• Title/Summary/Keyword: 희박분무

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Study on Film Boiling Heat Transfer of Spray Cooling in Dilute Spray Region (희박 분무영역에서의 분무냉각 막비등 열전달에 관한 연구)

  • Kim, Yeung-Chan
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1481-1486
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    • 2004
  • This report presents experimental results on the heat transfer coefficients in the boiling region of spray cooling for actual metallurgical process. In this study, the heat flux distribution of a two dimensional dilute spray impinging on hot plate was experimentally investigated. Based on the experimental results, they classified the heat transfer area into the stagnation region and wall-flow region. In the stagnation region, the local heat transfer coefficient relates mainly to the droplet-flow-rate supplied from spray nozzle directly, so the local heat transfer coefficients is good agreement with the predicted values from correlation for spray cooling proposed by former report However, the local heat transfer coefficient in wall-flow region is larger than predicted values, and it is found that the rebounding droplets-flow-rate must be accurately evaluated to predict the local heat transfer coefficient in this region.

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Study on Film Boiling Heat Transfer of Spray Cooling in Dilute Spray Region (희박 분무영역에서의 분무냉각 막 비등 열전달에 관한 연구)

  • Kim Yeung Chan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.2 s.233
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    • pp.279-286
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    • 2005
  • This study presents experimental results on the heat transfer coefficients in the film boiling region of spray cooling for actual metallurgical process. In this study, the heat flux distributions of a two dimensional dilute spray impinging on a hot plate were experimentally investigated. A stainless steel block was cooled down from intial temperature of about $800^{\circ}C$ by twin fluid (air-water) flat spray. It was found from the experimental results that the heat transfer area was classified into the stagnation region and wall-flow region. In the stagnation region, the experimental data of local heat transfer coefficient was closely correlated with the local droplet-flow-rate supplied from the spray nozzle directly. Thus, the local heat transfer coefficients are in good agreement with the predicted values from the correlations proposed by our previous study. In wall-flow region, however, remarkable differences are observed between experimental data and predicted values because the number of rebound droplets increase with increasing the distance from the stagnation point.

Film Boiling Heat Transfer Model of Spray Cooling Focusing on Rebound Motion of Droplets (액적의 리바운드 모션에 주목한 분무냉각 막비등 열전달 모델)

  • Kim, Yeung-Chan
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1317-1322
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    • 2004
  • In this report, the heat transfer model of spray cooling on hot surface was developed by focusing on the effect of rebound motion of droplets. In the model, it was assumed that droplets rebound repeatedly on the hot surface and heat transfer upon droplet impact is proportional to sensible heat which heats up the droplets to the saturation temperature. In addition, to take account of the contribution of th heat flux upon impact of rebound droplets, it was assumed that the rebound droplets are distributed following the Gaussian distribution from 0 to L, which distance L is determined by maximum flight distance $L_{max}$. Also the calculated results were compared with existing experimental results.

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Film Boiling Heat Transfer Model of Spray Cooling Focusing on Rebound Motion of Droplets (액적의 리바운드 모션에 주목한 분무냉각 막 비등 열전달 모델)

  • Kim Yeung Chan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.2 s.233
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    • pp.287-293
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    • 2005
  • In the present study, to determine the flow rate of droplets supplied to heat transfer surface after (j-1)th rebound, $D_X[j{\ge}2]^{\ast}$, it was assumed that the rebound droplets are distributed according to the Gaussian distribution from 0 to L, in which the flight distance L is determined by maximum flight distance $L_{max}$. We also assumed that $L_{max}$ is dependent on the air flow velocity and mean size of droplets. The local heat flux of a dilute spray in high temperature region was predicted using the newly evaluated $D_X[j{\ge}2]^{\ast}$. In addition, the predicted results by the present model were compared with the existing experimental data.

Effects of Fuel Composition on Flame Transfer Function in Lean Premixed Combustor (희박 예혼합 연소기에서 연료 조성이 화염전달함수 특성에 미치는 영향)

  • Kim, Jinah;Kim, Jihwan;Lee, Jeongwon;Kim, Daesik
    • Journal of ILASS-Korea
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    • v.20 no.3
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    • pp.135-140
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    • 2015
  • Flame transfer function is used to determine the relationship between flow fluctuations and heat release perturbations in a lean premixed gas turbine combustor. The characteristics of flame transfer function are known to depend greatly on flame geometries in addition to other various flow conditions. However, it is not easy to experimentally measure the flame transfer function under various actual combustor operating conditions in terms of time and cost. The current research tries to model the flame transfer function using CFD(Computational Fluid Dynamics). From the results, it is shown that the calculated steady flame geometry can be exactly captured with consideration of the wall heat transfer and radiations. Also, unsteady analysis results show the close characteristics of the flame transfer function to the measured one in both gain and phase.

