Sergio Camporeale | Politecnico di Bari (original) (raw)

Papers by Sergio Camporeale

Research paper thumbnail of Experimental investigation of a Wells turbine under dynamic stall conditions for wave energy conversion

Renewable Energy, Jun 1, 2023

Research paper thumbnail of Experimental Investigation of a New 3d Printed Wells Turbine Under Dynamic Stall Conditions for Wave Energy Conversion

Social Science Research Network, 2022

Research paper thumbnail of Perspective of the role of hydrogen in the 21st century energy transition

Energy Conversion and Management, 2022

Research paper thumbnail of Distributed heat and power generation: thermoeconomic analysis of Biomass-fired Rankine cycle systems with molten salts as heat transfer fluid

Distributed cogeneration systems can be used to serve onsite energy demands in industrial and com... more Distributed cogeneration systems can be used to serve onsite energy demands in industrial and commercial buildings. In market segments with highly variable heat-demand patterns, the thermal plant is often composed of a boiler that is operated at part load in case of low thermal demands. To improve the plant flexibility and its overall energy efficiency, the biomass boiler can be coupled to a combined heat and power (CHP) generation system, as an alternative to a heat-only plant. In this work, three thermodynamic configurations are compared: (A) a biomass furnace that acts as a heat-source for a steam Rankine cycle (ST) plant coupled to an organic Rankine cycle (ORC) engine; (B) the same as Case A but without the bottoming ORC; and (C): the same as Case A but without the steam cycle. All configurations assume the cogeneration of heat and power to match onsite energy demands. The plant adopts a molten salt (MS) circuit to transfer heat from the biomass furnace to the power generation system. The energy analysis assumes a ternary MS mixture operating up to 450 °C and with minimum temperature of 200 °C. Two organic fluids (Pentafluoropropane R245fa and Toluene) are considered, based on the temperature of heat available to the ORC engine. In the combined cycle of Case A, R245fa is selected and the maximum cycle temperature is 130 °C, with a global electrical efficiency of 16.6%. In Case C, when only the ORC system is used with Toluene as the working fluid, the electrical efficiency is 18.8% at the higher turbine inlet temperature of 330 °C. Production of hot water for cogeneration at different temperature levels is also considered. Based on the results of the thermodynamic simulations, upfront and operational costs assessments, and feed-in tariffs for renewable electricity, energy efficiency and investment profitability are estimated

Research paper thumbnail of Thermoacoustic Combustion Stability Analysis of a Bluff Body-Stabilized Burner Fueled by Methane–Air and Hydrogen–Air Mixtures

Energies, Apr 6, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of 3D CFD analysis of Mixture Formation in Direct-Injection Hydrogen-fueled Internal Combustion Engines

Journal of physics, Dec 1, 2022

Research paper thumbnail of Numerical characterization of hydrogen under-expanded jets with a focus on Internal Combustion Engines applications

International Journal of Engine Research

In the context of reducing carbon dioxide ([Formula: see text]) emissions, hydrogen is gaining mo... more In the context of reducing carbon dioxide ([Formula: see text]) emissions, hydrogen is gaining momentum as a possible fuel for Internal Combustion Engines (ICEs). In-cylinder direct injections allow for a higher specific power density while enabling different levels of charge stratification. The high-pressure injection leads to the onset of under-expanded jets, characterized by complex patterns of shock waves and expansion fans. In ICEs simulations, such physics needs to be correctly solved to obtain a reliable assessment of the mixture formation. In this paper, the main features of hydrogen under-expanded jets are examined under the conditions typically found in turbocharged engines. Improved correlations are provided for the assessment of the Mach disk height and diameter, up to a Nozzle Pressure Ratio (NPR) equal to 60. The dependency of the hydrogen-air mixing on the cylinder temperature has been analyzed, and the unsteady jet dynamics has been examined by continuously varying t...

