Hyundai Heavy Industries Co., Ltd. (or HHI) is the world's largest shipbuilding company. Its headquarters are in Ulsan, South Korea. HHI was founded in 1972 by Chung Ju-yung as a division of the Hyundai Group, and in 1974, completed building its first ships. In 2002, the company was spun-off from its parent company. HHI has four core business divisions: Shipbuilding, Offshore & Engineering, Industrial Plant & Engineering, and Engine & Machinery. HHI also has five non-core related subsidiaries: Hyundai Electric & Energy Systems, Hyundai Construction Equipment, Hyundai Robotics, Hyundai Heavy Industries Green Energy, and Hyundai Global Service.The Hyundai Group started as a small South Korean construction firm in 1947, headed by its founder, Korean entrepreneur Chung Ju-yung. Another widely known and closely related Korean company, the Hyundai Motor Company, was founded in 1967, five years prior to the founding of the Heavy Industry Group. The motor company was also founded by Chung. The name is an informal romanisation of the Korean 현대 (hyeondae) meaning "contemporary", which was Chung's vision for the group of companies that he founded.
As efforts to mitigate global warming have led to stricter regulations on greenhouse gas emissions, increasing attention has been directed toward alternative energy sources. Green hydrogen produced through water electrolysis powered by renewable energy is considered a promising energy carrier because it enables hydrogen production without carbon emissions, and related research has been actively pursued. In particular, power-to-gas technologies based on water electrolysis utilizing renewable energy have attracted significant interest, as they allow surplus electricity to be stored in the form of hydrogen. Anion exchange membrane water electrolysis(AEMWE), which combines the advantages of alkaline water electrolysis and polymer electrolyte membrane water electrolysis, is regarded as a next generation electrolysis technology. In addition to enabling the use of non-noble metal catalysts and hydrocarbon based membranes, which contribute to reduced system cost, AEMWE exhibits favorable flexibility, including the capability to operate over a wide current density range and to respond rapidly to load variations. While AEMWE is well suited for integration with renewable energy sources, such integration inevitably requires operation under highly dynamic conditions due to the inherent intermittency of renewable power. These fluctuating operating conditions can induce complex transient behaviors in AEMWE systems. Nevertheless, despite the practical relevance of such dynamic operation, system analysis of AEMWE under transient load conditions remains limited. Therefore, it is essential to analyze the dynamic characteristics of AEMWE system under fluctuating load conditions. In this study, a dynamic model of a quasi-two-dimensional AEMWE system was developed using AMESim ® . To obtain the temperature and pressure distributions, the cell was divided into 5 layers in perpendicular direction and further divided into anode and cathode to describe the mass transport. The stack model was developed based on numerical methods, considering the Nernst voltage, activation overvoltage and ohmic overvoltage. A detailed mass transport model including diffusion and electro osmotic drag(EOD) was implemented to accurately represent the operating characteristics of a dry cathode AEMWE system. The system model consists of a stack, pump, heat exchanger, gas-liquid separator, condenser, and dryer. According to the applied current density profile, the cell voltage exhibits overshoot and undershoot, which is governed by the ohmic overvoltage. As the current density increases, more water is transported by EOD, which reduces the water content at the outlet. Through this analysis, the proposed model is intended to support the development of stable control algorithms for AEMWE system and the optimal capacity design of balance of plants components.
Anion exchange membrane water electrolysis (AEMWE) is recognized as a promising route to low cost, high efficiency green hydrogen production. A comprehensive system model was developed and implemented in Aspen Plus®, in which a zero dimensional electrochemical stack was embedded via a Fortran subroutine, along with an iterative solution scheme implemented within the subroutine. The framework reveals the coupled interaction between mass balance and operating conditions governing water management, and quantitatively resolves phenomena that were previously treated conceptually through a numerical method, enabling direct quantification of water transport and predictive analysis of system behavior. The full Balance of Plant (BOP) (separator, heater, heat exchanger, pumps, chiller, condenser, and dryer) was represented, and simulations were performed across various operating conditions (current density, temperature, pressure). The results are analyzed in terms of the cell voltage, hydrogen purity, water transport, and BOP power consumption. Key findings include: (1) the cathode outlet water flow was reduced by 54.62% as current density increased from 0.4 to 1.8 A/cm2, underscoring the necessity of cathode water management; (2) hydrogen purity at the condenser varied widely with operating conditions, reaching 99.84% at 0.4 A/cm2, 40 °C and 50 bar; and (3) for high hydrogen production with a moderate energy penalty, operating at 80 °C and 25 bar under high current density was identified as preferable. The developed modeling framework is provided as a reliable tool for AEMWE system design and optimization, enabling systematic evaluation of tradeoffs among efficiency, purity, and production rate.
Concern for descriptions of the ocean environment, especially with respect to wave, current and wind, in deep and shallow waters, and ice, as a basis for the determination of environmental loads for structural design. Attention shall be given to statistical description of these and other related phenomena relevant to the safe design and operation of ships and offshore structures. The committee is encouraged to cooperate with the corresponding ITTC committee.
Wake-induced vibration (WIV) is a special case of vortex induced vibration, which occurs in tandem cylinders. The downstream cylinder moving across the wake from the upstream cylinder oscillates under the alternating lift force. In a previous study by the authors, the downstream cylinder was pivoted to the upstream cylinder, thereby developing a swinging motion, which was termed as the pendulum system of tandem cylinders (PSTC). They found that the PSTC exhibits higher energy conversion efficiency than the conventional translational system of tandem cylinders (TSTC). In this study, the changes in the WIV characteristics were investigated experimentally with varying geometry conditions, such as the shape of the upstream cylinder and the spacing between two cylinders. Nine cases were tested by combining three upstream cylinder shapes (i.e., circle, square, and diamond) and three cylinder spacing values (S/D = 3, 4, 5). For each case, the reduced velocity (U* = V/Df0) was varied in the 0 ≤ U* ≤ 50 range. In addition to the mechanical response measurement of the downstream cylinder, the electrical power generated by the swinging motion was also measured. Results show that the maximum response was obtained for the circular upstream cylinder and S/D = 3, which is inconsistent with that obtained in the previous study.
The development of electric vertical take-off and landing (eVTOL) aircraft using distributed propulsion systems is rapidly growing. As the aerodynamic performance can be significantly affected by interference due to propeller wake, aerodynamic analyses reflecting the power–on effects are required even in early design stages. Analyzing the eVTOL aircraft at all flight conditions using computational fluid dynamics (CFD) is generally inefficient in terms of computational time and cost. This study developed the practical rapid aerodynamic analysis tool (PEACE) that can account for the power-on effect, and its practicality was evaluated. Each method applied to this tool (unstructured source–doublet panel method, blade element momentum theory, and actuator disk theory) was validity with CFD data. Through the analysis of the wing-prop configuration, the feasibility of the tool regarding the aerodynamic interference of the propeller wake was confirmed. The optionally piloted personal air vehicle (OPPAV) developed by Korea Aerospace Research Institute was analyzed with and without propellers. The accuracy and practicality were confirmed by comparing the results with those from CFD simulation with actuator disk method results. The power–on effect of OPPAV was examined and analyzed for selected conditions of both forward and transition flight. The PEACE is identified to be computationally efficient and reasonably accurate time and cost in developing the eVTOL aircraft.
