The Experts below are selected from a list of 138 Experts worldwide ranked by ideXlab platform
Craig Turchi - One of the best experts on this subject based on the ideXlab platform.
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a comparison of supercritical carbon dioxide power Cycle configurations with an emphasis on csp applications
Energy Procedia, 2014Co-Authors: Ty Neises, Craig TurchiAbstract:Recent research suggests that an emerging power Cycle technology using supercritical carbon dioxide (s-CO2) operated in a Closed-Loop Brayton Cycle offers the potential of equivalent or higher Cycle efficiency versus supercritical or superheated steam Cycles at temperatures relevant for CSP applications. Preliminary design-point modeling suggests that s-CO2 Cycle configurations can be devised that have similar overall efficiency but different temperature and/or pressure characteristics. This paper employs a more detailed heat exchanger model than previous work to compare the recompression and partial cooling Cycles, two Cycles with high design-point efficiencies, and illustrates the potential advantages of the latter. Integration of the Cycles into CSP systems is studied, with a focus on sensible heat thermal storage and direct s-CO2 receivers. Results show the partial cooling Cycle may offer a larger temperature difference across the primary heat exchanger, thereby potentially reducing heat exchanger cost and improving CSP receiver efficiency.
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Thermodynamic Study of Advanced Supercritical Carbon Dioxide Power Cycles for Concentrating Solar Power Systems
Journal of Solar Energy Engineering, 2013Co-Authors: Craig Turchi, Ty Neises, Michael J. WagnerAbstract:Supercritical CO2 (s-CO2) operated in a Closed-Loop Brayton Cycle offers the potential of higher Cycle efficiency versus superheated or supercritical steam Cycles at temperatures relevant for concentrating solar power (CSP) applications. Brayton-Cycle systems using s-CO2 have a smaller weight and volume, lower thermal mass, and less complex power blocks versus Rankine Cycles due to the higher density of the fluid and simpler Cycle design. The simpler machinery and compact size of the s-CO2 process may also reduce the installation, maintenance, and operation cost of the system. In this work we explore s-CO2 Brayton Cycle configurations that have attributes that are desirable from the perspective of a CSP application, such as the ability to accommodate dry cooling and achieve greater than 50% efficiency, as specified for the U.S. Department of Energy SunShot goal. Recompression Cycles combined with intercooling and/or turbine reheat appear able to hit this efficiency target, even when combined with dry cooling. In addition, the intercooled Cycles expand the temperature differential across the primary heat exchanger, which is favorable for CSP systems featuring sensible-heat thermal energy storage.
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thermodynamic study of advanced supercritical carbon dioxide power Cycles for high performance concentrating solar power systems
International Conference on Fuel Cell Science Engineering and Technology FUELCELL Collocated with ASME International Conference on Energy Sustainabili, 2012Co-Authors: Craig Turchi, Ty Neises, Michael J. WagnerAbstract:In 2011, the U.S. Department of Energy (DOE) initiated a “SunShot Concentrating Solar Power R&D” program to develop technologies that have the potential for much higher efficiency, lower cost, and/or more reliable performance than existing CSP systems. The DOE seeks to develop highly disruptive Concentrating Solar Power (CSP) technologies that will meet 6¢/kWh cost targets by the end of the decade, and a high-efficiency, low-cost thermal power Cycle is one of the important components to achieve the goal. Supercritical CO2 (s-CO2) operated in a Closed-Loop Brayton Cycle offers the potential of equivalent or higher Cycle efficiency versus superheated or supercritical steam Cycles at temperatures relevant for CSP applications. Brayton-Cycle systems using s-CO2 have a smaller weight and volume, lower thermal mass, and less complex power blocks versus Rankine Cycles due to the higher density of the fluid and simpler Cycle design. The simpler machinery and compact size of the s-CO2 process may also reduce the installation, maintenance and operation cost of the system.Copyright © 2012 by ASME
Steven A. Wright - One of the best experts on this subject based on the ideXlab platform.
