Giovanni Ferrara

• PhD
• Professor (Associate) at University of Florence

div class="section abstract"> The use of hydrogen as a sustainable fuel in the short term is hampered by the impossibility of large scale use due low availability. In order to promote decarbonization, complementary solution for a smooth transition is to dilute it in a mixture with methane, in a current Port Fuel Injection (PFI) internal combustion...

div class="section abstract"> The motion of the intake and exhaust valves plays a pivotal role in determining operational efficiency and performance, especially in high-specific power 4-stroke engines. At high rpm levels, the dynamic behavior of the valve may deviate from the kinematic model established during the design phase. This discrepancy ari...

div class="section abstract"> The use of hydrogen in port fuel injection (PFI) engines faces challenges related to abnormal combustions that must be addressed, especially in transient operation. The in-cylinder air-to-fuel ratio and the amount of trapped exhaust gas have a significant impact on the probability of abnormal combustion as well as NOx...

div class="section abstract"> The intake and exhaust valve motion have, as known, a pivotal role in determining engine operation and performances. When dealing with high specific power engines, especially at high rpm, the dynamic behavior of the valve can differ from the kinematic one defined during the design phase. This is related to the high acc...

Darrieus-type vertical axis turbines are suitable for hydrokinetic applications, particularly when deployed in arrays within rivers and small watercourses. However, modelling their complex and unsteady hydrodynamic interactions, both among turbines and with channel boundaries and free water surface, remains a significant challenge. This study devel...

The process of liquefaction of gaseous fuels, such as natural gas or hydrogen, is an essential technology that helps reduce transportation costs over long distances. Cryogenic piston pumps play a critical role in these systems, as they compress the fuel up to 700 bar before vaporization and storage in high-pressure vessels. Due to the extreme tempe...

The escalating global production of plastic waste is a challenge that must be rapidly addressed, but it also conceals opportunities. Currently, only a minor portion of the worldwide plastic waste is recycled, with the remainder destined for either incineration or landfill. In this context, gasification emerges as a sustainable alternative to conven...

Gas evolution and flow patterns inside an alkaline electrolyzer cell strongly affect efficiency, although such effects have not been explored in detail to date. The present study aims to critically analyze the dependence of cell performance on the multiphase flow phenomena, defining some key metrics for its assessment using CFD. Six performance ind...

Experimental testing at the test rig still plays a key role in the development of new centrifugal compressor designs for industrial applications. Although a wide set of different probes is used as per common practice, the overall impact of the probes? dimensions on the stage performance and rangeability is often assumed to be negligible. In this st...

The potential of Darrieus-type Vertical Axis Turbines (VATs) in hydrokinetic applications, especially when deployed into arrays or clusters, has gained recognition in the field of distributed energy production. Due to the complex unsteady hydrodynamics of these turbines and the different flow scales involved, numerical studies to date have often fo...

High-pressure hydrogen storage is essential for maximizing hydrogen potential as a clean energy carrier. Achieving pressures up to 700 bar is necessary to increase its volumetric energy density and reciprocating compressors are favored for their ability to handle high flow rates. Furthermore, maintaining high purity of compressed gas necessitates t...

Structural simulations are key for designing the wheel of a turbocharger’s turbine. These simulations enable the assessment of components’ durability and performance in demanding conditions such as extreme exhaust gas temperatures, facilitate the development of the cooling strategies that essential for managing excessive heat, and allow enhancing t...

Experimental testing at the test rig still plays a key role in the development of new centrifugal compressor designs for industrial applications. Although a wide set of different probes is used as per common practice, the overall impact of the probes’ dimensions on the stage performance and rangeability is often assumed to be negligible. In this st...

To ensure a higher penetration of wind energy in local and national energy mixes, power variability induced by wind fluctuations needs to be limited. In this study, three power smoothing approaches are proposed and compared to the conventional unconstrained behavior. The first method makes use only of a state-of-the-art Li-Ion battery (BESS), while...

Gas turbines have been a key technology in many industrial sectors for over 50 years and they will continue to play a crucial role in the energetic scenario. Nevertheless, these systems are approaching their efficiency limits and performance improvements are becoming increasingly difficult to achieve. In this context, Pressure Gain Combustion (PGC)...

