• 제목/요약/키워드: Lean

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EVALUATION OF NOx REDUCTION CATALYST BY MODEL GAS FOR LEAN-BURN NATURAL GAS ENGINE

  • LEE C. H.;CHO B. C.
    • International Journal of Automotive Technology
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    • 제6권6호
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    • pp.591-598
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    • 2005
  • A three-way catalyst system of a natural gas vehicle (NGV) has characteristics of higher fuel consumption and higher thermal load than a lean-bum catalyst system. To meet stringent emission standards in the future, NGV with the lean-bum engine may need a catalyst system to reduce the amounts of HC, CO and NOx emission, although natural gas system has low emission characteristics. We conducted experiments to evaluate the conversion efficiency of the NOx reduction catalyst for the lean-burn natural gas engine. The NOx reduction catalysts were prepared with the ${\gamma}-Al_{2}O_3$ washcoat including Ba based on Pt, Pd and Rh precious metal. In the experiments, effective parameters were space velocity, spike duration of the rich condition, and the temperature of flowing model gas. From the results of the experiments, we found that the temperature for maximum NOx reduction was around $450^{\circ}C$, and the space velocity for optimum NOx reduction was around $30,000\;h^{-1}$ And we developed an evaluation model of the NOx reduction catalyst to evaluate the conversion performance of each other catalysts.

과농-희박연료가 교차로 공급되는 상호작용 화염의 화염날림에 관한 연구 (Effect of Lean-rich Fuel Staging to the Multiple Jet Flames on the Blowout Velocity)

  • 이병준;박경욱
    • 대한기계학회논문집B
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    • 제32권1호
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    • pp.7-14
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    • 2008
  • It has been reported that partially premixed interacting flame could be sustained till sonic exit velocities if eight small nozzles are arranged optimally and one nozzle on the center is fed small amount of fuel. But the equivalence ratios in this experiments were 20-60. In this research, experiments were conducted to know the effects of lean-rich staging in multiple jet flames on the blowout velocity. The fuel mole tractions in the fuel-air mixture, the nozzle exit velocity and the diameter between adjacent nozzles were alternatively changed. When the lower mole fraction fuel was fed to the nozzles located near the center and small amount of fuel to the center nozzle, flame was not extinguished even at the nozzle exit velocity of 200m/s. Also the interacting flame could be sustained till that velocity when four small size nozzles for lean mixture were located within the arrangement of four nozzles for rich mixture and configured optimally.

직접분사식 가솔린 엔진의 연소제어인자에 따른 희박연소 특성 연구 (A Study on the Lean Combustion Characteristics with Variation of Combustion Parameter in a Gasoline Direct Injection Engine)

  • 박철웅;오진우;김홍석
    • 한국자동차공학회논문집
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    • 제20권4호
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    • pp.39-45
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    • 2012
  • Today gasoline engines for vehicular application are not only faced with stringent emission regulation but also with increasing requirements to better fuel economy, while guaranteeing power density. The spray-guided type gasoline direct injection (GDI) engine has an advantage of improved thermal efficiency and lower harmful emissions. Centrally mounted high pressure injector and adjacent spark plug allow stable lean combustion due to the flexible mixture stratification. In the present study, the performance and emissions characteristics of developed spray-guided type GDI combustion system were evaluated at various excess air ratio conditions. The specific fuel consumption and nitrogen oxides ($NO_x$) emissions were reduced due to the achievement of stable lean combustion under flammability limit. Multiple injection strategy was not helpful to improve fuel consumption while further reduction of $NO_x$ emissions was possible.

