scholarly journals Influence of Supercritical Carbon Dioxide Brayton Cycle Parameters on Intelligent Circulation System and Its Optimization Strategy

2021 ◽  
Vol 2066 (1) ◽  
pp. 012074
Author(s):  
Kai Li ◽  
Kai Sun
Keyword(s):  
Carbon Dioxide ◽  
Power Generation ◽  
Supercritical Carbon Dioxide ◽  
Circulation System ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Optimization Strategy ◽  
Cycle System ◽  
The Impact ◽  
Supercritical Carbon

Abstract The supercritical carbon dioxide (SCO2) Brayton cycle takes advantage of the special physical properties of carbon dioxide near the critical point (31.1 °C, 7.39MPa), and has higher energy conversion efficiency than the current large-scale steam power cycle. This cycle can be widely used in the field of power generation, but a lot of research work is still needed in terms of component parameters and layout under different working conditions. In this regard, the purpose of this paper is to study the influence of supercritical carbon dioxide Brayton cycle parameters on cycle efficiency and its optimization strategy. Based on the first law of thermodynamics, this paper uses Aspen Plus software to establish S-CO2 Brayton cycle system models with different circulation arrangements. In this paper, the existing algorithm of the simulation system and the newly-built algorithm are used to build the S-CO2 shunt and recompression Brayton cycle system model, and the accuracy of the model is verified with experimental data from literature. Then this paper conducts disturbance experiments on the model to study the influence of heater heating, valve opening and precooler cooling on the system, and analyze the dynamic characteristics of the system. Experimental results show that the thermal efficiency of the simple Brayton cycle is much lower than that of the recompression Brayton cycle and the split recompression Brayton cycle under higher parameters. The compressor outlet pressure and the turbine inlet temperature have an effect on the efficiency of the recompression Brayton cycle. The impact is significant, and the optimal value of the compressor shunt coefficient is between 0.5-0.7, which provides a reference for the layout optimization method of the SCO2 Brayton cycle and the optimization of the same type of power generation cycle.

Testing of a New Turbocompressor for Supercritical Carbon Dioxide Closed Brayton Cycles

2018 ◽  
Author(s):  
Jim Pasch ◽  
David Stapp
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Maximum Pressure ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Development Platform ◽  
Cycle System ◽  
Turbine Inlet ◽  
Supercritical Carbon

Sandia National Laboratories (SNL) has recently purchased a supercritical carbon dioxide (sCO2) turbocompressor that operates at 118,000 rpm, 750 °C turbine inlet temperature, and 42.9 MPa compressor discharge pressure, and is sized to pressurize the flow for a 1 MWe closed Brayton cycle. The turbocompressor is a line replaceable unit designed by Peregrine Turbine Technologies (PTT) located in Wiscasset, Maine, as part of their closed Brayton electric power genset rated at 1 MWe. Both this machine and a 6MW variant are intended for commercial applications burning a variety of aircombustible fuels including biomass materials. Sandia purchased this turbocompressor as the first phase of a program to construct a 1 MWe commercially viable sCO2 recompression closed Brayton-cycle system. During this phase, the development platform resident at the SNL Brayton Lab was reconfigured to support testing of the PTT turbocompressor to moderate, or idle, conditions. The testing infrastructure at the Brayton Lab limited maximum pressure to 13.8 MPa. This pressure limitation consequently limited turbocompressor operations to a speed of 52,000 rpm and a turbine inlet temperature of 150 °C. While these conditions are far removed from the machine design point, they are sufficient to demonstrate a range of important features. Numerous testing objectives were identified and researched, most notably: the development of a reliable cycle bootstrapping process for a motorless turbocompressor; the demonstration of consistent start, steady state, and shutdown performance and operations; performance demonstration of the numerous internal seals and bearings designs that are new to this environment; demonstration of controllability via turbine back pressuring and turbine inlet temperature; and turbomachinery performance map validation. This paper presents the design and development of the testing platform, the PTT turbocompressor and progress achieved on each of the objectives.

scholarly journals An Optimization Study to Evaluate the Impact of the Supercritical CO2 Brayton Cycle’s Components on Its Overall Performance

2021 ◽  
Vol 11 (5) ◽  
pp. 2389
Author(s):  
Khaled Alawadhi ◽  
Abdullah Alfalah ◽  
Bashar Bader ◽  
Yousef Alhouli ◽  
Ahmed Murad
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Power Systems ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Optimization Study ◽  
The Impact ◽  
Sustainable Power ◽  
Supercritical Carbon

