Demonstration of Supercritical CO2 Closed Regenerative Brayton Cycle in a Bench Scale Experiment

2012 ◽  
Author(s):  
Motoaki Utamura ◽  
Hiroshi Hasuike ◽  
Kiichiro Ogawa ◽  
Takashi Yamamoto ◽  
Toshihiko Fukushima ◽  
...  
Keyword(s):  
Supercritical Co2 ◽  
High Speed ◽  
Flow Instability ◽  
Internal Flow ◽  
Ideal Gas ◽  
Test Facility ◽  
Brayton Cycle ◽  
Bench Scale ◽  
Compressibility Coefficient ◽  
Scale Experiment

Power generation with a supercritical CO2 closed regenerative Brayton cycle has been successfully demonstrated using a bench scale test facility. A set of a centrifugal compressor and a radial inflow turbine of finger top size is driven by a synchronous motor/generator controlled using a high-speed inverter. A 110 W power generating operation is achieved under the operational condition of rotational speed of 1.15kHz, CO2 flow rate of 1.1 kg/s, and respective thermodynamic states (7.5 MPa, 304.6 K) at compressor and (10.6 MPa, 533 K) at turbine inlet. Compressor work reduction owing to real gas effect is experimentally examined. Compressor to turbine work ratio in supercritical liquid like state is measured to be 28% relative to the case of ideal gas. Major loss of power output is identified as rotor windage. It is found the isentropic efficiency depends little on compressibility coefficient. Off design performance of gas turbine working in supercritical state is well predicted by a Meanline program. The CFD analysis on compressor internal flow indicates that the presence of backward flow around the tip region might create a locally depressurized region leading eventually to the onset of flow instability.

Performance Characteristics of an Operating Supercritical CO2 Brayton Cycle

2012 ◽  
Author(s):  
Thomas Conboy ◽  
Steven Wright ◽  
James Pasch ◽  
Darryn Fleming ◽  
Gary Rochau ◽  
...  
Keyword(s):  
Supercritical Co2 ◽  
Waste Heat ◽  
Electrical Power ◽  
Heat Removal ◽  
Test Facility ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Compact Size ◽  
Test Loop

Supercritical CO2 (S-CO2) power cycles offer the potential for better overall plant economics due to their high power conversion efficiency over a moderate range of heat source temperatures, compact size, and potential use of standard materials in construction [1,2,3,4]. Sandia National Labs (Albuquerque, NM, US) and the US Department of Energy (DOE-NE) are in the process of constructing and operating a megawatt-scale supercritical CO2 split-flow recompression Brayton cycle with contractor Barber-Nichols Inc. [5] (Arvada, CO, US). This facility can be counted among the first and only S-CO2 power producing Brayton cycles anywhere in the world. The Sandia-DOE test-loop has recently concluded a phase of construction that has substantially upgraded the facility by installing additional heaters, a second recuperating printed circuit heat exchanger (PCHE), more waste heat removal capability, higher capacity load banks, higher temperature piping, and more capable scavenging pumps to reduce windage within the turbomachinery. With these additions, the loop has greatly increased its potential for electrical power generation — according to models, as much as 80 kWe per generator depending on loop configuration — and its ability to reach higher temperatures. To date, the loop has been primarily operated as a simple recuperated Brayton cycle, meaning a single turbine, single compressor, and undivided flow paths. In this configuration, the test facility has begun to realize its upgraded capacity by achieving new records in turbine inlet temperature (650°F/615K), shaft speed (52,000 rpm), pressure ratio (1.65), flow rate (2.7 kg/s), and electrical power generated (20kWe). Operation at higher speeds, flow rates, pressures and temperatures has allowed a more revealing look at the performance of essential power cycle components in a supercritical CO2 working fluid, including recuperation and waste heat rejection heat exchangers (PCHEs), turbines and compressors, bearings and seals, as well as auxiliary equipment. In this report, performance of these components to date will be detailed, including a discussion of expected operational limits as higher speeds and temperatures are approached.

Design of an Experimental Test Facility for Supercritical CO2 Brayton Cycle

2014 ◽  
Author(s):  
Pardeep Garg ◽  
Pramod Kumar ◽  
Pradip Dutta ◽  
Thomas Conboy ◽  
Clifford Ho
Keyword(s):  
Heat Exchanger ◽  
Pressure Drop ◽  
Supercritical Co2 ◽  
Exchange Process ◽  
Test Facility ◽  
Brayton Cycle ◽  
Pressure Drops ◽  
Loop Design ◽  
Indian Institute Of Science ◽  
Cycle Temperature