가솔린엔진에서의 2차원 화염 가시화 (2-Dimensional Visualization of the Flame Propagation in a Four-Valve Spark-Ignition Engine)

  • 배충식
    • 한국연소학회지
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    • 제1권1호
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    • pp.65-73
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    • 1996
  • Flame propagation in a four-valve spark-ignition optical engine was visualized under lean-bum conditions with A/F=18 at 2000rpm. The early flame development in a four-valve pentroof-chamber single-cylinder engine was examined with imaging of the laser-induced Mie scattered light using an image-intensified CCD camera. Flame profiles along the line-of-sight were also visualized through a quartz piston window. Two-dimensional flame structures were visualized with a Proxitronic HF-1 fast motion camera system by Mie scattering from titanium dioxide particles along a planar laser sheet generated by a copper vapor laser. The flame propagation images were subsequently analysed with an image processing programme to obtain information about the flame structure under different tumble flow conditions generated by sleeved and non-sleeved intake ports. This allowed enhancement of the flame images and calculation of the enflamed area, and the displacement of its center, as a function of the tumble flow induced by the pentroof-chamber in the vicinity of spark plug. Image processing of the early flame development quantified the correlation between flame and flow characteristics near the spark plug at the time of ignition which has been known to be one of the most important factors in cyclic combustion variations in lean-burn engines. The results were also compared with direct flame images obtained from the natural flame luminosity of the lean mixture.

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의복설계를 위한 성인여성의 頸部 및 肩部의 유형화 II - 체형별.연령층별 변화 분석 - (A Study on the Shapes of Women′s Neck and Shoulder in Dressmaking - According to Body Type and Age Group -)

  • 김희숙
    • 복식문화연구
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    • 제8권5호
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    • pp.754-770
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    • 2000
  • The definite objects of this study are as follows ; 1. The study presents concrete objects of the shape of adult women's neck and shoulder after comparing and analyzing the features of five age groups ; the former young age, the latter young age, the former middle age, the latter middle age, the latter middle age and the old age. 2. The study presents concrete objects of adult women's neck and shoulder by the body types ; bend-forward type, straight type and lean-back type in order to be examined the body types. The results of this study are as follows ; 1. The shape of neck and shoulder needs the several concrete objects of each types because of the variable factors in size and body types. But the concrete objects of the types referred in five age groups contain all the important factors and enable to design the body suitable clothes. 2. This study shows that generally bend-forward type contains rising shoulder and lean-back type contains drooping shoulder, and straight type contains average value of neck and shoulder. The results of this study developed the body-suitable clothes of bend-forward type, straight type and lean-back type.

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스파크 점화 엔진에서 희박연소의 전자제어 히스테리시스 현상에 관한 실험적 연구 (A Experimental Study on the Electronic Control Hysteresis Phenomenon of Lean Burn in Spark Ignition Engine)

  • 김응채;김판호;서병준;김치원;이치우
    • Journal of Advanced Marine Engineering and Technology
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    • 제28권3호
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    • pp.475-481
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    • 2004
  • Recently it is strongly required on lower fuel consumption. lower exhaust emission, higher engine performance. and social demands in a spark ignition gasoline engine. In this study. the experimental engine used at test. it has been modified the lean burn gasoline engine. and used the programmable engine management system, and connected the controller circuit which is designed for the engine control. At the parametric study of the engine experiment, it has been controlled with fuel injection, ignition timing. swirl mode, equivalence ratio engine dynamometer load and speed as the important factors governing the engine performance adaptively. It has been found the combustion characteristics to overcome the hysteresis phenomena between normal and lean air-fuel mixing ranges. by mean of the look-up table set up the mapping values. at the optimum conditions during the engine operation. As the result, it is found that the strength of the swirl flow with the variation of engine speed and load is effective on combustion characteristics to reduce the bandwidth of the hysteresis regions. The results show that mass fraction burned and heat release rate pattern with crank angle are reduced much rather, and brake specific fuel consumption is also reduced simultaneously.

마이크로 터빈 연소기 주연소영역의 저 NOx 생성 특성 (The Low NOx Characteristics of the Primary Zone in Micro Turbine Combustor)

  • 손민규;안국영;이헌석;윤정중
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 추계학술대회논문집B
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    • pp.155-160
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    • 2001
  • The low NOx characteristics have been investigated to develop the combustor for micro turbine. The lean premixed combustion technology was applied to reduce the NOx emission. The test was conducted at the condition of high temperature and ambient pressure. The combustion air which has the temperature of $450\sim650K$ were supplied to the combustor through the air preheater. The temperature and emissions of NOx and CO were measured at the exit of combustor, The exit temperature and NOx were increased and CO was decreased with increasing inlet air temperature. The premixing chamber can be operated very lean condition of equivalence ratio around 0.35. The NOx was decreased with decreasing the equivalence ratio. The CO was decreased with decreasing the equivalence ratio, but the CO was increased with decreasing the equivalence ratio below 0.4. But, at the very lean condition of equivalence ratio below 0.35 both NOx and CO were increased because of the flame unstability. The NOx was decreased and CO was increased with increasing inlet air flowrate. This results can be used to determine the size of combustor. Consequently the performance of combustor shows the possibility of the application to the gas turbine system.

