• 제목/요약/키워드: exciplex

검색결과 65건 처리시간 0.024초

직분식 엔진에서 실린더 내 연료의 액.기상 거동에 미치는 텀블과 스월의 영향 (The Effects of Tumble and Swirl Flow on the Behavior of Liquid/Vapor Phases in a DI Gasoline Engine)

  • 강정중;최동석;김덕줄
    • 한국자동차공학회논문집
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    • 제10권2호
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    • pp.23-30
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    • 2002
  • This present study experimentally investigates the behavior of liquid and vapor phase of fuel mixtures with changing the in-cylinder air motion in an optically accessible engine. The conventional MPI/DOHC engine was modified to gasoline direct injection engine with swirl motion. The images of liquid and vapor phases were captured in the motoring operation condition using exciplex fluorescence method. Two dimensional spray fluorescence images of liquid and vapor phases were acquired to analyze spray behaviors and fuel distribution inside of cylinder respectively, In early injection timings $(BTDC\;270^{\circ},\;180^{\circ})$, tumble flow transported most of vapor phase to the lower region and the both sides of cylinder, so vapor phase didn't become uniform distribution up to the half of the compression stroke. In the case of swirl flow, the fuel mixture was confined near the swirl origin in upper region of cylinder. In late injection timings $(BTDC\;90^{\circ})$, tumble flow transported vapor phase to the intake valve and swirl flow to the exhaust valve.

분위기 온도에 따른 충돌 분무의 거동에 대한 실험 및 수치적 연구 (Experimental and Numerical Study on Behavior of Impinging Spray according to Ambient Temperature)

  • 심영삼;최경민;김덕줄
    • 한국자동차공학회논문집
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    • 제15권4호
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    • pp.124-131
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    • 2007
  • The numerical study on behavior of impinging spray from high-pressure swirl injector under various ambient temperatures was performed by using spray vaporization model and spray-wall impingement model implemented in modified KIVA code, and these spray models were estimated by comparison with experimental results. To compute the spray-wall impingement process, the Gosman model, which is based on the droplet behavior after impingement determined by experimental correlations, was used. The modified Abramzon and Sirignano model, that includes the effects of variable thermodynamic properties and non-unitary Lewis number in the gas film, was adapted for spray vaporization process. The exciplex fluorescence measurements were also conducted for comparison. The experimental and numerical analysis were carried out at the ambient pressures of 0.1 MPa and at the ambient temperature of 293 K and 473 K, and the spray characteristics, such as spray-wall impingement process, gas velocity field, SMD and vapor concentration, were acquired. It was found that the impinging spray develops active and SMD is small at vaporization conditions.

A Study on the Behavior Characteristics of Diesel Spray by Using a High Pressure Injection System with Common Rail Apparatus

  • Yeom, Jeong-Kuk;Hajime Fujimoto
    • Journal of Mechanical Science and Technology
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    • 제17권9호
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    • pp.1371-1379
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    • 2003
  • The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated. The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore, this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 22 MPa to 112 MPa using a high pressure injection system (ECD-U2). Also, we conducted simulation study by modified KIVA-II code. The results of simulation study are compared with experimental results. The images of liquid and vapor phase for free spray were simultaneously taken by exciplex fluorescence method. As experimental results, the vapor concentration of injected fuel is leaner due to the increase of atomization in the case of the high injection pressure than in that of the low injection pressure. The calculated results obtained by modified KIVA-II code show good agreements with experimental results.

Formation and Properties of Enyne Radical Cation

  • Kim, Bang-Duk;Shim, Sang-Chul;Noboyuki Ichinose;Sachiko Tojo;Tetsuro Majima
    • Journal of Photoscience
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    • 제8권2호
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    • pp.67-69
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    • 2001
  • Radical cations of DPBEY and PPCB were generated by ${\gamma}$-radiolysis and pulse radiolysis in halogenated solvents. The radical cation PPCB+ shows 505 (shoulder) and 520 nm absorption peaks with 700 ns lifetime in agreement with the laser flash photolysis work and strongly support the exciplex mechanism proposed for the photoreaction of PPCB and dimethylfumarate.