The realization of mathematical, multi-physics models for alkaline electrolyzers is crucial for advancing this technology. Lumped parameter models offer shorter simulation times, compared with other approaches, and practical industrial applications. If electrochemical models provide the polarization curve, the hydrogen production rate, and the devi...

div class="section abstract"> The regulatory framework of pollutant emissions concerning non-road small internal combustion engines is becoming increasingly challenging. The upcoming scenario threatens to cut out small two-stroke engines because of the fuel short circuit occurring during transfer and exhaust ports overlap, causing the emission of u...

The evaluation of thermally induced stresses is key for life-cycle analysis of turbochargers and the use of conjugated heat transfer (CHT) steady-state calculations coupled with structural analyses represents the state-of-the-art. In case of transient analyses, the different timescales of convective and conductive heat transfer mechanisms lead to h...

The study presents a combined experimental and numerical analysis of the impact of external losses in defining the real performance of a model stage. This is of particular importance in the early-validation phase, where novel solutions going beyond the state of the art need to be verified for the first time. Due to the number of simulations to be c...

In recent years, Darrieus turbines have received increasing attention by both the industrial and the academic sector due to their advantages for both wind and hydrokinetic applications. Experimental and numerical investigations showed that the interaction between closely spaced Darrieus rotors can lead to a significant increase in their efficiency....

The availability of accurate numerical tools for predicting the energy consumption of recreational crafts is pivotal in view of reducing the environmental impact on local waters. A computationally efficient digital twin capable of accurately predicting the boat resistance is thus required to account for the energy fluxes. In the study, an improved...

Cryogenic piston pumps are commonly found in cryogenic systems to pressurize low-temperature liquefied fuels, such as liquified natural gas (LNG) or hydrogen, which are then gasified and stored in high-pressure vessels. The main challenges to be tackled in the design of these machines concern the low operating temperatures, high discharge pressures...

Modern engines require continuous and detailed monitoring in order to minimize variations in performance and emissions during their operation. To this aim, the engine thermodynamic cycle must be brought into focus, with special emphasis on the combustion process. The in-cylinder pressure is the parameter that is most directly associated with the en...

The target of motorsport has always been maximising the performance. Increasingly stringent rules on fuel usage, however, have moved the research on engine design and control rules toward efficiency enhancement. Turbocharging is a typical solution to match both targets; however, it suffers from the turbo-lag phenomenon, especially when the maximum...

Weather routing (WR) systems are widely adopted in the maritime transport since safety of goods and saving of fuel are crucial for shipping companies. However, the need of protecting the local coasts and reducing CO 2 emission is making WR attractive even for the market of leisure boats, especially if comfort and safety are also accounted. In the p...

To date, the most industrially developed technology to produce green hydrogen is represented by alkaline water electrolysis (AWE). To improve on design and efficiency of these devices, however, multiphysics simulations based on Computational Fluid Dynamics (CFD) are needed, able to account for electrophysical phenomena and multiphase flows. Focusin...

In the field of Internal Combustion Engines (ICEs), increasingly stricter regulations on pollutant emissions have made necessary to continuously monitor engine operation. Indeed, in order to tackle fault-induced variations in engine performance, continuous, real-time data related to the engine’s thermodynamic cycle is needed: specifically, obtainin...

Among proposed solutions for power augmentation of Darrieus turbines, one of the most promising is represented by Radial Guide Vanes (RGVs) which can potentially increase both the velocity magnitude and the swirl of the incoming flow, without losing omni-directionality like in the case of diffusers. The main drawback of this technology is the incre...

Darrieus vertical-axis turbines are known for their complex aerodynamics connected to the continuous change in the angle of attack experienced by the blades, which often exceeds the static stall limit. Low fidelity tools such as the Blade Element Momentum Theory have been shown lately not to provide sufficient levels of accuracy, while the medium-f...

Pre-chamber turbulent jet ignition represents one of the most promising techniques to improve spark ignition engines efficiency and reduce pollutant emissions. This technique consists of igniting the air-fuel mixture in the main combustion chamber by means of several hot turbulent flame jets exiting a pre-chamber. In the present study, the combusti...

