• Nuclear Engineering and Technology
• /
• v.55 no.7
• /
• pp.2697-2711
• /
• 2023

In this study, the validity of reducing the number of gas turbine stages designed for a nitrogen Brayton cycle coupled to a sodium-cooled fast reactor was assessed. The turbine performance was evaluated through computational fluid dynamics (CFD) simulations under different off-design conditions controlled by a reduced flow rate and reduced rotational speed. Two different multistage gas turbines designed to extract almost the same specific work were selected: two- and three-stage turbines (mid-span stage loading coefficient: 1.23 and 1.0, respectively). Real gas properties were considered in the CFD simulation in accordance with the Peng-Robinson's equation of state. According to the CFD results, the off-design performance of the two-stage turbine is comparable to that of the three-stage turbine. Moreover, compared to the three-stage turbine, the two-stage turbine generates less entropy across the shock wave. The results indicate that under both design and off-design conditions, increasing the stage loading coefficient for a fewer number of turbine stages is effective in terms of performance and size. Furthermore, the Ellipse law can be used to assess off-design performance and increasing exponent of the expansion ratio term better predicts the off-design performance with a few stages (two or three).

• Nuclear Engineering and Technology
• /
• v.47 no.6
• /
• pp.647-661
• /
• 2015

The supercritical $CO_2$ (S-$CO_2$) Brayton cycle has recently been gaining a lot of attention for application to next generation nuclear reactors. The advantages of the S-$CO_2$ cycle are high efficiency in the mild turbine inlet temperature region and a small physical footprint with a simple layout, compact turbomachinery, and heat exchangers. Several heat sources including nuclear, fossil fuel, waste heat, and renewable heat sources such as solar thermal or fuel cells are potential application areas of the S-$CO_2$ cycle. In this paper, the current development progress of the S-$CO_2$ cycle is introduced. Moreover, a quick comparison of various S-$CO_2$ layouts is presented in terms of cycle performance.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2000.11a
• /
• pp.18-18
• /
• 2000

산업용 가스터빈에서 대기로 방출되는 배기열을 효과적으로 이용하기 위한 역 브레이튼 사이클 가스터빈(Reverse Brayton Cycle Gas Turbine) 엔진의 출력과 비연료 소비율 및 열효율을 기본 브레이튼 사이클 엔진, 재열사이클에 역 브레이튼 사이클을 추가한 엔진, 역 브레이튼 사이클에 중간냉각기를 추가한 엔진의 출력, 비연료 소비율 및 열효율을 비교하였다.(중략)

• Nuclear Engineering and Technology
• /
• v.39 no.2
• /
• pp.95-102
• /
• 2007

The conceptual design of the MIT modular pebble bed reactor is described. This reactor plant is a 250 Mwth, 120 Mwe indirect cycle plant that is designed to be deployed in the near term using demonstrated helium system components. The primary system is a conventional pebble bed reactor with a dynamic central column with an outlet temperature of 900 C providing helium to an intermediate helium to helium heat exchanger (IHX). The outlet of the IHX is input to a three shaft horizontal Brayton Cycle power conversion system. The design constraint used in sizing the plant is based on a factory modularity principle which allows the plant to be assembled 'Lego' style instead of constructed piece by piece. This principle employs space frames which contain the power conversion system that permits the Lego-like modules to be shipped by truck or train to sites. This paper also describes the research that has been conducted at MIT since 1998 on fuel modeling, silver leakage from coated fuel particles, dynamic simulation, MCNP reactor physics modeling and air ingress analysis.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.11a
• /
• pp.527-530
• /
• 2010

A performance test of an air cycle machine with an air to air heat exchanger was performed. The air cycle machine designed for avionics cooling in a fighter's external pod is a small turbo machine operated on the reverse Brayton air cycle driven by captured ram air which is the source of driving energy and it can be used as cooling fluid going through electronics in the pod during the flight. The air to air heat exchanger was also used to avoid moisture for avionics. The performance test have verified that the developed ACM and heat exchanger meet the design requirements.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.6
• /
• pp.95-103
• /
• 2014