Research paper thumbnail of Numerical characterization of hydrogen under-expanded jets: influence of the nozzle cross-section shape

Journal of Physics: Conference Series

This historical moment is characterized by a great awareness regarding the need to reduce the Gre... more This historical moment is characterized by a great awareness regarding the need to reduce the Greenhouse Gas emissions (GHG), which are responsible for the climate change and its detrimental consequences. Green hydrogen produced by means of Power-to-Gas technologies from renewables is gaining momentum as a possible clean fuel for the future mobility. In such a context, traditional injectors for hydrocarbon fuels are currently being tailored to be used with hydrogen. The short time available for the injection process leads to the employment of a high inlet pressure, resulting in the formation of an under-expanded jet. In this work, the main characteristics of these jets are analyzed by means of Computational Fluid Dynamics (CFD) for a Nozzle Pressure Ratio (NPR) equal to 10. Then, to provide insights regarding the dependence of the air-hydrogen mixing on section shape of the nozzle, comparisons have been performed by changing the nozzle cross-section (circular, rectangular, and ellip...

Research paper thumbnail of Bypass Control strategy of a Pump as Turbine in a Water Distribution Network for energy recovery

Journal of Physics: Conference Series

Water Distribution Networks (WDNs) are subject to leakages due to pipes aging, resulting in water... more Water Distribution Networks (WDNs) are subject to leakages due to pipes aging, resulting in water and pressure losses. These issues are solved by installing Pressure Reduction Valves (PRVs) to decrease the pressure in WDNs. Depending on the application, PRVs can waste large amount of energy, hence the substitution of PRVs with Pumps used as Turbines (PaTs) can be a good compromise in terms of economic and technical aspects to reduce leakages and recover energy. Currently the share of PaT is not yet fully developed due to the certain technical challenges yet to be addressed, as providing an affordable control strategy closer to the real working conditions in a WDN. Hence, more experimental activities are required. For these reasons, in this work an experimental campaign was carried with the aim to investigate the behavior of a PaT according to a possible layout that could be embedded into a WDN. Firstly, the machine was characterized both in pump and turbine modes. Moreover, the mach...

Research paper thumbnail of Cost-Effective CFD Analysis of the Acoustic Response of a Perforated Plate

Volume 3B: Combustion, Fuels, and Emissions

Given the current practice to perform lean-premixed combustion to decrease NOx emissions, thermoa... more Given the current practice to perform lean-premixed combustion to decrease NOx emissions, thermoacoustic instabilities have become one of the major drawbacks in gas turbine combustors. The necessity to control and limit such a deleterious phenomenon is mandatory to avoid structural damage of the burner. It has been demonstrated that perforated liners, if conveniently designed, can be very effective in reducing acoustic oscillations inside gas turbine combustors. Studying perforated plates traversed by bias flow can give a useful insight on sound absorption properties of liners, rather than investigate complex geometries. The present paper aims to carry out a numerically cost-effective, but reliable, CFD analysis to predict the acoustic impedance of perforated plates traversed by bias flow, and to grasp the details of the sound dissipation process. 2D axisymmetric simulations have been carried out and the governing equations solved by using the commercial code ANSYS Fluent®. Hypothes...

Research paper thumbnail of CFD Modelling of OWC Devices for Wave Energy Harnessing

Ocean Wave Energy Systems, 2021

This book chapter is focused on how to study the fluid dynamic behavior of a Wave Energy Converte... more This book chapter is focused on how to study the fluid dynamic behavior of a Wave Energy Converter (WEC) of the Oscillating Water Column (OWC) type by means of Computational Fluid Dynamics (CFD). The U-OWC plant installed in the harbor of Civitavecchia (Italy) is chosen as the case study. The CFD approach is described referring to ANSYS Fluent, release 17.2. The model is mainly oriented to investigate the interaction of single harmonic waves with the OWC device and allows the user to perform a preliminary wave-to-wire energy conversion process analysis. To limit the computational cost, a 2D model is developed. The presence of the Power Takeoff (PTO) system generally breaks the 2D configuration of this kind of device, and here an approach to overcome this problem is described in detail. The solution is the introduction of a porous medium region in the 2D computational domain, which emulates the effect of the PTO system on the fluid dynamic behavior of the flow inside the WEC.

