• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.299-304
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• 2011

A hydrogen fueled 2 stroke free-piston engine with reverse uni-flow scavenging have a advantageous structure for the backfire occurrence, but it can reduce thermal efficiency by the circuit-flow to go through a exhaust-port. In this research, varied boost pressure, SVOT and exhaust pressure are used in a 2stroke free-piston engine with hydrogen fueled for studying the possibility of increasing thermal efficiency of free-piston hydrogen engine. As a result, to increase thermal efficiency of free-piston are suitable to supply the mixture after port closed the exhaust rater than to use the scanvenging. And it was increased by the exhaust pressure, to achieve it must be used the lean-mixture at SVOT aBDC $34^{\circ}$.

• 대한기계학회논문집B
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• 제35권5호
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• pp.525-531
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• 2011

디젤엔진에서 배기가스 재순환(EGR; Exhaust Gas Recirculation)은 선택적 환원 촉매나 $NO_x$ 흡장 촉 매에 비해 $NO_x$ 배출 저감을 위한 가장 효과적인 기술이다. 점점 더 강화되어 가는 $NO_x$ 배출 규제를 만족시키기 위해서는 많은 양의 EGR 가스 공급이 필요하다. 저압 EGR은 일정한 과급 압력에서 가변형상 터보차져의 제어와 거의 독립적이기 때문에 EGR 공급 측면에서 보면 저압 EGR이 기존의 고압 EGR에 비해서 더 많은 장점을 갖는다. 본 연구에서는 저압 EGR이 연소 특성에 미치는 영향을 고압 EGR을 적용했을 때와 비교하였다. 각 EGR 루프에 대해 혼합기의 희석 정도에 따른 영향을 분석하기 위해 독립변수로써 희석비를 사용하였다. 저압 EGR을 적용하였을 때, 고압 EGR을 적용했을 때와 동등한 $NO_x$ 배출량을 유지하면서 연료 소비율과 매연 배출은 고압 EGR의 경우보다 좀 더 낮은 결과를 보였다.

• 한국자동차공학회논문집
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• 제18권5호
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• pp.136-144
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• 2010

Exhaust gas recirculation (EGR) is an emission control technology allowing significant NOx emission reduction from light-and heavy duty diesel engines. The future EGR type, dual loop EGR, combining features of high pressure loop EGR and low pressure loop EGR, was developed and optimized by using a commercial engine simulation program, GT-POWER. Some variables were selected to control dual loop EGR system such as VGT (Variable Geometry Turbocharger)performance, especially turbo speed, flap valve opening diameter at the exhaust tail pipe, and EGR valve opening diameter. Applying the dual loop EGR system in the light-duty diesel engine might cause some problems, such as decrease of engine performance and increase of brake specific fuel consumption (BSFC). So proper EGR rate (or mass flow) control would be needed because there are trade-offs of two types of the EGR (HPL and LPL) features. In this study, a diesel engine under dual loop EGR system was optimized by using design of experiment (DoE). Some dominant variables were determined which had effects on torque, BSFC, NOx, and EGR rate. As a result, optimization was performed to compensate the torque and BSFC by controlling start of injection (SOI), injection mass and EGR valves, etc.

• 한국산학기술학회논문지
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• 제19권12호
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• pp.41-46
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• 2018

본 연구에서는 바이오가스 기반 예혼합 압축착화(Homogeneous charged compression ignition, HCCI) 엔진에 수소를 첨가하였을 때, 연소실 내부 압력, 온도 배출가스에 미치는 영향에 대해 살펴보았다. 자세히는 수소 첨가량과 과다공기량(${\lambda}$) 변화에 따른 연소실 압력 온도, 그리고 생성물로서의 NO, $CO_2$ 배출 특성을 화학 반응 해석 프로그램을 사용하여 고찰하였다. 대상의 엔진은 2300cc 바이오가스 엔진 발전기로서 압축비 13:1, 발전량 15kW 급이다. 과급압은 1.2bar 고정 조건이며, rpm은 1800rpm의 정속 조건이다. 엔진 연소 방식은 예혼합 압축 착화를 모사하였다. 본 연구를 진행하기에 앞서 바이오가스의 주요 조성인 메탄의 연소 및 산화 메커니즘에 대한 선행 연구에 대한 고찰을 통하여 연소반응 메커니즘을 규명하기 위한 반응 메커니즘 연구 기술의 경향을 살펴보고, 본 연구에 적용 가능한 반응 메커니즘을 선정하여 해석을 진행하였다. 수소를 첨가할 때 NO는 증가하는 반면, $CO_2$등의 배출량은 감소하였고 실린더 내부 압력이 상승하며, 상승 구간이 진각 됨을 알 수 있었다. 또한, 희박영역에서 수소 첨가가 가연 한계를 증가시켰다.

