REVUE ROUMAINE DES SCIENCES TECHNIQUES — SÉRIE ÉLECTROTECHNIQUE ET ÉNERGÉTIQUE
The paper presents the vibration spectra of a twin-screw compressor driven at various functioning... more The paper presents the vibration spectra of a twin-screw compressor driven at various functioning regimes. The tests are performed to assess the potential of this rotary bladed machine as energy harvesting source. It is sought to determine the optimum spots on the compressor skid where piezoelectric harvesters can be placed, meeting the operational conditions. Like most of the industrial machinery, compressors exhibit inherent vibrations and heating during operation. The pulsatory effects of the compressed air trapped between the compressor’s male and female rotors inside the compressor also give birth to harmonics. It is important to evaluate the temperatures as well since piezoelectric harvesters should preferably operate close to room temperature so as not to deteriorate the material and avoid thermal hysteresis, which can ultimately lead to the loss of piezoelectric properties. The study herein involves acquiring vibrational data and representing it graphically as vibration spec...
ACTUALITĂŢI ŞI PERSPECTIVE ÎN DOMENIUL MAŞINILOR ELECTRICE (ELECTRIC MACHINES, MATERIALS AND DRIVES - PRESENT AND TRENDS), 2021
The paper presents the vibrational behaviour of a twin-screw compressor at various functioning re... more The paper presents the vibrational behaviour of a twin-screw compressor at various functioning regimes. The speed is varied by means of a 250 kW electric driving motor, via a frequency converter. The compressor can supply pressurized air up to ~16 bar into a buffer tank. The air is used for testing various equipment on test bench, such as expanders, pneumatic starters for gas turbine engines, or other compressors and blowers used for compressing air starting from a pressure higher than the atmospheric pressure. Like all other industrial equipment, compressors experience inherent vibrations in operation. The pulsatory effects of the air within the compressor also give birth to harmonics. The study herein involves gathering vibration data and represent it as vibration spectra. Raw vibration signals, employed for assessing the condition of the machinery, may not always be clear in the frequency spectrum for vibration analysis, thus being required to apply Fast Fourier Transform for con...
"ACTUALITĂŢI ŞI PERSPECTIVE ÎN DOMENIUL MAŞINILOR ELECTRICE (ELECTRIC MACHINES, MATERIALS AND DRIVES - PRESENT AND TRENDS)", 2021
The paper presents the functioning regimes of a 132 kW asynchronous three-phase machine, used for... more The paper presents the functioning regimes of a 132 kW asynchronous three-phase machine, used for the expander-generator system in a compressed air energy storage facility. The installation consists of a 110 kW twin-screw electro-compressor, which supplies pressurized air up to ~16 bar into a 50 cubic meters storage vessel. The compressed air is afterwards released from the reservoir into expander’s inlet, spinning its shaft. When the expander’s shaft spins the electric machine over its synchronous speed, this one enters in generator mode, supplying electric power into the grid. Two power analysers installed on the automation control cabinet monitor the generated/absorbed power and the power supplied/consumed by the system from the grid. Using the data acquired by means of PLC during commissioning tests, we plotted the power curves, differential pressure and significant temperatures, as well as the electric machine’s speed.
In order to increase the research capabilities in the field of lowweight intelligent materials an... more In order to increase the research capabilities in the field of lowweight intelligent materials and high structural performance, and also to increase energy efficiency, a study was conducted on improving the operating time of a hot air autoclave compressor with a buffer tank. The booster screw electro-compressor of 200 kW is designed to compress technological air to the installation’s necessary parameters at 1 ppm air purity, and the pressurized buffer tank is designed to reduce the number of start-ups of the compressor unit and its motor, in order to increase its lifespan. The pressure can vary in the designed buffer tank from 7 to 26 bar (abs). The autoclave parameters record thermodynamic modifications as it heats up to 400 °C at the working pressure. Cool air is required during the cooling process. The air mass exchanged during operation for cooling down to atmospheric temperature was calculated. The data obtained was used for validating an optimally designed buffer tank within t...