Research paper thumbnail of Pompe usate come turbine per il recupero energetico nelle reti di distribuzione idrica urbana

Research paper thumbnail of CSP/biomass hybrid externally fired gas turbines: thermo-economic assessment

Research paper thumbnail of Wind tunnel measurements for the characterization of a small scale monoplane Wells turbine

2018 IEEE International Workshop on Metrology for the Sea; Learning to Measure Sea Health Parameters (MetroSea), 2018

In the field of wave energy harnessing, Oscillating Water Column (OWC) devices are nowadays a con... more In the field of wave energy harnessing, Oscillating Water Column (OWC) devices are nowadays a consolidated technology. In OWC energy converters, waves generate an oscillating flow, whose energy can be effectively captured, for instance, by means of self-rectifying Wells turbines. In the design of Wells turbines, main issues are the improvement of their peak efficiency and the widening of their operational range. In order to reach these goals, a deep knowledge of the turbine fluid dynamic performance is essential. This paper presents the results of the experimental investigation of a small scale monoplane Wells turbine, tested in an open circuit low speed wind tunnel of the suction type in order to characterize its performance in terms of non-dimensional parameters, namely, torque and pressure drop coefficients and efficiency. The prototype under investigation, with blades of constant chord and NACA0015 profile, has been designed in order to be matched with a REWEC (Resonant Wave Energy Converter) breakwater, which had been located off the beach of Reggio Calabria. The REWEC under consideration was an excellent small scale model of full scale sea wave energy conversion devices for oceanic applications. Results have been compared with previous in-field tests, showing a very good agreement.

Research paper thumbnail of Selection, control and techno-economic feasibility of Pumps as Turbines in Water Distribution Networks

Renewable Energy, 2020

Water Distribution Networks (WDNs) are becoming an attractive area of application for small hydro... more Water Distribution Networks (WDNs) are becoming an attractive area of application for small hydropower, which can contribute to the development of distributed energy generation from renewable sources. Indeed, WDNs experience considerable water leakages due to their age and water management authorities often divide the WDNs by inserting Pressure Reducing Valves (PRVs), which waste a potentially recoverable hydraulic head. The replacement of PRVs with Pump as Turbines (PaTs) can be considered as an economically feasible solution to achieve both an effective pressure control and a throttling energy recovery. The selection, installation and control strategy of a PaT in a WDN must consider the variability of the pressure and the flow rate demand. Starting from the evaluation of the available head and the water demand, in this work, we describe a methodology to select from pump catalogues the most suitable PaT and the best control criteria for a specific WDN. Then, knowing the pump geometry, it is possible to predict the characteristic curve of the pump operating as a turbine by using a 1-D performance prediction model. The WDN of a town in the Apulia region (Southern Italy) has been used as a case study. Finally, a techno-economic evaluation has been carried out by considering both economic and environmental benefits.

Research paper thumbnail of Experimental characterization of the unsteady performance behavior of a Wells turbine operating at high flow rate coefficients

E3S Web of Conferences, 2020

Even if researchers are working on the exploitation of marine energy for more than thirty years, ... more Even if researchers are working on the exploitation of marine energy for more than thirty years, blue energy is not yet a consolidated reality and still contributes marginally to the world energy mix. For this reason, in the last years, the effort of the scientific community has been significantly intensified to further improve the know-how on marine energy harvesting. The goal is to allow ocean energy to effectively contribute to a more sustainable energy production in the next future. In the wide range of technologies for wave energy harvesting, Oscillating Water Column (OWC) devices are counted among of the most mature ones. Due to the oscillating nature of the generated air flow, which continuously inverts its direction, OWC devices need to be coupled with self-rectifying turbines, such as Wells, impulse, or biradial turbines. Wells turbines can reach high efficiencies, but their performance can show a hysteretic behaviour due to dynamic stall phenomena, especially in presence o...