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린 6시그마 분석을 통한 도면 주기 품질 향상 방안 연구 (A Study on the Quality Improvement of Mechanical Drawing Notes Using Lean 6 Sigma Analysis)

  • 전용구;허형조;이성배;박훈혁;안병국
    • 품질경영학회지
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    • 제48권3호
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    • pp.381-393
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    • 2020
  • Purpose: The purpose of this study was to find useful solutions by analyzing causes and results about defects on mechanical drawing notes and provide an automated tool with solutions to mechanical engineers. Methods: The collected data for defects on mechanical drawing notes were from ongoing development and mass production projects. Various measurement methods were used based on the Lean 6 Sigma analysis such as Process analysis, C&E diagram and some statistical analysis. Results: The results of this study are as follows; The results of the Lean 6 Sigma analysis, the validity of the selected indicators for improving drawing notes quality was verified through the verification of cause variables. The strategy established to improve the mechanical drawing notes was reflected as an automated program, and the defects were within a manageable range and achieved target Sigma level. Conclusion: Through the application of the "Mechanical drawing notes automation tool", it is expected to resolve the "Voice of Customer, VOC" and "Voice of Business, VOB".

다기능 복합 포장용 섬유보강 콘크리트 기층 재료의 역학적 특성평가 (Mechanical Performance of Fiber Reinforced Lean Concrete for Subbase of Newly Developed Multi-Functional Composite Pavement System)

  • 장영재;박철우;박영환;정우태;최성용;유평준
    • 한국도로학회논문집
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    • 제14권5호
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    • pp.21-29
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    • 2012
  • PURPOSES: This study is to investigate the mechanical performance of the fiber reinforced lean concrete with respect to different types of fibers. METHODS: Increased vehicle weight and other causes from the exposed conditions have accelerated the deteriorations of road pavement. A new multi-functional composite pavement system is being developed recently in order to extend service life and upgrade the pavement. A variety of tests were conducted before and after hardening of the concrete. RESULTS: From the test results, it was found that the use of different types of fibers did not affect the compressive strength development. This might be due to the inherent property of the lean concrete. When steel fibers were used relatively greater flexural strength and flexural fracture toughness were developed. Also addition of fly ash by replacing a part of Portland cement the fracture toughness was slightly increased. CONCLUSIONS: It has been known that the addition of fibers and use of mineral admixture can be positively considered in the development of multi-functional composite pavement system as its required mechanical performance is obtained.

희박 예혼합 가스터빈 연소기에서의 화염 전달 함수 소개 (Introduction to Flame Transfer Function in Lean Premixed Gas Turbine Combustor)

  • 김대식
    • 대한기계학회논문집B
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    • 제35권9호
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    • pp.975-979
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    • 2011
  • 희박 예혼합 가스터빈 연소기는 강화되는 NOx 배출가스 규제를 만족시키기 위한 가장 현실적인 방법으로 인식되고 있다. 그러나 이러한 희박 예혼합 연소기에서는 열발생파와 시스템 내부의 압력파 사이의 상호 피드백 관계에 의한 연소 불안정 현상으로 인하여 그 적용이 제한되거나, 이를 회피하기 위한 기술의 적용으로 인하여 설계 비용의 상승이 불가피하다. 본 논문에서는 연소 불안정 현상이 발생하는 기본 메커니즘을 소개하고, 연소 불안정 원인 규명의 일환으로 최근 활발히 연구되고 있는 화염전달 함수 측정이 실험적으로 규명되었고, 주요 측정 결과가 소개되었다.