Leading edge erosion of wind turbine blades is still an important challenge for wind energy professionals, both at research and industrial level. While the efficiency and durability of materials and coatings are improving rapidly, it is important to explore innovative solutions at the aerodynamic design level to mitigate the adverse effects of surf...

The use of vertical-axis turbines is raising interest in the field of hydropower production from rivers or water channels, where suitable mass flows are available, without the need of high water jumps or large construction sites. Like their wind-based counterparts, these machines have many advantages in terms of installation and maintenance, but su...

An accurate estimation of rotating stall is one of the key technologies for high-pressure centrifugal compressors. Several techniques have been proposed to detect the stall onset; inter alia, few dynamic pressure probes have been shown to not only properly detect the phenomenon, but also reconstruct the stall characteristics after an ensemble avera...

Increasingly stringent policy on carbon dioxide have proved to be a severe constraint on the design of light two-stroke (2S) engines. The enhancement of efficiency is claimed to be the main target to make these devices compliant with future regulations. Low-Pressure Direct Injection (LPDI) was found to be effective in the reduction of fuel short ci...

Analysis tools with a fidelity higher than the ubiquitous Blade Element Momentum (BEM) method are needed by now in wind energy; in particular, different research groups have recently proposed the application of the Actuator Line Method (ALM) to wind turbines, to exploit the benefits of an accurate discretization of the wake through Computational Fl...

A numerical approach for transient CFD analyses of autoclave curing process is presented, aimed at finding a trade-off between accuracy and computational cost that can make it industry-affordable. A steady-state, conjugated heat transfer (CHT) analysis is carried out for the simultaneous simulation of solid and fluid regions to obtain a spatial dis...

In case of stationary power production, the matching between the turbocharger and the engine can be optimized around a specific operating point, rather than throughout a wide range like in automotive applications. This, in turn, may enable a finer optimization of the aerodynamic efficiency in comparison to existing industrial standards. The present...

Energy Storage Systems (EES) are key to further increase the penetration in energy grids of intermittent renewable energy sources, such as wind, by smoothing out power fluctuations. In order this to be economically feasible; however, the ESS need to be sized correctly and managed efficiently. In the study, the use of discrete wavelet transform (Dau...

While most wind energy comes from large utility-scale machines, small wind turbines (SWTs) can still play a role in off-grid installations or in the context of distributed production and smart energy systems. Over the years, these small machines have not received the same level of aerodynamic refinement of their larger counterparts, resulting in a...

Geothermal energy is accredited as a flexible, controllable and green source of energy. Heat exchangers (HXs) are one of the most critical components of a geothermal power plant due to corrosion and scaling phenomena. Hence, improvements in the antiscaling and anticorrosion properties as well as heat transfer performance of the HX materials will le...

Active Noise Control (ANC) has been considered a promising technology for the abatement of acoustic noise from the mid-20th century. Feedback and Feedforward ANC algorithms, based on the destructive interference principle applied to acoustic waves, have been developed for different applications, depending on the spectrum of the noise source. Feedba...

Wind turbine blade erosion has risen to the attention of researchers and industry lately in an effort to keep ageing wind farms productive. Although not new, erosion-related blade damage seems to be more severe in recent, particularly off-shore, installations. With the high blade-tip speeds of modern wind turbines, installation in rainy locations c...

One of the key problems faced by researchers dealing with Computational Fluid Dynamics simulations and rotating machines is represented by how to extract the angle attack from a numerically computed flow field. If this issue has been addressed successfully for some applications, in case of airfoils moving in cycloidal motion (i.e. having a rotation...

Power augmentation devices in wind energy applications have been receiving increasing interest from both the scientific and the industrial community. In particular, Gurney Flaps (GFs) showed a great potential thanks to the passive functioning, the simple construction and the possibility to add them as a retrofit to existing rotors. Within this cont...

A centrifugal compressor volute should ideally collect the pressurized flow at the diffuser outlet and convey it to the outlet piping as efficiently as possible. The total pressure loss related to the conversion of a radial flow into an axial one, however, is often not negligible, especially for applications where severe dimensional constraints are...

