• Title/Summary/Keyword: Coaxial Non-Premixed Jet

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Basic Study on Lift-off Characteristics of Non-Premixed Flames of Methane-Air Jet in a Tube (관 내부 메탄-공기 분류 비예혼합 화염의 부상 특성 기초 연구)

  • Kim, Go-Tae;Kim, Nam-Il
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.4
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    • pp.431-438
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    • 2011
  • Flame lift-off conditions determine the operating conditions of burners. It is known that a flame can be lifted when the Schmidt number (Sc), which is the ratio of the dynamic viscosity to the mass diffusivity, is greater than unity. In this study, the flame lift-off characteristics of non-premixed flames of propane (Sc > 1) and methane (Sc < 1) in a coaxial outer air tube were experimentally compared. The experimental results indicated that stable lifted flames could be obtained even when Sc < 1 in a confined air tube. On the basis of the results of a simple numerical analysis, it was confirmed that a new flame stabilization mechanism exists in the tube. A velocity field is preferentially developed upstream of the flame, and it results in a new stabilization condition. This result can be very useful in explaining the stabilization of the flames of ordinary burners in which a flame is produced in a confined space.

Characteristics of NOx Emission in a Swirl Flow in Nonpremixed Turbulent Hydrogen Jet with Coaxial Air (수소 난류 확산화염에서의 선회류에 의한 배기배출물 특성)

  • Oh, Jeong-Seog;Yoon, Young-Bin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.3
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    • pp.275-282
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    • 2010
  • The effect of swirl flow on NOx in a nonpremixed turbulent hydrogen jet with coaxial air was studied. The swirl vane angle was varied from $30^{\circ}$ to $90^{\circ}$. The fuel jet air velocity and coaxial air velocity were varied in an attached flame region as $u_F=85{\sim}160m/s$ and $u_A=7{\sim}14m/s$. The objective of the current study was to analyze the characteristics of nitrous oxide emission in a swirl flow and to propose a new parameter for EINOx scaling. The experimental results show that EINOx decreases with the swirl vane angle and increased with flame length. Further, EINOx scaling factors can be determined by considering the effective diameter ($d_{F,eff}$) in a far field concept. The EINOx increased in proportion to the flame residence time (${\sim}{\tau_R}^{1/2.8}$) and the global strain rate (${\sim}{S_G}^{1/2.8}$).

Analysis of Gaseous Hydrogen/liquid Oxygen Combustion Processes at Supercritical State (초임계 압력에서 기체수소/액체산소의 연소과정 해석)

  • Kim, Tae-Hoon;Kim, Seong-Ku;Kim, Yong-Mo
    • Journal of ILASS-Korea
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    • v.15 no.4
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    • pp.189-194
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    • 2010
  • This study has been mainly motivated to numerically model the transcritical mixing and reacting flow processes encountered in the liquid propellant rocket engines. In the present approach, turbulence is represented by the extended k-$\varepsilon$ turbulence model. To account for the real fluid effects, the propellant mixture properties are calculated by using SRK (Souve-Redlich-Kwong) equation of state model. In order to realistically represent the turbulence-chemistry interaction in the turbulent non-premixed flames, the flamelet approach based on the real fluid flamelet library has been adopted. Based on numerical results, the detailed discussions are made for the real fluid effects and the precise structure of the transcritical cryogenic liquid nitrogen jet and gaseous hydrogen/liquid oxygen coaxial jet flame.

Characteristics of Non-premixed Synthetic Natural Gas-Air Flame with Variation in Fuel Compositions (합성천연가스의 조성변화에 따른 확산화염 연소특성)

  • Oh, Jeongseog;Dong, Sangeun;Yang, Jebok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.9
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    • pp.829-836
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    • 2013
  • The combustion characteristics with variations in synthetic natural gas (SNG) compositions were studied in a lab-scale combustor. The objective of the current study is to investigate the flame stabilization, flame structure, and spectrometry in a non-premixed SNG flame with varying fuel compositions. For the analysis of light emission in SNG flames, we used a spectrometer. As experimental conditions, the fuel jet velocity at the nozzle exit $u_F$ was varied from 5 to 40 m/s and the coaxial air velocity $u_A$ was varies from 0 to 0.43 m/s. The experiments showed that the flame stability increased with the hydrogen component in SNG.

Development of Real-Fluid based Flamelet Modeling for Liquid Rocket Injector (액체로켓분사기 해석을 위한 실제유체 기반의 난류연소모델 개발)

  • Kim, Seong-Ku;Choi, Hwan-Seok;Park, Tae-Seon
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2010.05a
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    • pp.150-155
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    • 2010
  • Liquid rocket injectors play crucial roles on propulsive performance, combustion stability, and heat transfer characteristics. Nevertheless, their developments have mainly relied on empirical methods and expensive hot-firing tests due to lack of fundamental understanding of high pressure combustion phenomena in the near-injector regions. The present study was motivated by recent efforts to develop reliable modeling of liquid rocket combustion. The turbulent combustion model based on the flamelet concept has been extended to take into account real-fluid behaviors occurred at supercritical pressures, and validated against measurements for a cryogenic nitrogen injection, a non-premixed turbulent jet flame at atmospheric pressure, and a LOx/$GH_2$ coaxial shear injector at a supercritical pressure.

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