• Journal of the Society of Naval Architects of Korea
• /
• v.28 no.2
• /
• pp.40-51
• /
• 1991

A Propeller design method using the newly developed blade section(KH18), which behaves better cavitation characteristics, is presented. Experimental results for two-dimensional foil sections show that the lift-drag curve and the cavitation-free bucket diagram of the new blade section are wider comparing to those of the existion NACA sections. This characteristic of the new section is particularly important for marine propeller applications since angle of attack variation of the propeller blade operating behind a non-uniform ship's wake is relatively large. A lifting surface theory is used for the design of a propeller with the developed section for a 2700 TEU container ship. Since the most suitable chordwise loading shape is not known a priori, chordwise loading shape is chosen as a design parameter. Five propellers with different chordwise loading shapes and different foil sections are designed and tested in the towing tank and cavitation tunnel at KRISO. It is observed by a series of extensive model tsets that the propeller(KP197) having the chordwise loading shape, which has less leading edge loading at the inner radii and more leading edge loading at the outer radii of 0.7 radius, has higher propulsive efficiency and better cavitation characteristics. The KP197 propeller shows 1% higher efficiency, 30% cavitation volume reduction and 9% reduction of fluctuating pressure level comparing to the propeller with an NACA section. More appreciable efficiency gain for the new blade section propeller would be expected by reduction of expanded blade area considering the better cavitation characteristics of the new blade section.

• Journal of the Korean Institute of Gas
• /
• v.20 no.6
• /
• pp.37-42
• /
• 2016

The purpose of this paper is to study for the emission gas control of passenger car. The first example, the PCSV never open when operating condition, but it opened by causing malfunction because of trouble. As a result, the purge gas entered into surge tank, a mount of fuel was displayed with excessive supply on tester. Therefore, it certified the bad-condition of the engine when idling by decreasing of fuel injection quantity from engine ECU. The second example, the hose activating a EGR valve didn't supply the vacuum pressure because of assembling the other part. Thus, it knew the bad-condition of engine that the EGR valve would not work normally by leaking with the other port. The third example, as the rear oxygen sensor of two sensor were fault-installing by changing the sensor of other a car it could not detect of oxygen quantity. Finally, it found the phenomenon of abruptly decreasing vehicle speed when braking a car. Therefore, the system including with emission control has to drastically manage by maximizing condition to role decreasing the emission gas.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.9
• /
• pp.6397-6402
• /
• 2015

This research was performed to review operating parameters, optimum condition and check characteristic of microbubble generation for using bubble size distribution according to venturi specification. Optimum operating condition have airflow rate 0.3 LPM, 3 bar(pressure tank) and connecting nozzle directly(without valve), it is advantageous to generate microbubble. In case of characteristic of microbubble generation according to venturi specification, effect that nozzle specification affects bubble size distribution is low impact. But considering performance aspects, when using nozzle that throat diameter 3-4 mm, $D_{50}$ are $54.98-61.19{\mu}m$(D3L15, D4L15), fraction of bubble less than $50{\mu}m$ are 0.326, 0.345. And it is superior to others. Besides, $D_{50}$ and fraction of bubble less than $50{\mu}m$ of throat length 20 mm are $49.40-54.98{\mu}m$, 0.447, respectively And nozzle that throat length 20 mm is relatively tendency to generate microbubble stably.

• Membrane Journal
• /
• v.8 no.2
• /
• pp.77-85
• /
• 1998

To treat effectively EDIR (electrodeposition ion removal) wastewater in terms of CO$_{Mn}$ 1,500~2,000 ppm generated from aluminum painting process, a RO (reverse osmosis) process was designed and installed to recover and reuse the concentrated solvent sent back to the electrocodeposition tank while the permeate reused as rinse water. A RO system in which three polyamide-spiral wound modules ($102\Phi \times 1,016L$ mm) connnected in series had been running to treat 20 m$^3$ in waste volume in 3 days batch operation at the condition of system recovery of 30 %, applied pressure 11.5 $kg_f/cm^2$ and room temperature. During 42 hours continuous operation leading to 5-fold decrease in waste volume, nearly constant permeation flux of 390 l/m$^2$-hr was maintained and the permeate with average CO$_{Mn}$, 300 ppm was obtained which could be used for washing the remaining paint solution in ion-exchange tower instead of demineralized water. Also COD$_{Mn}$ rejection as a function of running time was observed to be in the range of 78~87 % and the observed solvent rejections for ethyl cellusolve, buthyl cellusolve and n-butanol were 79 %, 87 % and 70 %, respectively.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.24 no.6
• /
• pp.659-677
• /
• 2022

