• Title/Summary/Keyword: 스월 안정화 화염

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An Experimental Study on Flame Structure and Combustion Instability Characteristics in Model Gas Turbine Combustor (모형 가스터빈 연소기에서 화염구조와 연소불안정 특성에 대한 실험적 연구)

  • Park, Sung-Soon;Kim, Min-Ki;Yoon, Ji-Su;Yoon, Young-Bin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.15 no.4
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    • pp.26-34
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    • 2011
  • The present work addresses structural characteristics of natural gas flames in a lean premixed swirl-stabilized combustor with an attention focused on the effect of the formation of recirculation zones on the combustion instability. It is known that the recirculation zone plays an important role in stabilizing a turbulent, premixed natural gas flames by providing a source of heat or radicals to the incoming premixed fuel and air. To improve our understanding of the role of recirculation zones, the flame structure was investigated for various mixture velocities, equivalence ratios and swirl numbers. The optically accessible combustor allowed for the application of laser diagnostics, and Particle Image Velocimetry(PIV) measurements was used to characterize the flame structure under both cold flow conditions and hot flow conditions. Dynamic pressures were also measured to investigate characteristics of combustion at the same time. The results indicates that the formation of recirculation zone is strongly related to the occurrence of thermo-acoustic instabilities.

An Experimental Study on Flame Structure and Combustion Instability Characteristics in Model Gas Turbine Combustor (모형 가스터빈 연소기에서 화염구조와 연소불안정 특성에 대한 실험적 연구)

  • Park, Sung-Soon;Kim, Min-Ki;Yoon, Ji-Su;Yoon, Young-Bin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.04a
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    • pp.445-452
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    • 2011
  • The present work addresses structural characteristics of natural gas flames in a lean premixed swirl-stabilized combustor with an attention focused on the effect of the formation of recirculation zones on the combustion instability. It is known that the recirculation zone plays an important role in stabilizing a turbulent, premixed natural gas flames by providing a source of heat or radicals to the incoming premixed fuel and air. To improve our understanding of the role of recirculation zones, the flame structure was investigated for various mixture velocities, equivalence ratios and swirl numbers. The optically accessible combustor allowed for the application of laser diagnostics, and Particle Image Velocimetry(PIV) measurements was used to characterize the flame structure under both cold flow conditions and hot flow conditions. Dynamic pressures were also measured to investigate characteristics of combustion at the same time. The results indicates that the formation of recirculation zone is strongly related to the occurrence of thermo-acoustic instabilities.

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Influence of changing combustor pressure on flame stabilization and NOx emission in swirl flame (연소실 압력변동이 스월 화염에서 화염 안정화와 NOx 배출에 미치는 영향)

  • Kim, Jong-Ryul;Choi, Gyung-Min;Kim, Duck-Jool
    • 유체기계공업학회:학술대회논문집
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    • 2006.08a
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    • pp.569-572
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    • 2006
  • In present study, the influence of changing combustor pressure on flame stabilization and nitrogen oxide (NOX) emission in the swirl flame with secondary fuel injection was investigated. The combustor pressure was controlled by suction at combustor exit. Pressure index ($P^*=Pabs/Patm$), where Pabs and Patm indicated the absolute pressure and atmosphere pressure, was controlled in the range of 0.7~1.15 for each equivalence ratio conditions. It could be observed that flame stable region became narrower with decreasing equivalence ratio and pressure index. In this combustion system, stable flames were formed until $P^*=\;0.7$. Emission index decreased with decreasing pressure index for overall equivalence ratio conditions and NOx reduction rates were almost identical for $P^*<1$ regardless of equivalence ratio though EINOx values showed different level with change of equivalence ratio for $P^*{\geq}1$. It is also observed that EINOx decreased with increasing secondary fuel injection ratio. Emission index of nitric oxide was controllable by adjusting the changing combustor pressure and injecting secondary fuel and this NOx reduction technology is applicable to industrial furnaces and air conditioning system.

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Coupling Behavior of Pressure and Heat Release Oscillations by Swirl Injection in Hybrid Rocket (스월에 의한 하이브리드 로켓의 연소압력과 연소반응 진동의 결합 거동)

  • Kim, Jungeun;Lee, Changjin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.7
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    • pp.567-574
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    • 2018
  • Swirl injection induces not only the increase in fuel regression rate but also the reduction of combustion pressure oscillation. This acts, in turn, to stabilize combustion process. Thus, this study primarily focuses on the change in flow structure in the main chamber by swirl injection. Then examining the change in flow structure was done to understand the physical process for stabilizing combustion. In the results, the application of swirl injection could suppress the generation of p' and q' in 500Hz band and could shift the phase difference and cross correlation. Further investigations with combustion visualization also show that the development of helical motion near surface region affects the small-sized vortex generation and shedding yielding combustion stabilization eventually.

