• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.6
• /
• pp.1-7
• /
• 2017

The atomization of a liquid into multiple droplets has many important industrial applications, including the atomization of fuels in combustion processes and coating of surfaces and particles. Ultrasonic atomizing nozzle has a transducer that receives electrical input in the form of a high frequency signal from a power generator and converts that into mechanical energy at the same frequency. Liquid is atomized into a fine mist spray using high frequency sound vibrations. In coating applications, the unpressurized, low-velocity spray reduces the amount of overspray significantly because the droplets tend to settle on the substrate, rather than bouncing off it. The spray can be controlled and shaped precisely by entraining the slow-moving spray in an ancillary air stream using specialized types of spray-shaping equipment. The desired patterns of spray can be obtained using an air stream. To simulate the water mist behavior of an ultrasonic atomizing nozzle using an air stream, the Lagrangian dispersed phase model was employed using the commercial code FLUENT. The effects of the nozzle contraction shape, water droplet size and the pneumatic pressure drop on the spray characteristics were investigated to obtain the optimal condition for coating applications.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.6
• /
• pp.29-36
• /
• 2017

In this study, acombined cogeneration power plant produced two types of thermal energy and electric or mechanical power in a single process. The performance of each component of the gas turbine-combined cogeneration system was expressed as a function of the fuel consumption of the entire system, and the heat and electricity performance of each component. The entire system consisted of two gas turbines in the upper system, and two heat recovery steam generators (HRSG), a steam turbine, and two district heat exchangers in the lower system. In the gas turbine combined cogeneration system, the performance test after 10,000 hours of operation time, which is subject to an ASME PTC 46 performance test, was carried out by the installation of various experimental facilities. The performance of the overall output and power plant efficiency was also analyzed. Based on the performance test data, the test results were compared to confirm the change in performance. This study performed thermodynamic system analysis of gas turbines, heat recovery steam generators, and steam turbines to obtain the theoretical results. A comparison was made between the theoretical and actual values of the total heat generation value of the entire system and the heat released to the atmosphere, as well as the theoretical and actual efficiencies of the electrical output and thermal output. The test results for the performance characteristics of the gas turbine combined cogeneration power plant were compared with the thermodynamic efficiency characteristics and an error of 0.3% was found.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.1
• /
• pp.666-671
• /
• 2018

A honeycomb panel is a plate made by attaching two surface plateson eitherside of a honeycomb core. The honeycomb plate hasexcellent specific strength and energy absorption and is suitable for use in regions where good impact resistance is required. Recently, with the increasing the need for a lightweight design to facilitate transportation, numerous studies have been conducted using aluminum honeycomb plates as body materials for vehicles such as automobiles and high-speed trains. In addition, honeycomb plates have excellent sound deadening properties, as well as excellent heat insulation and durability. Savings in weight using lightweight materials such as aluminum alloy for honeycomb panel's skin can lead to increase fuel economy and reduction in air pollution. In this study, in order to improve the design technology of the honeycomb plate material, the manufacturing technology of the aluminum honeycomb core and honeycomb plate material and various mechanical properties of the honeycomb plate were evaluated. From the results, it was found that the design of the manufacturing process of the aluminum honeycomb plate, as well as itsproduction and characteristics, were improved. The resulting excellent energy absorption capability of the honeycomb plate was due to the repetitive core buckling, indicating that the higher the compressive strength, the higher the strength per bonded area.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.27 no.2
• /
• pp.5-12
• /
• 2019

The study is carried out to survey the proper management and to propose an eco - friendly separation system through efficient screening and resource recovery of excavated materials containing waste from various excavating fields such as reconstruction of landfill sites for reuse, reclamation of unsanitary landfill and residential land development of waste dumping sites. The current status and screening process and analytical characteristics of the excavated materials containing waste were reviewed. Through the analysis of the samples such as separated combustibles, recyclable soils and residues collected from the on-site visits we were able to understand the characteristics of separated materials and excavated materials containing waste such as calorific value, elementary composition, TOC, foreign material content and LOI. It has been found that elimination of the moisture of excavations, removal of attached soil from the surfaces of the excavated combustibles and the quantitative supply method of the input devices are the main operating factors as essential factors for the optimal separation of excavated materials containing waste. For efficient management and recycling of excavated materials containing, it is necessary to set criteria of ash content in separated combustibles and criteria organic matter content in separated soils.