The use of power augmentation devices in wind energy applications has been receiving increasing interest from both the scientific and the industrial community. In particular, Gurney Flaps (GFs) showed a great potential thanks to the passive functioning, the simple construction and the possibility to add them as a retrofit to existing rotors. The po...

Small Darrieus vertical-axis wind turbines (VAWTs) have recently been proposed as a possible solution for adoption in the built environment as their performance degrades less in complex and highly-turbulent flows. Some recent analyses have even shown an increase of the power coefficient for the large turbulence intensities and length scales typical...

The research on two-stroke engines has been focused lately on the development of direct injection systems for reducing the emissions of hydrocarbons by minimizing the fuel short-circuiting. Low temperature combustion (LTC) may be the next step to further improve emissions and fuel consumption; however, LTC requires unconventional ignition systems....

An increasing number of vertical-axis wind turbine prototypes have reached the step in which the theoretically predicted performance needs to be validated in order to move to the next steps of a real commercial project. This step often faces the significant challenges posed by their airfoil aerodynamics that are more complex than those of conventio...

Wind industry needs high quality airfoil data (namely lift, drag and moment coefficients) for ranges of the angle of attack (AoA) much wider than those that one can commonly get from the relevant technical literature dealing with aerospace or turbomachinery applications. Accurate aerodynamic coefficients are useful both in case of horizontal-axis w...

The increasing attention in reducing pollutant emissions and fuel consumption in internal combustion engines is promoting the development of more sophisticated control systems for the diagnosis and the optimization of the combustion process. In this view, the real-time monitoring of the in-cylinder pressure is becoming mandatory in order to ensure...

Anaerobic digestion of biodegradable matrices is regarded as a confirmed technology for energy recovery through biogas and its use in heat and power plants. Based on that, bio-hydrogen production in a two-stage digestion process can be considered as an optimization of the process to improve its efficiency. In this study, a two-stage digestion syste...

Wind industry needs high quality airfoil data for ranges of the angle of attack (AoA) much wider than those provided by the relevant technical literature, especially for aerospace applications. This kind of data is useful both in case of horizontal-axis wind turbines (HAWTs) for the root region and for vertical-axis ones (VAWTs), where the AoA vari...

The increasingly strict European emissions standards are prompting researchers at improving further the combustion process in internal combustion engines, in order to reduce pollutant emissions and fuel consumption. To this end, more effective monitoring and control strategies need to be developed in the near future. In particular, the development...

This paper assessed the effect of dark fermentation, the fermentative phase in a two-stage anaerobic digestion system, in terms of digestate biostabilization efficiency. The digestates analyzed in this study were obtained from a pilot-scale system in which two different substrates were used in order to simulate both the digestion and co-digestion p...

Based on existing reports and databases, most of the installations in highly turbulent sites in fact fail to reach the expected energy yield, resulting in still or underperforming turbines that also give bad press for the technology. A better understanding of the real performance of wind turbines under highly turbulent conditions is then pivotal to...

Wind industry needs high quality airfoil data for a range of the angle of attack (AoA) much wider than that often provided by the technical literature, which often lacks data i.e. in deep- and post-stall region. Especially in case of vertical axis wind turbines (VAWTs), the blades operate at very large AoAs, which exceed the range of typical aviati...

The design of the volute (in terms of area distribution and shape of the cross section) has a relevant impact on the efficiency and the operating range of a centrifugal compressor. This latter aspect is even more relevant in turbochargers, where the compressor has to cover a functioning range much wider than that of industrial applications. In addi...

Based on existing reports and databases, most of the installations in highly turbulent sites in fact fail to reach the expected energy yield, resulting in still or underperforming turbines that also give bad press for the technology. A better understanding of the real performance of wind turbines under highly turbulent conditions is then pivotal to...

The increasing interest in deep-water floating applications and in wind turbine installations in turbulent flows, is putting vertical-axis wind turbines back again in research agendas. However, due to the lack of activities in past years, the accuracy and robustness of available design tools is much lower than the corresponding ones for horizontal-...

