• Title/Summary/Keyword: Premixed combustion

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Characteristics of High-Frequency Combustion Instabilities Occurring in Combustion Devices (연소장치에서 발생하는 고주파 연소 불안정 특성)

  • Seo, Seong-Hyeon
    • Journal of the Korean Society of Combustion
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    • v.17 no.1
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    • pp.30-36
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    • 2012
  • Dynamic characteristics of combustion occurring in various combustion devices have been extensively studied since most of high-performance combustion devices are susceptible to hazardous, unstable combustion that deteriorates combustor's lifetime. One of the most severe unstable combustion phenomena is high-frequency combustion instability in which heat release fluctuations from combustion are coupled to resonant modes of the combustor. Here in this study, characteristics of high-frequency combustion instabilities observed in three different combustion devices have been presented. Lean-premixed combustion instability occurs mainly due to equivalence ratio fluctuations which induce large heat release oscillations at lean conditions. Liquid-fueled combustion also shows high-frequency instability from energy coupling between pressure and heat release oscillations.

Large Eddy Simulation of Turbulent Premixed Combustion Flow around Bluff Body based on the G-equation with Dynamic sub-grid model (Dynamic Sub-grid 모델을 이용한 G 방정식에 의한 보염기 주위의 난류 예혼합 연소에 관한 대 와동 모사)

  • Park, Nam-Seob;Ko, Sang-Cheol
    • Journal of Advanced Marine Engineering and Technology
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    • v.34 no.8
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    • pp.1084-1093
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    • 2010
  • Large eddy simulation of turbulent premixed flame stabilized by the bluff body is performed by using sub-grid scale combustion model based on the G-equation describing the flame front propagation. The basic idea of LES modeling is to evaluate the filtered-front speed, which should be enhanced in the grid scale by the scale fluctuations. The dynamic subgrid scale models newly introduced into the G-equation are validated by the premixed combustion flow behind the triangle flame holder. The calculated results can predict the velocity and temperature of the combustion flow in good agreement with the experiment data.

Numerical Study on Combustion Charaterestics in a Constant Volume Combustor Having a Radical Injector (라디칼인젝터를 적용한 정적연소기의 연소특성에 관한 계산적 연구)

  • Jo, Sang-Mu;Jeon, Jae-Hyeuk;Jang, In-Sun;Jeong, Sung-Sik;Park, Kweon-Ha
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.9
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    • pp.1309-1316
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    • 2003
  • A premixed-compression-ignition engine has been studied to improve the efficiency and to decrease exhaust emissions. However those systems have some difficulties for controlling combustion process. Radical is an activated chemical species formed by a chemical chain reaction between reactant and product. When the chain reactions occur, the energy bond of species is broken easily by the released radicals. The combustion chamber of the premixed-compression-ingnition engine is consist of a main chamber with lean premixture and a subchamber with rich premixture. Those are connected by narrow cylinderical connections. With ignition start in the subchamber, many different kinds of radical is jetted into the main chamber. The premixed gas in main chamber is quickly burned up by the radical ignition in multi-pionts. In this paper, the combustion phenomena in a constant volume combustor having a radical injector are numerically analyzed. The some constants in the reaction rate equation are adjusted by the experimental results tested in the same geometrical chamber. The code is applied on the two combustors in a wide range of equivalence ratio. The results show that the burning time is much shorter in the combustor having radical injector.

The Effects of Secondary Fuel Injection on Combustion Oscillation

  • Shigeru Tachibana;Laurent Zimmer;Park, Gyung-Min;Takeshi Yamamoto;Ufosawa, Yoji-K;Seiji Yoshida;Kazuo Suzuki
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.376-379
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    • 2004
  • The purpose of this work is to develop an effective active control system for combustion instabilities of premixed combustors. For the first step, the natural modes of combustion oscillation were investigated for a methane-air premixed combustor and the controls by secondary fuel injection were examined. The main premixed flame is stabilized by a swirler with orifices for secondary injection installed on the central hub. For sensing purposes, a pressure transducer and a chemiluminescence sensor were placed on the appropriate positions. The acoustic characteristics and the source of the oscillation were analyzed by those signals. To test the controllability, two methods of actuations by secondary fuel injection were examined. One is the open loop control and the other is the closed loop control. The comparison of the reduction levels of p $_{rms}$ shows that the closed loop control with a phase-shift injection performs best in this condition.ition.n.

