• Journal of Advanced Marine Engineering and Technology
• /
• 제27권1호
• /
• pp.57-64
• /
• 2003

The characteristics of fuel spray have an important effect on engine performance such as power, specific fuel consumption and emission because fuel spray controls the mixing and combustion process in an engine. Therefore, if the characteristics of fuel spray can be measured, they can be effectively used for improving engine performance. The major factors controlling fuel spray are injection pressure, ambient pressure and engine speed. In this study, the experiment is performed in a high temperature and high pressure chamber. In experiments, spray tip penetration, spray angle and spray tip velocity are measured at various injection pressure (10 and 14 MPa), ambient pressure(3,4 and 5 MPa), fuel pump speed(500, 700 and 900 rpm). Experimental results are useful for deriving an experimental spray equation and design an optimal engine. The results showed that injection pressure, ambient pressure and fuel pump speed are important factors influencing on the characteristics of spray. 1) Injection pressure influences on the characteristics of spray. That is, as injection pressure is increased, spray angle is decreased but spray penetration and spray tip velocity is increased. 2) Spray angle and spray penetration are increased as fuel pump speed is increased.

• 한국전기전자재료학회논문지
• /
• 제32권2호
• /
• pp.93-99
• /
• 2019

A pressure sensor is a device that converts an applied physical pressure into an electrical signal. Such sensors have a range of applications depending on the pressure level, from low to high pressure. Sensors that use physical pressure, when compared to those operating under air pressure, are not widely applied as they are inefficient. To solve this problem, graphene oxide, which exhibits good mechanical and electrical characteristics, was used to increase the efficiency of these pressure sensors. Graphene oxide has properties that control the movement of charges within the dielectric. Exploiting these properties, we evaluated the change in electrical characteristics when pressure was applied according to the ratio and thickness of the oxidation graph added to the pressure sensor.

• 한국자동차공학회논문집
• /
• 제3권1호
• /
• pp.54-64
• /
• 1995

The effects of swirl on early flame development and late combustion characteristic were investigated using a high speed single-shot visualized 51 engine. LDV measurements were performed to get better understanding of the flow field in this combustion chamber. Spark plugs were located at half radius (R/2) and central location of bore. High speed schlieren photographs at 20,000 frames/sec were taken to visualize the detailed formation and development of the flame kernel with cylinder pressure measurements. This study showed that high swirl gave favorable effects on combustion-related performances in terms of the maximum cylinder pressure and flame growth rate regardless of spark position. However, at R/2 ignition the low swirl shown desirable effects at low engine speed gave worse performances as engine speed increased than without swirl. There were distinct signs of slow-down in flame growth during the period when the flame front expanded from 2.5mm in radius until it reached 5.0mm apparently due to the presence of ground electrode. There seemed to be heat transfer effect on the flame expansion speed which was evidenced in high swirl case by the slowdown of the late flame front presumably caused by relatively large heat loss from burned gas to wall compared with low- or no-swirl cases.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제49권8호
• /
• pp.445-450
• /
• 2000

Many successful developments and microscopic studies have been made on the high quality insulating materials. However, a little attention have given to the macroscopic interface in HV(High Voltage) insulating systems. In this study, AC interfacial breakdown strength and V-t characteristic of the interface between Epoxy/EPDM(ethylene propylene diene terpolymer) are investigated. Electrode system is designed to reduce the charges from electrodes and to have the tangential potentials along the interface between Epoxy/EPDM by FEM(finite elements method). The AC breakdown strength is observed when HV is given to the interface. It is shown that AC interfacial breakdown strength is improved by increasing interfacial pressure and oiling. In particular, it was saturated at certain interfacial pressure level. V-t characteristic is able to extend to the life time of the interface between Epoxy/EPDM. Oiling also plays a good roll in prolongation of the life time.

