Supercritical CO2 Gas Turbine Research Articles

Performance Analysis of WHR Systems for Marine Applications Based on sCO2 Gas Turbine and ORC

Waste heat recovery (WHR) can represent a solution to improve the efficiency of ships’ propulsion, helping to exceed stringent greenhouse gas emission limits. This is particularly suitable in the case of propulsion based on gas turbines due to their medium-high temperature level of the exhaust gases. This study analyzes the performance of a hybrid energy grid, in which the heat is recovered by the exhaust gases of an aeroderivative gas turbine, a GE LM2500+, when the bottoming system is a supercritical CO2 gas turbine. Given the issues and peculiarities related to the onboard installation, where size and weight are fundamental concerns, six WHR schemes have been analyzed. They span from the simple cycle to partial preheated and regenerative, to a cascade layout in which an ORC system receives thermal power by the sCO2 GT. The influence of the seawater temperature on the performance of the hybrid energy system has been also considered. The energetic and exergetic performance comparison of the different schemes has been carried out by using the commercial software Thermoflex. The results showed that an increase in overall performance by up to 29% can be obtained and that the increase in seawater temperature can lead to a decrease in the overall performance.

An optimized power conversion system for a stellarator-based nuclear fusion power plant

Fusion is a candidate base-load and load-following energy source for the future carbon-free energy mix, and stellarators are promising magnetic fusion reactors. Unlike all other fusion devices, which are pulsed, the stellarator is inherently steady-state. Thus it requires a different downstream power conversion system compared to tokamaks. In this paper, we conceive and optimize such a system for a stellarator power plant equipped with plasma-facing liquid metal walls in the 700–900 °C temperature range. We rely on a supercritical CO2 Brayton–Rankine Combined Cycle, and optimize the power plant via a genetic algorithm. We also compare the effect of the characteristic parameters on the stellarator performance. The efficiency of the power conversion system is 51% and net electrical efficiency of the complete plant (including reactor auxiliaries) is 34%. Such figures are remarkably higher compared to the state-of-the-art designs in the field of thermo-nuclear fusion plants, considering that the most optimistic and recent estimate foresee a heat-to-power conversion efficiency of about 34% for tokamak-like reactors. Finally, we discuss the technical feasibility of the two most critical components for operations: (i) the large-scale supercritical CO2 Gas Turbine, and (ii) the compact heat exchanger for the Brayton cycle. We obtain compact machines since the maximum diameter calculated for the s-CO2 compressor is about 1.2 m with a rotational speed of 3000 rpm, and the volume required to accommodate the heat exchange surface could achieve 40 m3 with an area density of 7900 m2/m3.

Operating scenario of 3GWth class FFHR power plant with bypass controlled supercritical CO2 gas turbine power generation system

Abstract In order to achieve high power generation efficiency, facility compactness, high safety, and high coexistence with fuel tritium in the 3 G Wth class FFHR(Force Free Helical Reactor) power plant, optimization, performance and operation scenario of the power generation system of the power plant model using the axial flow type uniaxial supercritical CO2 gas turbine power generation system were examined. As a result, the following conclusions were obtained. (1) The most efficient and compact axial flow uniaxial design supercritical CO2 gas turbine power generation system suitable for 3 G WthFFHR power plant has a maximum heat capacity of 1.5GWth×2, and the gas turbine conversion rate at that time was evaluated as 46.9 %(= 1,267MWe/2,700MWth). Therefore, split connection with two power generation systems is optimal for a 3 G Wth class FFHR power plant. Here, the operating speed of the turbo equipment was set to 3600 rpm in order to adapt this plant model to the power supply system in Japan. (2) Simultaneous supply of 818MWe/300 s electricity and 300MWth/30days heat is required at startup of the FFHR. (3) The in-house power during steady operation under the self-ignition condition was reduced to about 31.7MWe, and the amount of power generated at the transmission end was evaluated as 1,234MWe.

Demonstration Plan of Nuclear Fusion Power Generation Principle by Supercritical CO2 Gas Turbine in Oroshhi-2

We are proposing to connect a supercritical CO2 gas turbine (SCOT) power generator to the Operational Recovery of Separated Hydrogen and Heat Inquiry-2 (Oroshhi-2) nuclear fusion primary molten salt test loop constructed at the National Institute for Fusion Science and conduct a demonstration test of the power generation principle from the world’s first nuclear fusion simulated heat output. In this paper, we describe the results of a design study of the FLiNaK/CO2 intermediate heat exchanger and SCOT power generation system and related equipment that can be connected to the molten salt test loop. From the results of this study, it was concluded that the power generation principle verification test with 20-kW(electric)–class power generation with an efficiency of 20% is possible by the SCOT system connected to the FLiNaK test loop in Oroshhi-2 equipment via the intermediate heat exchanger.