• Computers and Concrete
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• 제16권6호
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• pp.919-932
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• 2015

This paper presents a new method for assessing the three-point-bending (3PB) strength of mortar beams in a non-destructive manner, based on neural network (NN) models. The models are based on the radial basis function (RBF) architecture and the fuzzy means algorithm is employed for training, in order to boost the prediction accuracy. Data for training the models were collected based on a series of experiments, where the cement mortar beams were subjected to various bending mechanical loads and the resulting pressure stimulated currents (PSCs) were recorded. The input variables to the NN models were then calculated by describing the PSC relaxation process through a generalization of Boltzmannn-Gibbs statistical physics, known as non-extensive statistical physics (NESP). The NN predictions were evaluated using k-fold cross-validation and new data that were kept independent from training; it can be seen that the proposed method can successfully form the basis of a non-destructive tool for assessing the bending strength. A comparison with a different NN architecture confirms the superiority of the proposed approach.

• 한국기계가공학회지
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• 제13권4호
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• pp.69-74
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• 2014

A waste gate valve (WGV) assembly for a gasoline turbocharger is typically manufactured by means of precision casting. In this study, however, it was newly manufactured in a more innovative way, metal injection molding (MIM) using Inconel 713C alloy, and its performance was tested in a 1.6L direct injection gasoline engine by a thermal shock durability test that lasted 300 hours, after which the results were compared to those of a precision-cast WGV assembly with regard to the engine intake boost pressure, turbine wheel speed, and transient intake pressure. It was found that the two WGV assemblies showed similar performance levels throughout the durability test.

• 한국항행학회논문지
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• 제14권1호
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• pp.93-101
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• 2010

본 논문에서는 터보차저 엔진에서 중요한 문제로 대두되는 응답 특성을 규명하고, 전 부하뿐만 아니라 빈번하게 운행되는 부분 부하 조건 하에서의 엔진 성능을 분석하고자 한다. 시험 결과 컴프레서의 압축비는 1260 rpm 까지는 직선 형태로 급격히 증가하고 이후에는 약 2.5 정도로 완만하게 증가하는 것으로 나타났다. 이때 제동 평균 유효 압력도 압축비에 따라 1260 rpm 까지는 직선적으로 급격하게 증가하다가 1600 rpm 이후부터는 급격히 감소하였다. 과급압이 증가될수록 연비, 공기 과잉률, 제동 평균 유효 압력이 향상되나 중저속 영역보다는 정격 회전수로 갈수록 높아지는 경향이 크게 나타나고 있다. 터보차저는 약 1260 rpm 에서부터 안정적으로 작동되는 것으로 나타났으며 저속 영역에서는 과급기의 특성상 효율이 낮게 나타났다. 이 연구의 결과는 터보차저 엔진의 안정적 부하와 속도 제어 방법에 응용할 수 있다.

• Design & Manufacturing
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• 제6권1호
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• pp.18-23
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• 2012

HI-WORTH T-32, a non-powered plasma cutter, is a portable cutter that utilizes compressor-plasma inverter. With a special air-pressure piston, the cutter is semiautomatic. When they were produced by die casting dies, the bodies or housings of the cutter have defects about 100 percent of defect rate due to blisters and thermal deformation. Therefore, they are produced by mechanical machining, which leads to a hike in material and machining costs and to the loss of productivity. And companies are left with insignificant profit margins. Besides mechanical machining, this study proposes to modify defective mold and cut down defective rate and boost productivity.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.86-93
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• 1999

Turbocharger has been used to increase the performance of diesel engine, especially ship engine , for years. Recently, the turbocharger is being adopted not only for an agricultural engine but also for an automobile engine. To improve the performance of diesel engine , the problem of the reduction of A/F ratio in high speed should be solved. Turbocharger is well known for its cost effectiveness, reliability and duration . In this study, an experiment was conducted to verify simulation program . The results for natural aspiration engine and turbocharged engine were compared. In order to estimate the characteristics of exhaust gas, D-13 mode was selected. Power, torque and BSFC of turbocharged engine were increased than those of natural aspiration engine by about 48%, 46% and 5%, respectively . The components in exhaust gas except NOx from turbocharger engine were less than the amount set up for 2000-year regulation.

• 자원ㆍ환경경제연구
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• 제16권3호
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• pp.629-641
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• 2007

Chinese government has implemented the West Development Strategy since 1999 to boost the region's growth and prevent the environmental degradation. Until now, the regional economy and living standard in Western China have been greatly improved, while it also indicated by the State Council that the ecological environment still deteriorated with part improvement, and pressure of water shortage increased. The paper focus on the relationship of GDP per capita and the volume of industrial waste water discharge of all the 12 provinces in Western China from 1989 to 2004, by the expanded EKC model in the cubic form. Results show that they mainly have down trend in the whole sample space but small up trend in the recent years. That means controlling of industrial wastewater discharge is still an important task to be insisted in the Western China.