• Clean Technology
• /
• v.27 no.1
• /
• pp.93-103
• /
• 2021

As the seriousness and necessity of responding to climate change and reducing carbon emissions increases, countries around the world are continuing their efforts to reduce greenhouse gases. Among various efforts, research on CCUS, capturing and utilizing carbon dioxide generated when using carbon-based fuels, is actively being conducted. Studies on pressurized oxy-fuel combustion (POFC) that can be used with CCUS are also being conducted by many researchers. The purpose of this study is to analyze basic information related to the flame structure and pollutant emissions of pressurized oxy-fuel combustion. For this, a counter-flow diffusion flame model was used to analyze the combustion characteristics according to pressure and oxygen concentration. As the pressure increased, the flame temperature increased and the flame thickness decreased due to a reaction rate improvement caused by the activation of the chemical reaction. As oxygen concentration increased, both the flame temperature and the flame thickness increased due to an improvement to the reaction rate and diffusion because of a change in oxidizer momentum. Analyzing the related heat release reaction by dividing it into three sections as the oxygen concentration increased showed that the chemical reaction from the oxidizer side was subdivided into two regions according to the mixture fraction. In addition, the emission index of NO classified according to the NO formation mechanism was analyzed. The formation trend of NO according to each analysis condition was presented.

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.1
• /
• pp.23-30
• /
• 2007

The ultimate objective of this study is to develop oxygen-enriched combustion techniques applicable to the system of practical industrial boiler. To this end the combustion characteristics of lab-scale LNG combustor were investigated as a first step using the method of numerical simulation by analyzing the flame characteristics and pollutant emission behaviour as a function of oxygen enrichment level. Several useful conclusions could be drawn based on this study. First of all, the increase of oxygen enrichment level instead of air caused long and thin flame called laminar flame feature. This was in good agreement with experimental results appeared in open literature and explained by the effect of the decrease of turbulent mixing due to the decrease of absolute amount of oxidizer flow rate by the absence of the nitrogen species. Further, as expected, oxygen enrichment increased the flame temperatures to a significant level together with concentrations of $CO_2$ and $H_2O$ species because of the elimination of the heat sink and dilution effects by the presence of $N_2$ inert gas. However, the increased flame temperature with $O_2$ enriched air showed the high possibility of the generation of thermal $NO_x$ if nitrogen species were present. In order to remedy the problem caused by the oxygen-enriched combustion, the appropriate amount of recirculation $CO_2$ gas was desirable to enhance the turbulent mixing and thereby flame stability and further optimum determination of operational conditions were necessary. For example, the adjustment of burner with swirl angle of $30\sim45^{\circ}$ increased the combustion efficiency of LNG fuel and simultaneously dropped the $NO_x$ formation.

• Journal of Soil and Groundwater Environment
• /
• v.11 no.2
• /
• pp.13-21
• /
• 2006

Polycyclic aromatic hydrocarbons (PAHs) are widespread soil contaminants and major environmental concerns. PAHs have extremely low water solubility and are strongly sorbed to soil. A potential technology for remediation of PAHcontaminated soils is a soil washing with surfactant solutions. While the use of surfactants significantly enhances the performance of soil remediation, operation costs are increased. Selective adsorption of PAHs by activated carbons is proposed to reuse the surfactants in the soil-washing process. The adsorption isotherms of pure chemicals (Triton X-100 and phenanthrene) onto three granular activated carbons were obtained. The selective adsorption of phenanthrene in mixed solution was examined at various concentrations of phenanthrene and Triton X-100. The selectivity results were discussed with pore size distribution of activated carbons and molecular sizes of phenanthrene and the Triton X-100 monomer. The selectivity for phenanthrene was much larger than 1 regardless of the particle size of activated carbons. The selective adsorption using activated carbons with proper pore size distribution would greatly reduce the material cost for the soil washing process by the reuse of the surfactants.

• Korean Journal of Soil Science and Fertilizer
• /
• v.43 no.6
• /
• pp.1035-1039
• /
• 2010

For 65 national forest areas in 1993 to 2008, the ambient sulfur dioxide ($SO_2$) concentrations were measured monthly using passive samplers and compared to the those of urban areas in order to investigate the characteristics of temporal and spatial distribution. In the forest areas, annual average concentration of sulfur dioxide gradually decreased from the beginning year of monitoring to 1997 and then had no significant change, such as the annual trend in urban areas monitored by Ministry of Environment. For the monitoring term, average concentration of sulfur dioxide in the forest areas was 5.6ppb, which was lower than the 10.1ppb in the urban areas and the EC ecological standard level (7.6 ppb). Seasonally, both in forest areas and urban areas the monthly average concentrations were much higher in winter and spring due to much more heating fuel consumption, and lowest in summer. Regional comparison to other regions of Gyeongbuk and Gyeonggi province showed that the concentration of sulfur dioxide was the highest during year. A significant positive correlation between sulfur oxides' emissions and sulfur dioxide concentration by province was observed, reflecting that the size and proximity of sources of atmospheric sulfur oxides could be important factors in determination.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2020.06a
• /
• pp.283-283
• /
• 2020