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분사압력변화가 증발자유디젤분무의 혼합기형성과정에 미치는 영향 (Effect of the Change in Injection Pressure on the Mixture Formation Process in Evaporative Free Diesel Spray)

  • 염정국;정성식
    • 동력기계공학회지
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    • 제9권4호
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    • pp.214-219
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    • 2005
  • The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated. The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore, this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 72MPa to 112MPa by using a common rail injection system(ECD-U2). The images of liquid and vapor phase in the evaporating free diesel spray are simultaneously taken by exciplex fluorescence method. As a result, it can be confirmed that the distribution of vapor concentration is more uniform in the case of the high injection than in that of the low injection pressure.

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An Advanced Method for Behavior-Characteristics Analysis of Diesel Fuel Spray

  • Yeom, Jeong-Kuk
    • 동력기계공학회지
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    • 제18권3호
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    • pp.5-13
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    • 2014
  • In order to control emissions from engine, it is necessary to understand the mixture formation process of diesel spray. In this study, analysis of diesel fuel(n-Tridecane, $C_{13}H_{28}$) spray under a high temperature and pressure was performed by a general-purpose program, ANSYS CFX release 11.0, and the results of these are compared with experimental results of diesel fuel spray using the Exciplex Fluorescence Method. The simulation results of diesel spray is analyzed by using the combination of Large-Eddy Simulation(LES) and Lagrangian Particle Tracking(LPT), and then injection pressure was selected as an analysis parameter. Consequently, it was found that the experimental results and the numerical results are consistent with each other, and then in order to investigate the behavior characteristics of evaporative diesel spray, the effectiveness of the use of CFX of commercial code is definitely validated.

증발디젤분무의 거동특성해석을 위한 계산기법 적용에 관한 기초 연구 (Basic Study on the Application of a Computational Technique to Behavior Characteristics Analysis of the Evaporative Diesel Spray)

  • 염정국
    • 동력기계공학회지
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    • 제14권6호
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    • pp.5-12
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    • 2010
  • In this study, an analysis of evaporative diesel spray and an usefulness of a general-purpose program, ANSYS CFX release 11.0, are investigated through the comparison and investigation of the experimental results carried out under an evaporative field, in which there is phase transition, by an exciplex fluorescence method and the results analyzed by the CFX program. The diesel fuel called n-Tridecane, $C_{13}H_{28}$, is injected from a single-hole nozzle (l/d=1.0mm/0.2mm) into a constant volume chamber under a high temperature and pressure. In the same condition as the experimental condition, the analysis was carried out. Both results of the spray tip penetration were almost coincident at each time. The results have validated the usefulness of this analysis. As a result, if the ambient pressure is high, the spray tip penetration will be shortened and move toward the nozzle exit.

Mechanistic Studies on the Anormalous Photocycloaddition Reaction of 5-Styryl-1,3-dimethyluracil and 2,3-Dimethyl-2-butene: Formation of the “Apparent Forbidden” [$_\pi4_s + _\pi2_s$] Cycloadduct

  • Eun Ju Shin;Ho Kwon Kang;Sang Chul Shim
    • Bulletin of the Korean Chemical Society
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    • 제12권4호
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    • pp.434-437
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    • 1991
  • Irradiation of 5-styryl-1,3-dimethyluracil (5-SDU) with 2,3-dimethyl-2-butene (DMB) gives a [4+2] cycloadduct which is converted into a [2+2] cycloadduct on the prolonged irradiation. Triplet sensitization, quenching, and external heavy atom effect on the [4+2] photocycloaddition reaction demonstrate the singlet pathway and salt effect excludes a radical ion pair precursor possibility. Polar solvents increase the reaction efficiency implying a polar exciplex involvement in the [4+2] photocycloaddition reaction. Inverse temperature dependence both on the reaction and DMB fluorescence quenching of 5-SDU indicates the presence of a singlet exciplex intermediate.