• 제목/요약/키워드: Lean

검색결과 1,775건 처리시간 0.034초

희박연소기관용 용량방전식 다회수스파크 점화장치의 개발에 관한 기초 연구 (A basic study on development of multiple- spark capacitor discharge igniter for lean burn engine)

  • 이상준;나성오;이종태
    • 대한기계학회논문집B
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    • 제20권11호
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    • pp.3676-3685
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    • 1996
  • Enhancement of the ignitability was necessary to realize the lean burn engine. The characteristics of multiple-spark capacitor discharge igniter(MSCDI) usefulness of which for lean burn was examined in constant volume combustion chamber and evaluated in spark ignition engine. Noise of MSCDI for engine was restricted by adoption of low voltage control system. It was found that the adaptability for high engine speed was remarkable. Lean limit in engine with MSCDI was extended 10% than conventional coil ignition system. Also maximum brake thermal efficiency was almost enhanced 1%.

산업부산물을 활용한 비구조용 콘크리트의 건조수축 특성에 관한 실험적 연구 (An Experimental Study on the Non-Structural Lean Concrete's Dry Shrinkage with industrial by-product)

  • 황무연;양완희;박동철;김우재
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2017년도 춘계 학술논문 발표대회
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    • pp.216-217
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    • 2017
  • Slag cement or ternary blended cement is mainly used for non-structural lean concrete for the purpose of foundation work or protection of the waterproof layer on the roof of buildings. However, such non-structural lean concrete has a lot of drying shrinkage cracks, which makes it difficult to maintain the quality of the structure. Therefore, in this study, the compressive strength and the drying shrinkage of ternary blended cement(blended of portland cement, blast furnace slag, fly ash from combined heat and power Plant) for non-structural lean concrete were examined. As a result, it was confirmed that this non-structural lean concrete reduced drying shrinkage compared to the conventional ternary blended cement using fly ash from power plant.

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NOx저감을 위한 연료희박 재연소 기법의 실험 및 수치적 연구 (Experimental and Numerical Investigation for NOx Reduction with Fuel Lean Reburning System)

  • 김학영;백승욱;손희;김세원
    • 한국연소학회지
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    • 제14권2호
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    • pp.18-25
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    • 2009
  • Fuel lean reburning method is very attractive way in comparison with conventional reburning method for reducing NOX. Meanwhile, the knowledge of the how flue gas re-circulated, temperature distribution and species concentration is crucial for the design and operation of an effective fuel lean reburning system. For this reason, numerical analysis of fuel lean reburning system is a very important and challenge task. In this work, the effect of fuel lean reburn system on NOX reduction has been experimentally and numerically conducted. Experimental study has been conducted with a 15kW lab scale furnace. Liquefied Petroleum Gas is used as main fuel and reburn fuel. To carry out numerical study, the finite-volume based commercial computational fluid dynamics (CFD) code FLUENT6.3 was used to simulate the reacting flow in a given laboratory furnace. Steady state, three dimensional analysis performed for turbulent reactive flow and radiative heat transfer in the furnace.

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린 건설 관리 방식의 공사 전 설계 진행에 관한 연구 -미국 벨뷰 어린이 병원 사례 조사- (A Study on Preconstruction Process in Support of Lean Project Delivery System - Case Study of Children's Hospital at Bellevue, Wa, U.S.A. -)

  • 김용우;김광호
    • 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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    • 제14권4호
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    • pp.47-54
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    • 2008
  • Preconstruction process in a lean project delivery system was studied in one large healthcare project working for a general contractor. Researchers joined a new lean delivery project for approximately six weeks and participated in preconstruction process including design coordination, management coordination, and target costing while concurrently interviewing other project participants and employees, recording activity in meetings, and otherwise observing the process. The preconstruction process in lean project delivery system, called integrated project design, showed many benefits such as brining expertise of downstream players (i.e., mechanical and electrical contractors) into the design phase. However, lack of leadership and lack of design-integrator blocked the successful application of a new concept of design process.

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The Added-Value Metric - A Complementary Performance Measure for Six Sigma and Lean Production

  • Setijono, Djoko;Dahlgaard, Jens J.
    • International Journal of Quality Innovation
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    • 제8권1호
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    • pp.1-14
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    • 2007
  • The Six Sigma and Lean Production methodologies suggest that creating value for customers is the objective of a production process or an organisation. In the production context, "added value" dominates the discussion about the creation of value to customers. However, "added value" is often only defined conceptually or discussed at a strategic level, and the link between added value and customer value has not yet been well conceptualised. Therefore, the purpose of the paper is to develop a methodology to measure added value in order to complement the existing performance measures in Six Sigma and Lean Production by conceptualising the link between customer value and added value. The conceptual link "confirms" that quality, time, and costs are the elements of added value, which are transformed into a metric to express customer value. The implementation of the metric recommends the adoption of Lean (Six) Sigma and Lean Accounting (Activity Based Costing), which thus implies that "leanness" is an important "feature" of added value.

쇠고기 등급판정을 위한 이동형 컴퓨터시각 장치 및 살코기 추출 알고리즘 개발 (Development of Mobile Type Computer Vision System and Lean Tissue Extraction Algorithm for Beef Quality Grading)

  • 최선;;황헌
    • Journal of Biosystems Engineering
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    • 제30권6호통권113호
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    • pp.340-346
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    • 2005
  • Major quality features of the beef carcass in most countries including Korea are size, marbling state of the lean tissue, color of the fat and lean tissue, and thickness of back fat of the 13th rib. To evaluate the beef quality, extracting loin parts from the sectional image of the 13th beef rib is crucial and is the first step. However, because of the inhomogeneous distribution and fuzzy pattern of the fat and lean tissues on the beef cut, it is difficult to extract automatically the proper contour of the lean tissue. In this paper, a prototype mobile beef quality measurement system, which can be implemented practically at the beef processing site was developed. The developed system was composed of the hand held image acquisition unit and mobile processing unit mounted with touch-pad screen. Algorithms to extract the boundary of the lean tissue and a proper tool to evaluate the marbling status have been developed using color image processing. The boundary extraction algorithm showed successful results for the beef cuts with simple and moderate patterns of the lean tissue and fat. However, it had some difficulty in eliminating complex pattern of the extraneous tissues adhered to the lean tissue in the boundary extraction. The developed algorithms were implemented to the prototype mobile processing unit.

