• 한국가스학회지
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• 제11권4호
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• pp.54-58
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• 2007

본 연구에서는 13L급 전자제어식 디젤 엔진을 혼소 엔진으로 개조하여 얻은 결과를 다루고 있다. 혼소 엔진 개조 후 차량의 출력, 연료경제성, 운전성 등을 파악하기 위하여 일정한 경로의 고속도로를 주행하였다. 개조된 차량은 최대 85%의 대체율을 가지며 500 km의 거리를 혼소 모드로 주행하였다. 차량의 주행성능은 디젤 모드의 경우와 거의 동일하였으나, 추월 가속성능이 약간 떨어지는 경향이 있었다. 엔진의 최대출력, 열효율, 배기가스 측정을 위하여 차량 시험과는 별도로 엔진 시험도 동시에 수행하였다. ND-13모드에서 배출가스 배출량 측정 실험을 수행한 결과, 산화촉매를 장착한 혼소모드에서의 배출가스 배출량은 디젤모드에서와 출력은 동일하게 유지하면서 K2006 규제를 만족함을 알 수 있었다.

• Journal of Power Electronics
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• 제13권5호
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• pp.806-813
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• 2013

This paper aims to compare the performance of three phase induction motor drives using Five Leg Inverter (FLI) and Three Leg Inverter (TLI) configurations. An Indirect Field Oriented Control (IFOC) method using a TLI is well established and incorporated for high performance speed drives in various industries. The FLI dual motor drive system on the other hand shows good workability in the independent control of two induction motor drives simultaneously. In this experiment, the IFOC method is utilized for both drive systems, and Space Vector Pulse Width Modulation (SVPWM) is used to generate pulses for both inverters. For the FLI, the Double Zero Sequence (DZS) Injection technique is used to generate the modulation signal. The complete experiment setup is done by using a DSpace 1103 controller board. The individual motor performances are analyzed using similar schemes, equipment setups and controller parameter values. The results show similar speed performance response capability between the single motor operation using a TLI system and the two motor operation using a FLI system based on the variable speed range either in forward or reverse operation. They also show similar load rejection abilities. However, the single motor with a TLI has a better power quality aspect such as ripple current and total harmonics distortion (THD).

• 에너지공학
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• 제25권1호
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• pp.122-130
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• 2016

본 연구에서는 1.5MW급의 발전용 디젤 엔진을 대상으로 상용 프로그램인 GT-Power를 이용하여 천연가스와 디젤 혼합연소 엔진 모델을 구축하였으며 이를 통해 기존의 디젤 연소를 하는 경우와 천연가스-디젤 혼합연소를 하는 경우의 엔진 성능 변화를 부하율(50%, 75%, 100%)에 따라 비교하였다. 또한 도서지역에서 실제로 사용되고 있는 부생유를 적용하는 경우의 영향에 대한 연구를 진행하였다. 그 결과 엔진의 운전 조건 변화 없이 천연가스를 디젤과 60% 혼합비로 연소하는 경우 최대 32%의 BSFC 증가를 보였으며 천연가스와 부생유를 혼합연소 하는 경우에도 디젤을 혼합 연소하는 경우와 크게 다르지 않은 결과를 보였다. 이러한 BSFC 증가의 원인을 연료의 불완전 연소율 증가로 제시하고 이에 대한 최적화를 진행했으며 그 결과 60% 혼소율 조건에서 약 2%의 개선효과를 보였다.

• 동력기계공학회지
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• 제18권4호
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• pp.11-16
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• 2014

Although smoke emitted from ships is not included in IMO(International Maritime Organiztion) regulation yet, it is one of the substance what is polluting mainly the air. Especially, its concentration is very high when an engine is started and a load is rapidly changed. This is caused by unburned fuel what is injected more than necessary quantity after combustion period. It is possible to decrease smoke concentration emitted at starting engine by controlling fuel injection quantity, but it is concerned that time to rated speed must be spent. Then a governor what can reduce the smoke concentration without a loss of time to rated speed is needed. We adopted a electro-hydraulic governor what can control dual fuel start limit function and achieved very low level of smoke concentration without greater the loss of time to rated speed.