In order to ensure a high level of performance and to comply with the increasingly severe limitations in terms of fuel consumption and pollution emissions, modern diesel engines need continuous monitoring of their operating conditions by their control units. With particular focus on turbocharged engines, which are presently the standard in a large...

Gurney Flaps (GFs) can enhance the aerodynamic performance of airfoils, making them generate more lift and delaying the onset of stall. Since their potential was discovered in the early ‘70 s, GFs have been applied in several fields, including wind turbines. Here, the research has been focused mostly on the use of GFs in Horizontal Axis Wind Turbin...

After almost 20 years of absence from research agendas, interest in the vertical axis wind turbine (VAWT) technology is presently increasing again, after the research stalled in the mid 90's in favor of horizontal axis wind turbines (HAWTs). However, due to the lack of research in past years, there are a significantly lower number of design and cer...

The wind industry needs airfoil data for ranges of angle of attack (AoA) much wider than those of aviation applications, since large portions of the blades may operate in stalled conditions for a significant part of their lives. Vertical axis wind turbines (VAWTs) are even more affected by this need, since data sets across the full incidence range...

Anaerobic digestion of sewage sludge generally produces an amount of biogas that is not enough to cover the energy requirements of the digester. One possibility to increase the biogas production is to co-digest, together with sewage sludge, other substrates, for istance the organic fraction of municipal solid waste. Alternatively, a preliminary ste...

The reduction of landfill gas emissions is a central issue of the Directive 99/31/EC. Biofilters and biocovers have been identified as an alternative and cost-effective technologies to mitigate impacts due to CH4 and NMVOCs emissions. The Life Cycle Assessment demonstrates the environmental sustainability of biofiltration systems, with the aim of i...

The increasing application of new concepts for the combustion process in internal combustion engines, e.g. HCCI or RCCI, is mainly aimed at reducing pollutant emissions and fuel consumption. A typical drawback of these technologies is the difficulty of properly controlling the combustion process in the area of medium-high brake mean effective press...

Thanks to the renewed interest in vertical-axis wind turbines, research efforts are devoted at improving the accuracy of present simulation tools, many of which are underdeveloped if compared to those for horizontal-axis turbines. In particular, recent studies demonstrated that a correction for the “virtual camber” effect has a major impact on the...

Recent innovations in engine control and diagnostics are providing room for development of innovative combustion approaches (e.g., low-temperature combustion) able to minimize the creation of pollutants. To ensure the constant fulfillment of the prescribed thermodynamic conditions, however, a fast real-time monitoring of the in-cylinder pressure is...

In centrifugal compressor design, the volute plays a key role in defining the overall efficiency and operating range of the stage. The flow at the impeller outlet is indeed characterized by a high kinetic energy content, which is first converted to potential energy in the diffuser downstream. The compressed gas is then collected by the volute at th...

Recent studies showed that a prompt detection of the stall inception, connected with a specific model to predict its associated aerodynamic force, could provide room for an extension of the left margin of the operating curve of high-pressure centrifugal compressors. In industrial machines working in the field, however, robust procedures to detect a...

To improve the efficiency of Darrieus wind turbines, which still lacks from that of horizontal-Axis rotors, computational fluid dynamics (CFD) techniques are now extensively applied, since they only provide a detailed and comprehensive flow representation. Their computational cost makes them, however, still prohibitive for routine application in th...

To improve the efficiency of Darrieus wind turbines, which still lacks from that of horizontal-axis rotors, Computational Fluid Dynamics (CFD) techniques are now extensively applied, since they only provide a detailed and comprehensive flow representation. Their computational cost makes them, however, still prohibitive for routine application in th...

Turbocharged engines are setting themselves as the present standard in case of high-performance engines for sport applications. The coupling of a turbomachine with an internal combustion engine poses, however, some serious challenges, especially regarding the time lags and the transitory flow conditions. In particular, focus is presently being paid...

Recent studies showed that a prompt detection of the stall inception, connected with a specific model to predict its associated aerodynamic force, could provide room for an extension of the left margin of the operating curve of high-pressure centrifugal compressors. In industrial machines working in the field, however, robust procedures to detect a...

