• Title/Summary/Keyword: Single droplet combustion

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Effect of Initial Diameter on the Soot Generation of Toluene Fuel Droplet (초기 직경 변화가 Toluene 액적의 Soot 생성에 미치는 영향)

  • Lim, Young Chan;Suh, Hyun Kyu
    • Journal of ILASS-Korea
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    • v.20 no.4
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    • pp.261-267
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    • 2015
  • The main purpose of this study is to provide the information of soot generation of toluene fuel droplet. To achieve this, this paper provides the experimental results on the different initial diameter of toluene droplet combustion characteristics conducted under equivalent ambient pressure ($P_{amb}$) and oxygen concentration ($O_2$) conditions. Visualization of single fuel droplet was performed with high resolution CCD camera and visualization system. At the same time, ambient pressure ($P_{amb}$) and oxygen concentration ($O_2$) were maintained by ambient condition control system. Soot volume fraction ($f_v$) was analyzed and compared on the basis of intensity ratio ($I/I_0$) of background image. The result of soot generation was almost the same regardless of initial droplet diameter since thermophoretic flux is not much changed under the same ambient conditions. Soot standoff ratio (SSR) of 2 mm diameter showed unstable variation characteristics due to the short available measuring time.

Mathematical Modeling of the Effect of External Radiative Heating on Heat and Mass Transfer Between A Semi-transparent Diesel Fuel Droplet and Quiescent Air

  • Woo In-Sung;Choi Sung-Eul;Stamatov Venelin
    • International Journal of Safety
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    • v.3 no.1
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    • pp.20-26
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    • 2004
  • The system considered in this model consists of a single, semi- transparent, diesel fuel droplet, which is immobile in the heating area and surrounded by a quiescent air. A uniform external radiation field surrounds the droplet. Results from mathematical simulation suggest that because of the higher surface temperature, the external radiative heating of the droplet can promote an earlier ignition of the fuel vapour/air mixture. The radiative heating of the droplet increases the mass transfer from the droplet to the surrounding gas-phase, thus, decreasing the heterogeneity of the fuel droplet/air system.

Interaction of burning droplets with internal circulation (내부순환유동을 고려한 연소하는 액적들의 상호작용)

  • Cho, Chong-Pyo;Kim, Ho-Young;Chung, Jin-Taek
    • 한국연소학회:학술대회논문집
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    • 2004.06a
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    • pp.183-191
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    • 2004
  • The burning characteristics of interacting droplets with internal circulation in a convective flow are numerically investigated at various Reynolds numbers. The transient combustion of 2-dimensionally arranged droplets, both the fixed droplet distances of 5 radii to 40 radii horizontally and 4 radii to 24 radii vertically, is studied. The results obtained from the present numerical analysis reveal that the transient flame configuration and retardation of droplet internal motion with the horizontal or vertical droplet spacing substantially influence lifetime of interacting droplets. At a low Reynolds number, lifetime of the two droplets with decreasing horizontal droplet spacing increases monotonically, whereas their lifetime with decreasing vertical droplet spacing decreases due to flow acceleration. This flow acceleration effect is reversed when the vertical droplet spacing is smaller than 5 radii in which decreasing flame penetration depth causes the reduction of heat transfer from flame to droplets. At a high Reynolds number, however, lifetime of the first droplet is hardly affected by either the horizontal droplet spacing or flow acceleration effect. Lifetime with decreasing vertical droplet spacing increases due to reduction of flame penetration depth. Lifetime of interacting droplets exhibits a strong dependence on Reynolds number, the horizontal droplet spacing and the vertical droplet spacing and can be con-elated well with these conditions to that of single burning droplet.

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Investigation of a droplet combustion with nongray gas radiation effects (단일액적연소현상에서 비회색체복사에 관한 연구)

  • Choe, Chang-Eun;Park, Jae-Hyeon;Park, Seung-Uk
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.10
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    • pp.1363-1370
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    • 1997
  • Single liquid droplet combustion processes including heating, evaporation, droplet burning and flame radiation were theoretically investigated by adopting nongray gas radiation model for the radiative transfer equation (RTE). n-Heptane was chosen as a fuel and the numerical results were compared with the experimental data available in the literature. The discrete ordinate method (DOM) was employed to solve the radiative transfer equation and the weighted sum of gray gases model (WSGGM) was applied to account for nongray effect by CO$_{2}$, and H$_{2}$0. Therefore, detailed effects by nongray gas and its comparison with the gray gas model could be figured out in the results. It is found that the radiative heat flux is higher when the nongray model is used, thereby reducing the maximum gas temperature and the flame thickness, but the total burning time increases due to the deceased conductive heat flux in nongray model. Consequently, a better agreement with experimental data could be obtained by using nongray model.

Autoignition Phenomena of a Single Diesel/1-Butanol Mixture Droplet (디젤/1-부탄올 혼합연료 단일액적의 자발화 현상)

  • Kim, Hyemin
    • Journal of ILASS-Korea
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    • v.23 no.2
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    • pp.90-95
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    • 2018
  • The goal of this study is to experimentally observe the autoignition phenomena of a diesel/1-butanol mixture droplet in ambient pressure and $700^{\circ}C$ condition. A volume ratio of 1-butanol in the fuel was set to 25, 50 and 75%. A single droplet was installed at the tip of fine thermocouple, and the electric furnace dropped down to make elevated temperature condition. Droplet behavior during the experiment could be divided into 3 stages including droplet heating, puffing and autoignition/combustion. Puffing process intensively observed for the case of 1-butanol volume ratio of 25 and 50%, but did not occur at 75%. Increase of 1-butanol volume ratio hindered rise of the droplet temperature and delayed ignition. In addition, puffing process also affected on autoignition, so the ignition delay of 1-butanol volume ratio of 50% was became longer than that of 75% case.