• 한국가스학회지
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• 제26권3호
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• pp.45-53
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• 2022

디젤엔진의 배출물 개선을 위해 탄소수가 낮은 천연가스를 혼합하여 사용하는 천연가스-디젤 혼소 연소가 각광받고 있다. 특히 자발화 특성에 차이가 있는 디젤과 천연가스의 특성을 이용한 반응성 제어 압축착화(reactivity controlled compression ignition, RCCI) 연소 전략을 통해 기존 디젤엔진의 효율과 배출가스를 동시에 개선시키는 연구가 활발하게 진행되어 왔다. 상사점보다 앞당겨진 디젤 직접 분사시기 적용을 통해 실린더 전체 영역의 균일 혼합기를 형성하여 전체적으로 희박한 자발화 기반 연소를 달성함으로써 질소산화물 (NOx) 및 입자상물질 (PM) 저감과 제동열효율 개선을 동시에 달성할 수 있다. 하지만 매우 희박한 저부하 영역에서 불완전 연소량이 증가하는 단점이 존재하며, 안정적인 연소 구현을 위해 디젤 분사시기가 민감하게 제어되어야 하는 어려움도 존재한다. 본 연구에서는 앞서 언급된 저부하 영역에서의 천연가스-디젤 혼소 엔진의 효율 및 배기 개선을 확인하고, 동시에 발전용 엔진 구동 영역에서 디젤 분사시기에 따른 연소안정성을 평가하였다. 실험에는 6 L급 상용디젤 엔진이 사용되었으며, 1,800 rpm, 50% 부하 영역 (~50 kW)에서 실험이 진행되었다. 제동효율 및 연소안정성을 개선하기 위한 전략으로 분무 패턴이 다른 2개의 인젝터를 적용하였으며, 천연가스/디젤 비율과 디젤 분사시기를 바꿔가면서 실험이 진행되었다. 실험 결과, 협각 분사가 추가된 수정 인젝터에서 제동 열효율이 증가하는 것을 확인하였다. 또한 연소안정성 및 출력, 그리고 강화된 배기 규제를 고려하였을 때 수정 인젝터의 분무 패턴이 예혼합연소 형성에 적합하였고 이를 통해 질소산화물 배출량을 Tier-V 기준치인 0.4 g/kWh 이하로 저감함으로써 RCCI 연소 가능 영역을 확장할 수 있음을 실험적으로 확인하였다.

• Applied Science and Convergence Technology
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• 제26권6호
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• pp.189-194
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• 2017

Effects of gas injection scheme and rf driving current configuration in a dual turn inductively coupled plasma (ICP) system were analyzed by 3D numerical simulation using CFD-ACE+. Injected gases from a tunable gas nozzle system (TGN) having 12 horizontal and 12 vertical nozzles showed different paths to the pumping surface. The maximum velocity from the nozzle reached Mach 2.2 with 2.2 Pa of Ar. More than half of the injected gases from the right side of the TGN were found to go to the pump without touching the wafer surface by massless particle tracing method. Gases from the vertical nozzle with 45 degree slanted angle soared up to the hottest region beneath the ceramic lid between the inner and the outer rf turn of the antenna. Under reversed driving current configuration, the highest rf power absorption region were separated into the two inner islands and the four peaked donut region.

• 한국세라믹학회지
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• 제35권2호
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• pp.172-179
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• 1998

Valve lifter namely tappet is supported by lifter hole which is located upper side of camshaft in cylinder block transforms rotatic mvement of camshaft into linear movement and helps to open and shut the en-gine valve as an engine parts. The face of valve lifter which is continuously contacting with camshaft brings about abnormal wears such as unfair wear and early wear because it is severely loaded in the valve train system. These wears act as a defect like over-clearance and cause imperfect combustion of fuel during the valve lifting in the combustion chamber. Consequently this imperfect combustion makes the engine out-put decrease and has cause on air pollution. To prevent these wears therefore The valve lifter cast in me-tal developed into SiC ceramics valve lifter which has an excellence in wear and impact resistance As a results the optimum process conditions like injection condition mixture ratio and debonding process could be established. After sintering fine-sinered dual microstructure in which prior ${\alpha}$-SiC matches well with new SiC(${\beta}$-SiC) produced by reaction among the ${\alpha}$-SiC carbon and silicon was obtained. Based on the study it is verified that mechanical properties of SiC valve lifter are excellent in Vickers hardness 1100-1200 bending strength (300-350 Pa) fracture toughness(1.5-1.7 Mpa$.$m1/2) Through engine dynamo test-ing SiC valve lifter and metal valve lifter are examined and compared into abnormal phenomena such as early fracture unfair and early wear. It is hoped that this research will serve as an important springboard for the future study of heavy duty diesel engine parts developed by ceramics which has a good wear resis-tance relaibility and lightability.