Compressed Air Energy Storage (CAES) installations are used for storing electrical power, under t... more Compressed Air Energy Storage (CAES) installations are used for storing electrical power, under the form of potential energy from compressed air. The heat generated during compression can be stored to improve the efficiency of compression-expansion cycle. The solution presented consists of a 100 kW screw compressor driven by a 110 kW asynchronous three-phase motor. The compressor supplies air into vessels which store it until a high electrical energy demand arises. At that time, the compressed air is released into a 132 kW screw expander whose shaft spins a 132 kW asynchronous generator, producing electric power and supplying it into the electrical grid. Before expansion, the air must be preheated in order to avoid the freezing of expansion equipment. If the heat generated during compression is used for air preheating before expansion, the process is adiabatic. A demonstrative model of the installation is currently being developed, with the expander part being completed so far. The ...
During compression, a gas heats up, almost in all cases this heat being wasted, either by cooling... more During compression, a gas heats up, almost in all cases this heat being wasted, either by cooling the gas because it is too hot for the application, or by storing the gas and letting the compressed gas cool naturally in the storage tank. This paper presents a waste-energy (heat) recovery system from the gases compressed by an oil-free screw compressor. The gases compressed by this compressor have a very high temperature compared to an oil injected screw compressor, due to the fact that the oil used to lubricate the rotors also acts as a heat sink, the oil free variant which is used when you want a very high purity of the gas, has higher tolerances and more friction between the rotors which result in a higher gas temperature. The recovery system uses a heat exchanger to extract the waste energy from the gas and at the same time it will cool it for immediate use. Depending on the requirements, the energy recovered may be used immediately to produce useful work or stored for a later us...
Using electric energy in a potentially explosive atmosphere raises several problems that must be ... more Using electric energy in a potentially explosive atmosphere raises several problems that must be solved when designing, manufacturing and during the operation of electric equipment. Their approach requires special attention, considering the multiple technical, economical and labour safety aspects. The ingress protection for the electrical part of the valves is ensured by the capsulation assembly, comprising the protection measures applied for preventing the ignition of the surrounding atmosphere. The labyrinth seal through which the gas flow passes is designed so as to confine a potential ignition inside actuator’s flameproof enclosure. Numerical simulations were conducted for determining the combustion behaviour and the optimum width and geometry of the labyrinth canals.
2021 International Conference on Applied and Theoretical Electricity (ICATE), 2021
Nowadays, automation systems for naval propulsion groups with gas turbines use programmable logic... more Nowadays, automation systems for naval propulsion groups with gas turbines use programmable logic controllers for a precise and reliable control. The automation system is designed so as to be able to connect using signal cables to the transducers monitoring the engine’s parameters, via adapters, so that the command and regulation functions to be fully automatized. These signals are managed by means of the software program implemented in the PLC, and subsequent data acquisition. One of the important problems is the available resource of the propulsion group, until capital repair is required. The remaining lifetime depends on the operating regimes of the gas turbine engine. This problem is more pronounced in the propulsion groups equipping navy ships, where the dynamic regimes of gas turbine engines are much more demanding, and hence the pre-established operating limits may be exceeded. The automation configuration presented herein ensures the accurate computation and precise control of essential parameters for which the direct measurement is not possible using transducers. These parameters are the exhaust gas temperature, the power developed by the engine and implicitly the torque developed at propeller shaft.
The oil free compressors were specially designed for air compression. The National Research and D... more The oil free compressors were specially designed for air compression. The National Research and Development Institute for Gas Turbines COMOTI gained a great deal of experience in producing/designing certified oil injection screw compressors for the natural gas field and for several years it has been focusing its research on the use of “dry” (oil-free) compressors in natural gas compression and more recently in hydrogen compression. Working with an explosive gas, one of an idea was to use a nitrogen barrier in oil bearing sealing, which are open source of gases in the atmosphere for such compressors. Worldwide, on-site nitrogen generators have been developed for a purity range of 95…99.5%, and that nitrogen can be supplied in any environment conditions. The present paper will address nitrogen flow with low percentage of oxygen for bearing sealing at the working pressure, the nitrogen consumption, ideas for H2 re-injection and the influence over the global efficiency of the process. D...