• 대한기계학회논문집B
• /
• 제24권9호
• /
• pp.1157-1165
• /
• 2000

A classic examples of the abnormal combustions are the knock and misfire, which raise noxious performance and life of the engine. A heavy knock can also cause severe damages to the engine itself, which gives more reason why it must be detected and corrected. With the response of the today's requirements, we have researched the new diagnostic system which uses the breakdown voltage characteristics between electrodes of spark plug. This breakdown voltage depends on the pressure, temperature and even the shape and material of electrodes. But there is no data of breakdown voltage in case of using the spark plug as a electrodes. So, in this study, we show the breakdown voltage characteristic by pressure and temperature in constant volume bomb, which will make it possible to diagnose the engine combustion phenomenon.

• 소성∙가공
• /
• 제3권1호
• /
• pp.51-62
• /
• 1994

Cup drawing test and U-bending test were performed to evaluate the friction characteristics of sheet materials for the different deformation modes involved in stamping process. The coefficient of friction calculated from the each test was compared to that obtained from the draw bead friction test. It was clarified that the cup drawing test could be simply used for evaluating the friction characteristic of sheet material in deep drawing process with high contacting pressure. However the U-bending test is suitable to evaluate the frictional characteristic of sheet material in bending process with low contacting pressure.

• 설비공학논문집
• /
• 제10권4호
• /
• pp.398-410
• /
• 1998

Two-phase flow phenomena are observed in many industrial facilities and make much importance of optimum design for nuclear power plant and the liquid transportation system. The particular flow pattern depends on the conditions of pressure, flow velocity, and channel geometry. However, the research on drag reduction in two-phase flow is not intensively investigated. Therefore, experimental investigations have been carried out to analyze the drag reduction and void fraction by polymer addition in the two-phase flow system. We find that the polymer solution changes the characteristic of two-phase flow. The peak position of local void friction moves from tile wall of the pipe to the center of the pipe when polymer concentration increase. And then we predict that it is closely related with the frau reduction.

• 동력기계공학회지
• /
• 제16권6호
• /
• pp.92-97
• /
• 2012

In this study, ER fluids were working fluid and yield shear stress of attained dispersive ER fluids made by analyzed to adapt effectively at the practical equipment like three port ER valve. In addition, movement of ER particle was observed by using a microscope the same as the strength of electric field with Bingham characteristic. Basis material was presented to develop 3 port ER-Valve by quantitatively comparing and analyzing entrance, load and outlet flow's differences of 3 port rectangular tubes. This study, after designing and producing the 3port ER-Valve, considered the characteristic of pressure drop, outlet and load flow rate by changing the strength of electric field on ER fluids flowing between electrodes.

• Journal of Biosystems Engineering
• /
• 제36권5호
• /
• pp.314-318
• /
• 2011

Arm-type implements of tractor are mainly utilized for the slope land operation. The proposed hydraulic system was implemented to arm-type implements of tractor. An experiment was conducted to evaluate response characteristics of the designed arm-type implement control system attached by three-point hitch of tractor at various conditions, such as engine speed, pumping rate and cylinder input flow. Effects of the valve response time didn't affect engine speed. The flow rate of pump and cylinder changed to the pressure loss. Also, the pressure loss was within 2 MPa and the response characteristic was sufficient enough to use as the arm-type implement system.

• 한국연소학회지
• /
• 제15권4호
• /
• pp.53-57
• /
• 2010

The purpose of the present work is to investigate the effect of gasoline-premixing on a combustion and emissions characteristics in a compression ignition engine. For studying combustion characteristics, a combustion pressure and rate of heat release (ROHR) were measured using a single-cylinder DI compression ignition engine with a common-rail injection system and premixed fuel injection system. In addition, exhaust emissions characteristics were studied using emission analyzers and smoke meter. The experimental results showed that the case of gasoline-premixing had longer ignition delay and lower combustion pressure compared to the cases of diesel direct injection. Furthermore, premixed gasoline-air mixture reduced NOx emissions due to low peak of ROHR.