A supercritical CO2 test facility is currently being developed at Indian Institute of Science, Bangalore, India to analyze the performance of a closed loop Brayton cycle for concentrated solar power (CSP) generation. The loop has been designed for an external heat input of 20 kW, a pressure range of 75–135 bar, flow rate of 11 kg/min, and a maximum cycle temperature of 525 °C. The operation of the loop and the various parametric tests planned to be performed are discussed in this paper. The paper addresses various aspects of the loop design with emphasis on design of various components such as regenerator and expansion device. The regenerator design is critical due to sharp property variations in CO2 occurring during the heat exchange process between the hot and cold streams. Two types of heat exchanger configurations 1) tube-in-tube (TITHE) and 2) printed circuit heat exchanger (PCHE) are analyzed and compared. A PCHE is found to be ∼5 times compact compared to a TITHE for identical heat transfer and pressure drops. The expansion device is being custom designed to achieve the desired pressure drop for a range of operating temperatures. It is found that capillary of 5.5 mm inner diameter and ∼2 meter length is sufficient to achieve a pressure drop from 130 to 75 bar at a maximum cycle temperature of 525 °C.

scholarly journals Design of a Centrifugal Compressor Stage and a Radial-Inflow Turbine Stage for a Supercritical CO2 Recompression Brayton Cycle by Using 3D Inverse Design Method

2017 ◽  
Author(s):  
Jiangnan Zhang ◽  
Pedro Gomes ◽  
Mehrdad Zangeneh ◽  
Benjamin Choo
Keyword(s):  
Centrifugal Compressor ◽  
Supercritical Co2 ◽  
Design Method ◽  
Ideal Gas ◽  
Inverse Design ◽  
Brayton Cycle ◽  
Real Gas ◽  
Radial Inflow Turbine ◽  
Inverse Design Method ◽  
The Ideal

It is found that the ideal gas assumption is not proper for the design of turbomachinery blades using supercritical CO2 (S-CO2) as working fluid especially near the critical point. Therefore, the inverse design method which has been successfully applied to the ideal gas is extended to applications for the real gas by using a real gas property lookup table. A fast interpolation lookup approach is implemented which can be applied both in superheated and two-phase regimes. This method is applied to the design of a centrifugal compressor blade and a radial-inflow turbine blade for a S-CO2 recompression Brayton cycle. The stage aerodynamic performance (volute included) of the compressor and turbine is validated numerically by using the commercial CFD code ANSYS CFX R162. The structural integrity of the designs is also confirmed by using ANSYS Workbench Mechanical R162.

A Supercritical CO2 Gas Turbine Power Cycle for Next-Generation Nuclear Reactors

2002 ◽  
Author(s):  
Vaclav Dostal ◽  
Michael J. Driscoll ◽  
Pavel Hejzlar ◽  
Neil E. Todreas
Keyword(s):  
Gas Turbine ◽  
Oil Recovery ◽  
Supercritical Co2 ◽  
Power Plants ◽  
Ideal Gas ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Pinch Point ◽  
Good Efficiency

Although proposed more than 35 years ago, the use of supercritical CO2 as the working fluid in a closed circuit Brayton cycle has so far not been implemented in practice. Industrial experience in several other relevant applications has improved prospects, and its good efficiency at modest temperatures (e.g., ∼45% at 550°C) make this cycle attractive for a variety of advanced nuclear reactor concepts. The version described here is for a gas-cooled, modular fast reactor. In the proposed gas-cooled fast breeder reactor design of present interest, CO2 is also especially attractive because it allows the use of metal fuel and core structures. The principal advantage of a supercritical CO2 Brayton cycle is its reduced compression work compared to an ideal gas such as helium: about 15% of gross power turbine output vs. 40% or so. This also permits the simplification of use of a single compressor stage without intercooling. The requisite high pressure (∼20 MPa) also has the benefit of more compact heat exchangers and turbines. Finally, CO2 requires significantly fewer turbine stages than He, its principal competitor for nuclear gas turbine service. One disadvantage of CO2 in a direct cycle application is the production of N-16, which will require turbine plant shielding (albeit much less than in a BWR). The cycle efficiency is also very sensitive to recuperator effectiveness and compressor inlet temperature. It was found necessary to split the recuperator into separate high- and low-temperature components, and to employ intermediate recompression, to avoid having a pinch-point in the cold end of the recuperator. Over the past several decades developments have taken place that make the acceptance of supercritical CO2 systems more likely: supercritical CO2 pipelines are in use in the western US in oil-recovery operations; 14 advanced gas-cooled reactors (AGR) are employed in the UK at CO2 temperatures up to 650°C; and utilities now have experience with Rankine cycle power plants at pressures as high as 25 MPa. Furthermore, CO2 is the subject of R&D as the working fluid in schemes to sequester CO2 from fossil fuel combustion and for refrigeration service as a replacement for CFCs.

