Salvatore Caltabellotta - Academia.edu (original) (raw)
Uploads
Papers by Salvatore Caltabellotta
Energies, 2021
As is widely known, internal combustion engines are not able to complete the expansion process of... more As is widely known, internal combustion engines are not able to complete the expansion process of the gas inside the cylinder, causing theoretical energy losses in the order of 20%. Several systems and methods have been proposed and implemented to recover the unexpanded gas energy, such as turbocharging, which partially exploits this energy to compress the fresh intake charge, or turbo-mechanical and turbo-electrical compounding, where the amount of unexpanded gas energy not used by the compressor is dedicated to propulsion or is transformed into electric energy. In all of these cases, however, maximum efficiency improvements between 4% and 9% have been achieved. In this work, the authors deal with an alternative propulsion system composed of a CNG-fueled spark ignition engine equipped with a turbine-generator specifically dedicated to unexpanded exhaust gas energy recovery and with a separated electrically driven turbocompressor. The system was conceived specifically for hybrid pro...
As is known, internal combustion engines based on Otto or Diesel cycles cannot complete the expan... more As is known, internal combustion engines based on Otto or Diesel cycles cannot complete the expansion process of the gas inside the cylinder, thus losing a relevant energy content, in the order of 30% of total. The residual energy of the unexpanded gas has been partially exploited through the use of an exhaust gas turbine for turbocharging the internal combustion engine; further attempts have been made with several compound solutions, with an electric generator connected to the turbocharger allowing to convert into electrical energy the quota power produced by the turbine which is not used by the compressor, or with a second turbine downstream the first to increase the exhaust gas energy recovery. Turbo-compound solutions were also employed in large marine Diesel engines, where the second turbine downstream the first was used to deliver more power to the main propeller shaft. In all these cases the overall efficiency increments remained within 5%. If completely recovered by the use of a properly designed expander-generator unit, the energy content of the unexpanded incylinder gas could substantially increase the overall efficiency of the thermal unit. In the present paper the authors evaluate, by means of simple yet effective calculations, the efficiency attainable by a thermal unit composed of a spark ignition engine endowed of an exhaust gas energy recovery expander connected to a proper generator. The proposed thermal unit, which is particularly suitable for hybrid propulsion solutions, has been evaluated both in the naturally aspirated and in the supercharged version. The efficiency of each thermal unit is also compared to reference baseline engine, thus highlighting the real benefit introduced by the adoption of the proposed thermal unit. As result, it was found that the complete and efficient recovery of the unexpanded gas energy has the potential to increase the overall efficiency of the propulsion system by 10-15%, depending on the characteristics of the thermal engine and of the exhaust energy expander-generator unit.
Journal of Engineering for Gas Turbines and Power, 2022
In-cylinder expansion of internal combustion engines based on Diesel or Otto cycles cannot be com... more In-cylinder expansion of internal combustion engines based on Diesel or Otto cycles cannot be completely brought down to ambient pressure, causing a 20% theoretical energy loss. Several systems have been implemented to recover and use this energy such as turbocharging, turbomechanical and turbo-electrical compounding, or the implementation of Miller cycles. In all these cases however, the amount of energy recovered is limited allowing the engine to reach an overall efficiency incremental improvement between 4% and 9%. Implementing an adequately designed expander–generator unit could efficiently recover the unexpanded exhaust gas energy and improve efficiency. In this work, the application of the expander–generator unit to a hybrid propulsion vehicle is considered, where the onboard energy storage receives power produced by an expander–generator, which could hence be employed for vehicle propulsion through an electric drivetrain. Starting from these considerations, a simple but effec...
Sustainability
Global warming (GW) and urban pollution focused a great interest on hybrid electric vehicles (HEV... more Global warming (GW) and urban pollution focused a great interest on hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs) as cleaner alternatives to traditional internal combustion engine vehicles (ICEVs). The environmental impact related to the use of both ICEV and HEV mainly depends on the fossil fuel used by the thermal engines, while, in the case of the BEV, depends on the energy sources employed to produce electricity. Moreover, the production phase of each vehicle may also have a relevant environmental impact, due to the manufacturing processes and the materials employed. Starting from these considerations, the authors carried out a fair comparison of the environmental impact generated by three different vehicles characterized by different propulsion technology, i.e., an ICEV, an HEV, and a BEV, following the life cycle analysis methodology, i.e., taking into account five different environmental impact categories generated during all phases of the entire life of...
