Numerical Study of the Axial Gap and Hot Streak Effects on Thermal and Flow Characteristics in Two-Stage High Pressure Gas Turbine

Choi, Myung Gon; Ryu, Jaiyoung

doi:10.3390/en11102654

Cited by 18 publications

(19 citation statements)

References 26 publications

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“…To enable a comprehensive analysis of the drag on the pod, simulations were conducted over a large parameter space covering various BR (0.25, 0.36), pod speeds (50-350 m/s), pod lengths (10.75-86 m), tube pressures (101.325-1013. 25 Pa, equivalent to 0.001-0.01 atm), and tube temperatures (275-325 K). The study objectives with regard to these parameters are presented below.…”

Section: Resultsmentioning

confidence: 99%

“…Under inlet-type boundary conditions, the far-field pressure is non-reflecting for a one-dimensional flow. The pod speed at the inlet was set to 25,50,75,100,125,150,175,200,225,250,275,300,325, or 350 m/s (Ma = 0.07203, 0.1441, 0.2161, 0.2881, 0.3601, 0.4322, 0.5042, 0.5762, 0.6483, 0.7203, 0.7923, 0.8643, 0.9364, or 1.0084, respectively). The pressure at the inlet was 101.325, 250, 500, 750, or 1013.25 Pa, and the temperature was 275, 300, or 325 K. The outlet was a pressure-type outlet.…”

Section: Computational Fluid Dynamics Simulationmentioning

confidence: 99%

“…As separated flow and stalling phenomena are strictly related to boundary layer behavior, the transition SST model should be able to simulate these phenomena, which are critical in transonic-speed Hyperloop applications [23]. According to previous studies, the transition SST model adequately predicts flow transition and flow separation for a wide range of angles of attack [24,25].…”

Section: Mathematical Modelmentioning

confidence: 99%

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Numerical Analysis of Aerodynamic Characteristics of Hyperloop System

Kang

Ham

et al. 2019

Energies

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The Hyperloop system is a new concept that allows a train to travel through a near-vacuum tunnel at transonic speeds. Aerodynamic drag is one of the most important factors in analyzing such systems. The blockage ratio (BR), pod speed/length, tube pressure, and temperature affect the aerodynamic drag, but the specific relationships between the drag and these parameters have not yet been comprehensively examined. In this study, we investigated the flow phenomena of a Hyperloop system, focusing on the effects of changes in the above parameters. Two-dimensional axisymmetric simulations were performed in a large parameter space covering various BR values (0.25, 0.36), pod lengths (10.75–86 m), pod speeds (50–350 m/s), tube pressures (~100–1000 Pa), and tube temperatures (275–325 K). As BR increased, the pressure drag was significantly affected. This is because of the smaller critical Mach number for a larger BR. As the pod length increased, the total drag and pressure drag did not change significantly, but there was a considerable influence on the friction drag. As the pod speed increased, strong shock waves occurred near the end of the pod. At this point, the flows around the pod were severely choked at both BR values, and the ratio of the pressure drag to the total drag converged to its saturation level. At tube pressures above 500 Pa, the friction drag increased significantly under the rapidly increased turbulence intensity near the pod surface. High tube temperatures increase the speed of sound, and this reduces the Mach number for the same pod speed, consequently delaying the onset of choking and reducing the aerodynamic drag. The results presented in this study are applicable to the fundamental design of the proposed Hyperloop system.

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Section: Resultsmentioning

confidence: 99%

Section: Computational Fluid Dynamics Simulationmentioning

confidence: 99%

Section: Mathematical Modelmentioning

confidence: 99%

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Numerical Analysis of Aerodynamic Characteristics of Hyperloop System

Kang

Ham

et al. 2019

Energies

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“…Many studies have examined the heat flow characteristics of the surface of normal turbine blades under various conditions. Choi and Ryu [9] investigated the effects of the axial gap and inlet temperature conditions on the thermal flow characteristics of a blade surface. They claimed that the thermal load on the surface of rotor blades increased when the axial gap decreased.…”

Section: Introductionmentioning

confidence: 99%

Effects of Leading-Edge Modification in Damaged Rotor Blades on Aerodynamic Characteristics of High-Pressure Gas Turbine

Dam

Ryu

2020

Mathematics

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The flow and heat-transfer attributes of gas turbines significantly affect the output power and overall efficiency of combined-cycle power plants. However, the high-temperature and high-pressure environment can damage the turbine blade surface, potentially resulting in failure of the power plant. Because of the elevated cost of replacing turbine blades, damaged blades are usually repaired through modification of their profile around the damage location. This study compared the effects of modifying various damage locations along the leading edge of a rotor blade on the performance of the gas turbine. We simulated five rotor blades—an undamaged blade (reference) and blades damaged on the pressure and suction sides at the top and middle. The Reynolds-averaged Navier–Stokes equation was used to investigate the compressible flow in a GE-E3 gas turbine. The results showed that the temperatures of the blade and vane surfaces with damages at the middle increased by about 0.8% and 1.2%, respectively. This causes a sudden increase in the heat transfer and thermal stress on the blade and vane surfaces, especially around the damage location. Compared with the reference case, modifications to the top-damaged blades produced a slight increase in efficiency about 2.6%, while those to the middle-damaged blades reduced the efficiency by approximately 2.2%.

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“…As global warming and the depletion of energy resources have intensified, the growth in worldwide energy demand currently faces the difficulty of installing new power generation facilities as a result of limited funding and the strengthening of environmental regulations. Thus, combined cycle power plants (CCPPs), which consist of gas turbines and steam turbines, are becoming more important as the global demand for electrical power increases [1,2]. CCPPs manipulate discarded heat energy and store in hot gas into rotational energy, and the gas turbine compresses air and mixes it with fuel that is heated to a high temperature.…”

Section: Introductionmentioning

confidence: 99%

Design of Laminated Seal for Triple Offset Butterfly Valve (350 °C) Used in Combined Cycle Power Plants

et al. 2019

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In combined cycle power plants (CCPPs), the bypass butterfly valve is a key component to facilitate regulation of exhaust gas energy available at the turbine and to not produce too much boost pressure. The conventional damper valve causes leakage, back flow into the turbine, and damage of the blade, and the existing dual-layered seal with polytetrafluoroethylene (PTFE) and metal should be frequently replaced owing to its low durability and deterioration of mechanical properties under a high temperature. This study devised a triple offset butterfly valve with a new type of seal by alternatively laminating stainless steel and graphite to improve valve performance at the high temperature (350 °C). The slope angles of the seal contact surface to prevent friction were calculated using the mathematical models of the triple offset. Thermal-structure coupled analyses by varying the number of graphite and thickness were conducted, and the seven-layer model with the graphite thickness of 0.8 mm, which shows airtightness and smooth operation, was chosen. The contact stresses behaviors of the graphite at 350 °C and at −196 °C were investigated, and it was found that the graphite is in charge of improving driving performance of the disc at the high temperature and sealing performance at the cryogenic temperature. The performance tests and the field tests of the suggested model verified its performance at the working temperature.

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Numerical Study of the Axial Gap and Hot Streak Effects on Thermal and Flow Characteristics in Two-Stage High Pressure Gas Turbine

Cited by 18 publications

References 26 publications

Numerical Analysis of Aerodynamic Characteristics of Hyperloop System

Numerical Analysis of Aerodynamic Characteristics of Hyperloop System

Effects of Leading-Edge Modification in Damaged Rotor Blades on Aerodynamic Characteristics of High-Pressure Gas Turbine

Design of Laminated Seal for Triple Offset Butterfly Valve (350 °C) Used in Combined Cycle Power Plants

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