Evaluating the possibility to store CO2 in salt mines is made complex because of the lack of nece... more Evaluating the possibility to store CO2 in salt mines is made complex because of the lack of necessary data and different mechanisms that act on different time scales. This analysis can be made using traditional methods of geographical survey, lab experiments and digital simulations. Storing of CO2 needs to be done in a stable geological area. The cavity must be thoroughly analysed for dimensions, depth, permeability and porosity. Based on studies made by the University of Petroşani some areas subject to collapse have been monitored using topography and sonic measurements with the aim to understand their possible evolution. Monitoring caverns and underground cavities is done using sonar. The sonar is a good instrument to manage a cavern, it increases its safety while it is being exploited and offers important data for the geomechanics model. CavInfo software package has been specially created to analyse and show individual caverns or systems of caverns. CavView II software allows fo...
Worldwide there is an increasing trend for the study and use of new sources of renewable energy. ... more Worldwide there is an increasing trend for the study and use of new sources of renewable energy. Municipal solid wastes are becoming increasingly used as an energy source in waste-to-energy projects. Anaerobic digestion (AD) is a mature technology for energy production by converting organic fraction of municipal solid waste (OFMSW) into biogas. For this purpose, there were approached fundamental aspects of AD, the types of digesters and the performance of anaerobic treatment systems of OFMSW in order to propose the most suitable technology for an experimental pilot plant with the aim of optimizing the production of biogas. Thus, from the analysis of studies conducted it resulted that the dry AD technology in on one stage is best suited to the anaerobic treatment of OFMSW. This paper also makes an overview of the pilot plant intended for the analysis of various parameters such as process temperature, pH, organic load and the production of biogas.
REVUE ROUMAINE DES SCIENCES TECHNIQUES — SÉRIE ÉLECTROTECHNIQUE ET ÉNERGÉTIQUE
The paper presents the vibration spectra of a twin-screw compressor driven at various functioning... more The paper presents the vibration spectra of a twin-screw compressor driven at various functioning regimes. The tests are performed to assess the potential of this rotary bladed machine as energy harvesting source. It is sought to determine the optimum spots on the compressor skid where piezoelectric harvesters can be placed, meeting the operational conditions. Like most of the industrial machinery, compressors exhibit inherent vibrations and heating during operation. The pulsatory effects of the compressed air trapped between the compressor’s male and female rotors inside the compressor also give birth to harmonics. It is important to evaluate the temperatures as well since piezoelectric harvesters should preferably operate close to room temperature so as not to deteriorate the material and avoid thermal hysteresis, which can ultimately lead to the loss of piezoelectric properties. The study herein involves acquiring vibrational data and representing it graphically as vibration spec...
ACTUALITĂŢI ŞI PERSPECTIVE ÎN DOMENIUL MAŞINILOR ELECTRICE (ELECTRIC MACHINES, MATERIALS AND DRIVES - PRESENT AND TRENDS), 2021
The paper presents the vibrational behaviour of a twin-screw compressor at various functioning re... more The paper presents the vibrational behaviour of a twin-screw compressor at various functioning regimes. The speed is varied by means of a 250 kW electric driving motor, via a frequency converter. The compressor can supply pressurized air up to ~16 bar into a buffer tank. The air is used for testing various equipment on test bench, such as expanders, pneumatic starters for gas turbine engines, or other compressors and blowers used for compressing air starting from a pressure higher than the atmospheric pressure. Like all other industrial equipment, compressors experience inherent vibrations in operation. The pulsatory effects of the air within the compressor also give birth to harmonics. The study herein involves gathering vibration data and represent it as vibration spectra. Raw vibration signals, employed for assessing the condition of the machinery, may not always be clear in the frequency spectrum for vibration analysis, thus being required to apply Fast Fourier Transform for con...