During the international effort to develop the next generation nuclear reactor technologies, many new power cycle concepts were derived to improve efficiency and reduce the capital cost. Among many innovative power cycles, it was identified that the supercritical $CO_2$ (S-$CO_2$) Brayton cycle technology has a big potential to outperform the existing steam cycle and eventually replace it. The S-$CO_2$ cycle achieves high efficiency with very compact size, which is the ultimate advantage for a power cycle to have. The S-$CO_2$ cycle has a great potential not only for the future nuclear applications but also for general heat sources such as coal, natural gas, and concentrated solar. In this paper, a brief introduction to the S-$CO_2$ power cycle technologies will be first provided, and a short summary of current research and development status of the power cycle technology around the world will be followed. Especially the research works performed by KAIST, KAERI and several related research institutions in Korea will be reviewed in more detail, since they have recently developing a strong infrastructure to test these ideas by constructing a demonstration facility while producing many innovative ideas to improve and realize the concept.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.12
• /
• pp.1421-1426
• /
• 2014

To improve the inherent safety of the sodium-cooled fast reactor (SFR), the supercritical $CO_2$ ($S-CO_2$) Brayton cycle is being considered as an alternative power conversion system to steam the Rankine cycle. In the $S-CO_2$ system, a PCHE (printed circuit heat exchanger) is being considered. In this type of heat exchangers, diffusion bonding is used for joining the thin plates. In this study, the diffusion bonding characteristics of various austenitic alloys were evaluated. The tensile properties were measured at temperatures starting from the room temperature up to $650^{\circ}C$. For the 316H and 347H types of stainless steel, the tensile ductility was well maintained up to $550^{\circ}C$. However, the Incoloy 800HT showed lower strength and ductility at all temperatures. The microstructure near the bond line was examined to understand the reason for the loss of ductility at high temperatures.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.42 no.10
• /
• pp.858-869
• /
• 2014

Most of the aerospace propulsion is based on the Brayton cycle, in which the combustion is held through the constant pressure process, but further improvement of performance by increasing compression ratio is challenged by mechanical limits. Detonation propulsions, regarded promising for high-speed propulsion for a lase decade, is more rigorously studied in these days as a game-changer for the improvement of thermodynamic efficiency of propulsion and power generation systems. Since, the additional compression by the strong shock of the detonation wave is considered increasing thermodynamics efficiency that is hardly achievable by the conventional compression systems. Present paper will give an introduction the latest technical trends on the Pulse Detonation Engines(PDEs) and the activities on the Pressure Gain Combustion (PGC) based on Constant Volume Combustion (CVC).

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.10
• /
• pp.787-793
• /
• 2015

In response to the growing interest in supercritical carbon dioxide ($S-CO_2$) power cycle technology because of its potential enhancement in compactness and efficiency, the $S-CO_2$ cycles have been studied intensively in the fields of nuclear power, concentrated solar power (CSP), and fossil fuel power generation. Despite this interest, there are relatively few studies on waste heat recovery applications. In this study, the $S-CO_2$ cycle that has a split flow with preheating was modeled and simulated. The variation in the power was investigated with respect to the changes in the value of a design parameter. Under the simulation conditions considered in this study, it was confirmed that the design parameter has an optimal value that can maximize the power in the $S-CO_2$ power cycle that has a split flow with preheating.

• Transactions of the Korean hydrogen and new energy society
• /
• v.5 no.2
• /
• pp.91-98
• /
• 1994

In this study hydrogen gas and oxygen gas are used to make a pollution-free engine which is a closed system with the components such as a combustor, two turbines, a radiator and a compressor. One of the two turbines produces main power, and the other is used to drive a compressor to compress unburned gases and to return them to the combustor. Some of the water from the radiator is pumped to cool down the internal wall of the combustor and to be used as a working fluid which expands from liquid state to vapor state to get more expansion work. The possibility of operating the whole system is checked by the thermodynamic analysis to make the closed engine system. The calculations in the thermal analysis are based on the Brayton cycle and the Rankine cycle. The closed system in this study shows similar efficiency as usual internal combustion engines, but it produces water only without air pollution such as $NO_x$ and soot.