국가의 논의 타작물 재배 권장 정책과 농한기 수익을 위해서 동절기에도 농사가 가능한 시설농업이 발달했으며, 1990년 초부터 재배면적이 증가하여 2000년에는 10만 ha를 넘어섰고, 2018년에는 80만ha의 규모를 보이고 있다(농사로, 2019). 시설농업단지의 동절기 난방을 위한 에너지원으로 화석연료와 전기열원을 사용하고 있고, 특히 강변의 경우 지하수를 난방 열원으로 사용가능해 수막재배를 이용한 대규모 시설단지가 발달함에 따라 지하수의 이용량이 증가하고, 2015년 농업용 지하수 이용량은 연간 20억 톤에 이른다(GIMS, 2019). 난방이 필요한 동절기에 수막용수를 위한 지하수 이용량이 급증하여 계절적인 수위변화를 보이며, 특히 강변의 대규모 시설농업단지의 지하수의 부족현상이 빈번히 발생하는 실정이다(송성호, 2017). 본 연구지역은 낙동강 하구댐 설치 전만조 시 해수의 유입으로 암반지하수의 심도가 증가할수록 EC가 증가하는 특성을 보이는 곳으로, 지하수의 이용량이 급증하는 동절기에 특히 급격히 증가하여 지하수의 안정적인 수질관리를 위해 염분변화의 관리가 필요한 지역이다. 지하수의 계절적인 변화를 위해 시설농업단지내에 지하수 관측정이 설치되어 관측되고 있으며 본 연구에서는 관측정의 2013년 1월~2019년 1월까지 지하수의 EC변화를 관측하였다. 지하수의 수위(GL.m), 온도, EC를 1시간 주기로 관측하여 계적적인 변화를 분석하였고, EC의 증가가 큰 곳은 심도별로 센서(다중심도)를 설치하여 염도의 변화를 관측하였다. 지하수성분의 지질학적 기원분석을 위한 양음이온 분석을 연 1회 실시하였다. 또한 관측정의 심도별 변화를 알기 위해 동일지역에 충적, 암반 관측정을 따로 설치하고 관측하여 지표수와 지하수의 심도별 영향의 차이를 분석하였다. 동일지역의 관측결과 평균 5m이하의 수위변화를 보이나, 5m 이상의 수위변동을 보이는 관측망은 15년 14개소 17년 19개소로 증가추세를 보이며, 이는 주로 밀집된 시설하우스 단지의 수막재배를 위한 겨울철 지하수 사용량 증가가 원인인 것으로 판단된다. 본 연구지역은 강변지역에 밀집된 시설하우스단지의 동절기 수막재배를 위한 지하수 과다 사용으로 수위급감 및 수량부족현상이 반복되고 있어, 예방과 대책강구를 위해 지표수의 함양과 지하수사용량의 상관관계 분석과 자료축적 및 추가연구를 위한 장기관측이 요구된다.

• Journal of Internet of Things and Convergence
• /
• v.10 no.1
• /
• pp.1-6
• /
• 2024

In order to increase the use of electric vehicles (EVs) and minimize grid strain, microgrid using renewable energy must take an important role. Microgrid may use fossil fuels such as small diesel power, but in many cases, they can be supplied with energy from renewable energy, which is an eco-friendly energy source. However, renewable energy such as solar and wind power have variable output characteristics. Therefore, in order to meet the charging and discharging energy demands of electric vehicles and at the same time supply load power stably, it is necessary to review the configuration of electric vehicle charging infrastructure that utilizes diesel power or electric vehicle-to-grid (V2G) as a parallel energy source in the microgrid. Against this background, this study modelized a microgrid that can stably supply power to loads using solar power, wind power, diesel power, and V2G. The proposed microgrid uses solar power and wind power generation as the primary supply energy source to respond to power demand, and determines the operation type of the load's electric vehicles and the rotation speed of the load synchronous machine to provide stable power from diesel power for insufficient generations. In order to verify the system performance of the proposed model, we studied the stable operation plan of the microgrid by simulating it with MATLAB /Simulink.