Design Methodology of Supercritical CO2 Brayton Cycle Turbomachineries

2012 ◽  
Author(s):  
Jekyoung Lee ◽  
Jeong Ik Lee ◽  
Yoonhan Ahn ◽  
Hojoon Yoon
Keyword(s):  
Supercritical Co2 ◽  
Design Methodology ◽  
Design Method ◽  
Ideal Gas ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Validation And Verification ◽  
Property Variation ◽  
Linear Property

The supercritical CO2(S-CO2) Brayton Cycle is gaining attention due to its high thermal efficiency at relatively low turbine inlet temperature and compactness of turbomachineries. For designing turbomachineries of the S-CO2 Cycle, however, most of existing codes based on ideal gas assumption are not proven yet to be accurate near the supercritical condition. Furthermore, many of existing design computer programs usually focuses on a specific type of turbomachinery, e.g. axial or radial, which makes hard to compare performance of both types at the same design condition. Since both axial and radial types of turbomachineries were pointed out as an equally possible candidate for the S-CO2 Brayton cycle, in order to compare and determine the best effective type of turbomachinery requires considering both types under the same design conditions. Taking into consideration of these facts, some modifications to the conventional design methodology of gas cycle turbomachinery are necessary to design a turbomachinery for the S-CO2 cycle. Especially, a modified design method should consider non-linear property variation of CO2 near the critical point to obtain an accurate result. Thus, the modified design method for the S-CO2 Brayton cycle turbomachineries is suggested in this paper and the method was implemented in the in-house code. In addition, some preliminary results will be discussed with the plan for validation and verification of the code.

Performance Characteristics of an Operating Supercritical CO2 Brayton Cycle

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Thomas Conboy ◽  
Steven Wright ◽  
James Pasch ◽  
Darryn Fleming ◽  
Gary Rochau ◽  
...  
Keyword(s):  
Supercritical Co2 ◽  
Waste Heat ◽  
Electrical Power ◽  
Heat Removal ◽  
Test Facility ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Compact Size ◽  
Test Loop

Supercritical CO2 (S-CO2) power cycles offer the potential for better overall plant economics due to their high power conversion efficiency over a moderate range of heat source temperatures, compact size, and potential use of standard materials in construction. Sandia National Labs (Albuquerque, NM) and the U.S. Department of Energy (DOE-NE) are in the process of constructing and operating a megawatt-scale supercritical CO2 split-flow recompression Brayton cycle with contractor Barber-Nichols Inc. (Arvada, CO). This facility can be counted among the first and only S-CO2 power producing Brayton cycles anywhere in the world. The Sandia-DOE test-loop has recently concluded a phase of construction that has substantially upgraded the facility by installing additional heaters, a second recuperating printed circuit heat exchanger (PCHE), more waste heat removal capability, higher capacity load banks, higher temperature piping, and more capable scavenging pumps to reduce windage within the turbomachinery. With these additions, the loop has greatly increased its potential for electrical power generation, and its ability to reach higher temperatures. To date, the loop has been primarily operated as a simple recuperated Brayton cycle, meaning a single turbine, single compressor, and undivided flow paths. In this configuration, the test facility has begun to realize its upgraded capacity by achieving new records in turbine inlet temperature (650 °F/615 K), shaft speed (52,000 rpm), pressure ratio (1.65), flow rate (2.7 kg/s), and electrical power generated (20 kWe). Operation at higher speeds, flow rates, pressures, and temperatures has allowed a more revealing look at the performance of essential power cycle components in a supercritical CO2 working fluid, including recuperation and waste heat rejection heat exchangers (PCHEs), turbines and compressors, bearings and seals, as well as auxiliary equipment. In this report, performance of these components to date will be detailed, including a discussion of expected operational limits as higher speeds and temperatures are approached.

Comparison of Gas System Analysis Code GAMMA+ to S-CO2 Compressor Test Data

2015 ◽  
Author(s):  
Seong Jun Bae ◽  
Yoonhan Ahn ◽  
Hong-Sik Lim ◽  
Jae Eun Cha ◽  
Jeong Ik Lee
Keyword(s):  
Experimental Data ◽  
Critical Point ◽  
Supercritical Co2 ◽  
Transient Analysis ◽  
System Analysis ◽  
Early Stage ◽  
Test Facility ◽  
Brayton Cycle ◽  
Gas System ◽  
Compressor Inlet

The CO2 compressor control is one of the most important issues to operate a Supercritical CO2 (S-CO2) Brayton cycle with a high thermal efficiency because it is operated near the critical point to reduce the compressing work. Therefore, our research team has accumulated the CO2 compressor data from the S-CO2 compressor test facility called SCO2PE (Supercritical CO2 Pressurizing Experiment). The data can be obtained under various compressor inlet conditions, especially near the critical point of CO2. Despite the growing interest in the S-CO2 Brayton cycle, research on the cycle transient analysis, especially in case of CO2 compressor inlet condition variation, is still in its early stage. So, in this study, the validation and verification of the gas system transient analysis code GAMMA+ is carried out by utilizing the experimental data of SCO2PE. To simulate the SCO2PE by the GAMMA+ code, the code was revised to reflect the compressor performance and add an expansion valve option. Moreover, the NIST database was connected to the GAMMA+ code for more accurate CO2 properties near the critical point. Prior to the transient analysis with the whole SCO2PE loop, major components such as a compressor and a heat exchanger were separately tested with the steady state data of SCO2PE. The loss of cooling water accident was assumed as the transient situation by observing the operating condition variations of the SCO2PE while the mass flow rate of water loop was decreased. Thus, the experimental data of SCO2PE was compared with the revised GAMMA+ code under the planned transient.

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