scholarly journals Thermal Performance Analysis of a Direct-Heated Recompression Supercritical Carbon Dioxide Brayton Cycle Using Solar Concentrators

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4358 ◽  
Author(s):  
Jinping Wang ◽  
Jun Wang ◽  
Peter D. Lund ◽  
Hongxia Zhu
Keyword(s):  
Incidence Angle ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Beam Radiation ◽  
Solar Concentrators ◽  
Cooling Temperature ◽  
Turbine Inlet ◽  
Cycle Efficiency

In this study, a direct recompression supercritical CO2 Brayton cycle, using parabolic trough solar concentrators (PTC), is developed and analyzed employing a new simulation model. The effects of variations in operating conditions and parameters on the performance of the s-CO2 Brayton cycle are investigated, also under varying weather conditions. The results indicate that the efficiency of the s-CO2 Brayton cycle is mainly affected by the compressor outlet pressure, turbine inlet temperature and cooling temperature: Increasing the turbine inlet pressure reduces the efficiency of the cycle and also requires changing the split fraction, where increasing the turbine inlet temperature increases the efficiency, but has a very small effect on the split fraction. At the critical cooling temperature point (31.25 °C), the cycle efficiency reaches a maximum value of 0.4, but drops after this point. In optimal conditions, a cycle efficiency well above 0.4 is possible. The maximum system efficiency with the PTCs remains slightly below this value as the performance of the whole system is also affected by the solar tracking method used, the season and the incidence angle of the solar beam radiation which directly affects the efficiency of the concentrator. The choice of the tracking mode causes major temporal variations in the output of the cycle, which emphasis the role of an integrated TES with the s-CO2 Brayton cycle to provide dispatchable power.

Brayton Cycle As an Alternate Power Conversion Option for Sodium Cooled Fast Reactor

2019 ◽  
Author(s):  
Jofred Joseph ◽  
Satish Kumar ◽  
Tanmay Vasal ◽  
N. Theivarajan
Keyword(s):  
Power Conversion ◽  
Rankine Cycle ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Generation System ◽  
Fast Reactors ◽  
Turbine Inlet Temperature ◽  
Power Cycle ◽  
Power Generation System ◽  
Cycle Efficiency

Abstract Enhancing the safety and economic competitiveness are major objectives in the development of advanced reactor designs with emphasis on the design of systems or components of the nuclear systems. Innovative power cycle development is another potential option to achieve these objectives. Sodium cooled fast reactor (SFR) is one among the six reactor design concepts identified by the Gen IV International Forum for development to meet the technology goals for new nuclear energy system. Similar to the power cycle used in conventional fossil fuel based thermal power plants, sodium-cooled fast reactors have adopted the Rankine cycle based power conversion system. However, the possibility of sodium water reaction is a major concern and it becomes necessary to adopt means of early detection of leaks and isolation of the affected SG module for mitigating any adverse impact of sodium water reaction. The high exothermic nature of the reaction calls for introducing an intermediate sodium heat transport loop, leading to high overall plant cost hindering commercialization of sodium fast reactors. The Indian Prototype Fast Breeder Reactor (PFBR) also uses Rankine cycle in the power generation system. The superheated steam temperature has been set at 490 degree Celsius based on optimisation studies and material limitations. Additional Fast Breeder reactors are planned in near future and further work is being done to develop more advanced sodium cooled fast reactors. The closed Brayton cycle is a promising alternative to conventional Rankine cycle. By selecting an inert gas or a gas with milder reaction with sodium, the vigorous sodium water reaction can be avoided and significant cost savings in the turbine island can be achieved as gas turbine power conversion systems are of much smaller size than comparable steam turbine systems due to their higher power density. In the study, various Brayton cycle designs on different working gases have been explored. Supercritical-CO2 (s-CO2), helium and nitrogen cycle designs are analyzed and compared in terms of cycle efficiency, component performance and physical size. The thermal efficiencies at the turbine inlet temperature of Indian PFBR have been compared for Rankine cycle and Brayton cycle based on different working fluids. Also binary mixtures of different gases are investigated to develop a more safe and efficient power generation system. Helium does not interact with sodium and other structural materials even at very high temperatures but its thermal performance is low when compared to other fluids. Nitrogen being an inert gas does not react with sodium and can serve to utilise existing turbomachinery because of the similarity with atmospheric air. The supercritical CO2 based cycle has shown best thermodynamic performance and efficiency when compared to other Brayton cycles for the turbine inlet temperature of Indian PFBR. CO2 also reacts with sodium but the reaction is mild compared to sodium water reaction. The cycle efficiency of the s-CO2 cycle can be further improved by adopting multiple reheating, inter cooling and recuperation.