Research paper thumbnail of Simplified prediction model of the discharging time of a shell-and-tube LHTES

Applied Thermal Engineering, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Research paper thumbnail of Pump as turbine for throttling energy recovery in water distribution networks

SECOND INTERNATIONAL CONFERENCE ON MATERIAL SCIENCE, SMART STRUCTURES AND APPLICATIONS: ICMSS-2019, 2019

Nowadays, a great effort is increasingly put by the scientific community into a more sustainable ... more Nowadays, a great effort is increasingly put by the scientific community into a more sustainable energy management, which requires a higher harvesting of renewable energy sources with respect to conventional ones. In the framework of distributed electricity production, Pumps as Turbines (PaTs), i.e. pumps operated in reverse mode, are becoming more and more tempting, being very cost effective with respect to customized hydro turbines. For instance, Water Distribution Networks (WDNs) are equipped by pressure relief valves (PRVs) in order to regulate flow rates and to reduce leakages. The replacement of PRVs with PaTs could be a feasible practice to achieve both an effective pressure control and a throttling energy recovery. The preliminary identification of specific speed of a pump to be used as a turbine is fundamental in order to find the best suitable solution. However, the insertion of a PaT must consider the variability of water demand and pressure patterns. The hydraulic variability in a water distribution network does not permit to define a unique operating point for a PaT and this aspect is a further obstacle for the functional planning of such a system. In this framework, the present work aims at proposing a methodology to find the more suitable PaT for a specific WDN, starting from the analysis of the pressure and flow rate patterns. The methodology is based on the selection of an existing machine from a pump catalogue. Then, knowing its geometrical information, it is possible to predict the characteristic curve of the pump operating as turbine by using a 1-D performance prediction model. The WDN of a town in the Apulia region (Southern Italy) has been used as a case study, in order to select a PaT useful for throttling energy recovery. Finally, a techno-economic evaluation has been carried out.

Research paper thumbnail of Convective Effects in a Latent Heat Thermal Energy Storage

Heat Transfer Engineering, 2019

Convection within a latent heat thermal energy storage (LHTES) shell-and-tube device filled with ... more Convection within a latent heat thermal energy storage (LHTES) shell-and-tube device filled with phase change material (PCM) has been studied by means of numerical simulations. Both, the heat transfer fluid and the PCM mass, momentum and energy equations are solved and coupled with a conjugate heat transfer model. The study highlights three specific zones within the PCM: the top convective-dominated part, the curvilinear solid-liquid interface, and the bottom conductive-dominated part. The PCM melts from the top to the bottom, therefore the main mechanism of melting appears to be confined in the top part of the solid PCM. However, the flow details reveal a convective cell that includes the whole melted PCM from the top to the bottom of the PCM enclosure. Even though the problem is widely studied by means of experiments and numerical simulations, here the convective flow has been studied quantitatively. During the melting phase the viscous and thermal boundary layers at the walls has been reported at different heights from the bottom of the device. Results show in detail the phenomenology of the melting process within a shelland-tube LHTES supporting the development of design solutions that could enhance the heat transfer of such device.

Research paper thumbnail of Implementation of a passive control system for limiting cavitation around hydrofoils

IOP Conference Series: Earth and Environmental Science, 2019

The performance and the durability of hydraulic systems can be significantly compromised by cavit... more The performance and the durability of hydraulic systems can be significantly compromised by cavitation. To the aim of delaying cavitation inside turbomachinery, a new passive cavitation control system is proposed in this work. The mentioned system has been applied to a NACA0009 hydrofoil, which accurately reproduces the flow field around real impeller blades. Basically, it consists of slots generating a connection between the suction and the pressure side of the foil. This connection results in a pressure rise close to the leading edge of the foil. Numerical simulations have been performed with the open-source CFD code OpenFOAM and the results have been compared to experimental data available in the literature. The simulations allow to investigate the flow field unsteadiness and the possible flow separation induced by the slots. The passive cavitation control system provides remarkable advantages, i.e., strong reduction of the vapour volume fraction (-93%) accompanied by a reasonable level of loss of performance (lift coefficient reduction equal to-25% and drag coefficient increase equal to +42%). This result is particularly interesting in consideration that the leading edge is only a small part of the entire vane of an impeller.

