• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.5
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• pp.549-555
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• 2016

This research was performed to determine the oil separation characteristics of the specially designed oil filter installed in a PCV cylinder head passage. The oil filter was specially designed with fleece for separating oil mist from blow-by gas. The fleece, made of fiber fabric material, is placed in the oil filter case to absorb oil mist with a small pressure drop during blow-by gas through the filter. To do this, 3-D CFD analysis was simulated for the simplified PCV system with the oil filter using the commercial code, Ansys CFX. Results showed that the oil filter's efficiency with fleece sharply increased as oil droplet size increased.

• Journal of Drive and Control
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• v.13 no.2
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• pp.1-9
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• 2016

In this paper, an elementary force fighting problem was investigated. The problem is encountered when a double-rod type EHA(electro-hydrostatic actuator) is combined with a single-rod type EHA to build a redundant actuator system with synchronized motion. When the rod-side chambers of the two different types of EHAs have the same effective piston areas and are simultaneously pressurized by an external load, the two EHAs behave identically, sharing the external load equally. However, when the piston head-side chamber of the single rod type EHA, having a larger effective area than the rod-side chamber, is pressurized by the external load, an abnormal force fighting between the two EHAs occurs, unless their pump speeds are properly decoupled. In this study, the output drive forces of each EHA were obtained from the cylinder pressure signals and applied to the position control for each EHA to maintain the balance between their pump speeds. Adding minor force difference feedback loops to the position control, the force fighting phenomena could be eliminated and steady state synchronization errors were reduced. The power consumption of the pumps also could be remarkably reduced, avoiding unnecessarily high load pressures to the pumps.

• Journal of the Korean Society of Safety
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• v.34 no.2
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• pp.22-27
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• 2019

Bikers can be subjected to accidents during their bicycling. Helmets are only good, if any, for their head protection. A wearable airbag can protect the human neck area if it is properly designed. This airbag system is composed of an inflater and an airbag. The inflater contains a pressurized gas cylinder and a piercing device. The airbag is an inflatable fabric surrounding the human neck. When a bicycle accident happens, a sensor captures the motion of the biker and a microcomputer sends a signal to open a valve in the inflator to supply the pressurized gas to the airbag. An important issue of this system is that the airbag should be quickly inflated to protect the human neck. This paper deals with the airbag inflation time simulation and some issues to design a wearable airbag system. Also, a prototype was tested to show its feasibility using a human dummy mounted on a running cart.

• Journal of Biosystems Engineering
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• v.7 no.1
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• pp.53-61
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• 1982

As an attempt to reduce the consumption of petroleum resources and to improve the performance of a kerosene engine, a series of experiments was conducted using several kinds of ethanol-kerosene blends under the various compression ratios. The engine used in this study was a single-cylinder, four-cycle kerosene engine having a compression ratio of 4.5. To investigate the feasibility of ethanol-kerosene blends in the original engine, kerosene and blends of 5-percent, 10-percent, and 20-percent-ethanol, by volume, with kerosene were used. And to investigate the feasibility of improving the performance of the kerosene engine, a portion of the cylinder head was cut off to increase the compression ratio up to 5.0 by reducing the combustion chamber volume. Kerosene and blends of 30-percent and 40-percent-ethanol, by volume, with kerosene were used for the modified engine with an increased compression ratio. Variable speed tests at wide-open throttle were also conducted at five speed levels in the range of 1000 to 2200 rpm for each compression ratio and fuel type. Volumetric efficiency, engine torque, and brake specific fuel consumption were determined, and brake thermal efficiency based on the lower heating values of kerosene and ethanol was calculated. The results obtained in the study are summarized as follows: A. Test with the original engine: (1) No abnormal conditions were found when burning ethanol-kerosene blends in the original engine. (2) Volumetric efficiency increased with ethanol concentration in blends. When burning blends of 5-percent, 10-percent, and 20-percent ethanol, by volume, with kerosene, average volumetric efficiency increased 1.6 percent, 2.6 percent, and 4.1 percent respectively, than when burning kerosene. (3) Mean engine torque increased 5.2 percent for 5-percent-ethanol blend, 9.3 percent for 10-percent-ethanol blend, and 11.5 percent for 20-percent-ethanol blend than for kerosene. Increase in engine torque when using ethanol-kerosene blends was due to the improved combustion characteristics of ethanol as well as an increase in volumetric efficiency. (4) Up to ethanol concentration of 20 percent, mean brake specific fuel consumption was nearly constant inspite of the difference in heating value between ethanol and kerosene. (5) Brake thermal efficiency increased 0.3 percent for 5-percent-ethanol blend, 3.8 percent for 10-percent-ethanol blend, and 6.8 percent for 20-percent-ethanol blend than for kerosene. B. Test with the modified engine with an increased compression ratio: (1) When burning kerosene, mean volumetric efficiency, engine torque, and brake thermal efficiency were somewhat lower than for the original engine. (2) Engine torque increased 15.1 percent for 30-percent-ethanol blend and 18.4 percent for 40-percent-ethanol blend than for kerosene. (3) There was no significant difference in brake specific fuel consumption regardless of ethanol concentration in blends. (4) Brake thermal efficiency increased 15.0 percent for 30-percent-ethanol blend and 19. 5 percent for 40-percent-ethanol blend than for kerosene.