scholarly journals Performance Analysis of the Supercritical Carbon Dioxide Re-compression Brayton Cycle

2020 ◽  
Vol 10 (3) ◽  
pp. 1129 ◽  
Author(s):  
Mohammad Saad Salim ◽  
Muhammad Saeed ◽  
Man-Hoe Kim
Keyword(s):  
Carbon Dioxide ◽  
Performance Analysis ◽  
Supercritical Carbon Dioxide ◽  
Mass Fraction ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Exergy Destruction ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet ◽  
Compressor Inlet

This paper presents performance analysis results on supercritical carbon dioxide ( s C O 2 ) re-compression Brayton cycle. Monthly exergy destruction analysis was conducted to find the effects of different ambient and water temperatures on the performance of the system. The results reveal that the gas cooler is the major source of exergy destruction in the system. The total exergy destruction has the lowest value of 390.1   kW when the compressor inlet temperature is near the critical point (at 35 °C) and the compressor outlet pressure is comparatively low ( 24   MPa ). The optimum mass fraction (x) and efficiency of the cycle increase with turbine inlet temperature. The highest efficiency of 49% is obtained at the mass fraction of x = 0.74 and turbine inlet temperature of 700 °C. For predicting the cost of the system, the total heat transfer area coefficient ( U A T o t a l ) and size parameter (SP) are used. The U A T o t a l value has the maximum for the split mass fraction of 0.74 corresponding to the maximum value of thermal efficiency. The SP value for the turbine is 0.212 dm at the turbine inlet temperature of 700 °C and it increases with increasing turbine inlet temperature. However the SP values of the main compressor and re-compressor increase with increasing compressor inlet temperature.

Advanced High Temperature Gas-Cooled Reactor Systems

2008 ◽  
Author(s):  
Yasuyoshi Kato
Keyword(s):  
Gas Turbine ◽  
Power Conversion ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Co2 Gas ◽  
Flow Channels ◽  
Turbine Inlet ◽  
Conversion System ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

Three systems have been proposed for advanced high temperature gas-cooled reactors (HTGRs): a supercritical carbon dioxide (S-CO2) gas turbine power conversion system; a new MicroChannel Heat Exchanger (MCHE); and a once-through-then-out (OTTO) refueling scheme with burnable poison (BP) loading. An S-CO2 gas turbine cycle attains higher cycle efficiency than a He gas turbine cycle due to reduced compression work around the critical point of CO2. Considering temperature lowering at the turbine inlet by 30°C through the intermediate heat exchange, the S-CO2 indirect cycle achieves efficiency of 53.8% at turbine inlet temperature of 820°C and turbine inlet pressure of 20 MPa. This cycle efficiency value is higher by 4.5% than that (49.3%) of a He direct cycle at turbine inlet temperature of 850°C and 7 MPa. A new MCHE has been proposed as intermediate heat exchangers between the primary cooling He loop and the secondary S-CO2 gas turbine power conversion system; and recuperators of the S-CO2 gas turbine power conversion system. This MCHE has discontinuous “S”-shape fins providing flow channels with near sine curves. Its pressure drop is one-sixth reference to the conventional MCHE with zigzag flow channel configuration while the same high heat transfer performance inherits. The pressure drop reduction is ascribed to suppression of recirculation flows and eddies that appears around bend corners of zigzag flow channels in the conventional MCHE. An optimal BP loading in an OTTO refueling scheme eliminates the drawback of its excessively high axial power peaking factor, reducing the power peaking factor from 4.44 to about 1.7; and inheriting advantages over the multi-pass scheme because of the lack of fuel handling and integrity checking systems; and reloading. Because of the power peaking factor reduction, the maximum fuel temperatures are lower than the maximum permissible values of 1250°C for normal operation and 1600°C during a depressurization accident.