The rising environmental problems due to fossil fuels’ consumption have pushed researchers and technologists to develop sustainable power systems. Due to properties such as abundance and nontoxicity of the working fluid, the supercritical carbon (sCO2) dioxide Brayton cycle is considered one of the most promising technologies among the various sustainable power systems. In the current study, a mathematical model has been developed and coded in Matlab for the recompression of the supercritical carbon dioxide Brayton cycle sCO2-BC. The real gas properties of supercritical carbon dioxide (sCO2) were incorporated into the program by pairing the NIST’s Refporp with Matlab© through a subroutine. The impacts of the various designs of the cycle’s individual components have been investigated on the performance of sCO2−BC. The impact of various sedative cycle parameters, i.e., compressor’s inlet temperature (T1), and pressure (P1), cycle pressure ratio (Pr), and split mass fraction (x), on the cycle’s performance (ηcyc) were studied and highlighted. Moreover, an optimization study using the genetic algorithm was carried out to find the abovementioned cycle’s optimized values that maximize the cycle’s per-formance under provided design constraints and boundaries.

Parametric Investigation of Supercritical Carbon Dioxide Brayton Cycle for High Temperature Gas-Cooled Reactor (HTGR)

2018 ◽  
Author(s):  
Gang Zhao ◽  
Ping Ye ◽  
Xiaoyong Yang ◽  
Jie Wang
Keyword(s):  
Carbon Dioxide ◽  
High Temperature ◽  
Supercritical Carbon Dioxide ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Pebble Bed ◽  
Split Flow ◽  
Under Construction ◽  
High Temperature Gas ◽  
Supercritical Carbon

High-temperature Gas-cooled Reactor Pebble-bed Module (HTR-PM) is under construction in Shidao Bay, Shandong of China. It is supposed to be the world’s first pebble-bed modular commercial demonstration plant for High Temperature Gas-cooled Reactor (HTGR). In HTR-PM project, water-Rankine cycles have been used in the power conversion system. Meanwhile, supercritical carbon dioxide (S-CO2) Brayton cycle has shown great potentials for future HTGR technology. Comparing with typical helium Brayton cycle, in S-CO2 cycle where critical properties of carbon dioxide are utilized, compressor work may reduce significantly and thermal efficiency may improve greatly. Furthermore, the general sizes of S-CO2 cycle equipment, such as heat exchanger and turbine, would be orders of magnitude smaller than water-Rankine system at similar power output. Therefore, parameters study of S-CO2 were conducted in this paper for future HTGR. Firstly, a physical model of S-CO2 Brayton cycles was built and the performance of cycles were analyzed. Secondly, compression ratio, temperature ratio, the inlet temperature of turbine, inlet parameters of compressor, and recuperated effectiveness were discussed as key cycle parameters. For heat capacities of CO2 are significantly different as a function of temperature and pressure, flow recompression was considered. Calculation was based on a split-flow cycle configuration. The split flow ratio was also analyzed. Finally, the parameters of S-CO2 cycle were optimized for HTGR. In conclusion, S-CO2 Brayton cycle will be a good option for future HTGR.

scholarly journals Design of a 1 MWth Supercritical Carbon Dioxide Primary Heat Exchanger Test System

2020 ◽  
Author(s):  
Matthew Carlson ◽  
Francisco Alvarez
Keyword(s):  
Carbon Dioxide ◽  
Power Generation ◽  
Heat Exchanger ◽  
Supercritical Carbon Dioxide ◽  
Storage System ◽  
Thermal Storage ◽  
Ambient Air ◽  
Test System ◽  
Brayton Cycle ◽  
Supercritical Carbon

Abstract Concentrating Solar Power (CSP) plants have the potential to provide dispatchable renewable power generation to support the baseload need currently supplied primarily by coal and nuclear plants and peaking power capability to reduce the use of natural gas for load following. However, these plants have had difficulty achieving widespread use due to the low cost of combined photovoltaic and battery systems capable of providing similar services to the electricity grid. A new generation of CSP technologies must be developed to reduce the levelized cost of electricity (LCOE) to 6 cents/kWh by leveraging heat transfer fluids (HTF) capable of operation at higher temperatures and coupling with higher efficiency power conversion cycles. Three promising pathways for Generation 3 CSP (Gen3CSP) technology development have been funded by the U.S. Department of Energy (DOE) leveraging solid, liquid, and gaseous HTFs to transfer heat to a supercritical carbon dioxide (sCO2) Brayton cycle. The primary heat exchangers (PHX) necessary to couple these high-temperature HTFs to sCO2 are an essential new technology that must be demonstrated at a scale relevant to commercial CSP to validate design expectations for performance, lifetime, and operability. The demonstration of these PHXs need a reliable 1 MWth-scale sCO2 test system that can provide sCO2 coolant to the PHX in a compact package suitable for installation near any Gen3CSP thermal storage system. This paper outlines the final design of such a system including the expected operating range and off-design capabilities. The system uses a dense-phase high pressure canned motor pump as the sCO2 circulator and ambient air as the ultimate heat sink operating at pressures up to 250 bar and temperatures up to 715 °C with capability to supply up to 5.3 kg/s of sCO2 flow to the primary heat exchanger. Key component requirements for this system have been frozen and procurement is underway. The expected completion date for heated acceptance testing of this system is September of 2020. This system is also capable of being upgraded through the addition of a turbo-compressor and turbo-generator to operate as a complete sCO2 Brayton cycle with power generation in order to demonstrate an integrated solar to sCO2 power pilot plant and understand transient interactions between the thermal storage system, sCO2 turbomachinery, and ambient air temperature. In addition, this upgrade would provide experience with plant operating considerations including balancing charging the thermal storage system with generating and dispatching power to the electrical grid. A roadmap for this upgrade will be discussed including limitations and requirements for the necessary turbomachinery.