• Journal of Biosystems Engineering
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• v.6 no.2
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• pp.1-8
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• 1982

The objective of this study was to find out the technical feasibility of ethanol-diesel fuel blends as a diesel engine fuel. Fuel properties essential to the proper operation of a diesel engine were determined for blends containing several concentrations of ethanol in No. 2 diesel fuel. A single-cylinder diesel engine for a power tiller was used for the engine tests, in which load, speed and fuel consumption rate were measured. The fuels used in tests were No. 2 diesel fuel and a blend containing 10-percent ethanol and 90-percent No. 2 diesel fuel. The results of the study are summarized as follows. 1. It was not possible to blend ethanol and No. 2 diesel fuel as a homogeneous solution even though anhydrous ethanol was used. The problem of blending ethanol in No. 2 diesel fuel could be solved by adding butanol about 5% of the amount of ethanol in the blends. 2. Because ethanol had a much lower boiling point ($78.3^{\circ}C$ under atmospheric pressure) than a diesel fuel, it was necessary to store ethanol-diesel fuel blends airtight in order to prevent them from evaporation losses of ethanol. 3. The addition of ethanol to No. 2 diesel fuel lowered the fuel viscosity and the cetane rating, but a blend of 10% ethanol and 90% diesel fuel had a viscosity and a cetane rating well above the KS minimum values for No. 2 diesel fuel. 4. At the rated speed, the specific fuel consumption of No.2 diesel fuel was lower than that of the 10% ethanol blend for the almost entire range of load. However, under the overload condition the specific fuel consumption was lower for the 10% ethanol blend. 5. Under the variable-speed full-load tests, both fuels produced approximately the same torque and power. At the speeds of 1600rpm or below, the specific fuel consumption of No. 2 diesel fuel was lower than that of the 10% ethanol blend. At the speeds of 1600rpm or above, however, the specific fuel consumption was lower for the 10% ethanol blend. 6. At the ambient temperature above $15^{\circ}C$, the use of the 10% ethanol blend in the engine created a vapor lock in the fuel injection pump and stalled the engine. The vapor locking problem was overcome by chilling the surroundings of the fuel injection pump and the cylinder head with water.

• Journal of Energy Engineering
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• v.17 no.4
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• pp.189-197
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• 2008

In this study, a system to measure continuously the fuel concentration in a steady flow rig on the basis of Rayleigh scattering is presented. The system can be employed to measure both the temporal and the spatial distribution. Also, it is possible to calibrate the system for the measurement of accurate absolute concentration. Firstly, the system was tested at a calibration chamber for the determination of scattering cross section from propane, butane, acetylene, Freon-12 and Genetron 143a. After this, the system was adapted to a steady flow rig to measure the temporal and spatial fuel concentration. The rig is composed of cylinder head, intake manifold, injector, and transparent cylinder which can simulate internal combustion engine. To cope with the interference of Mie scattering, which is main obstacle of the measuring concentration with Rayleigh scattering, a hardware filter was installed for reducing the number density of particles. Furthermore a software filter was developed, which is based on the rise time and the time constant of the photomultiplier-amplifier system. In addition, background noisy was reduced by adjusting the optical array and applying the pin hall and beam trap. The results show that LRS can provide useful information about concentration field and the software filter is very effective method to remove Mie interference.