Thermodynamic and Economic Analysis and Multi-Objective Optimization of Supercritical CO2 Brayton Cycles

2015 ◽  
Author(s):  
Hang Zhao ◽  
Qinghua Deng ◽  
Wenting Huang ◽  
Zhenping Feng
Keyword(s):  
Supercritical Co2 ◽  
Exergy Efficiency ◽  
Temperature Cycle ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Multi Objective Optimization ◽  
Turbine Inlet Temperature ◽  
Multi Objective ◽  
Turbine Inlet ◽  
Thermodynamic Performance

Supercritical CO2 Brayton cycles (SCO2BC) offer the potential of better economy and higher practicability due to their high power conversion efficiency, moderate turbine inlet temperature, compact size as compared with some traditional working fluids cycles. In this paper, the SCO2BC including the SCO2 single-recuperated Brayton cycle (RBC) and recompression recuperated Brayton cycle (RRBC) are considered, and flexible thermodynamic and economic modeling methodologies are presented. The influences of the key cycle parameters on thermodynamic performance of SCO2BC are studied, and the comparative analyses on RBC and RRBC are conducted. Based on the thermodynamic and economic models and the given conditions, the Non-dominated Sorting Genetic Algorithm II (NSGA-II) is used for the Pareto-based multi-objective optimization of the RRBC, with the maximum exergy efficiency and the lowest cost per power ($/kW) as its objectives. In addition, the Artificial Neural Network (ANN) is chosen to establish the relationship between the input, output, and the key cycle parameters, which could accelerate the parameters query process. It is observed in the thermodynamic analysis process that the cycle parameters such as heat source temperature, turbine inlet temperature, cycle pressure ratio, and pinch temperature difference of heat exchangers have significant effects on the cycle exergy efficiency. And the exergy destruction of heat exchanger is the main reason why the exergy efficiency of RRBC is higher than that of RBC under the same cycle conditions. Compared with the two kinds of SCO2BC, RBC has a cost advantage from economic perspective, while RRBC has a much better thermodynamic performance, and could rectify the temperature pinching problem that exists in RBC. Therefore, RRBC is recommended in this paper. Furthermore, the Pareto front curve between the cycle cost/ cycle power (CWR) and the cycle exergy efficiency is obtained by multi-objective optimization, which indicates that there is a conflicting relation between them. The optimization results could provide an optimum trade-off curve enabling cycle designers to choose their desired combination between the efficiency and cost. Moreover, the optimum thermodynamic parameters of RRBC can be predicted with good accuracy using ANN, which could help the users to find the SCO2BC parameters fast and accurately.

scholarly journals Parametric Investigation and Thermoeconomic Optimization of a Combined Cycle for Recovering the Waste Heat from Nuclear Closed Brayton Cycle

2016 ◽  
Vol 2016 ◽  
pp. 1-12
Author(s):  
Lihuang Luo ◽  
Hong Gao ◽  
Chao Liu ◽  
Xiaoxiao Xu
Keyword(s):  
Mass Fraction ◽  
Waste Heat ◽  
Combined Cycle ◽  
Cycle Performance ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet ◽  
Overall Efficiency ◽  
Economic Analyses

A combined cycle that combines AWM cycle with a nuclear closed Brayton cycle is proposed to recover the waste heat rejected from the precooler of a nuclear closed Brayton cycle in this paper. The detailed thermodynamic and economic analyses are carried out for the combined cycle. The effects of several important parameters, such as the absorber pressure, the turbine inlet pressure, the turbine inlet temperature, the ammonia mass fraction, and the ambient temperature, are investigated. The combined cycle performance is also optimized based on a multiobjective function. Compared with the closed Brayton cycle, the optimized power output and overall efficiency of the combined cycle are higher by 2.41% and 2.43%, respectively. The optimized LEC of the combined cycle is 0.73% lower than that of the closed Brayton cycle.