Hydrogen is emerging as a next-generation energy source and development and supply of FCEV (hydrogen fuel cell electric vehicle) is expected to occur rapidly. Accordingly, measures to respond to hydrogen car accidents are required and researches on the safety of hydrogen cars are being actively conducted. In this study, In this study, we developed a hydrogen car accident scenarios suitable for domestic conditions for the safety evaluation of hydrogen car in road tunnels through analysis of existing experiments and research data and analyzed and presented the hazard distance according to the accident results of the hydrogen car accident scenarios. The accident results according to the hydrogen car accident scenario were classified into minor accidents, general fires, jet flames and explosions. The probability of occurrence of each accident results are predicted to be 93.06%, 1.83%, 2.25%, and 2.31%. In the case of applying the hydrogen tank specifications of FCEV developed in Korea, the hazard distance for explosion pressure (based on 16.5 kPa) is about 17.6 m, about 6 m for jet fire, up to 35 m for fireball in road tunnel with a standard cross section (72 m²).

• Korean Chemical Engineering Research
• /
• v.57 no.1
• /
• pp.42-50
• /
• 2019

As the industry develops in Korea, the use of hazardous chemicals is increasing rapidly and chemical accidents are increasing accordingly. Most of the chemical accidents are caused by leaks of hazardous chemicals, but there are also accidents in which all the substances are released instantaneously due to sudden high temperature/pressure or defection of the storage tanks. This is called catastrophic failure and its frequency is very low, but consequence is very huge when it occurs. In Korea, there were 15 casualties including three deaths due to catastrophic rupture of water tank in 2013, and 64 instances of failures from 1919 to 2004 worldwide. In case of catastrophic failure, it would be able to overflow outside the bund that reduces the evaporation rate and following consequence. This incident is called overtopping. Overseas, some researchers have been studying the amount of external overflow depending on bund conditions in the event of such an accident. Based on the previous research, this study identified overtopping fraction by condition of bund in accordance with Korea Chemicals Controls Act Using CFD simulation. As a result, as the height increases and the distance to the facility decreases while meeting the minimum standard of the bund capacity, the overtopping effect has decreased. In addition, by identifying the effects of overtopping according to atmospheric conditions, types of materials and shapes of bunds, this study proposes the design of the bund considering the effect of overtopping caused by catastrophic failure with different bund conditions.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.221-221
• /
• 2015

Sustainable use of water resource and conservation of water quality are essential problems in the world. Especially, problems of water quality are serious one for human health as well as ecological system of all creatures on the earth. Recently, the importance of total effluent load as well as the concentrations of pollutant materials has been recognized not only for the conservation of water quality but also for sustainable water use in watersheds. However, the measurement or estimation of total effluent load from non-point source area such as farm lands or forests may be more difficult because both of concentration and discharge of the water are greatly changed depending on various factors especially metrological conditions such as rainfall, while the measurement from a point source area may be easy because the concentration of pollutant materials and amount of discharge water are relatively steady. Therefore, the total effluent load from a non-point source is often estimated by statistical relationships between concentration and discharge, which is called as L-Q equation. However, a lot of work and time are required to collect and analyze water samples and to get the accurate relationship or regressive equation. So, we proposed a new system for direct measurement of total effluent load of water quality from non-point source areas to solve the problem. In this system, the overflow depth at a hydraulic weir is measured with a pressure gage every hourly interval to calculate the amount of hourly discharge at first. Then, the operating time of a small electric pump to collect an amount of water which is proportional to the discharge is calculated to intake the water into a storage tank. The stored water is taken out a few days later in a case of storm event or several weeks later in a case of non-rainfall event and the concentrations of water quality such as total nitrogen and phosphorous are analyzed in a laboratory. Finally, total load of the water quality can be calculated by multiplying the concentration by the total volume of discharge. The system was installed in a small experimental forestry watershed to check the performance and know the total load of water quality from the forest. It was found that the system to collect a proportional amount of water to actual discharge operated perfectly and a total load of water quality was analyzed accurately. As the result, it was expected that the system will be very available to know the total load from a non-point source area.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.4
• /
• pp.610-619
• /
• 2022

