• Journal of Power System Engineering
• /
• v.18 no.3
• /
• pp.36-41
• /
• 2014

The structure of a variable liquid column oscillator(a VLCO) is analogous to that of the tuned liquid column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. The VLCO is a system absorbing high kinetic energy of accelerated motions of the multiple floating bodies in the effect of air springs occurred by installation of inner air chambers. Thus, VLCO can improve the efficiency of energy than wave energy converters of the activating object type made in Pelamis Company. In this research, the experiment was performed in two models of same draft. The one is that weights were filled, and the other is that water was filled. The numerical results were estimated by assuming that do not exist internal flow, and the results were compared with the results of experiments.

• Journal of Advanced Marine Engineering and Technology
• /
• v.31 no.8
• /
• pp.1020-1027
• /
• 2007

As a national enterprise has been expanded over and over, the worldwide energy consumption has been growing necessarily. Moreover, as recently energy spendings are on the increase in countries such as BRICs, it has resulted that a rise in the price of both oil and mineral resources and instability between supply and demand become serious issue in the world resources market. The recent high price of oil and mineral resources have a deep influence on economy and threaten energy security and even national prosperity of Korea. In addition to these, exhaustion of fossil fuels and the enhanced greenhouse effect which results from gases emitted as a result of fossil fuels has been in serious questions which occur a great deal of effort to secure clean energy resources all around the world. As it is considerably possible for Korea that the Kyoto protocol may come into effect on and after 2013, it is essential to require the technological development to promote energy efficiency as well as to develope safe and renewable energy resources. The wind energy technology which converts kinetic energy into electrical energy has been in the focus of the world's attention. In this study, two-dimensional numerical analyses were conducted to observe subsidence aspects of the sea bottom on differently applied loads and various ground conditions.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.49 no.12
• /
• pp.673-678
• /
• 2000

The dielectric barrier discharge(DBD) is a common method to create a nonthermal plasma in which electrical energy is used to create electrons with a high average kinetic energy. The unique aspect of dielectric barrier discharges is the large array of short lifetime(10ns) silent discharges created over the surface of the dielectric. A silent discharge is generated when the applied voltage exceeds the breakdown voltage of the carrier gas creating a conduction path between the applied electrode and grounded electrode. As charge accumulates on the dielectric, the electric field is reduced below the breakdown field of the carrier gas and the silent discharge self terminates preventing the DBD cell from producing a thermal arc. In fact, the most significant application of dielectric barrier discharges is to generate ozone for contaminated water treatment. Therefore, experiments were perfomed at 1∼2[bar] pressure using a coaxial geometry single dielectric barrier discharge for ozone concentrations and energy densities. The main result show that the concentration and efficiency of ozone are influenced by gas nature, gas quantity, gas pressure, supplied voltage and frequency.

• Journal of the Society of Naval Architects of Korea
• /
• v.53 no.4
• /
• pp.266-274
• /
• 2016

Many researchers have been trying to improve the propulsion efficiency of a propeller. In this study, the numerical analysis is carried out for the POW(Propeller Open Water test) performance of a propeller equipped with an energy saving device called PHVC(Propeller Hub Vortex Control). PHVC is aimed to control the propeller hub vortex behind the propeller so that the rotational kinetic energy loss can be reduced. The unsteady Reynolds Averaged Navier-Stokes(URANS) equations are assumed as the governing flow equations and are solved by using a commercial CFD(Computational Fluid Dynamics) software, where SST k-ω model is selected for turbulence closure. The computed characteristic values, thrust, torque and propulsion efficiency coefficients for the target propeller with and without PHVC and the local flows in the propeller wake region are validated by the model test results of KRISO LCT(Large Cavitation Tunnel). It is concluded from the present numerical results that CFD can be a good promising method in the assessment of the hydrodynamic performance of PHVC in the design stage.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.22 no.1
• /
• pp.110-116
• /
• 2014

For the prevention of environmental pollution, there have been many researches which are eco-friendly vehicles in the automobile industry. In this paper, we studied for the non-pneumatic tires(NPT)can increase fuel consumption compared to conventional pneumatic tires. On driving, energy loss of tires occur when tires impact an obstacle on the road. This energy loss directly is relate to the fuel efficiency. Therefore, the energy loss of non-pneumatic tires is compared before and after impact. In this study, the results of energy loss of non-pneumatic tires and pneumatic tires was compared, when tires are rolled over an obstacle. As a result, the energy loss of non-pneumatic tires was less than pneumatic tires. This researches were performed the ABAQUS using finite element method and obtained the difference of velocity and kinetic energy from the program.