Effect of Turbine Inlet Temperature on Blade Tip Leakage Flow and Heat Transfer

2009 ◽  
Author(s):  
Sung In Kim ◽  
Md Hamidur Rahman ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Turbine Inlet Temperature ◽  
Maximum Heat ◽  
Tip Leakage ◽  
Turbine Inlet ◽  
Blade Tip

One of the most critical gas turbine engine components, rotor blade tip and casing, are exposed to high thermal load. It becomes a significant design challenge to protect the turbine materials from this severe situation. As a result of geometric complexity and experimental limitations, Computational Fluid Dynamics (CFD) tools have been used to predict blade tip leakage flow aerodynamics and heat transfer at typical engine operating conditions. In this paper, the effect of turbine inlet temperature on the tip leakage flow structure and heat transfer has been studied numerically. Uniform low (LTIT: 444 K) and high (HTIT: 800 K) turbine inlet temperature have been considered. The results showed the higher turbine inlet temperature yields the higher velocity and temperature variations in the leakage flow aerodynamics and heat transfer. For a given turbine geometry and on-design operating conditions, the turbine power output can be increased by 1.48 times, when the turbine inlet temperature increases 1.80 times. Whereas the averaged heat fluxes on the casing and the blade tip become 2.71 and 2.82 times larger, respectively. Therefore, about 2.8 times larger cooling capacity is required to keep the same turbine material temperature. Furthermore, the maximum heat flux on the blade tip of high turbine inlet temperature case reaches up to 3.348 times larger than that of LTIT case. The effect of the interaction of stator and rotor on heat transfer features is also explored using unsteady simulations.

scholarly journals Can a Wastewater Treatment Plant Power Itself? Results from a Novel Biokinetic-Thermodynamic Analysis

J ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 614-637
Author(s):  
Mustafa Erguvan ◽  
David W. MacPhee
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Energy Demand ◽  
Treatment Plant ◽  
Developed Countries ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet ◽  
Energy And Exergy

The water–energy nexus (WEN) has become increasingly important due to differences in supply and demand of both commodities. At the center of the WEN is wastewater treatment plants (WWTP), which can consume a significant portion of total electricity usage in many developed countries. In this study, a novel multigeneration energy system has been developed to provide an energetically self-sufficient WWTP. This system consists of four major subsystems: an activated sludge process, an anerobic digester, a gas power (Brayton) cycle, and a steam power (Rankine) cycle. Furthermore, a novel secondary compressor has been attached to the Brayton cycle to power aeration in the activated sludge system in order to increase the efficiency of the overall system. The energy and exergy efficiencies have been investigated by varying several parameters in both WWTP and power cycles. The effect of these parameters (biological oxygen demand, dissolved oxygen level, turbine inlet temperature, compression ratio and preheater temperature) on the self-efficiency has also been investigated. It was found here that up to 109% of the wastewater treatment energy demand can be produced using the proposed system. The turbine inlet temperature of the Brayton cycle has the largest effect on self-sufficiency of the system. Energy and exergy efficiencies of the overall system varied from 35.7% to 46.0% and from 30.6% to 33.55%, respectively.