Comparison of Lean Combustion Performance in a Spark-Ignition Engine Fueled with Natural Gas and Hydrogen (스파크점화 엔진에서 천연가스와 수소의 희박연소 성능 비교)

  • Park, Hyunwook;Lee, Junsun;Oh, Seungmook;Kim, Changup;Lee, Yonggyu;Kang, Kernyong
    • Journal of ILASS-Korea
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    • v.26 no.4
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    • pp.204-211
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    • 2021
  • Lean combustion performance of natural gas and hydrogen was compared in a spark-ignition engine. The lean combustion engine operation with natural gas was limited due to combustion instability at an excess air ratio (EAR) above 1.8. The total hydrocarbon (THC) emissions increased significantly with increasing EAR. The nitrogen oxides (NOX) emissions were also high due to the limitation of increasing EAR. The lean combustion engine operation with hydrogen showed superior combustion stability as well as low THC and NOX emissions, even at high EARs. However, boosting technology was required to reach the high EARs.

Lean Burn Combustion Characteristics of Propane Premixed Flame in Electric Field (전기장 인가에 따른 프로판 예혼합 화염의 희박연소 특성)

  • Minseok Kim;Junyoung Choi;Taehun Kim;Hyemin Kim
    • Journal of ILASS-Korea
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    • v.28 no.1
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    • pp.24-31
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    • 2023
  • In this study, characteristics of a propane-air premixed flame sin DC electric field was investigated. The stainless steel Bunsen burner and the stainless steel ring were used as electrode, and the high voltage supply was used for applying electric field. Flammability range increased significantly when the positive voltage was applied because of extension of LBO limit, while it shrank when the negative voltage was applied. The reason for this was not much related to the burning velocity, but the induced flow around the burner by electric field. withNOx production slightly increased after positive voltage was applied in identical equivalence ratio. Nevertheless, it was advantageous to apply the positive electric field to reduce the NOx since the extension of LBO limit makes the burner possible to operate in very low equivalence ratio.

Design of Venturi Dump Surface for Pre-filming Airblast Injector (예막 공기충돌형 분사기의 벤추리 덤프면 설계)

  • Shin, Dongsoo;Choi, Myunghwan;Radhakrishnan, Kanmaniraja;Koo, Jaye;Jung, Seungchai
    • Journal of the Korean Society of Propulsion Engineers
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    • v.22 no.4
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    • pp.44-54
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    • 2018
  • In a spray experiment using a venturi mounted on a lean premixed LPP injector, droplets appear to have non-uniform distributions. To solve this problem, the exit angle of the venturi was changed to form a dump surface on the nozzle neck. The dump surface improved the atomization performance and minimized droplet loss while forming recirculation zone in the venturi exit. In order to solve the non-uniform spray of the injector, the flow characteristics inside the venturi and SMD of the spray are compared. Finally, an optimum venturi shape is selected to minimize the spray loss and improve the spray performance.

뉴스와 토픽

  • Korean Federation of Science and Technology Societies
    • The Science & Technology
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    • v.35 no.7 s.398
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    • pp.6-9
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    • 2002
  • 간 커피에서 배터리 재료 추출/편두통의 원인 밝혀져/세계의 산호초가 파괴되고 있다/초고속의 기상 예보용 슈퍼컴퓨터/바르는 발기부전 치료제/설탕으로 오염물질 제거/화성 지하에 거대 얼음층/목성의 위성에 생명체 존재 가능성 희박/목성에서 위성 11개 새로 발견/22번째 아미노산 발견/플라스틱 분무로 식물해충 제거/외계 물체가 공룡의 멸종은 물론 번성과도 관련

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Study of Combustion Characteristics with Variations of Combustion Parameter in Ultra-Lean LPG Direct Injection Engine (연소제어인자의 변화에 따른 직접분사식 초희박 LPG엔진의 연소특성 연구)

  • Park, Yun Seo;Park, Cheol Woong;Oh, Seung Mook;Kim, Tae Young;Choi, Young;Lee, Yong Gyu
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.6
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    • pp.607-614
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    • 2013
  • Nowadays, automotive manufacturers have developed various technologies to improve fuel economy and reduce harmful emissions. The ultra-lean direct injection engine is a promising technology because it has the advantage of improving thermal efficiency through the deliberate control of fuel and ignition. This study aims to investigate the development of a spray-guided-type lean-burn LPG direct injection engine through the redesign of the combustion system. This engine uses a central-injection-type cylinder head in which the injector is installed adjacent to the spark plug. Fuel consumption and combustion stability were estimated depending on the ignition timing and injection timing at various air-fuel ratios. The optimal injection timing and ignition timing were based on the best fuel consumption and combustion stability.