• 한국분무공학회지
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• 제13권2호
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• pp.85-90
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• 2008

This paper presents the performance and emissions characteristics of a small spark-ignited gasoline engine. The engine used in this paper is a single cylinder, diaphragm carburetor, two-stroke, air-cooled 26cc SI engine for brush cutter. For the performance of the engine, RPM, torque, and fuel consumption were measured and HC, CO, and NOx measured for the emissions according to the change of the dynamometer load at wide open throttle (WOT) position. The results showed that the excess air ratio decreased and torque increased with increasing loads, the torque and brake specific fuel consumption were the optimum driving condition at the 7000 rpm, HC and CO emissions increased with increasing loads and with an decrease in excess air ratio over 7000 rpm.

• 한국기계가공학회지
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• 제18권6호
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• pp.26-32
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• 2019

Ball end mills used for high-speed and high-precision machining require longer machining time than flat end mills or face cutters, since the tool diameter is limited and the rigidity is reduced by the characteristics of the tool's cutting edge: at the top end of the tool, the cutting speed approaches zero and hardly removes any material. Because there is little material removal at the top end of the ball end mill, the outer cutting edge performs the majority of the work; this irregular cutting force deforms the tool and shortens its life. In this study, we attached an eddy-current sensor to a tool to measure the deformation from the cutting force and we used a tool dynamometer to measure the cutting force. We found that the change in cutting force is dependent on the change in feed rate during square-shaped processing and, as the feed rate is accelerated, the cutting force also increases. Higher cutting forces increase tool deformation.

• 한국공작기계학회논문집
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• 제11권2호
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• pp.95-102
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• 2002

Due to the development of the CNC machine tool and CAM software, sculptured surface machining can be broadly used in die and mold industries and ball end milling process is often used for the sculptured surface machining. It is found out how feedrate affects the precision of the machining and also tried to study the most suitable feedrate in specific cutting condition. Two eddy current sensors were used far measuring tool deflections of X, Y axis, dynamometer for cutting force and roundness tester for roundness. It was found that the tool deflection is getting better as tool path is going to further from the center of convex surface. The reason is that the cutting force is increased as the tool approaches to the center. Examining the roundness, cutting force and tool deflection characteristics, it was found that the most suitable feedrate is 90mm/min in convex surface and 120mm/min in concave surface.

• Journal of Advanced Marine Engineering and Technology
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• 제22권6호
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• pp.754-762
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• 1998

Exhaust emissions in diesel engine are affected by fuel properties but the reason for this is not clear. Especially the recent strong interest in using low-grade fuel demands extensibe investigation in order to clarify the exhaust emissions. Bio-Diesel oil has a great possibility to solve the pollution problem caused by the exhaust gas from diesel engine vehicles. The use of bio-oils in diesel engines has received considerable atten-tion to the forseeable depletion of world oil supplies. So bio-diesel oil has been attracted with attentions for alternative and clean energy source. The purpose of this paper is to evaluate the fea-sibility of the rice-bran oil for alternative fuel in a diesel engine with rgard to exhaust emis-sions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.58-60
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• 1999

This paper presents dynamic performance prediction using Matlab / simulink after parameter estimation of synchronous reluctance motor considering iron loss. Test motor is 3 phase SynRM with the segmental rotor, rating power is 0.175KW. Experiment equipment is consists of testing motor, dynamometer, vector invertor dynamocontroller, and power analyser. The stator iron loss and rotor iron loss are modelled by additional windings on three-phase winding axis. These windings are transformed into d-q axis, and are represented as equivalent eddy current windings. P-Q circle diagram method and single phase standstill method are used to measure motor parameters considering iron loss.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.972-973
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• 2006