Research paper thumbnail of Experimental investigation of a Wells turbine under dynamic stall conditions for wave energy conversion

Renewable Energy, Jun 1, 2023

Research paper thumbnail of Experimental Investigation of a New 3d Printed Wells Turbine Under Dynamic Stall Conditions for Wave Energy Conversion

Social Science Research Network, 2022

Research paper thumbnail of Perspective of the role of hydrogen in the 21st century energy transition

Energy Conversion and Management, 2022

Research paper thumbnail of Distributed heat and power generation: thermoeconomic analysis of Biomass-fired Rankine cycle systems with molten salts as heat transfer fluid

Distributed cogeneration systems can be used to serve onsite energy demands in industrial and com... more Distributed cogeneration systems can be used to serve onsite energy demands in industrial and commercial buildings. In market segments with highly variable heat-demand patterns, the thermal plant is often composed of a boiler that is operated at part load in case of low thermal demands. To improve the plant flexibility and its overall energy efficiency, the biomass boiler can be coupled to a combined heat and power (CHP) generation system, as an alternative to a heat-only plant. In this work, three thermodynamic configurations are compared: (A) a biomass furnace that acts as a heat-source for a steam Rankine cycle (ST) plant coupled to an organic Rankine cycle (ORC) engine; (B) the same as Case A but without the bottoming ORC; and (C): the same as Case A but without the steam cycle. All configurations assume the cogeneration of heat and power to match onsite energy demands. The plant adopts a molten salt (MS) circuit to transfer heat from the biomass furnace to the power generation system. The energy analysis assumes a ternary MS mixture operating up to 450 °C and with minimum temperature of 200 °C. Two organic fluids (Pentafluoropropane R245fa and Toluene) are considered, based on the temperature of heat available to the ORC engine. In the combined cycle of Case A, R245fa is selected and the maximum cycle temperature is 130 °C, with a global electrical efficiency of 16.6%. In Case C, when only the ORC system is used with Toluene as the working fluid, the electrical efficiency is 18.8% at the higher turbine inlet temperature of 330 °C. Production of hot water for cogeneration at different temperature levels is also considered. Based on the results of the thermodynamic simulations, upfront and operational costs assessments, and feed-in tariffs for renewable electricity, energy efficiency and investment profitability are estimated

Research paper thumbnail of Thermoacoustic Combustion Stability Analysis of a Bluff Body-Stabilized Burner Fueled by Methane–Air and Hydrogen–Air Mixtures

Energies, Apr 6, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of 3D CFD analysis of Mixture Formation in Direct-Injection Hydrogen-fueled Internal Combustion Engines

Journal of physics, Dec 1, 2022

Research paper thumbnail of Numerical characterization of hydrogen under-expanded jets with a focus on Internal Combustion Engines applications

International Journal of Engine Research

In the context of reducing carbon dioxide ([Formula: see text]) emissions, hydrogen is gaining mo... more In the context of reducing carbon dioxide ([Formula: see text]) emissions, hydrogen is gaining momentum as a possible fuel for Internal Combustion Engines (ICEs). In-cylinder direct injections allow for a higher specific power density while enabling different levels of charge stratification. The high-pressure injection leads to the onset of under-expanded jets, characterized by complex patterns of shock waves and expansion fans. In ICEs simulations, such physics needs to be correctly solved to obtain a reliable assessment of the mixture formation. In this paper, the main features of hydrogen under-expanded jets are examined under the conditions typically found in turbocharged engines. Improved correlations are provided for the assessment of the Mach disk height and diameter, up to a Nozzle Pressure Ratio (NPR) equal to 60. The dependency of the hydrogen-air mixing on the cylinder temperature has been analyzed, and the unsteady jet dynamics has been examined by continuously varying t...