"ACTUALITĂŢI ŞI PERSPECTIVE ÎN DOMENIUL MAŞINILOR ELECTRICE (ELECTRIC MACHINES, MATERIALS AND DRIVES - PRESENT AND TRENDS)", 2021
The paper presents the functioning regimes of a 132 kW asynchronous three-phase machine, used for... more The paper presents the functioning regimes of a 132 kW asynchronous three-phase machine, used for the expander-generator system in a compressed air energy storage facility. The installation consists of a 110 kW twin-screw electro-compressor, which supplies pressurized air up to ~16 bar into a 50 cubic meters storage vessel. The compressed air is afterwards released from the reservoir into expander’s inlet, spinning its shaft. When the expander’s shaft spins the electric machine over its synchronous speed, this one enters in generator mode, supplying electric power into the grid. Two power analysers installed on the automation control cabinet monitor the generated/absorbed power and the power supplied/consumed by the system from the grid. Using the data acquired by means of PLC during commissioning tests, we plotted the power curves, differential pressure and significant temperatures, as well as the electric machine’s speed.
In order to increase the research capabilities in the field of lowweight intelligent materials an... more In order to increase the research capabilities in the field of lowweight intelligent materials and high structural performance, and also to increase energy efficiency, a study was conducted on improving the operating time of a hot air autoclave compressor with a buffer tank. The booster screw electro-compressor of 200 kW is designed to compress technological air to the installation’s necessary parameters at 1 ppm air purity, and the pressurized buffer tank is designed to reduce the number of start-ups of the compressor unit and its motor, in order to increase its lifespan. The pressure can vary in the designed buffer tank from 7 to 26 bar (abs). The autoclave parameters record thermodynamic modifications as it heats up to 400 °C at the working pressure. Cool air is required during the cooling process. The air mass exchanged during operation for cooling down to atmospheric temperature was calculated. The data obtained was used for validating an optimally designed buffer tank within t...
Compressed Air Energy Storage (CAES) installations are used for storing electrical power, under t... more Compressed Air Energy Storage (CAES) installations are used for storing electrical power, under the form of potential energy from compressed air. The heat generated during compression can be stored to improve the efficiency of compression-expansion cycle. The solution presented consists of a 100 kW screw compressor driven by a 110 kW asynchronous three-phase motor. The compressor supplies air into vessels which store it until a high electrical energy demand arises. At that time, the compressed air is released into a 132 kW screw expander whose shaft spins a 132 kW asynchronous generator, producing electric power and supplying it into the electrical grid. Before expansion, the air must be preheated in order to avoid the freezing of expansion equipment. If the heat generated during compression is used for air preheating before expansion, the process is adiabatic. A demonstrative model of the installation is currently being developed, with the expander part being completed so far. The ...
During compression, a gas heats up, almost in all cases this heat being wasted, either by cooling... more During compression, a gas heats up, almost in all cases this heat being wasted, either by cooling the gas because it is too hot for the application, or by storing the gas and letting the compressed gas cool naturally in the storage tank. This paper presents a waste-energy (heat) recovery system from the gases compressed by an oil-free screw compressor. The gases compressed by this compressor have a very high temperature compared to an oil injected screw compressor, due to the fact that the oil used to lubricate the rotors also acts as a heat sink, the oil free variant which is used when you want a very high purity of the gas, has higher tolerances and more friction between the rotors which result in a higher gas temperature. The recovery system uses a heat exchanger to extract the waste energy from the gas and at the same time it will cool it for immediate use. Depending on the requirements, the energy recovered may be used immediately to produce useful work or stored for a later us...