Numerical Simulation of the Performance of an Axial Compressor Operating With Supercritical Carbon Dioxide

2018 ◽  
Author(s):  
Jinlan Gou ◽  
Wei Wang ◽  
Can Ma ◽  
Yong Li ◽  
Yuansheng Lin ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Numerical Simulation ◽  
Supercritical Carbon Dioxide ◽  
Critical Point ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Axial Compressor ◽  
Brayton Cycle ◽  
Supercritical Carbon

Using supercritical carbon dioxide (SCO2) as the working fluid of a closed Brayton cycle gas turbine is widely recognized nowadays, because of its compact layout and high efficiency for modest turbine inlet temperature. It is an attractive option for geothermal, nuclear and solar energy conversion. Compressor is one of the key components for the supercritical carbon dioxide Brayton cycle. With established or developing small power supercritical carbon dioxide test loop, centrifugal compressor with small mass flow rate is mainly investigated and manufactured in the literature; however, nuclear energy conversion contains more power, and axial compressor is preferred to provide SCO2 compression with larger mass flow rate which is less studied in the literature. The performance of the axial supercritical carbon dioxide compressor is investigated in the current work. An axial supercritical carbon dioxide compressor with mass flow rate of 1000kg/s is designed. The thermodynamic region of the carbon dioxide is slightly above the vapor-liquid critical point with inlet total temperature 310K and total pressure 9MPa. Numerical simulation is then conducted to assess this axial compressor with look-up table adopted to handle the nonlinear variation property of supercritical carbon dioxide near the critical point. The results show that the performance of the design point of the designed axial compressor matches the primary target. Small corner separation occurs near the hub, and the flow motion of the tip leakage fluid is similar with the well-studied air compressor. Violent property variation near the critical point creates troubles for convergence near the stall condition, and the stall mechanism predictions are more difficult for the axial supercritical carbon dioxide compressor.

scholarly journals Advanced Supercritical Carbon Dioxide Brayton Cycle Development

2015 ◽  
Author(s):  
Mark Anderson ◽  
James Sienicki ◽  
Anton Moisseytsev ◽  
Gregory Nellis ◽  
Sanford Klein
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Brayton Cycle ◽  
Supercritical Carbon

Supercritical Carbon Dioxide Heat Transfer in Horizontal Semicircular Channels

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Alan Kruizenga ◽  
Hongzhi Li ◽  
Mark Anderson ◽  
Michael Corradini
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Supercritical Carbon Dioxide ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Brayton Cycle ◽  
Heat Exchanger Design ◽  
Transfer Behavior ◽  
Supercritical Carbon

Competitive cycles must have a minimal initial cost and be inherently efficient. Currently, the supercritical carbon dioxide (S-CO2) Brayton cycle is under consideration for these very reasons. This paper examines one major challenge of the S-CO2 Brayton cycle: the complexity of heat exchanger design due to the vast change in thermophysical properties near a fluid’s critical point. Turbulent heat transfer experiments using carbon dioxide, with Reynolds numbers up to 100 K, were performed at pressures of 7.5–10.1 MPa, at temperatures spanning the pseudocritical temperature. The geometry employed nine semicircular, parallel channels to aide in the understanding of current printed circuit heat exchanger designs. Computational fluid dynamics was performed using FLUENT and compared to the experimental results. Existing correlations were compared, and predicted the data within 20% for pressures of 8.1 MPa and 10.2 MPa. However, near the critical pressure and temperature, heat transfer correlations tended to over predict the heat transfer behavior. It was found that FLUENT gave the best prediction of heat transfer results, provided meshing was at a y+ ∼ 1.

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