본 논문에서는 고압전동기를 직접 드라이브 할 수 있는 H-브릿지 멀티레벨 인버터를 제안한다. 전동기의 부하장치로는 에디커런트 다이나모메타를 사용하였다. H-브릿지 멀티레벨 인버터는 여러 개의 단상 Power Cell을 직렬로 연결함으로써 저전압 전력용 반도체를 사용하여 고전압을 얻을 수 있고, 정현파에 가까운 출력전압 파형을 얻을 수 있는 멀티레벨 인버터 토폴로지이다. H-브릿지 멀티레벨 인버터의 주요 장점은 Power Cell의 모듈화, 셀 단위의 보호동작 용이, 확장성 향상 그리고 제어 신호 및 Power Cell의 신뢰성 향상에 있다. 본 논문에서 제안하는 H-브릿지 멀티레벨 인버터는 상당 3개의 Power Cell이 직렬로 연결되어 총 9개의 Power Cell로 구성이 되어, 선간전압은 13레벨이며 dv/dt가 적으며 입력 단 THD를 크게 낮출 수 있다. 정격용량 180kVA 이고 출력전압이 480V인 H-브릿지 멀티레벨 인버터를 제작하여 와전류 다이나모메타 부하 시험을 통해 제안된 방법의 타당성과 신뢰성을 입증하였다.

• 한국유체기계학회 논문집
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• 제7권5호
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• pp.29-35
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• 2004

The turbine efficiency is an important factor in power plant, and accurate evaluation of steam turbine performance is the key issue in turbo machinery industry. The difficulty of evaluating the steam turbine performance due to its high steam temperature and pressure environment makes the most steam turbine tests to be replaced by air similarity test. This paper presents how to decide the similarity conditions of the steam turbine test and describes its limitations and assumptions. The test facility was developed and arranged to conduct an air similarity turbine performance test with various inlet pressure, temperature and mass flow rate. The eddy-current type dynamometer measures the turbine-generated shaft power and controls the rotating speed. Pressure ratio of turbine can be controled by back pressure control valve. To verify its test results, uncertainty analysis was performed and relative uncertainty of turbine efficiency was obtained.

• 대한기계학회논문집B
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• 제40권8호
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• pp.485-494
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• 2016

본 연구는 TMED 방식 병렬형 하이브리드 차량을 이용하여 회생제동 회수율 및 연비 특성 실험에 대한 것이다. 회생제동 기술은 하이브리드 차량의 에너지 효율 향상을 위해 필수적인 기술로 판단되어 연구를 수행하였다. 따라서 병렬형 하이브리드 차량과 Eddy Current 방식의 차대동력계를 통해 IM240 모드 실험 시 초기 SOC 상태, 주행 모드 특성, 운전자의 운전특성에 따른 연비 특성을 회생 제동 측면에서 전류 특성 및 전류수지에 대한 비교 분석을 수행하였다. 본 연구결과, 초기 SOC 상태가 낮을수록 하이브리드 차량의 엔진 작동 시간이 증가 하고 에너지 효율이 낮아지는 것을 알 수 있었다. 또한 주행 모드 특성, 운전자의 운전 특성에 따른 연비 특성 실험 결과 평균 연비 차이는 크게 나지 않았지만, 최종 SOC 상태에 따라서 모드 종료 후 엔진 작동 유무의 차이가 있음을 알 수 있었다.

• 한국기계가공학회지
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• 제16권2호
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• pp.28-33
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• 2017

Recently, the operation of precision pocket machining has been studied for the high speed and accuracy in industry to increase production and quality. Moreover, the demand for products with complex 3D free-curved surface shapes has increasing rapidly in the development of computer systems, CNC machining, and CAM software in various manufacturing fields, especially in automotive engineering. The type of aluminum (Al6061) that is widely used in aerospace fields was used in this study, and end-mill down cutting was conducted in fillet cutting at a corner with end-mill tools for various process conditions. The experimental results may demonstrate that the end mill cutter with four blades is more advantageous than that of the two blades on shape forming in the same condition precise machining conditions. It was also found that cutting forces and tool deformation increased as the cutting speed increased. When the tool was located at $45^{\circ}$ (four locations), the corner was found to conduct the maximum cutting force rather than the start point of the workpiece. The experimental research is expected to increase efficiency when the economical precision machining methods are required for various cutting conditions in industry.