• 한국수소및신에너지학회논문집
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• 제24권6호
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• pp.472-479
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• 2013

A free piston linear engine could be operated under HCCI combustion due to its variable compression ratios. To obtain HCCI combustion, the free piston linear engine needs a high compression ratio to achieve auto-ignition of the fuel/air mixture. In this study, an idea for obtaining a high compression ratio using the transition from SI combustion to HCCI combustion was proposed. The fuel used in this study is hydrogen, which is considered to be an environmentally friendly fuel. Besides, the effects of key parameters such as equivalence ratio (${\phi}$), load resistance ($R_L$) and intake temperature ($T_{in}$) on the SI-HCCI transition were numerically investigated. The simulation results show that the SI-HCCI transition is successful without any significant reduction of in-cylinder pressure as the intake temperature is increased from $T_{in}$=300K (SI mode) to $T_{in}$=450K (HCCI mode), while the load resistance and equivalence ratio are retained respectively at $R_L=120{\Omega}$ and ${\phi}$=0.6 in both SI mode and HCCI mode.

• Journal of Advanced Marine Engineering and Technology
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• 제23권3호
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• pp.346-351
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• 1999

This paper is a research for removing the hunting which came about during the parallel running of the alternators which four-pole six-phase have the converter with twelve diodes to rectify all the waves. Druing the parallel running the hunting came about under the period of 0.2-0.3{sec} not when it's load was the resistance but the capacity at the rpm band 1575[rpm] 1690[rpm] This hunting in our judgement was not come about from the general hunting causes which have been already known to but the special example. And so we checked that the hunting came about or not as per the changes of the rpm exciting current load current and converter and converter output voltage and the following facts were revealed. -The hunting occured during the constant voltage charging where r. p. m band is from 1575[rpm] to 1690[rpm] - The hunting did not came about during the constant power charging in which there was the large difference between the converter output voltage and the battery voltage. -The hunting did not came about in the low rpm band. We could see from the above facts that the existence of the hunting inducing point at the con-stant voltage charging band was the direct cause of the hunting. After trying every possible means to remove the hunting inducing point we could know that the modification of the synchronous generator is suitable for he purpos in view of the small engine room.

• 대한기계학회논문집A
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• 제20권1호
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• pp.213-221
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• 1996

An assembly sequence is considered to be optimal when is minimizes assembly cost while satisfying assembly constraints. To derive such an optimal sequence for robotic assembly, this paper proposes a method using a simulated annealing algorithm. In this method, an energy funciton is derived inconsideration of both the assembly constraints and the assembly cost. The energy function thus derived is iteratively minimized until no further change in energy occurs. During the minimization, the energy is occationally perturbed probabilistically in order to escape from local minima. The minimized energy yields an optimal assembly sequence. To show the effectiveness of the proposed method, case studies are presented for industrial products such as an electrical relay and an automobil alternator. The performance is analyzed by comparing the results with those of a neural network-based method, based upon the optimal solutions of an expert system.

• Journal of Advanced Marine Engineering and Technology
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• 제33권6호
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• pp.880-885
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• 2009

The ships have a lot of electric machinery needed to supply electricity from the moment of launching coming out of dry dock to docking at jetty. Thus, the ships always have to use alternator and electric machinery that has low efficiency under the low load. Many government service ships like the MMU training ship have been spending lots of time at jetty rather than sailing at sea. These ships are operated under the condition of low load due to the operation of basic machinery at jetty and electric machineries are driven with the status of low efficiency. This paper would suggest the energy saving method for these ships. The investigation describes that shore connection is a great asset to these ships and that the flow rate control by adjusting revolution with the adoption of inverter is better than flow rate control by using throttle valve to save energy. The result is based on the investigation of cooling pump at MMU training ship.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 추계학술대회 논문집
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• pp.267-272
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• 1999

The auxiliary power supply system fur passenger service of railway car has been developed from MA(Motor-Alternator) to CVCF Inverter (Static Inverter). Generally, a customer wants to apply tile new control method and device for auxiliary power supply of railcar However, if the auxiliary power supply is supplied to extended existing line, the maintenance cost of the old system is less expensive than new developed system, so, the customer specifies that the auxiliary power supply has compatibility with existing one completely. At that time, the hardware is nearly same as existing system except small changes of accessories for better performance. This paper describes the flicker control using feed-forward method of auxiliary power supply system for new 50 electric railcars, which are delivered to Korean National Railroad (KNR) Kwa-chon Line. The existing power supply system has damping resistor box to stabilize the DC input (1.5 ㎸). At this time, for better system efficiency the new system has not include resistor box but new control method including feed-forward control is applied. This control algorithm realizes the better stabilization of input power compared to the result of the existing system, which includes resistor box

• 한국수소및신에너지학회논문집
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• 제26권6호
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• pp.638-644
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• 2015

This paper describes the continuing effort to analysis and design on dynamic and electrical behavior of gamma-type free piston Stirling engine/generator with dual-opposed linear generator for domestic micro-CHP (Combined Heat and Power) system. The double acting Stirling engine/generator has one displacer and two power piston which are supported by flexure springs. Two power pistons oscillate with symmetric sinusoidal displacement and are connected with moving magnet type linear generators for power generation. To operate Stirling engine/generator, combustion heat of natural gas is supplied to hot-end and heat is rejected from cold-end by cooling water. The temperature difference across the displacer induces the oscillating motion, and it can be explained with mass-spring vibration system. The purpose of this paper is to describe the design process of linear generator for the double acting free-piston Stirling engine.