Hydrogen is emerging as an alternative fuel for eco-friendly ships because it reacts with oxygen to produce electrical energy and only water as a by-product. However, unlike regular fossil fuels, hydrogen has a material with a high risk of explosion due to its low ignition point and high flammability range. In order to safely use hydrogen in ships, it is an essential task to study the flow characteristics of hydrogen leakage and diffusion need to be studied. In this study, a numerical analysis was performed on the effect of leakage, ventilation, etc. on ventilation performance when hydrogen leaks in an enclosed space such as inside a ship. ANSYS CFX ver 18.1, a commercial CFD software, was used for numerical analysis. The leakage rate was changed to 1 q, 2 q, and 3 q at 1 q = 1 g/s, the ventilation rate was changed to 1 Q, 2 Q and 3 Q at 1 Q = 0.91 m/s, and the ventilation method was changed to type I, type II, type III to analyze the ventilation performance was analyzed. As the amount of leakage increased from 1 q to 3 q, the HMF in the storage room was about 2.4 to 3.0 times higher. Furthermore, the amount of ventilation to reduce the risk of explosion should be at least 2 Q, and it was established that type III was the most suitable method for the formation of negative pressure inside the hydrogen tank storage room.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.23 no.6
• /
• pp.535-547
• /
• 2021

A policy to expand the hydrogen economy has been established in Korea and the supply of FCEV is being expanded to realize a hydrogen society. Therefore, the supply of FCEV is expected to increase rapidly, and a solution to respond to accidents of FCEV is required. In this study, an experimental study was conducted to analyze the effect of the hydrogen jet flame generated by a FCEV on the inner wall of the tunnel and the characteristics of the internal radiant heat. For the experiment, the initial pressure of hydrogen tank was set to 700 bar, and the injection nozzle diameter was set to 1.8 mm in order to make the same as the conditions generated in the FCEV. In addition, a tunnel fire resistance test specimen having the same strength as the compressive strength of concrete applied to general tunnels of 40 MPa was manufactured and used in the experiment. The results were analyzed for the separation distance (2 m and 4 m) between the hydrogen release nozzle and the tunnel fire resistance test concrete. As the result, the maximum internal temperature of the test concrete was measured to 1,349.9℃ (2 m separation distance), and the radiant heat around the jet flame was up to 39.16 kW/m².

• Journal of Korean Society of Disaster and Security
• /
• v.16 no.1
• /
• pp.61-70
• /
• 2023

This study presents an analytical study of investigating the effect of shock waves generated by the hydrogen detonation and damage to structures for the safety evaluation of hydrogen storage facilities against detonation. Blast scenarios were established considering the volume of the hydrogen storage facility of 10 L to 50,000 L, states of charge (SOC) of 50% and 100%, and initial pressures of 50 MPa and 100 MPa. The equivalent TNT weight for hydrgen detonation was determined considering the mechanical and chemical energies of hydrogen. A hydrogen detonation model for the converted equivalent TNT weight was made using design equations that improved the Kingery-Bulmash design chart of UFC 3-340-02. The hydrogen detonation model was validated for overpressure and impulse in comparison to the past experimental results associated with the detonation of hydrogen tank. A parametric study based on the blast scenarios was performed using the validated hydrogen detonation model, and design charts for overpressure and impulse according to the standoff distance from the center of charge was provided. Further, design charts of the three-stage structural damage and standoff distance of adjacent structures according to the level of overpressure and impact were proposed using the overpressure and impulse charts and pressure-impulse diagrams.