Effect of Ambient Temperature and Droplet Size of a Single Emulsion Droplet on Auto-ignition and Micro-explosion (단일 유화액적에서의 분위기 온도와 액적크기에 따른 자발화와 미소폭발의 영향)

  • Jeong, In-Cheol;Lee, Kyung-Hwan
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.1
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    • pp.49-55
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    • 2007
  • The characteristics of auto-ignition and combustion process of a single droplet of emulsified fuel suspended in a high-temperature air chamber have been investigated experimentally with various droplet sizes, surrounding temperatures, and water contents. The used fuels was n-Decane and it was emulsified with varied water contents whose maximum is 30%. The high-speed camera has been adopted to measure the ignition delay and flame life time. It was also applied to observe micro-explosion behaviors. The increase of droplet size and chamber temperature cause the decrease of the ignition delay time and flame life-time. As the water contents increases, the ignition delay time increases and the micro-explosion behaviors are strengthened. The starting timings of micro-explosion and fuel puffing are compared for different droplet sizes and the amount of water contents.

Microexplosive Vaporization of Miscible Binary Fuel Droplets (미세폭발을 가진 혼화 이성분 연료 액적의 증발 현상)

  • Ghassemi, Hojat;Baek, Seung-Wook;Khan, Qasim Sarwar
    • 한국연소학회:학술대회논문집
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    • 2005.10a
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    • pp.120-131
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    • 2005
  • The evaporation characteristics of single and multicomponent droplets hanging at the tip of a quartz fiber are studied experimentally at the different environmental conditions under normal gravity. Heptane and Hexadecane are selected as two fuels with different evaporation rates and boiling temperatures. At the first step, the evaporation of single component droplet of both fuels has been examined separately. At the next step the evaporation of several blends of these two fuels, as a binary component droplet, has been studied. The temperature and pressure range is selected between 400 and 700 $^{\circ}C$, and 0.1 and 2.5 MPa, respectively. High temperature environment has been provided by a falling electrical furnace. The initial diameter of droplet was in range of 1.1 and 1.3 mm. The evaporation process was recorded by a high speed CCD camera. The results of binary droplet evaporation show the three staged evaporation. In the the first stage the more volatile component evaporates. The droplet temperature rises after an almost non evaporating period and in the third stage a quasi linear evaporation takes place. The evaporation of the binary droplet at low pressure is accompanied with bubble formation and droplet fragmentation and leads to incomplete microexplosion. The component concentration affects the evaporation behavior of the first two stages. The bubble formation and droplet distortion does not appear at high environment pressure. Nomenclature

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Combustion Characteristics of Single Droplet of Diesel with Bio-diesel for Their Mixing Ratios and Sizes (경유와 바이오 디젤 액적의 혼합비율과 크기에 따른 연소특성)

  • Jeong, Man-Seok;Lee, Kyung-Hwan
    • Journal of Energy Engineering
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    • v.18 no.2
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    • pp.101-107
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    • 2009
  • The combustion characteristics of a single droplet of diesel and bio-diesel have been investigated experimentally with varying droplet size, ambient temperature and compound ratio in a high temperature chamber. The fuels used were diesel with bio-diesel contents varied from 0% to 100%. Each experiment has been performed from 970K to 1070K by 50K intervals. Imaging with a high-speed digital camera was adopted to measure the ignition delay and flame life-time, as well as to observe micro-explosion behavior. The increase of droplet size and decrease of furnace temperature cause an increase of the ignition delay time. As the bio-diesel content decreases, the ignition delay increases and the micro-explosion behavior is strengthened. It is also confirmed that the full combustion time decreases as the micro-explosion occurred.

Investigation on Behavior of HAN-based Propellant Droplet at High Temperature (고온에서 HAN 계열 추진제 액적의 거동에 대한 연구)

  • Hwang, Chang Hwan;Baek, Seung Wook;Han, Cho Young;Kim, Su Kyum;Jeon, Hyung Yeol
    • 한국연소학회:학술대회논문집
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    • 2012.11a
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    • pp.329-332
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    • 2012
  • The droplet behavior of 83.9 wt.% HAN water solution was investigated experimentally with various ambient temperature and nitrogen environment. At the initial stage of evaporation under thermal decomposition temperature of HAN, gradual decreasing of droplet diameter was observed. After that, the droplet started to expand due to the internal pressure build up by water nucleation inside the droplet. The micro explosion was observed at higher temperature than the decomposition temperature of HAN and the remaining droplet showed similar behavior of single composition droplet. The decreasing rate was augmented as the ambient temperature increasing.

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Non-Steady Group Combustion of Liquid Fuel Droplets (액체연료 액적군 의 비정상 집단연소)

  • 김호영
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.8 no.6
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    • pp.544-552
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    • 1984
  • A non-steady group combustion model of a spherical droplets cloud has been developed to access the non-steady effects of collective behavior of fuel droplets on combustion characteristics and cloud structure. A system of conservation equations of droplets cloud in axisymmetric spherical coordinate was solved by numerical methods for n-Butylbenzene(C$_{10}$ / $H_{14}$) It was found that the effect of initial droplet size on combustion characteristics is dominated compare with effects of cloud size and number density of droplets. For dense droplets cloud, external group combustion mode is established during main part of cloud life time, and internal and single droplet combustion modes are simultaneously established for the dilute droplets cloud. Radius of cloud and external envelope flame are slowly decreased during main part of cloud life time, and suddenly decreased at end of combustion period.d.