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Non-Nuclear Validation Test Results of a Closed Brayton Cycle Test-Loop
AIP Conference Proceedings, 2007Co-Authors: Steven A. WrightAbstract:Both NASA and DOE have programs that are investigating advanced power conversion Cycles for planetary surface power on the moon or Mars, or for next generation nuclear power plants on earth. Although open Brayton Cycles are in use for many applications (combined Cycle power plants, aircraft engines), only a few closed Brayton Cycles have been tested. Experience with closed Brayton Cycles coupled to nuclear reactors is even more limited and current projections of Brayton Cycle performance are based on analytic models. This report describes and compares experimental results with model predictions from a series of non‐nuclear tests using a small scale closed loop Brayton Cycle available at Sandia National Laboratories. A substantial amount of testing has been performed, and the information is being used to help validate models. In this report we summarize the results from three kinds of tests. These tests include: 1) test results that are useful for validating the characteristic flow curves of the turbomachinery for various gases ranging from ideal gases (Ar or Ar/He) to non‐ideal gases such as CO2, 2) test results that represent shut down transients and decay heat removal capability of Brayton loops after reactor shut down, and 3) tests that map a range of operating power versus shaft speed curve and turbine inlet temperature that are useful for predicting stable operating conditions during both normal and off‐normal operating behavior. These tests reveal significant interactions between the reactor and balance of plant. Specifically these results predict limited speed up behavior of the turbomachinery caused by loss of load, the conditions for stable operation, and for direct cooled reactors, the tests reveal that the coast down behavior during loss of power events can extend for hours provided the ultimate heat sink remains available.
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Non-Nuclear Validation Test Results of a Closed Brayton Cycle Test-Loop
AIP Conference Proceedings, 2007Co-Authors: Steven A. WrightAbstract:Both NASA and DOE have programs that are investigating advanced power conversion Cycles for planetary surface power on the moon or Mars, or for next generation nuclear power plants on earth. Although open Brayton Cycles are in use for many applications (combined Cycle power plants, aircraft engines), only a few closed Brayton Cycles have been tested. Experience with closed Brayton Cycles coupled to nuclear reactors is even more limited and current projections of Brayton Cycle performance are based on analytic models. This report describes and compares experimental results with model predictions from a series of non‐nuclear tests using a small scale closed loop Brayton Cycle available at Sandia National Laboratories. A substantial amount of testing has been performed, and the information is being used to help validate models. In this report we summarize the results from three kinds of tests. These tests include: 1) test results that are useful for validating the characteristic flow curves of the turbomachinery for various gases ranging from ideal gases (Ar or Ar/He) to non‐ideal gases such as CO2, 2) test results that represent shut down transients and decay heat removal capability of Brayton loops after reactor shut down, and 3) tests that map a range of operating power versus shaft speed curve and turbine inlet temperature that are useful for predicting stable operating conditions during both normal and off‐normal operating behavior. These tests reveal significant interactions between the reactor and balance of plant. Specifically these results predict limited speed up behavior of the turbomachinery caused by loss of load, the conditions for stable operation, and for direct cooled reactors, the tests reveal that the coast down behavior during loss of power events can extend for hours provided the ultimate heat sink remains available.Both NASA and DOE have programs that are investigating advanced power conversion Cycles for planetary surface power on the moon or Mars, or for next generation nuclear power plants on earth. Although open Brayton Cycles are in use for many applications (combined Cycle power plants, aircraft engines), only a few closed Brayton Cycles have been tested. Experience with closed Brayton Cycles coupled to nuclear reactors is even more limited and current projections of Brayton Cycle performance are based on analytic models. This report describes and compares experimental results with model predictions from a series of non‐nuclear tests using a small scale closed loop Brayton Cycle available at Sandia National Laboratories. A substantial amount of testing has been performed, and the information is being used to help validate models. In this report we summarize the results from three kinds of tests. These tests include: 1) test results that are useful for validating the characteristic flow curves of the turbomachi...
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operational results of a closed Brayton Cycle test loop
SPACE TECHNOLOGY AND APPLICATIONS INT.FORUM-STAIF 2005: Conf.Thermophys in#N#Micrograv;Conf Comm Civil Next Gen.Space Transp; 22nd Symp Space Nucl.Pow, 2005Co-Authors: Steven A. Wright, Robert Fuller, Ronald J Lipinski, Kenneth Nichols, Nicholas R BrownAbstract:A number of space and terrestrial power system designs plan to use nuclear reactors that are coupled to Closed‐loop Brayton Cycle (CBC) systems to generate electrical power. Because very little experience exists regarding the operational behavior of these systems, Sandia National Laboratories (through its Laboratory Directed Research and Development program) is developing a closed‐loop test bed that can be used to determine the operational behavior of these systems and to validate models for these systems. Sandia has contracted Barber‐Nichols Corporation to design, fabricate, and assemble a Closed‐loop Brayton Cycle (CBC) system. This system was developed by modifying commercially available hardware. It uses a 30 kWe Capstone C‐30 gas‐turbine unit (www.capstoneturbine.com) with a modified housing that permits the attachment of an electrical heater and a water cooled chiller that are connected to the turbo‐machinery in a closed loop. The test‐loop reuses the Capstone turbine, compressor, and alternator. The Capstone system’s nominal operating point is 1150 K turbine inlet temperature at 96,000 rpm. The annular recuperator and portions of the Capstone control system (inverter) and starter system are also reused. The rotational speed of the turbo‐machinery is controlled either by adjusting the alternator load by either using the electrical grid or a separate load bank. This report describes the test‐loop hardware SBL‐30 (Sandia Brayton Loop‐30kWe). Also presented are results of early testing and modeling of the unit. The SBL‐30 hardware is currently configured with a heater that is limited to 80 kWth with a maximum outlet temperature of ∼1000 K.