Thermodynamic optimization and equipment development for a high efficient fossil fuel power plant with zero emissions

Abstract The transition to oxy-fuel combustion cycles is a perspective way to decrease harmful emissions into the atmosphere in the energy sector. The oxy-fuel, supercritical carbon dioxide Allam cycle (NET Power oxy-combustion cycle) is a promising technology with high efficiency. Emissions of carbon dioxide into the atmosphere could be decreased by 98.9% using this cycle for electricity production, which is 8–17% higher compare to gas turbine combined cycle with post-combustion carbon capture. However, there are several challenges on the way of its implementation, one of which is the development of a supercritical carbon dioxide gas turbine. The aim of the present study was to develop a construction of a high-power supercritical CO2 gas turbine with optimal thermodynamic parameters of the Allam cycle and to evaluate technical, environmental and economic characteristics of zero emission technology for the electricity production. To reach the goal, the calculation algorithm allowing to model the oxy-fuel combustion cycles was developed. The results of thermodynamic optimization showed that the highest value of cycle net efficiency equal to 56.5% is achieved for the turbine inlet temperature and pressure of 1083 °C and 30 MPa, the turbine outlet pressure of 3 MPa and the coolant temperature of 200 °C. The formed equipment requirements were used to create the design of a 335 MW supercritical carbon dioxide gas turbine, the main features of which were described in detail. The results of environmental characteristics analysis showed, that the specific amount of CO2 emitted from the cycle to the atmosphere is 0.0038 kg/kWh. The results of economic feasibility evaluation for the Allam cycle showed that the total specific investment costs including the price for carbon storage are equal to $1307.5/kW, which is quite competitive value.

Design and Analysis of an Axial Bypass Compressor Blade in a Supercritical CO2 Gas Turbine

Design and Analysis of an Axial Bypass Compressor Blade in a Supercritical CO2 Gas Turbine

Research on Flow Characteristics of Supercritical CO2 Axial Compressor Blades by CFD Analysis

A supercritical CO2 gas turbine of 20MPa is suitable to couple with the Na-cooled fast reactor since Na - CO2 reaction is mild at the outlet temperature of 800K, the cycle thermal efficiency is relatively high and the size of CO2 gas turbine is very compact. In this gas turbine cycle, a compressor operates near the critical point. The property of CO2 and then the behavior of compressible flow near the critical point changes very sharply. So far, such a behavior is not examined sufficiently. Then, it is important to clarify compressible flow near the critical point. In this paper, an aerodynamic design of the axial supercritical CO2 compressor for this system has been carried out based on the existing aerodynamic design method of Cohen1). The cycle design point was selected to achieve the maximum cycle thermal efficiency of 43.8%. For this point, the compressor design conditions were determined. They are a mass flow rate of 2035kg/s, an inlet temperature of 308K, an inlet static pressure of 8.26MPa, an outlet static pressure of 20.6MPa and a rotational speed of 3600rpm. The mean radius was constant through axial direction. The design point was determined so as to keep the diffusion factor and blade stress within the allowable limits. Number of stages and an expected adiabatic efficiency was 14 and 87%, respectively. CFD analyses by FLUENT have been done for this compressor blade. The blade model consists of one set of a guide vane, a rotor blade and a stator blade. The analyses were conducted under the assumption both of the real gas properties and also of the modified ideal gas properties. Using the real gas properties, analysis was conducted for the 14th blade, whose condition is remote from the critical point and the possibility of divergence is very small. Then, the analyses were conducted for the blade whose conditions are nearer to the critical point. Gradually, divergence of calculation was encountered. Convergence was relatively easy for the modified ideal gas properties. Main output of calculation is a value of the mass flow rate, which was larger than the design value. However the discrepancy of mass flow rates between CFD and design reduced if the 3-dimensional effects are taken into consideration. Absolute velocity distributions, relative velocity distributions and static pressure distributions surrounding rotor blade and stator blade were obtained. The characteristics of these distributions were consistent with those of the fundamental theory and these analyses were justified.