• New & Renewable Energy
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• v.19 no.4
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• pp.61-71
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• 2023

The necessity of energy utilization using livestock manure has been proposed with the decrease in domestic agricultural land. Livestock manure solid fuel has been investigated as a promising energy resource owing to its convenient storage and use in agricultural and livestock fields. Additional electricity production is possible through the integration of a biomass combustion boiler with the organic Rankine cycle (ORC). In this study, a mathematical system model of the cattle manure solid fuel boiler integrated with the ORC was developed to analyze the components' performance under variable operating conditions. A sensitivity analysis was conducted to confirm the electrical efficiency of the ORC turbine and the applicability of this system. The minimum required waste heat recovery rate was derived considering the system marginal price and levelized cost of electricity of the ORC. The simulation results showed that, in Korea, more than 77.98% of waste heat recovery and utilization in ORC turbines is required to achieve economic feasibility through ORC application.

• Journal of Ocean Engineering and Technology
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• v.38 no.2
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• pp.74-85
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• 2024

Offshore wind turbines are supported by various foundations, each with its considerations in design and construction. Gravity, monopile, and suction bucket foundations encounter geotechnical issues, while jacket and tripod foundations face fatigue problems. Considering this, a gravity foundation based on a steel skirt was developed, and a monopile foundation was analyzed for Pile-Soil Interaction using the p-y curve and 3D finite element method (3D FEM). In addition, for suction bucket foundations, the effects of lateral and vertical loads were analyzed using 3D FEM and centrifuge tests. Fatigue analysis for jacket and tripod foundations was conducted using a hotspot stress approach. Some hybrid foundations and shape optimization techniques that change the shape to complement the problems of each foundation described above were assessed. Hybrid foundations could increase lateral resistance compared to existing foundations because of the combined appendages, and optimization techniques could reduce costs by maximizing the efficiency of the structure or by reducing costs and weight. This paper presents the characteristics and research directions of the foundation through various studies on the foundation. In addition, the optimal design method is presented by explaining the problems of the foundation and suggesting ways to supplement them.

• Journal of Wind Energy
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• v.15 no.3
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• pp.21-29
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• 2024

Wind power is highly variable due to the intermittent nature of wind. This can lead to power grid instability and decreased efficiency. Therefore, it is necessary to improve wind power prediction performance to minimize the negative impact on the power system. Recently, wind power prediction using machine learning has gained popularity, and ensemble models in machine learning have shown high prediction accuracy. RF, GB, XGB and LGBM are decision tree-based ensemble models and have high predictive performance in wind power, but these models have problems from over-fitting and strong dependence on certain variables. However, the stacking model can improve prediction performance by combining individual models and compensate for the shortcomings of each model. In this study, The MAE of RF, XGB and LGBM is 310.42 kWh, 217.07 kWh and 265.20 kWh, respectively, while the stacking model based on RF, XGB and LGBM is 202.33 kWh. Stacking models can improve prediction performance. Finally, it is expected to contribute to electricity supply and demand planning.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.403-410
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• 2020

This paper focuses on the design of a 12-kW small-scale supercritical CO₂ test loop. A theoretical study, stabilization, and optimization of carbon dioxide were carried out with the application of a solar heat source based on solar thermal data in Pohang. The thermodynamic cycle of the test facility is a Rankine cycle (transcritical cycle), which contains liquid, gas, and supercritical CO₂. The system is designed to achieve 6.98% efficiency at a maximum pressure of 12 MPa and a maximum temperature of 70℃. In addition, the optimum turbine inlet temperature and pressure were calculated to increase the cycle efficiency, and the application of an internal heat exchanger (IHX) was simulated. It was found that the maximum efficiency increases to 18.75%. The simulation confirmed that the efficiency of the cycle is 6.7% in May and 6.26% in June.

• Plant Journal
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• v.14 no.3
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• pp.29-34
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• 2018

In this study, the output and thermal efficiency of Taean Integrated Gasification Combined Cycle Plant were calculated by using the manufacturer's basic design data and the performance correction factor for each atmospheric temperature, and the actual performance was measured at summer and winter representative points. The results were compared with the calculated values to verify their validity. The thermal efficiency is the highest at around $15^{\circ}C$ and lower at lower temperature and higher temperature. This is similar to that of natural gas Combined Cycle Power Plant, but the thermal efficiency has drastically decreased due to the increase of power consumption of the air separation unit at relatively high temperature. The output is highest in the range of 5 to $15^{\circ}C$, and is kept almost constant at below $5^{\circ}C$ and declines above $15^{\circ}C$. The reason why the output does not increase at low temperatures is that the torque limit of the shaft is activated by the increase of the flow rate due to the nitrogen injection of the gas turbine combustor. In order to improve the performance in the future, efforts should be made to improve the power generation output and to reduce the power consumption of the air separation unit in summer.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.5
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• pp.565-571
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• 2018

This paper designed the main blade in V-shape and tried to identify the design conditions by changing the main blade number and sub-blade number. Power output and power coefficient increased as main blade number increased. Sample 2 shows a 50% increase in power output compared to sample1. Sample 3 and sample4 increased by 92.8% and 114.7%, respectively. Sample 2 shows a 38.4% increase in power coefficient compared to sample1. Sample 3 and sample4 increased by 92.3% and 107.7%, respectively. Power output and power coefficient increased as sub-blade number increased. Sample 6 shows a 33.3% increase in power output compared to sample 5 and Sample 7 increased by 42.1%. Compared to sample5, efficiency increased by 35.3% for sample 5 and 47.1% for sample 7. The highest power output and power coefficient were measured when main blade and sub-blade were each 30 number. Sample 8 increased power output by 5.6% and power efficiency by 3.7% compared to sample 4. Compared to sample 7, sample 8 increased power efficiency by 12% and power output by 17.3%.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.14-23
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• 1998