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dynamic modeling and control of nuclear reactors coupled to closed loop Brayton Cycle systems using simulink
SPACE TECHNOLOGY AND APPLICATIONS INT.FORUM-STAIF 2005: Conf.Thermophys in#N#Micrograv;Conf Comm Civil Next Gen.Space Transp; 22nd Symp Space Nucl.Pow, 2005Co-Authors: Steven A. Wright, Travis SanchezAbstract:The operation of space reactors for both in‐space and planetary operations will require unprecedented levels of autonomy and control. Development of these autonomous control systems will require dynamic system models, effective control methodologies, and autonomous control logic. This paper briefly describes the results of reactor, power‐conversion, and control models that are implemented in SIMULINK™ (Simulink, 2004). SIMULINK™ is a development environment packaged with MatLab™ (MatLab, 2004) that allows the creation of dynamic state flow models. Simulation modules for liquid metal, gas cooled reactors, and electrically heated systems have been developed, as have modules for dynamic power‐conversion components such as, ducting, heat exchangers, turbines, compressors, permanent magnet alternators, and load resistors. Various control modules for the reactor and the power‐conversion shaft speed have also been developed and simulated. The modules are compiled into libraries and can be easily connected in different ways to explore the operational space of a number of potential reactor, power‐conversion system configurations, and control approaches. The modularity and variability of these SIMULINK™ models provides a way to simulate a variety of complete power generation systems. To date, both Liquid Metal Reactors (LMR), Gas Cooled Reactors (GCR), and electric heaters that are coupled to gas‐dynamics systems and thermoelectric systems have been simulated and are used to understand the behavior of these systems. Current efforts are focused on improving the fidelity of the existing SIMULINK™ modules, extending them to include isotopic heaters, heat pipes, Stirling engines, and on developing state flow logic to provide intelligent autonomy. The simulation code is called RPC‐SIM (Reactor Power and Control‐Simulator).
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Operational Results of a Closed Brayton Cycle Test‐Loop
AIP Conference Proceedings, 2005Co-Authors: Steven A. Wright, Robert Fuller, Ronald J Lipinski, Kenneth Nichols, Nicholas R BrownAbstract:A number of space and terrestrial power system designs plan to use nuclear reactors that are coupled to Closed‐loop Brayton Cycle (CBC) systems to generate electrical power. Because very little experience exists regarding the operational behavior of these systems, Sandia National Laboratories (through its Laboratory Directed Research and Development program) is developing a closed‐loop test bed that can be used to determine the operational behavior of these systems and to validate models for these systems. Sandia has contracted Barber‐Nichols Corporation to design, fabricate, and assemble a Closed‐loop Brayton Cycle (CBC) system. This system was developed by modifying commercially available hardware. It uses a 30 kWe Capstone C‐30 gas‐turbine unit (www.capstoneturbine.com) with a modified housing that permits the attachment of an electrical heater and a water cooled chiller that are connected to the turbo‐machinery in a closed loop. The test‐loop reuses the Capstone turbine, compressor, and alternator. The Capstone system’s nominal operating point is 1150 K turbine inlet temperature at 96,000 rpm. The annular recuperator and portions of the Capstone control system (inverter) and starter system are also reused. The rotational speed of the turbo‐machinery is controlled either by adjusting the alternator load by either using the electrical grid or a separate load bank. This report describes the test‐loop hardware SBL‐30 (Sandia Brayton Loop‐30kWe). Also presented are results of early testing and modeling of the unit. The SBL‐30 hardware is currently configured with a heater that is limited to 80 kWth with a maximum outlet temperature of ∼1000 K.
Ty Neises - One of the best experts on this subject based on the ideXlab platform.