성층화된 화염을 이용한 희박 예혼합화염의 날림 특성 제어 (Control the Blow-off Characteristics of Lean Premixed Flames Utilizing a Stratified Flame Concept)

  • 이원남;안태국;남연우
    • 한국연소학회지
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    • 제17권4호
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    • pp.11-20
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    • 2012
  • The Blow-off characteristics of LPG/air lean pre-mixed flames were experimentally investigated using a double and a multiple concentric coflow burners. Experiments were conducted to understand the effects of recirculation motion, thermal interaction between flames, and stratified flame configuration. Here, the stratified premixed flame is a "new concept" of a flame that sequentially contains fuel rich, stoichiometric, and fuel lean reaction zones in a flame. The blow-off from a lean premixed flame was significantly suppressed with recirculation motion. The recirculation motion by itself, however, was not sufficient to prevent the blow-off when the equivalence ratio became low. The existence of a inner premixed flame could also help to prevent the blow-off of lean premixed flame; however, the blow-off suppression effect was rather diminished by weakened recirculation motion with the presence of inner flame. The inner flame could be separated from an outer flame on a multiple concentric coflow burner, causing recirculation motion as well as thermal interaction between flames to become effective; therefore, the blow-off was further suppressed. The lean premixed flame could be stabilized with a fuel rich premixed flames that was produced with the supply of fuel through an inner nozzle. The penetration of lean premixed gas from outside into the fuel stream produced a lifted rich premixed flame. Chemiluminescence images of OH, CH, and $C_2$ radicals confirmed the structure of a stratified premixed flame. The stable premixed flames could be obtained at the very fuel lean condition by applying the stratified premixed flame concept.

직접분사식 LPG 엔진의 연소전략 및 공기과잉률 변화에 따른 연소특성 비교 (Comparison of Combustion Characteristics with Combustion Strategy and Excess Air Ratio Change in a Lean-burn LPG Direct Injection Engine)

  • 조시현;박철웅;오승묵;윤준규
    • 한국자동차공학회논문집
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    • 제22권6호
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    • pp.96-103
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    • 2014
  • Liquefied Petroleum Gas(LPG) has attracted attention as a alternative fuel. The lean-burn LPG direct injection engine is a promising technology because it has an advantage of lower harmful emissions. This study aims to investigate the effect of combustion strategy and excess air ratio on combustion and emission characteristics in lean-burn LPG direct injection engine. Fuel consumption and combustion stability were measured with change of the ignition timing and injection timing at various air/fuel ratio conditions. The lean combustion characteristics were evaluated as a function of the excess air ratio with the single injection and multiple injection strategy. Furthermore, the feasibility of lean operation with stratified mixture was assessed when comparing the combustion and emission characteristics with premixed lean combustion.

흡입 스월유동이 Sl기관의 희박연소에 미치는 영향 (The Effects of Intake Swirl Flow en Lean Combustion in an Sl Engine)

  • 정구섭;전충환;장영준
    • Journal of Advanced Marine Engineering and Technology
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    • 제25권6호
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    • pp.1298-1307
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    • 2001
  • Recently, the efforts to improve fuel economy and to reduce pollutant emission have become the main subject in the development of a gasoline engine. A lean combustion engine admitted as the best alternative is relatively lower fuel consumption rate and exhaust emissions. In this study, it is focused on intensifying intake flow field as one of methods to improve the performance of the lean combustion. First, three different types of suitable swirl control valve(SC7) with high swirl and tumble ratio are selected through steady flow experiment, being installed in a spark ignition engine. The relationship between lean misfire limit and torque was investigated with injection timing and spark ignition timing. Also, the effect of intensified swirl new on the combustion Stability and exhaust emissions was experimently examined by the measuring in-cylinder pressure and combustion variation. The results show that the engine with swirl control calve is superior to other conventional engine on the lean misfire limit, specific torque, combustion variation and emission, and the appropriate injection timing and spark ignition timing exist according to the type of swirl control valve.

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BMW N53 직접분사식 가솔린 엔진의 초희박 연소특성에 관한 연구 (A Study on the Ultra Lean Combustion Characteristics of the BMW N53 GDI Engine)

  • 김홍석;오진우;김성대;박철웅;이석환;정용일
    • 한국자동차공학회논문집
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    • 제19권6호
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    • pp.82-89
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    • 2011
  • Ultra lean combustion with stratified air-fuel mixture is one of the methods that can improve fuel economy of gasoline engines. The aim of this study is to show that how much fuel economy is improved and what are differences in engine control of the ultra lean combustion compared with stoichiometric combustion. In this study, the BMW N53 GDI engine, which is one of ultra lean combustion GDI engines introduced in the market recently, was tested at various engine operating conditions. Results indicated that fuel consumption rates were improved by 11.9~25.8% by the ultra lean combustion compared with stoichiometric combustion. It was also found that multiple fuel injection, multiple spark, early intake valve opening, and large vlave overlap duration were the features of the ultra lean combustion for combustion stability and emission improvement.