Energies, 2021
As is widely known, internal combustion engines are not able to complete the expansion process of... more As is widely known, internal combustion engines are not able to complete the expansion process of the gas inside the cylinder, causing theoretical energy losses in the order of 20%. Several systems and methods have been proposed and implemented to recover the unexpanded gas energy, such as turbocharging, which partially exploits this energy to compress the fresh intake charge, or turbo-mechanical and turbo-electrical compounding, where the amount of unexpanded gas energy not used by the compressor is dedicated to propulsion or is transformed into electric energy. In all of these cases, however, maximum efficiency improvements between 4% and 9% have been achieved. In this work, the authors deal with an alternative propulsion system composed of a CNG-fueled spark ignition engine equipped with a turbine-generator specifically dedicated to unexpanded exhaust gas energy recovery and with a separated electrically driven turbocompressor. The system was conceived specifically for hybrid pro...
As is known, internal combustion engines based on Otto or Diesel cycles cannot complete the expan... more As is known, internal combustion engines based on Otto or Diesel cycles cannot complete the expansion process of the gas inside the cylinder, thus losing a relevant energy content, in the order of 30% of total. The residual energy of the unexpanded gas has been partially exploited through the use of an exhaust gas turbine for turbocharging the internal combustion engine; further attempts have been made with several compound solutions, with an electric generator connected to the turbocharger allowing to convert into electrical energy the quota power produced by the turbine which is not used by the compressor, or with a second turbine downstream the first to increase the exhaust gas energy recovery. Turbo-compound solutions were also employed in large marine Diesel engines, where the second turbine downstream the first was used to deliver more power to the main propeller shaft. In all these cases the overall efficiency increments remained within 5%. If completely recovered by the use of a properly designed expander-generator unit, the energy content of the unexpanded incylinder gas could substantially increase the overall efficiency of the thermal unit. In the present paper the authors evaluate, by means of simple yet effective calculations, the efficiency attainable by a thermal unit composed of a spark ignition engine endowed of an exhaust gas energy recovery expander connected to a proper generator. The proposed thermal unit, which is particularly suitable for hybrid propulsion solutions, has been evaluated both in the naturally aspirated and in the supercharged version. The efficiency of each thermal unit is also compared to reference baseline engine, thus highlighting the real benefit introduced by the adoption of the proposed thermal unit. As result, it was found that the complete and efficient recovery of the unexpanded gas energy has the potential to increase the overall efficiency of the propulsion system by 10-15%, depending on the characteristics of the thermal engine and of the exhaust energy expander-generator unit.
Journal of Engineering for Gas Turbines and Power, 2022
In-cylinder expansion of internal combustion engines based on Diesel or Otto cycles cannot be com... more In-cylinder expansion of internal combustion engines based on Diesel or Otto cycles cannot be completely brought down to ambient pressure, causing a 20% theoretical energy loss. Several systems have been implemented to recover and use this energy such as turbocharging, turbomechanical and turbo-electrical compounding, or the implementation of Miller cycles. In all these cases however, the amount of energy recovered is limited allowing the engine to reach an overall efficiency incremental improvement between 4% and 9%. Implementing an adequately designed expander–generator unit could efficiently recover the unexpanded exhaust gas energy and improve efficiency. In this work, the application of the expander–generator unit to a hybrid propulsion vehicle is considered, where the onboard energy storage receives power produced by an expander–generator, which could hence be employed for vehicle propulsion through an electric drivetrain. Starting from these considerations, a simple but effec...
Sustainability
Global warming (GW) and urban pollution focused a great interest on hybrid electric vehicles (HEV... more Global warming (GW) and urban pollution focused a great interest on hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs) as cleaner alternatives to traditional internal combustion engine vehicles (ICEVs). The environmental impact related to the use of both ICEV and HEV mainly depends on the fossil fuel used by the thermal engines, while, in the case of the BEV, depends on the energy sources employed to produce electricity. Moreover, the production phase of each vehicle may also have a relevant environmental impact, due to the manufacturing processes and the materials employed. Starting from these considerations, the authors carried out a fair comparison of the environmental impact generated by three different vehicles characterized by different propulsion technology, i.e., an ICEV, an HEV, and a BEV, following the life cycle analysis methodology, i.e., taking into account five different environmental impact categories generated during all phases of the entire life of...