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a comparison of supercritical carbon dioxide power Cycle configurations with an emphasis on csp applications
Energy Procedia, 2014Co-Authors: Ty Neises, Craig TurchiAbstract:Recent research suggests that an emerging power Cycle technology using supercritical carbon dioxide (s-CO2) operated in a Closed-Loop Brayton Cycle offers the potential of equivalent or higher Cycle efficiency versus supercritical or superheated steam Cycles at temperatures relevant for CSP applications. Preliminary design-point modeling suggests that s-CO2 Cycle configurations can be devised that have similar overall efficiency but different temperature and/or pressure characteristics. This paper employs a more detailed heat exchanger model than previous work to compare the recompression and partial cooling Cycles, two Cycles with high design-point efficiencies, and illustrates the potential advantages of the latter. Integration of the Cycles into CSP systems is studied, with a focus on sensible heat thermal storage and direct s-CO2 receivers. Results show the partial cooling Cycle may offer a larger temperature difference across the primary heat exchanger, thereby potentially reducing heat exchanger cost and improving CSP receiver efficiency.
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Thermodynamic Study of Advanced Supercritical Carbon Dioxide Power Cycles for Concentrating Solar Power Systems
Journal of Solar Energy Engineering, 2013Co-Authors: Craig Turchi, Ty Neises, Michael J. WagnerAbstract:Supercritical CO2 (s-CO2) operated in a Closed-Loop Brayton Cycle offers the potential of higher Cycle efficiency versus superheated or supercritical steam Cycles at temperatures relevant for concentrating solar power (CSP) applications. Brayton-Cycle systems using s-CO2 have a smaller weight and volume, lower thermal mass, and less complex power blocks versus Rankine Cycles due to the higher density of the fluid and simpler Cycle design. The simpler machinery and compact size of the s-CO2 process may also reduce the installation, maintenance, and operation cost of the system. In this work we explore s-CO2 Brayton Cycle configurations that have attributes that are desirable from the perspective of a CSP application, such as the ability to accommodate dry cooling and achieve greater than 50% efficiency, as specified for the U.S. Department of Energy SunShot goal. Recompression Cycles combined with intercooling and/or turbine reheat appear able to hit this efficiency target, even when combined with dry cooling. In addition, the intercooled Cycles expand the temperature differential across the primary heat exchanger, which is favorable for CSP systems featuring sensible-heat thermal energy storage.
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thermodynamic study of advanced supercritical carbon dioxide power Cycles for high performance concentrating solar power systems
International Conference on Fuel Cell Science Engineering and Technology FUELCELL Collocated with ASME International Conference on Energy Sustainabili, 2012Co-Authors: Craig Turchi, Ty Neises, Michael J. WagnerAbstract:In 2011, the U.S. Department of Energy (DOE) initiated a “SunShot Concentrating Solar Power R&D” program to develop technologies that have the potential for much higher efficiency, lower cost, and/or more reliable performance than existing CSP systems. The DOE seeks to develop highly disruptive Concentrating Solar Power (CSP) technologies that will meet 6¢/kWh cost targets by the end of the decade, and a high-efficiency, low-cost thermal power Cycle is one of the important components to achieve the goal. Supercritical CO2 (s-CO2) operated in a Closed-Loop Brayton Cycle offers the potential of equivalent or higher Cycle efficiency versus superheated or supercritical steam Cycles at temperatures relevant for CSP applications. Brayton-Cycle systems using s-CO2 have a smaller weight and volume, lower thermal mass, and less complex power blocks versus Rankine Cycles due to the higher density of the fluid and simpler Cycle design. The simpler machinery and compact size of the s-CO2 process may also reduce the installation, maintenance and operation cost of the system.Copyright © 2012 by ASME
P. G. Rousseau - One of the best experts on this subject based on the ideXlab platform.
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Control Options for Load Rejection in a Three-Shaft Closed Cycle Gas Turbine Power Plant
Journal of Engineering for Gas Turbines and Power, 2006Co-Authors: B. W. Botha, P. G. RousseauAbstract:An important issue to be addressed in power plants is the continued operation during load transients, such as load following and load rejection. It is inevitable that with new power plant technology, new control strategies will be required. One such technology investigated for commercial power plants is that of a three-shaft recuperative inter-cooled Closed-Loop Brayton Cycle with a high-temperature gas-cooled nuclear reactor as the heat source and helium as coolant. Because of its unique configuration, the utilization of traditional power plant control strategies is limited. In order to address this, detailed Cycle analyses were performed to identify new potential control strategies. The analyses were done using the Flownex thermohydraulic systems CFD simulation software since it is ideally suited for component and system integration. It also enables designers to simulate complex load scenarios and design-suitable controller algorithms. It was therefore possible to investigate control options for one of the most severe load control scenarios, i.e., that of full load rejection due to the loss of the grid power. This paper briefly describes the various control strategies investigated and presents details of the two strategies showing the most promising results with regard to load rejection.
