• Journal of Mechanical Science and Technology
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• v.18 no.11
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• pp.2058-2065
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• 2004

A light collecting probe named Multi-color Integrated Cassegrain Receiving Optics (MICRO) is applied to spark-ignited spherical spray flames to obtain the flame propagation speed in freely falling droplet suspension produced by an ultrasonic atomizer. Two MICRO probes are used to monitor time-series signals of OH chemiluminescence from two different locations in the flame. By detecting the arrival time difference of the propagating flame front, the flame propagation speed is calculated with a two-point delay-time method. In addition, time-series images of OH chemiluminescence are simultaneously obtained by a high-speed digital CCD camera to ensure the validity of the two-point delay-time method by the MICRO system. Furthermore, the relationship between the spray properties measured by phase Doppler anemometer (PDA) and the flame propagation speed are discussed with three different experimental conditions by changing the fuel injection rate. It was confirmed that the two-point delay-time method with two MICRO probes is useful and convenient to obtain the flame propagation speed and that the flame propagation speed depends on the spray properties.

• Journal of the Korean Society of Safety
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• v.19 no.3 s.67
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• pp.20-25
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• 2004

In order to obtain the flame Propagation speed in freely falling droplet suspension Produced by an ultrasonic atomizer, a light collecting probe named Multi-color Integrated Cassegrain Receiving Optics (MICRO) is applied to spark-ignited spherical spray flames. Two MICRO probes are used to monitor time-series signals of OH chemilumine-scence from two different locations in the flame. The flame propagation speed is calculated by detecting the arrival time difference of the propagating flame front. In addition, time-series images of OH chemiluminescence are simultaneously obtained by a high-speed digital CCD camera to ensure the validity of the MICRO system. Furthermore, relationship between the spray properties measured by phase Doppler anemometer (PDA) and the flame propagation speed are discussed with k different experimental conditions by changing the fuel injection rate. It was confirmed that the MICRO probe system was very useful and convenient to obtain the flame propagation speed and that the flame propagation speed was different depending on the spray properties.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.182-185
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• 1998

This paper describes a field orientation control of an induction motor without any speed transducer and proposes a wide-range speed control strategy with the field orientation algorithm. The difference at impedances between the direct and quadrature axis at the injected signal is used for the sensorless field orientation control. But this algorithm has some limitations and should be supported by other method at high speed. In this paper, a sensorless speed control at an induction motor for wide speed range operation is proposed. The proposed algorithm is verified by experimental results.

• Transactions of Materials Processing
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• v.15 no.1 s.82
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• pp.57-64
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• 2006

High speed milling experiment on the hardened mold steel (CALMAX at hardness of HRC 55) is carried out using small diameter ball endmills. Tool lift and wear characteristics under the various machining parameters are investigated Effect of dynamic runout on the wear of the tool is also studied. For most of the cases, catastrophic chipping of tool edge is not observed and uniformly distributed wear on the flank surface of the tool is obtained. It is found that lower rate of tool wear is obtained as the cutting speed is increased. Also, high pick feed rate is found to be more favorable in terms of the tool wear and material removal rate.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.114-120
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• 2005

High speed milling experiment on the hardened mold steel (CALMAX at hardness of HRc 55) is carried out using small diameter ball endmill. Tool lift and wear characteristics under the various machining parameters are investigated. Effect of dynamic runout on the wear of the tool is also studied. For most of the cases, catastrophic chipping of tool edge is not observed and uniformly distributed wear on the flank surface of the tool is obtained. It is found that lower rate of tool wear is obtained as the cutting speed is increased. Also, high pick feed rate is found to be more favorable in terms of tool wear and material removal rate.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.103-105
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• 1993

This paper proposed a new direct vector control scheme using high frequency current injection. This scheme has some attractive features such as using no flux sensor or speed sensor, robustness of parameter variation, capability of accurate vector control at very low speed. Compared to other direct vector control scheme, this scheme doesn't depends on phase delay and difference of magnitude of estimated flux, rotor resistance and all inductances except stator resistance. These features are proved by computer simulation and experimental results.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1994-1996
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• 2002

This paper reports a novel high-speed fluid injection system employing a simple magnetic micoractuator. This magnetic microacutator consists of current carrying copper beams and permanent magnet under the beams. There were many efforts to magnetic microactuator realization using conducting coils [1-2]. Even though many of magnetic microactuators were successfully fabricated and tested, it is true that most them suffer complex fabrication processes and thus higher production costs than electrostatic counterparts. In this research, efforts were concentrated on the microactuator realization that has simple structure, low production cost, and mass production possibility.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.116-122
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• 2012

The purpose of this study is to investigate the overall spray behavior characteristics for various injection conditions in a gasoline direct injection(GDI) injector with multi-hole. The spray characteristics, such as the spray penetration, the spray angle, and the injection quantity, were studied through the change of the injection pressure, the ambient pressure, and the energizing duration in a high-pressure chamber with a constant volume. The n-heptane with 99.5% purity was used as the test fuel. In a constant volume chamber, the injected spray was visualized by the spray visualization system, which consisted of the high-speed camera, the metal-halide lamp, the injector control device, and the image analysis system with the image processing program. It was revealed that the injection quantity was mainly affected by the difference between the injection pressure and the ambient pressure. For low injection pressure conditions, the injection quantity was decreased by the increase of the ambient pressure, while it nearly maintained regardless of the ambient pressure at high injection pressure. According to the increase of the ambient pressure in the constant volume chamber, the spray development became slow, consequently, the spray tip penetration decreased, and the spray area increased. In additions, the circular cone area decreased, and the vortex area increased.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.40-57
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• 2004

The effects of triple (pilot, main and after) injection on combustion and emission characteristics in a HSDI (High-Speed Direct Injection) diesel engine were investigated using a single-cylinder optical diesel engine equipped with a common-rail injection system. The pilot injection affected the spray and combustion evolution of the following main injection. It was found that the pilot injection reduced the ignition delay, which led to lowered NOx (Nitric Oxides) level, and increased IMEP (Indicated Mean Effective Pressure) due to slow combustion pace during an expansion stroke. The after-injection was shown to be effective in reducing PM (Particulate Matter) even when a small amount of fuel was added. The results suggest that a proper combination of individual injection strategy could bring about a good synergetic effect on engine performance and emission.

• Journal of Fisheries and Marine Sciences Education
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• v.12 no.2
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• pp.142-151
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• 2000

The studies on the electronic control fuel injection system for a DI diesel engine have done for reducing the exhaust emission and improving fuel consumption. The electronic control fuel injection system is classified into a common rail system, a unit injector system and a high pressure injection system. The characteristics of these systems are largely depends on the operating characteristics of its solenoid that have high speed on-off operation. In order to improve these characteristics of fuel injection system, it is necessary to design the optimal shape of solenoid and select the input method of its power source. It was proposed HELENOID, COLENOID, DISOLE, and Multipole Solenoid in the studies of design for the optimal shape of solenoid. The studies on the energizing method, input method for power of solenoid were dealt with the conventional energizing method, the chopping method and the pre-energizing method. In order to find out the high response characteristics of solenoid, it is necessary to test the performance of optimally designed solenoid with a new energizing method. In this paper, the solenoid of multi-pole type with plat armature and its power control unit to control input current by the chopping method designed, and its response tests were performed according to its energizing conditions. As a result, the maximum input current for solenoid was controlled by the period of first stage exciting current and chopping duty ratio of control stage exciting current, and the fastest "on" time was able to get 0.46ms. The conditions of fastest "on" time was 0.3ms for first stage exciting current, 0.16ms for control exciting current and 75% for chopping duty ratio.