Research paper thumbnail of Numerical characterization of hydrogen under-expanded jets: influence of the nozzle cross-section shape

Journal of Physics: Conference Series

This historical moment is characterized by a great awareness regarding the need to reduce the Gre... more This historical moment is characterized by a great awareness regarding the need to reduce the Greenhouse Gas emissions (GHG), which are responsible for the climate change and its detrimental consequences. Green hydrogen produced by means of Power-to-Gas technologies from renewables is gaining momentum as a possible clean fuel for the future mobility. In such a context, traditional injectors for hydrocarbon fuels are currently being tailored to be used with hydrogen. The short time available for the injection process leads to the employment of a high inlet pressure, resulting in the formation of an under-expanded jet. In this work, the main characteristics of these jets are analyzed by means of Computational Fluid Dynamics (CFD) for a Nozzle Pressure Ratio (NPR) equal to 10. Then, to provide insights regarding the dependence of the air-hydrogen mixing on section shape of the nozzle, comparisons have been performed by changing the nozzle cross-section (circular, rectangular, and ellip...

Research paper thumbnail of Bypass Control strategy of a Pump as Turbine in a Water Distribution Network for energy recovery

Journal of Physics: Conference Series

Water Distribution Networks (WDNs) are subject to leakages due to pipes aging, resulting in water... more Water Distribution Networks (WDNs) are subject to leakages due to pipes aging, resulting in water and pressure losses. These issues are solved by installing Pressure Reduction Valves (PRVs) to decrease the pressure in WDNs. Depending on the application, PRVs can waste large amount of energy, hence the substitution of PRVs with Pumps used as Turbines (PaTs) can be a good compromise in terms of economic and technical aspects to reduce leakages and recover energy. Currently the share of PaT is not yet fully developed due to the certain technical challenges yet to be addressed, as providing an affordable control strategy closer to the real working conditions in a WDN. Hence, more experimental activities are required. For these reasons, in this work an experimental campaign was carried with the aim to investigate the behavior of a PaT according to a possible layout that could be embedded into a WDN. Firstly, the machine was characterized both in pump and turbine modes. Moreover, the mach...

Research paper thumbnail of Cost-Effective CFD Analysis of the Acoustic Response of a Perforated Plate

Volume 3B: Combustion, Fuels, and Emissions

Given the current practice to perform lean-premixed combustion to decrease NOx emissions, thermoa... more Given the current practice to perform lean-premixed combustion to decrease NOx emissions, thermoacoustic instabilities have become one of the major drawbacks in gas turbine combustors. The necessity to control and limit such a deleterious phenomenon is mandatory to avoid structural damage of the burner. It has been demonstrated that perforated liners, if conveniently designed, can be very effective in reducing acoustic oscillations inside gas turbine combustors. Studying perforated plates traversed by bias flow can give a useful insight on sound absorption properties of liners, rather than investigate complex geometries. The present paper aims to carry out a numerically cost-effective, but reliable, CFD analysis to predict the acoustic impedance of perforated plates traversed by bias flow, and to grasp the details of the sound dissipation process. 2D axisymmetric simulations have been carried out and the governing equations solved by using the commercial code ANSYS Fluent®. Hypothes...

Research paper thumbnail of CFD Modelling of OWC Devices for Wave Energy Harnessing

Ocean Wave Energy Systems, 2021

This book chapter is focused on how to study the fluid dynamic behavior of a Wave Energy Converte... more This book chapter is focused on how to study the fluid dynamic behavior of a Wave Energy Converter (WEC) of the Oscillating Water Column (OWC) type by means of Computational Fluid Dynamics (CFD). The U-OWC plant installed in the harbor of Civitavecchia (Italy) is chosen as the case study. The CFD approach is described referring to ANSYS Fluent, release 17.2. The model is mainly oriented to investigate the interaction of single harmonic waves with the OWC device and allows the user to perform a preliminary wave-to-wire energy conversion process analysis. To limit the computational cost, a 2D model is developed. The presence of the Power Takeoff (PTO) system generally breaks the 2D configuration of this kind of device, and here an approach to overcome this problem is described in detail. The solution is the introduction of a porous medium region in the 2D computational domain, which emulates the effect of the PTO system on the fluid dynamic behavior of the flow inside the WEC.

