• 제목/요약/키워드: Homogeneous Mixture

검색결과 303건 처리시간 0.024초

균일 혼합기를 이용한 이론 공연비 직접분사 가솔린 엔진 개발에 관한 실험적 연구 (A Study on the Development of Stoichiometric Direct Injection Gasoline Engine by Homogeneous Charge)

  • 이내현;유철호;최규훈
    • 한국자동차공학회논문집
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    • 제6권2호
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    • pp.32-42
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    • 1998
  • Lean burn gasoline engine is recognized as a promising way to meet better fuel economy. Lean burn engine is classified into port injection and direct injection(DI), DI is more active technique for improving fuel economy with ultra-lean operation, Nowadays, port injected lean burn engine has been produced by many Japan maker. Also, DI engine is also possible for production owing to improvement in control technique of spray, flow air fuel ratio. DI engine uses either homogeneous stoichiometric mixture or stratified mixture by controlling injection timing to be early or late respectively. HM(homogeneous mixture) is worse than SM(stratified mixture) in view of ultra-lean operation in partical load and Nox reducion by using EGR control. But, HM has advanteges in cold starting and emission reduction during transient operation, This paper describes experimental variables and bench test results of HM GDI engine.

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Homogeneous Centroid Neural Network에 의한 Tied Mixture HMM의 군집화 (Clustering In Tied Mixture HMM Using Homogeneous Centroid Neural Network)

  • 박동철;김우성
    • 한국통신학회논문지
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    • 제31권9C호
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    • pp.853-858
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    • 2006
  • 음성인식에서 TMHMM(Tied Mixture Hidden Markov Model)은 자유 매개변수의 수를 감소시키기 위한 좋은 접근이지만, GPDF(Gaussian Probability Density Function) 군집화 오류에 의해 음성인식의 오류를 발생시켰다. 본 논문은 TMHMM에서 발생하는 군집화 오류를 최소화하기 위하여 HCNN(Homogeneous Centroid Neural Network) 군집화 알고리즘을 제안한다. 제안된 알고리즘은 CNN(Centroid Neural Network)을 TMHMM상의 음향 특징벡터에 활용하였으며, 다른 상태에 소속된 확률밀도가 서로 겹쳐진 형태의 이질군집 지역에 더 많은 코드벡터를 할당하기 위해서 본 논문에서 새로 제안이 제안되는 이질성 거리척도를 사용 하였다. 제안된 알고리즘을 한국어 고립 숫자단어의 인식문제에 적용한 결과, 기존 K-means 알고리즘이나 CNN보다 각각 14.63%, 9,39%의 오인식률의 감소를 얻을 수 있었다.

좁은 분사각을 갖는 인젝터를 이용한 예혼합 압축착화 엔진의 분사조건에 따른 분무 및 연소특성에 관한 연구 (A Study on the Spray and Combustion Characteristics of a HCCI Engine according to Injection Conditions using a Narrow Angle Injector)

  • 김형민;김영진;류재덕;이기형
    • 한국분무공학회지
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    • 제11권3호
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    • pp.161-167
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    • 2006
  • As the exhaustion of petroleum resources and air pollution problems are getting serious recently, there are growing interests in premixed diesel engines which have the potential of achieving a more homogeneous mixture near TDC compared to conventional diesel engines. Early studies have shown that the fuel injection frequency and spray angle affected the mixture formation and combustion in a HCCI(Homogeneous Charge Compression Ignition) engine. Therefore, the purpose of this study is to investigate the relationship between combustion and mixture formations by injection timing and frequency using a narrow angle injector, NADI (Narrow Angle Direct Injection). In this study, we found that the fuel injection timing and injection frequency affect the mixture formations and then affect combustion in the HCCI engine.

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분사시기 및 분사각 변화에 따른 HCCI 엔진의 혼합기 분포 및 연소특성에 관한 연구 (A Study on the Characteristics of Mixture Formation and Combustion in HCCI Engine according to the Various Injection Angles and Timings)

  • 김형민;류재덕;이기형
    • 한국자동차공학회논문집
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    • 제14권4호
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    • pp.20-25
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    • 2006
  • Recently, there has been an interest in premixed diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to conventional diesel engines. Early studies are shown that in a HCCI(Homogeneous Charge Compression Ignition) engine, the fuel injection timing and injection angle affects the mixture formations. Thus the purpose of this study was to investigate relationship of combustion and mixture formations according to injection timing and injection angle in a common rail direct injection type HCCI engine using a early injection method called the PCCI(Premixed Charge Compression Ignition). From this study, we found that the fuel. injection timing and injection angle affect the mixture formations and in turn affects combustion in the PCCI engine.

엔진오일에 물이 혼합될 때 터보챠져 저어널 베어링의 열유체윤활 해석 (Thermohydrodynamic Lubrication Analysis of Turbocharger Journal Bearing Involving the Mixture of Water within Engine Oil)

  • 전상명
    • 한국자동차공학회논문집
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    • 제20권1호
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    • pp.131-140
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    • 2012
  • In this study, using the governing equation for thermohydrodyamic lubrication involving the homogeneous mixture of incompressible fluid derived by based on the principle of continuum mechanics, it is discussed the effects of water within engine oil on the performance of high speed journal bearing of a turbocharger. The governing equations are the general equations being able to be applied on the mixture of Newtonian fluid and non- Newtonian fluid. Here, the fluid viscosity index, n of power-law non-Newtonian fluid is supposed to be 1 for the application of the journal bearing in a turbocharger lubricated with the mixture of two Newtonian fluid, for example, water within engine oil. The results related with the bearing performance are shown that the bearing friction is to decrease and the side leakage and bearing load increase as increasing the water content in an engine oil.