• 한국가스학회지
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• 제21권5호
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• pp.9-15
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• 2017

천연가스 연료는 매장량과 경제성 측면에서 미래 가치가 매우 높기 때문에 여러 가지 이용 기술 개발이 활발하게 이루어지고 있으며 내연기관을 이용한 발전 분야에서도 그 중요성이 점점 증가하고 있는 실정이다. 천연가스 연료를 이용하는 MW급 발전용 대형 왕복엔진의 경우 연료공급시스템의 고도화 개발이 필요한데 그 중에서도 천연가스 분사기의 개발은 실질적인 천연가스 연료 이용을 위한 핵심이다. 본 연구에서는 천연가스 분사기를 상부에 위치한 솔레노이드의 전자기력에 의해 구동되고 하부의 밸브 바디부 전기자와 이동판이 상하로 움직이는 구조의 분사밸브 형태로 고안 및 설계하였으며 이 시작품의 동특성을 엔진 흡기 모사 조건에서 실험하였다. 지난 연구에서는 전기자의 변위와 지름 및 솔레노이드 코어 지름을 변경해 가면서 실험을 수행하였으며, 그 후속으로 솔레노이드 코어의 금속 재질 변경과 메인 하우징의 입구 크기 및 공급 압력에 따른 분사밸브의 동특성을 살펴보았다.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2224-2236
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• 2014

The performance of an isolated high voltage full bridge converter is improved using a voltage doubler. In a conventional high voltage full bridge converter, the diode of the transformer secondary voltage undergoes a voltage spike due to the leakage inductance of the transformer and the resonance occurring with the parasitic capacitance of the diode. In addition, in the phase shift control, conduction loss largely increases from the freewheeling mode because of the circulating current. The efficiency of the converter is thus reduced. However, in the proposed converter, the high voltage dual converter consists of a voltage doubler because the circulating current of the converter is reduced to increase efficiency. On the other hand, in the proposed converter, an input current is distributed when using parallel input / serial output and the output voltage can be doubled. However, the voltages in the 2 serial DC links might be unbalanced due to line impedance, passive and active components impedance, and sensor error. Considering these problems, DC injection is performed due to the complementary operations of half bridge inverters as well as the disadvantage of the unbalance in the DC link. Therefore, the serial output of the converter needs to control the balance of the algorithm. In this paper, the performance of the conventional converter is improved and a balance control algorithm is proposed for the proposed converter. Also, the system of the 1.5[kW] PCS is verified through an experiment examining the operation and stability.

• 연구논문집
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• 통권27호
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• pp.75-86
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• 1997

Combined cycle power plant is a system where a gas turbine or steam turbine is used to produce shaft power to drive a generator for producing electrical power and the steam from the HRSG is expanded in a steam turbine for additional shaft power. Combined cycle plant is a one from of cogeneration. The temperature of the exhaust gases from a gas turbine ranges from $400^\circC$ to $600^\circC$, and can be used effectively in a heat recovery steam generator to produce steam. Combined cycle can be classed as a "topping(gas turbine)" and a "bottoming(steam turbine)" cycle. The first cycle, to which most of the heat is supplied, is called the topping cycle. The wasted heat it produces is then utilized in a second process which operates at a lower temperature level and is therefore referred to as a "bottoming cycle". The combination of gas/steam turbine power plant managed to be accepted widely because, first, each individual system has already proven themselves in power plants with a single cycle, therefore, the development costs are low. Secondly, the air as a working medium is relatively non-problematic and inexpensive and can be used in gas turbines at an elevated temperature level over $1000^\circC$. The steam process uses water, which is likewise inexpensive and widely available, but better suited for the medium and low temperature ranges. It, therefore, is quite reasonable to use the steam process for the bottoming cycle. Only recently gas turbines attained inlet temperature that make it possible to design a highly efficient combined cycle. In the present study, performance analysis of a dual pressure combined-cycle power plant is carried out to investigate the influence of topping cycle to combined cycle performance.