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Development of a Mathematical Compressor Model to Predict Surge in a Closed Loop Brayton Cycle
Volume 3: Turbo Expo 2003, 2003Co-Authors: B. W. Botha, B. Du Toit, P. G. RousseauAbstract:The accuracy by which the compressor performance is estimated plays a major role in predicting the transient performance of a gas turbine Brayton Cycle. Numerical prediction has proven to be a valuable tool to reduce development costs of such Cycles. This document subsequently discusses the expansion of the well-known Greitzer prediction model used for unstable transient compressor operation. The expansion allows for compressibility effects in the compressor as well as integrating the compressor with a turbine in an open Cycle. After this it addresses the effect of flow feedback to the compressor inlet due to a closed Cycle configuration. From the one-dimensional form of the conservation laws, three partial differential equations are derived governing the dynamics of fluid flow through the compressor. The simulation results for a simple open Cycle configuration compares favorably with that published by Greitzer. A similar approach was used for the closed Cycle resulting in an oscillation in compressor inlet pressure due to the feedback from the turbine outlet. The study presents a first step into investigating the possibility of including a generic surge and rotating stall model into an existing software code capable of solving complex thermodynamic systems including turbo-machine Cycles.
Daejong Kim - One of the best experts on this subject based on the ideXlab platform.
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Design Space of Foil Bearings for Closed-Loop Supercritical CO2 Power Cycles Based on Three-Dimensional Thermohydrodynamic Analyses
Journal of Engineering for Gas Turbines and Power, 2015Co-Authors: Daejong KimAbstract:The closed loop Brayton Cycle with super critical CO2 (S-CO2) as an operating fluid is an attractive alternative to conventional power Cycles due to very high power density. Foil gas bearings using CO2 is the most promising for small S-CO2 turbomachinery but there are many problems to address; large power loss due to high flow turbulence, lack of design/analysis tool due to non-ideal gas behavior, and lack of load capacity when they are used for large systems.This paper presents high level design/analysis tool involving three-dimensional thermo-hydrodynamic analyses of radial foil bearings considering real gas effect and flow turbulence inside the film. Simulations are performed for radial foil bearing with 34.9mm in diameter lubricated with CO2 and N2 under various ambient conditions up to above 40 bar gauge pressure. The simulation results using the turbulence model still under-predict the measured data in open literature. However, the error between the prediction and measurements decreases as either speed or ambient pressure increases. In addition, general behavior of substantial increase in power loss with ambient pressure agrees with the measured data. The simulation results indicate the importance of detailed THD analysis of the foil bearings for prediction of power loss under severe turbulent condition.A conceptual layout of rotor system for 10MWe S-CO2 loop is also presented along with realistic rotor weight and bearing load. A hybrid foil bearings with diameter of 102mm is suggested for gas generator rotor, and its power losses and minimum film thicknesses at various operating conditions are presented.Copyright © 2015 by ASME
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Design Space of Foil Bearings for Closed Loop Supercritical CO2 Power Cycles Based on Three-Dimensional Thermo-Hydrodynamic Analyses
Volume 7A: Structures and Dynamics, 2015Co-Authors: Daejong KimAbstract:The closed loop Brayton Cycle with super critical CO2 (S-CO2) as an operating fluid is an attractive alternative to conventional power Cycles due to very high power density. Foil gas bearings using CO2 is the most promising for small S-CO2 turbomachinery but there are many problems to address; large power loss due to high flow turbulence, lack of design/analysis tool due to non-ideal gas behavior, and lack of load capacity when they are used for large systems. This paper presents high level design/analysis tool involving three-dimensional thermo-hydrodynamic analyses of radial foil bearings considering real gas effect and flow turbulence inside the film. Simulations are performed for radial foil bearing with 34.9mm in diameter lubricated with CO2 and N2 under various ambient conditions up to above 40 bar gauge pressure. The simulation results using the turbulence model still under-predict the measured data in open literature. However, the error between the prediction and measurements decreases as either speed or ambient pressure increases. In addition, general behavior of substantial increase in power loss with ambient pressure agrees with the measured data. The simulation results indicate the importance of detailed THD analysis of the foil bearings for prediction of power loss under severe turbulent condition. A conceptual layout of rotor system for 10MWe S-CO2 loop is also presented along with realistic rotor weight and bearing load. A hybrid foil bearings with diameter of 102mm is suggested for gas generator rotor, and its power losses and minimum film thicknesses at various operating conditions are presented.