FIRE Code를 사용한 정적연소기의 메탄-공기 균질 혼합기 연소특성 연구 (A Study on Combustion Characteristics of Methane-air Homogeneous Mixture in a Constant Volume combustion Chamber by FIRE Code)

  • 이석영;허강열
    • 한국연소학회지
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    • 제11권2호
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    • pp.28-36
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    • 2006
  • A constant volume combustion chamber was used to investigate the combustion characteristics. of homogeneous charge of methane-air mixture under various initial pressure, equivalence ratio and ignition times. The constant volume combustion chamber(CVCC) mostly has been studied by the experiments of visualization until now. So it is needed the numerical analysis of fluid and combustion characteristics in chamber by the more detail simulation. In this paper, the numerical analysis is tried to approach basically the homogeneous charge combustion phenomena under the various conditions, and the combustion phenomena in chamber is numerically analyzed by the commercial FIRE code. As a results, the combustion phenomena which were mean temperature, OH radical and reaction rate in chamber were investigated and it showed that the smallest flame growth occurs for the lean state and the increase of initial charged pressure condition due to the reduced OH radical.

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수축-확대 채널내부의 캐비테이션 유동해석 (CAVITATING FLOW ANALYSIS OF CONVERGING-DIVERGING CHANNEL)

  • 김미선;하콩투;박원규
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2011년 춘계학술대회논문집
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    • pp.14-19
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    • 2011
  • Two difference cavitation models based on the homogeneous mixture model are used to study cavitating flows through converging-diverging channel. Here, the cloud cavities, pressure distributions and other results have been obtained and compared to evaluate two cavitation models. What's more, differences are observed in the simulated results, due to the differences in characteristics of each model. Analytical results shows that the new improvement cavitation model is validated to have better effects on simulating cavitating flows

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정적연소기에서의 메탄-공기 혼합기의 연소특성(1) : 균질급기 (Combustion Characteristics of Methane-Air Mixture in a Constant Volume Combustion Chamber(1): Homogeneous Charge)

  • 최승환;전충환;장연준
    • 한국자동차공학회논문집
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    • 제11권3호
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    • pp.48-57
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    • 2003
  • A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at spark plug and the combustion characteristics of homogeneous charge methane-air mixture under various initial pressure, excess air ratio and ignition times in quiescent mixture. The flow characteristics such as mean velocity and turbulence intensity was analyzed by hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer and flame propagation acquired by ICCD camera were used to investigate the effect of initial pressure, excess air ratio and ignition times on pressure, combustion duration, flame speed and burning velocity. Mean velocity and turbulence intensity had the maximum value at 200 or 300ms and then decreased to near 0 value gradually after 3 seconds. Combustion duration, flame speed and burning velocity were observed to be promoted with excess air ratio of 1.1, lower initial pressure and ignition time of 300ms.

비정렬 격자계에서 균질혼합 모델을 이용한 2차원 수중익형 주위의 캐비테이션 유동 해석 (CAVITATION FLOW ANALYSIS OF 2-D HYDROFOIL USING A HOMOGENEOUS MIXTURE MODEL ON UNSTRUCTURED MESHES)

  • 안상준;권오준
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2011년 춘계학술대회논문집
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    • pp.20-24
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    • 2011
  • In this paper, numerical simulation of cavitation flow for modified NACA66 hydrofoil was made by using the multi-phase RANS equation based on pseudo-compressibility. The Homogeneous mixture model comprised of the mixture continuity, mixture momentum and liquid volume fraction equations was utilized. A vertex-centered finite-volume method was used in conjunction 2nd-order Roe's FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing The Spalart-Allmaras one equation model was employed for the closure of turbulence. Reasonable agreements were obtained between the calculation results and the experiment for pressure coefficients on the hydrofoil surface.

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Mie 산란 방법과 엔트로피 해석 방법을 이용한 혼합연료비에 따른 분무 균질도 특성에 관한 연구 (A Study on the Macro-Scopic Spray Characteristic of Homogeneous Degree for the GDI Injector According to Mixture(Gasoline-Diesel) Ratio Using Mie-Scattering Method and the Entropy Analysis)

  • 이창희;이기형;이창식;배재일
    • 대한기계학회논문집B
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    • 제27권1호
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    • pp.69-75
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    • 2003
  • In this study, his technique was applied to a GDI spray in order to investigate the mixture distribution. In addition, the homogeneity degree and diffusion effect according to ambient temperature in the high pressure chamber were analyzed by using an entropy analysis method. From this experiment, we could find that entropy analysis is very effective method for the analysis of mixture formation, and the entropy values increase with the progress of uniformity in diffusion Process. we tried to provide the fundamental data for parameter which effects on the spray macroscopic characteristics with mixture ratio of diesel and gasoline. In addition, the mixture formation was analyzed by using entropy analysis. The entropy analysis is based on the concept of statistical entropy, and it identifies the degree of homogeneity in the fuel concentration. From the entropy analysis results we could find that the direct diffusion phenomena is a dominant factor in the formation of a homogeneous mixture at downstream of GDI spray especially in vaporizing conditions. As to increasing ambient temperature and increasing gasoline rate, the entropy intensity using the statistic thermodynamics method is increased because evaporation rate is higher gasoline than diesel.