• Environmental Analysis Health and Toxicology
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• v.6 no.1_2
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• pp.71-82
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• 1991

Rat embryos were cultured out of the mother from the head-fold stages, 9.5 days to 11.5 days during which they start to develop the brain, eyes, ears and cardiovascular system etc. We principally did the basic experiment in order to establish the best condition of the rat whole embryo culture in our laboratory. The temperature in the culture system was maintained 37$^{\circ}C$$\pm$0.2$^{\circ}C$ for 48 hrs. The culture was carried out in humidified atmosphere of the air, intially, the bottles were equilibrated with 5% $O_2$,5% $CO_2$, and 90% $N_2$gas mixture. After 22 or 24 and 29 or 30 hrs the cultures were reequilibrated with 20% $O_2$, 5% $CO_2$,75% $N_2$and 40% $O_2$, 5% $CO_2$, 55%$N_2$respectively. Various types of sera were tested and for the purpose of minimizing the quantity of rat serum, artificial medium was also tried and it was determined that rat serum supported normal growth over a period of 48 hrs, based on total growth analysis and structural comparisons with in vivo specimens.

• Korean Journal of Construction Engineering and Management
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• v.19 no.6
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• pp.115-123
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• 2018

The primary objective of this study is to develop an all-in-one based steel pipe pile cutting robot prototype that improves the conventional steel pipe pile head cutting work in safety, quality, and productivity. For this, the following research works are conducted sequentially; 1)literature review and expert survey, 2)selection of core technology using AHP analysis, 3)deduction of detail design, 4)verification of structural stability, 5)development of full-scale prototype. As a result leveling laser and laser detector(94.46), plasma cutter(96.72), rotary grapple(98.45) are selected as a core technologies. As an outcome, it is analyzed that gripper, cylinder pivot bracket and gripper base are structurally stable. Their maximum stresses are shown as 43.0%, 19.4%, 5.3% compared to their yield strength respectively. The development of full-scale prototype in this study will be utilized for the development of the all-in-one attachment based steel pipe pile cutting robot commercialization model.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.1
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• pp.97-104
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• 2015

This study is a part of the high pressure injection system development on the Turbo GDI engine in order to reduce smoke emission in case of using the low volatile(high DI) fuel which is used as normal gasoline fuel in the US market. Firstly, theoretical approach was done regarding gasoline fuel property, performance, definition of particle matters and its creation as well as problems of the high DI fuel. In this experimental study, 2L Turbo GDI engine was selected and optimized system parameter was inspected by changing fuel, fuel injection mode (single/multiple), fuel pressure, distance between injector tip and combustion chamber, start of injection, intake valve timing in engine dyno at all engine speed range with full load. In case of normal gasoline fuel, opacity was contained within 2% in all conditions. On the other hands, in case of low volatile fuel (high DI fuel), it was confirmed that the opacity was rapidly increased above 5,000 rpm at 14.5 ~ 20 MPa of fuel pressure and there were almost no differences on the opacity(smoke) between 17 MPa and 20 MPa fuel pressure. According to the SOI retard, smoke decrease tendency was observed but intake valve close timing change has almost no impact on the smoke level in this area. Consequently, smoke decrease was observed and 16% at 6000rpm respectively with injector washer ring installed. By removing injector washer to make injector tip closer to the combustion chamber, smoke decrease was observed by 46% at 5,500 rpm, 42% at 6,000 rpm. It is assumed that the fuel injection interaction with cylinder head, piston head, intake and exhaust valve is reduced so that impingement is reduced in local area.

• Corrosion Science and Technology
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• v.14 no.2
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• pp.54-58
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• 2015

A heavy oil of low quality has been mainly used in the diesel engine of the merchant ship as the oil price has been significantly jumped for several years. Thus, a combustion chamber of the engine has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of the combustion chamber has been getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the engine parts such as exhaust valve, piston crown and cylinder head surrounded with combustion chamber are more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these engine parts is very important to prolong their lifetime in a economical point of view. In this study, 1.25Cr-0.5Mo filler metal was welded with SMAW method in the forged steel which would be generally used with piston crown material. And the corrosion properties of weld metal, heat affected and base metal zones were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% $H_2SO_4$ solution. The weld metal and base metal zones exhibited the highest and lowest values of hardness respectively. And, the corrosion resistance of the heat affected and weld metal zones was also increased than that of the base metal zone. Furthermore, it appeared that the corrosive products with red color and local corrosion like as a pitting corrosion were more frequently observed on the surface of the base metal zone compared to the heat affected and weld metal zones. Consequently, it is suggested that the mechanical and corrosion characteristics of the piston crown can be predominantly improved by repair welding method using the 1.25Cr-0.5Mo electrode.