turbines and appraising their performance. Using BEM theory, mono-dimensional mathematical codes can be created. They have very short processing times and high reliability. However, this is related to the solution of a few problems peculiar to these mathematical models. The problems of these numerical codes are well known in scientific literature: the impossibility of describing inside the mono-dimensional code the three-dimensional radial flow along the blades; the possibility of running into numerical instabilities which prevent the code from converging on the correct solution. In this work the author will show how to mathematically describe lift coefficients so as to eliminate the lack of description for centrifugal pumping. Finally, to ascertain the accuracy of numerical results, these will be compared to experimental data taken from scientific literature. In particular, simulated numerical code data will be compared with the experimental data for the power and efficiency curves of NREL Phase II and NREL Phase VI wind turbines.