Research paper thumbnail of Pompe usate come turbine per il recupero energetico nelle reti di distribuzione idrica urbana

Research paper thumbnail of CSP/biomass hybrid externally fired gas turbines: thermo-economic assessment

Research paper thumbnail of Wind tunnel measurements for the characterization of a small scale monoplane Wells turbine

2018 IEEE International Workshop on Metrology for the Sea; Learning to Measure Sea Health Parameters (MetroSea), 2018

In the field of wave energy harnessing, Oscillating Water Column (OWC) devices are nowadays a con... more In the field of wave energy harnessing, Oscillating Water Column (OWC) devices are nowadays a consolidated technology. In OWC energy converters, waves generate an oscillating flow, whose energy can be effectively captured, for instance, by means of self-rectifying Wells turbines. In the design of Wells turbines, main issues are the improvement of their peak efficiency and the widening of their operational range. In order to reach these goals, a deep knowledge of the turbine fluid dynamic performance is essential. This paper presents the results of the experimental investigation of a small scale monoplane Wells turbine, tested in an open circuit low speed wind tunnel of the suction type in order to characterize its performance in terms of non-dimensional parameters, namely, torque and pressure drop coefficients and efficiency. The prototype under investigation, with blades of constant chord and NACA0015 profile, has been designed in order to be matched with a REWEC (Resonant Wave Energy Converter) breakwater, which had been located off the beach of Reggio Calabria. The REWEC under consideration was an excellent small scale model of full scale sea wave energy conversion devices for oceanic applications. Results have been compared with previous in-field tests, showing a very good agreement.

Research paper thumbnail of Selection, control and techno-economic feasibility of Pumps as Turbines in Water Distribution Networks

Renewable Energy, 2020

Water Distribution Networks (WDNs) are becoming an attractive area of application for small hydro... more Water Distribution Networks (WDNs) are becoming an attractive area of application for small hydropower, which can contribute to the development of distributed energy generation from renewable sources. Indeed, WDNs experience considerable water leakages due to their age and water management authorities often divide the WDNs by inserting Pressure Reducing Valves (PRVs), which waste a potentially recoverable hydraulic head. The replacement of PRVs with Pump as Turbines (PaTs) can be considered as an economically feasible solution to achieve both an effective pressure control and a throttling energy recovery. The selection, installation and control strategy of a PaT in a WDN must consider the variability of the pressure and the flow rate demand. Starting from the evaluation of the available head and the water demand, in this work, we describe a methodology to select from pump catalogues the most suitable PaT and the best control criteria for a specific WDN. Then, knowing the pump geometry, it is possible to predict the characteristic curve of the pump operating as a turbine by using a 1-D performance prediction model. The WDN of a town in the Apulia region (Southern Italy) has been used as a case study. Finally, a techno-economic evaluation has been carried out by considering both economic and environmental benefits.

Research paper thumbnail of Experimental characterization of the unsteady performance behavior of a Wells turbine operating at high flow rate coefficients

E3S Web of Conferences, 2020

Even if researchers are working on the exploitation of marine energy for more than thirty years, ... more Even if researchers are working on the exploitation of marine energy for more than thirty years, blue energy is not yet a consolidated reality and still contributes marginally to the world energy mix. For this reason, in the last years, the effort of the scientific community has been significantly intensified to further improve the know-how on marine energy harvesting. The goal is to allow ocean energy to effectively contribute to a more sustainable energy production in the next future. In the wide range of technologies for wave energy harvesting, Oscillating Water Column (OWC) devices are counted among of the most mature ones. Due to the oscillating nature of the generated air flow, which continuously inverts its direction, OWC devices need to be coupled with self-rectifying turbines, such as Wells, impulse, or biradial turbines. Wells turbines can reach high efficiencies, but their performance can show a hysteretic behaviour due to dynamic stall phenomena, especially in presence o...