Using electric energy in a potentially explosive atmosphere raises several problems that must be ... more Using electric energy in a potentially explosive atmosphere raises several problems that must be solved when designing, manufacturing and during the operation of electric equipment. Their approach requires special attention, considering the multiple technical, economical and labour safety aspects. The ingress protection for the electrical part of the valves is ensured by the capsulation assembly, comprising the protection measures applied for preventing the ignition of the surrounding atmosphere. The labyrinth seal through which the gas flow passes is designed so as to confine a potential ignition inside actuator’s flameproof enclosure. Numerical simulations were conducted for determining the combustion behaviour and the optimum width and geometry of the labyrinth canals.
2021 International Conference on Applied and Theoretical Electricity (ICATE), 2021
Nowadays, automation systems for naval propulsion groups with gas turbines use programmable logic... more Nowadays, automation systems for naval propulsion groups with gas turbines use programmable logic controllers for a precise and reliable control. The automation system is designed so as to be able to connect using signal cables to the transducers monitoring the engine’s parameters, via adapters, so that the command and regulation functions to be fully automatized. These signals are managed by means of the software program implemented in the PLC, and subsequent data acquisition. One of the important problems is the available resource of the propulsion group, until capital repair is required. The remaining lifetime depends on the operating regimes of the gas turbine engine. This problem is more pronounced in the propulsion groups equipping navy ships, where the dynamic regimes of gas turbine engines are much more demanding, and hence the pre-established operating limits may be exceeded. The automation configuration presented herein ensures the accurate computation and precise control of essential parameters for which the direct measurement is not possible using transducers. These parameters are the exhaust gas temperature, the power developed by the engine and implicitly the torque developed at propeller shaft.
The oil free compressors were specially designed for air compression. The National Research and D... more The oil free compressors were specially designed for air compression. The National Research and Development Institute for Gas Turbines COMOTI gained a great deal of experience in producing/designing certified oil injection screw compressors for the natural gas field and for several years it has been focusing its research on the use of “dry” (oil-free) compressors in natural gas compression and more recently in hydrogen compression. Working with an explosive gas, one of an idea was to use a nitrogen barrier in oil bearing sealing, which are open source of gases in the atmosphere for such compressors. Worldwide, on-site nitrogen generators have been developed for a purity range of 95…99.5%, and that nitrogen can be supplied in any environment conditions. The present paper will address nitrogen flow with low percentage of oxygen for bearing sealing at the working pressure, the nitrogen consumption, ideas for H2 re-injection and the influence over the global efficiency of the process. D...
Evaluating the possibility to store CO2 in salt mines is made complex because of the lack of nece... more Evaluating the possibility to store CO2 in salt mines is made complex because of the lack of necessary data and different mechanisms that act on different time scales. This analysis can be made using traditional methods of geographical survey, lab experiments and digital simulations. Storing of CO2 needs to be done in a stable geological area. The cavity must be thoroughly analysed for dimensions, depth, permeability and porosity. Based on studies made by the University of Petroşani some areas subject to collapse have been monitored using topography and sonic measurements with the aim to understand their possible evolution. Monitoring caverns and underground cavities is done using sonar. The sonar is a good instrument to manage a cavern, it increases its safety while it is being exploited and offers important data for the geomechanics model. CavInfo software package has been specially created to analyse and show individual caverns or systems of caverns. CavView II software allows fo...
Worldwide there is an increasing trend for the study and use of new sources of renewable energy. ... more Worldwide there is an increasing trend for the study and use of new sources of renewable energy. Municipal solid wastes are becoming increasingly used as an energy source in waste-to-energy projects. Anaerobic digestion (AD) is a mature technology for energy production by converting organic fraction of municipal solid waste (OFMSW) into biogas. For this purpose, there were approached fundamental aspects of AD, the types of digesters and the performance of anaerobic treatment systems of OFMSW in order to propose the most suitable technology for an experimental pilot plant with the aim of optimizing the production of biogas. Thus, from the analysis of studies conducted it resulted that the dry AD technology in on one stage is best suited to the anaerobic treatment of OFMSW. This paper also makes an overview of the pilot plant intended for the analysis of various parameters such as process temperature, pH, organic load and the production of biogas.
Uploads