• Journal of the Korean Institute of Telematics and Electronics T
• /
• v.36T no.1
• /
• pp.71-78
• /
• 1999

This paper presents a new type of energy generative ER suspension system which does not require external power sources. This is accomplished by converting vibration energy(kinetic energy) into electrical energy. In order to undertake this, an appropriate size of the ER damper is manufactured by incorporation a mechanism which changes the linear motion of the ER damper to the rotary motion. This rotary motion is amplified by gears and activates a generator to produce the electrical energy. The efficiency of energy generation is evaluated and the level of damping force with generated power is also investigated. Then, the ER suspension system is applied to the quarter car model, and its vibration isolation is experimentally evaluated with respect to the piston speed.

• Journal of Drive and Control
• /
• v.9 no.1
• /
• pp.1-9
• /
• 2012

Nowadays, various researches about eco-friendly vehicles such as hybrid electric vehicle, fuel cell vehicle and electric vehicle have been actively carried out. Since most of these green cars have electric motors, the regenerative energy technology can be used to improve the fuel economy and the energy efficiency of vehicles. The regenerative brake is an energy recovery mechanism which slows a vehicle by converting its kinetic energy into electric energy, which can be either used immediately or stored until needed. This technology plays a significant role in achieving the high energy usage. However, there are some technical problems for controlling the regenerative braking and the electro-hydraulic brake during switching at transient region. In this paper, the performance simulator for fuel-cell vehicle is developed and transient response characteristics of the regenerative braking system are analyzed in the various driving situations. And the hardware-in-the-loop simulation of electro-hydraulic brake is performed to validate the transient characteristics of the regenerative braking system for fuel-cell electric vehicle.

• Journal of Industrial and Engineering Chemistry
• /
• v.68
• /
• pp.57-68
• /
• 2018

The main objective of this study is to prepare the bionanocomposite films using mungbean starch (MBS), PVA, ZnS, and plasticizers, and to evaluate the physical properties, thermal stability, and photocatalytic activity. The bionanocomposite films were cross-linked by heat-curing process. The ZnS and bionanocomposite films were characterized by FT-IR, XRD, and SEM. The results indicated that the mechanical properties and water resistance enhanced up to 1.2-1.5 times by the addition of nano-ZnS particles, and the thermal stability was improved by the addition of nano-ZnS particles. The photocatalytic activity of the bionanocomposite films added nano-ZnS particles was examined using bisphenol A (BPA) and methyl orange (MO). In addition, the photodegradation efficiency of BPA and MO was evaluated using the pseudo-first order kinetic model (PFOK).

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.12
• /
• pp.592-599
• /
• 2018

The kinetics and thermodynamics of the adsorption of acid blue 40 from an aqueous solution by activated carbon were examined as a function of the activated carbon dose, pH, temperature, contact time, and initial concentration. The adsorption efficiency in a bathtub was increased at pH 3 and pH 11 due to the presence of sufonate ions ($SO_3{^-}$) and amine ions ($NH_2{^+}$). The equilibrium adsorption data were fitted to the Langmuir, Freundlich and Temkin isotherms. The results indicated that the Langmuir model provides the best correlation of the experimental data. The separation factor of the Langmuir and Freundlich model showed that the adsorption treatment of acid blue 40 by activated carbon could be an effective adsorption process. The adsorption energy determined by the Temkin equation showed that the adsorption step is a physical adsorption process. Kinetics analysis of the adsorption process of acid blue 40 on activated carbon showed that a pseudo second order kinetic model is more consistent than a pseudo second order kinetic model. The estimated activation energy was 42.308 kJ/mol. The enthalpy change (80.088 J/mol) indicated an endothermic process. The free energy change (-0.0553 ~ -5.5855 kJ/mol) showed that the spontaneity of the process increased with increasing adsorption temperature.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.41 no.10
• /
• pp.685-691
• /
• 2017

In this study, the influence of mass flow rate on the isentropic efficiency of the steam turbine nozzle stage is investigated. A realistic three-dimensional numerical model, which is based on the compressible Navier-Stokes equations, is developed for the steam phase. The comprehensive conservation laws and a kinetic model for steam are investigated. With two different models for the three-dimensional geometry of the nozzle stage, the pressure and temperature distributions, velocity, Mach number. and Markov energy loss coefficient are calculated. A maximum efficiency of 96.66％ is found at a mass flow rate of 0.9 kg/s in model A. In model B, a maximum efficiency of 97.32％ is found at a rate of 1.6 kg/s. It is determined that the isentropic nozzle efficiency increases as the Markov energy loss coefficient decreases through a nearly linear relationship.