• 한국수소및신에너지학회논문집
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• 제24권3호
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• pp.206-215
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• 2013

A linear engine has advantages in terms of volume and weight, because there are no rotating parts. Thus, it is considered that linear engines might be suitable in hybrid vehicles. However, the linear engine has challenges in terms of the engine ignition timing and efficiency, so the engine has not been commercialized yet. In this study, the dynamic and combustion characteristics of the linear engine might be specified by various loads which are changed by conductance. The engine used in this experiment consists of two combustion chambers, four compressors, two linear alternators and a mover with a piston head and magnets. The way fuel is supplied in the experiment is by propane fuel being mixed with air in the carburetor, then being delivered into combustion cylinders via compressors. In the experiment, conductance is altered from 0.04 to 0.16mho, and the ignition timing is ahead by just 5.0mm from the maximum stroke. As a result of the experiment, frequency, stroke, input calories and maximum pressure are decreased when the conductance is increased. Meanwhile, IMEP, generation efficiency and electric power are increased when the conductance is increased. Therefore, it might confirm that high conductance generates more efficient electric power, but that thermal efficiency is the highest in the state of 0.08mho.

• 대한기계학회논문집B
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• 제39권4호
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• pp.371-378
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• 2015

전기자동차 레인지 익스텐더는 소형 엔진으로 구동되는 발전기 시스템(초소형 파워팩)으로서 자동차 운행 중 지속 충전을 통하여 운전 거리 및 시간을 연장한다. 기존 가솔린 엔진 파워팩은 복잡한 구조와 낮은 에너지 밀도로 인하여 고출력 소형 시스템 구현에 한계가 있다. 반면, 가스터빈 파워팩은 출력밀도가 매우 높고 고속화를 통해 시스템의 소형화가 가능하다. 본 연구에서는 전기자동차 레인지 익스텐더로 활용하기 위하여 초소형 가스터빈, 자동차용 알터네이터, 배터리를 사용한 초소형 가스터빈 파워팩 실험장치를 개발하고, 무부하 및 부하 조건에서 동력전달 기어비 및 알터네이터 전기부하에 따른 운전 특성 및 발전 성능을 측정하였다. 실험 결과, 부하 변화에 따른 발전 성능의 변화는 없었으며, 코어터빈 속도가 150 krpm 일 때 최대 전기적 출력은 0.8 kW 로 측정되었다. 또한, 동력축의 3:1 감속을 통해 전기적 출력은 1.5 kW 로 88% 증가하였다. 따라서, 본 연구의 초소형 가스터빈 파워팩은 배터리 부하변동에 대해 안정적인 전력생산이 가능하며, 전기자동차용 레인지 익스텐더로 적용가능함을 확인하였다.

• 한국산학기술학회논문지
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• 제18권6호
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• pp.703-709
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• 2017

한국형 기동헬기(이하 수리온) 사업은 군이 운용중인 노후헬기를 국산헬기로 대체하기 위하여 연구개발한 사업으로 소요군의 전투력 향상과 운용, 유지 경제성을 고려한 사업이다. 수리온 보조동력장치는 주 발전기의 고장 시 장착 된 교류발전기로 체계에 비상 전원을 공급하는 장치이며 시동모터는 배터리의 전기적 에너지를 기계적 회전에너지로 변환 하여 보조동력장치 엔진을 회전시키는 장치이다. 수리온의 전력화 및 운용이 지속됨에 따라 시동모터의 결함이 발견되었고 이를 해소하기 위한 개선 활동을 진행하였다. 고장모드 분석에서는 결함발생에 대한 현상을 확인하고 결함원인을 5가지로 분류하였다. 5가지 인자에 대한 분석결과 결함의 주요 원인은 기계적 마모이며 이는 스프링 압력과 관련이 있다는 사실을 확인 하였다. 이론적으로 결정 된 압력조절을 통해 250회의 시험검증을 수행하였고 4개의 샘플링 마모량으로 회귀분석을 수행한 결과 모두 0.05이하의 유의수준을 보였기에 대립가설을 채택 하였다. 결론적으로 브러쉬 이상마모와 마모로 인한 파손은 압력조절을 통해 해결할 수 있었으며 시험을 통해 마모량 예측 및 결과 타당성을 확인 할 수 있었다.