Effect of Mixing Section Resonance Mode on Dynamic Combustion Characteristics in a Swirl-Stabilized Combustor (스월-안정화 연소기에서 혼합기 공진모드가 동적 연소특성에 미치는 영향)

  • Han, Sunwoo;Lee, Shinwoo;Hwang, Donghyun;Ahn, Kyubok
    • Journal of ILASS-Korea
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    • v.27 no.1
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    • pp.18-25
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    • 2022
  • Hot-firing tests were performed to experimentally confirm the effect of the eigenmode in the fuel-air mixing section on combustion instability by changing mixing section length, inlet mean velocity, equivalence ratio, and swirler geometry. A premixed gas composed of air and ethylene was supplied to the combustion chamber through an mixing section and an axial swirler. As the mixing section length increased, the inlet velocity perturbation decreased, but the combustion instability increased more. It was found that the resonance frequency of the first longitudinal mode in the mixing section shifted to the third longitudinal mode as the length of the mixing section increased. The results implied that the transition of the resonace frquency by changing the length of the mixing section might cause combustion instability.

Influence of changing combustor pressure and secondary fuel injection on flame stabilization and emission characteristic in swirl flame (연소실 압력변동과 2차 연료 분사가 스월 화염에서 화염안정화와 배출 특성에 미치는 영향)

  • Kim, Jong-Ryul;Choi, Gyung-Min;Kim, Duck-Jool
    • 한국연소학회:학술대회논문집
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    • 2007.05a
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    • pp.133-138
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    • 2007
  • Influence of changing combustor pressure on flame stabilization and emission index in the swirl-stabilized flame was investigated The combustor pressure was controlled by suction fan at combustor exit. Pressure index ($P^{\ast}=P_{abs}/P_{atm}$), where $P_{abs}$ and $P_{atm}$ indicated the absolute pressure and atmosphere pressure, respectively, was controlled in the range of $0.7{\sim}1.3$ for each equivalence ratio conditions. The flammable limits of swirl flames were largely influenced by changing combustor pressure and they showed similar tendency with laminar flames. $NO_x$ emission index decreased with decreasing pressure index for overall equivalence ratio conditions. R.m.s. of pressure fluctuations is increased with decreasing combustor pressure. This flame fluctuation caused incomplete combustion , hence CO emission index increased. These oscillating flames were measured by simultaneous $CH{\ast}$ chemiluminescence time-series visualization and pressure fluctuation measurement.

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Effect of Swirl Cup Geometry on Spray Characteristics in Gas Turbine Engine (가스터빈 연소기의 스월컵 형상이 분무특성에 미치는 영향)

  • 김동준;박종훈;고현석;윤영빈
    • Journal of the Korean Society of Propulsion Engineers
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    • v.6 no.2
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    • pp.29-36
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    • 2002
  • Experiments have been performed to investigate the effect of secondary venturi tip angle on flow and spray characteristics in gas turbine combustor with a swirl cup assembly. Three variations of secondary venturi tip angle are made: converging, straight and diverging angles. It is found that the variation of venturi tip angle results in the significant changes of flow and spray characteristics in gas turbine combustors, such as the size and location of recirculation zones. drop size and mass distribution affecting combustion efficiency and NOx emissions. In diverge case, central toroidal recirculation zone(CTRZ) exists near the exit, which is known to be beneficial for flame stability. But in converge case, the finest SMD distribution and uniform mass distribution are found and CTRZ is longer than other cases. Consequently, high combustion efficiency and low pollutant emission are expected in converge case.

Combustion Characteristics of CH4 Nonpremixed Flame with Recession Distance (메탄 비예혼합 화염의 후퇴거리에 따른 연소특성)

  • Kim, Jun-Hee;Ku, Kun-Woo;Hong, Jung-Goo;Lee, Choong-Won;Kim, In-Su;Cheong, In-Mo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.3
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    • pp.285-291
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    • 2012
  • A lot of research on the stability of nonpremixed flames has focused on the fuel-nozzle and quarl geometries. Of the work carried out, only a small amount has focused on the stability of the nonpremixed flame according to the recession distance and air-nozzle geometry. Therefore, in this study, a coaxial-diffusion-type gas burner with a swirler is designed for the systematic investigation of the combustion characteristics of a $CH_4$ flame depending on the recession distance and secondary air-nozzle geometry. 1st air is flowed through the swirler, and 2nd air is flowed through each nozzle. It is shown that the secondary air velocity greatly influences the flame length and shape. There is an optimum recession distance for each nozzle for the best combustion efficiency. In this study, it is shown that the optimized recession distance is nearly half the outer diameter of the air-supply nozzle.