Research paper thumbnail of Simplified prediction model of the discharging time of a shell-and-tube LHTES

Applied Thermal Engineering, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Research paper thumbnail of Pump as turbine for throttling energy recovery in water distribution networks

SECOND INTERNATIONAL CONFERENCE ON MATERIAL SCIENCE, SMART STRUCTURES AND APPLICATIONS: ICMSS-2019, 2019

Nowadays, a great effort is increasingly put by the scientific community into a more sustainable ... more Nowadays, a great effort is increasingly put by the scientific community into a more sustainable energy management, which requires a higher harvesting of renewable energy sources with respect to conventional ones. In the framework of distributed electricity production, Pumps as Turbines (PaTs), i.e. pumps operated in reverse mode, are becoming more and more tempting, being very cost effective with respect to customized hydro turbines. For instance, Water Distribution Networks (WDNs) are equipped by pressure relief valves (PRVs) in order to regulate flow rates and to reduce leakages. The replacement of PRVs with PaTs could be a feasible practice to achieve both an effective pressure control and a throttling energy recovery. The preliminary identification of specific speed of a pump to be used as a turbine is fundamental in order to find the best suitable solution. However, the insertion of a PaT must consider the variability of water demand and pressure patterns. The hydraulic variability in a water distribution network does not permit to define a unique operating point for a PaT and this aspect is a further obstacle for the functional planning of such a system. In this framework, the present work aims at proposing a methodology to find the more suitable PaT for a specific WDN, starting from the analysis of the pressure and flow rate patterns. The methodology is based on the selection of an existing machine from a pump catalogue. Then, knowing its geometrical information, it is possible to predict the characteristic curve of the pump operating as turbine by using a 1-D performance prediction model. The WDN of a town in the Apulia region (Southern Italy) has been used as a case study, in order to select a PaT useful for throttling energy recovery. Finally, a techno-economic evaluation has been carried out.

Research paper thumbnail of Convective Effects in a Latent Heat Thermal Energy Storage

Heat Transfer Engineering, 2019

Convection within a latent heat thermal energy storage (LHTES) shell-and-tube device filled with ... more Convection within a latent heat thermal energy storage (LHTES) shell-and-tube device filled with phase change material (PCM) has been studied by means of numerical simulations. Both, the heat transfer fluid and the PCM mass, momentum and energy equations are solved and coupled with a conjugate heat transfer model. The study highlights three specific zones within the PCM: the top convective-dominated part, the curvilinear solid-liquid interface, and the bottom conductive-dominated part. The PCM melts from the top to the bottom, therefore the main mechanism of melting appears to be confined in the top part of the solid PCM. However, the flow details reveal a convective cell that includes the whole melted PCM from the top to the bottom of the PCM enclosure. Even though the problem is widely studied by means of experiments and numerical simulations, here the convective flow has been studied quantitatively. During the melting phase the viscous and thermal boundary layers at the walls has been reported at different heights from the bottom of the device. Results show in detail the phenomenology of the melting process within a shelland-tube LHTES supporting the development of design solutions that could enhance the heat transfer of such device.

Research paper thumbnail of Implementation of a passive control system for limiting cavitation around hydrofoils

IOP Conference Series: Earth and Environmental Science, 2019

The performance and the durability of hydraulic systems can be significantly compromised by cavit... more The performance and the durability of hydraulic systems can be significantly compromised by cavitation. To the aim of delaying cavitation inside turbomachinery, a new passive cavitation control system is proposed in this work. The mentioned system has been applied to a NACA0009 hydrofoil, which accurately reproduces the flow field around real impeller blades. Basically, it consists of slots generating a connection between the suction and the pressure side of the foil. This connection results in a pressure rise close to the leading edge of the foil. Numerical simulations have been performed with the open-source CFD code OpenFOAM and the results have been compared to experimental data available in the literature. The simulations allow to investigate the flow field unsteadiness and the possible flow separation induced by the slots. The passive cavitation control system provides remarkable advantages, i.e., strong reduction of the vapour volume fraction (-93%) accompanied by a reasonable level of loss of performance (lift coefficient reduction equal to-25% and drag coefficient increase equal to +42%). This result is particularly interesting in consideration that the leading edge is only a small part of the entire vane of an impeller.