Analysis of Integrated Cooling Systems for Gas Turbine Power Plants

2017 ◽  
Author(s):  
Waleed El-Damaty ◽  
Mohamed Gadalla
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Air Cooling ◽  
Turbine Inlet Temperature ◽  
Current Increase ◽  
Turbine Inlet ◽  
Compact Size

With the current increase in electricity consumption and energy demand, most of the research focus is shifted towards the means of increasing the power plants efficiency in order to produce more electricity by using as less fuel as possible. Gas turbine power plants specifically have been under the study in the recent years due to its feasibility, low capital cost, simple design, compact size and higher efficiency compared to steam turbine power plants. There are a lot of operating conditions that affect the performance of the gas turbine which includes the inlet air climatic conditions, mass flow rate and the turbine inlet temperature. Many improvements and enhancements became applicable through the advancement in the material and cooling technologies. Cooling techniques could be used to cool the inlet air entering the compressor by utilizing evaporative coolers and mechanical chillers, and to cool the turbine blades in order to avoid a decline in the life of turbine blades due to unwanted exposure to thermal stresses and oxidation. Internal convection cooling, film cooling and transpiration cooling are the three main techniques that can be used in the process of turbine blades cooling. The main objective of this proposal is to improve the durability and performance of gas turbine power plants by proposing the usage of integrated system of solid desiccant with Maisotsenko cooler in the turbine blade cooling and inlet air cooling processes. Four configurations were presented and the results were an increase in the efficiency of the gas turbine cycle for all the cases specially the two stage Maisotsenko desiccant cooling system where the efficiency increased from 33.33% to 34.17% as well as maintaining the turbine inlet temperature at a desired level of 1500°K.

Turbine Inlet Temperature Measurements in a T 8200 kW Gas Turbine Using Water Vapor Emission

2021 ◽  
Author(s):  
Dale R. Tree ◽  
Dustin Badger ◽  
Darrel Zeltner ◽  
Mohsen Rezasoltani
Keyword(s):  
Water Vapor ◽  
Gas Turbine ◽  
Guide Vane ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Test Cell ◽  
Temperature Measurements ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet

Abstract The measurement of turbine inlet temperature is challenging because of high temperatures and complicated physical access, but continuous measurement of the turbine inlet temperature is very important for maximizing turbine efficiency and increasing durability. This paper provides in-situ turbine rotor inlet temperature (TRIT) measurements in an 8200 kW operating gas turbine engine. The measurements were obtained using integrated spectral infrared (ISIR) emission from the water vapor of the combustion gases entering the turbine rotor. The method utilizes a sapphire optical fiber to convey the signal from the turbine wall to outside the turbine casing. All components are capable of long-term exposure to the turbine operating conditions. The temperature measurements were obtained at 6 operating conditions between 50% and full load. The TRIT temperature was also determined using more than 20 test cell inputs and Solar Turbine’s commercial test cell engine model. The two temperatures (measured and modeled) were within 11 K (less than 1%) across the load sweep. Uncertainty calculations suggest that the uncertainty of the measurement can be expected to be ±2.9% within a confidence interval of 95%. The method also yields the nozzle guide vane surface temperature which was found to increase monotonically with increasing load.

Aerodynamic Performance Measurements of a Film-Cooled Turbine Stage: Experimental Results

2002 ◽  
Author(s):  
R. C. Keogh ◽  
G. R. Guenette ◽  
C. M. Spadaccini ◽  
T. P. Sommer ◽  
S. Florjancic
Keyword(s):  
Film Cooling ◽  
High Performance ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Experimental Results ◽  
Inlet Temperature ◽  
Turbine Stage ◽  
Performance Measurements ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet

Modern high performance gas turbine engines utilize film cooling to reduce the heat load on high-pressure turbine stage components, thereby increasing the maximum turbine inlet temperature at which the cycle can operate. However, increased turbine inlet temperature comes at the expense of a reduction in turbine efficiency. The objective of this research is to measure the aerodynamic performance of a film cooled turbine stage and to quantify the loss caused by film cooling. An un-cooled turbine stage was first fabricated with solid blading and tested using a newly developed short duration measurement technique. The stage was then modified to incorporate vane, blade and rotor casing film cooling. The film-cooled stage was then tested over a range of coolant-to-mainstream mass flow and temperature ratios for the same range of operating conditions (pressure ratios and corrected speeds) as the un-cooled turbine. This paper presents the experimental results for these two series of tests.

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