The present study investigates numerically particle laden flow through compressor cascade. In general, a lot of turbine engines are affected by various particles which are suspending in the atmosphere. Especially in the case of aircraft aviating in volcanic, industrial and desert region including many particles, each components of engine system are damaged severely. That damage modes are erosion of compressor binding and rotor path components, partial or total blockage of cooling passage and engine control system degradation.. Initial damages can not be serious but cumulation of damages influences on safety of aircraft control and economical maintenance cost of engine system can be increased. When dust, materials and volcanic particles in the atmosphere flow in the compressor, it is necessary to predict damaged and deposited region of compressor blades. To the various flow inlet angle, predictions of particles trajectory in compressor cascade by Lagrangian method are presented and impulses by impaction of particles at blade surface are calculated. By the definition of particle deposition efficiency, characteristics of particles impact are considered quantitatively. With these prediction and experimental data, erosion rates are predicted for two materials - ceramic, soft metal - on compressor blade surface. Improvements like coating of blade surface could be found, by above prediction.

• Tribology and Lubricants
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• v.36 no.2
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• pp.105-115
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• 2020

This paper presents a numerical study on the rotordynamic analysis of a dual-spool turbofan engine in the context of blade defect events. The blades of an axial-type aeroengine are typically well aligned during the compressor and turbine stages. However, they are sometimes exposed to damage, partially or entirely, for several operational reasons, such as cracks due to foreign objects, burns from the combustion gas, and corrosion due to oxygen in the air. Herein, we designed a dual-spool rotor using the commercial 3D modeling software CATIA to simulate blade defects in the turbofan engine. We utilized the rotordynamic parameters to create two finite element Euler-Bernoulli beam models connected by means of an inter-rotor bearing. We then applied the unbalanced forces induced by the mass eccentricities of the blades to the following selected scenarios: 1) fully balanced, 2) crack in the low-pressure compressor (LPC) and high pressure compressor (HPC), 3) burn on the high-pressure turbine (HPT) and low pressure compressor, 4) corrosion of the LPC, and 5) corrosion of the HPC. Additionally, we obtained the transient and steady-state responses of the overall rotor nodes using the Runge-Kutta numerical integration method, and employed model reduction techniques such as component mode synthesis to enhance the computational efficiency of the process. The simulation results indicate that the high-vibration status of the rotor commences beyond 10,000 rpm, which is identified as the first critical speed of the lower speed rotor. Moreover, we monitored the unbalanced stages near the inter-rotor bearing, which prominently influences the overall rotordynamic status, and the corrosion of the HPC to prevent further instability. The high-speed range operation (>13,000 rpm) coupled with HPC/HPT blade defects possibly presents a rotor-case contact problem that can lead to catastrophic failure.

• Journal of the Korean Association of Geographic Information Studies
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• v.20 no.2
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• pp.47-59
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• 2017

This study aims to assess offshore wind energy resources around Jeju Island using the InVEST Offshore Wind model. First the wind power density around the coast of Jeju was calculated using reanalysis data from the Korean Local Analysis and Prediction System (KLAPS). Next, the net present value (NPV) for the 168MW offshore wind farm scenario was evaluated taking into consideration factors like costs (turbine development, submarine cable installation, maintenance), turbine operation efficiency, and a 20year operation period. It was determined that there are high wind resources along both the western and eastern coasts of Jeju Island, with high wind power densities of $400W/m^2$ calculated. To visually evaluate the NPV around Jeju Island, a classification of five grades was employed, and results showed that the western sea area has a high NPV, with wind power resources over $400W/m^2$. The InVEST Offshore Wind model can quickly provide optimal spatial information for various wind farm scenarios. The InVEST model can be used in combination with results of marine ecosystem service evaluation to design an efficient marine spatial plan around Jeju Island.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.69-76
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• 2018

The present study analyzed the effect of film hole position of 45 degree ribbed cooling channel on film cooling performance of gas turbine blades. We also investigated the influence of the ribs under the fixed blowing ratio. Three-dimensional numerical model was constructed and extensive simulation was conducted using the commercial code (Fluent ver. 17.0) under steady-state condition. Base on the simulation results, We investigated the cooling effectiveness, flow velocity, streamline, and pressure coefficient. Moreover, We analyzed the effect of cooling hole position on ejection of the secondary flow caused by the rib structure. From the results, It was found that internal flow of the cooling channel forms a vortex pair in the counterclockwise from the top side, and clockwise from the bottom side. For the channels with ribs, the vortex flow generated by the ribs caused a higher pressure difference near the hole outlet, resulting in at least 12% higher cooling effectiveness than the channel without ribs. Additionally, when the hole is located on the left side of the ribbed channel (Rib-Left), it can be found that the secondary flow generated by the ribs hits against wall surface near the hole to form a flow in the direction of the hole inclination angle. Therefore, It is considered that the region where the cooling gas discharged to the blade surface stays in the main flow boundary layer is wider than the other cases. In this case, The largest pressure coefficient difference was observed near the outlet of the hole, and as a result, the discharge of the cooling gas was accelerated and the cooling efficiency was slightly increased.