The wind industry needs airfoil data for ranges of Angle of Attack (AoA) much wider than those of aviation applications, since large portions of the blades may operate in stalled conditions for a significant part of their lives. Vertical axis wind turbines (VAWTs) are even more affected by this need, since data sets across the full incidence range...

In centrifugal compressor design, the volute plays a key role in defining the overall efficiency and operating range of the stage. The flow at the impeller outlet is indeed characterized by a high kinetic energy content, which is first converted to potential energy in the diffuser downstream. The compressed gas is then collected by the volute at th...

Small Darrieus Vertical-Axis Wind Turbines (VAWTs) are presently seen as a relevant research topic for the wind energy community, since they are thought to perform better than horizontal-axis rotors in the complex and highly-turbulent flow typical of the urban environment. Indeed, a preliminary wind tunnel test campaign on a H-Darrieus VAWT showed...

After almost 20 years of absence from research agendas, interest in the vertical axis wind turbine (VAWT) technology is presently increasing again, after the research stalled in the mid 90's in favour of horizontal axis turbines (HAWTs). However, due to the lack of research in past years, there are a significantly lower number of design and certifi...

Recent experiments and theoretical models showed that the aerodynamic performance of H-Darrieus wind turbines can even be enhanced in case of moderate skew angles, which are typical of installations in the urban environment. In this study, a design procedure oriented to the maximization of the annual energy yield in skewed flow, instead of the maxi...

Hybrid energy systems are an interesting solution for the electrification of remote, off-grid users, which usually are obligated to satisfy their electricity demand by means of quite old technologies, like for example diesel generators. An energy mix including also renewable energy sources (such as wind and PV) would lead to a reduction of supply c...

The benefits of wind turbine rooftop installations are related to the exploitation both of a higher elevation within the atmospheric boundary layer and of possible local accelerated flows originated by the interaction between the wind and the surrounding landscape. The selection of the proper turbine positioning is however pivotal to ensure maximiz...

The performance of large reciprocating compressors is strongly dependent on the geometry of gas chambers and valve pockets, both directly influencing the pressure losses along the flow path. Reliable and accurate numerical models are necessary for a proper prediction of the thermodynamic cycle of the compressor, hence of both the efficiency and the...

Darrieus vertical axis wind turbines (VAWTs) have been recently identified as the most promising solution for new types of applications, such as small-scale installations in complex terrains or offshore large floating platforms. To improve their efficiencies further and make them competitive with those of conventional horizontal axis wind turbines,...

The growth of world energy demand combined with global warming and climate change is one of the most urgent global challenges and induced policy measures to foster the use of renewable energy sources. In order to cope with the intrinsic variability of solar and wind, active management of distribution networks and customers is required, if the creat...

The main drawbacks of two stroke (2S) engines consist in poor engine efficiency and high level of pollutant emissions. The contemporary opening of transfer and exhaust ports during the scavenging process causes the short circuit of fresh air-fuel mixture in case of indirect injection or carbureted engines. Despite the intrinsic strengths such as hi...

The present research frontier on wind turbine wake analysis is leading to a massive use of large-eddy simulations to completely solve the flow field surrounding the rotors; on the other hand, there is still room for lower-fidelity models with a more affordable computational cost to be used in extended optimization analyses, e.g. for a park layout d...

In the textile industry, the drying process is a time consuming and energy expensive operation that influences strongly the cost of the textile finishing operations. For this reason, the study of innovative techniques plays a key role to decrease the energy consumption, the costs and the environmental impact. After a first mechanical process, the m...

Anaerobic Digestion of biodegradable substrates could be considered a promising process in terms of both bio-fuels and bio-products production. In this respect, biohydrogen production during the acidogenic phase and polyhydroxyalkanoate generation through the metabolites circulation, can be considered the new borders of process optimization. The re...

Due to the rapid progress in high-performance computing and the availability of increasingly large computational resources, Navier-Stokes computational fluid dynamics (CFD) now offers a cost-effective, versatile and accurate means to improve the understanding of the unsteady aerodynamics of Darrieus wind turbines and deliver more efficient designs....