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The Study for Designs of Lean-Premixed low NOx Combustor (희박-예혼합 저 NOx 연소기 설계에 대한 연구)

  • Lim, Am-Ho;Kim, Han-Suck;Ann, Kuk-Young;Lee, Sang-Min;Kim, Yong-Mo
    • 한국연소학회:학술대회논문집
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    • 2003.12a
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    • pp.83-88
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    • 2003
  • The concept of lean-premixed combustion in gas turbine combustor operation has become a standard in recent years as an effective means to meet stringent environmental standards on NOx emissions. Various types of air-fuel premixer, which affect greatly NOx emission and stability of lean-premixed low NOx combustor, were investigated experimentally to reduce the NOx emission. One type of the premixers is selected by experiments and applied it to 70kW class lean-premixed gas turbine combustor. The exit temperature and emissions of CO and NOx were measured with equivalence ratios at ambient pressure. From the results, the emissions of CO and NOx were influenced by the type of air-fuel premixer. As the mixing length of air and fuel is longer, the NOx and CO emission were decreased in the primary reaction zone. Compared with of conventional combustor, the lean-premixed low NOx combustor has low NOx emission characteristics.

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A Study on Combustion and Emission Characteristics of a Diesel Engine Fuelled with Premixed Gasoline/Pilot Diesel (디젤 엔진에서 예혼합 가솔린/파일럿 디젤 이종연료의 연소 및 배출가스 특성에 관한 연구)

  • Kim, Minjae;Lim, Jonghan;Kang, Kernyong;Lee, Seokhwan
    • Transactions of the Korean Society of Automotive Engineers
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    • v.25 no.3
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    • pp.326-335
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    • 2017
  • It is known that diesel engines have the disadvantage of high emission levels of NOx and PM. Therefore, many combustion strategies have been developed to reduce these harmful NOx and PM emissions in a diesel engine. Among these strategies, HCCI(Homogeneous Charge Compression Ignition) and PCCI(Premixed Charge Compression Ignition) are the most popular as these can reduce NOx and PM simultaneously. However, when a single fuel like diesel is applied, it is difficult to control the combustion phase and this can lead to power reduction. In this study, premixed gasoline and pilot diesel were used to overcome the problems of controllability of the combustion phase and harmful emissions. We injected gasoline directly into the combustion chamber and the gasoline/air mixture was ignited with a pilot diesel fuel near the top dead center. The results showed that the combustion and emission characteristics of dual-fuel combustion were comparable to those of conventional diesel combustion. When we applied the dual-fuel PCCI combustion concept, more than 90 % of NOx and PM emission was reduced simultaneously without significant degradation of efficiency compared to conventional diesel combustion.

Activation Energy Asymptotics Revisited (II) - Diffusion-Flame Structure in the Premixed-Flame Regime (활성화에너지점근법의 재고찰 (II) - 예혼합화염영역에서 확산화염구조)

  • Kim, Jong-Soo
    • Journal of the Korean Society of Combustion
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    • v.9 no.4
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    • pp.35-46
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    • 2004
  • Activation energy asymptotics (AEA) for Linan#s premixed-flame regime is revisited in this paper. First, the detailed AEA procedure for the premixed-flame regime is demonstrated, so that the practitioners of AEA could easily apply the method to their own problems. In addition, the controversies surrounding the premixed-flame regime, namely the closure controversy and fast-time instability paradox, are explained. Finally, the limitation of AEA, mainly arising from the wrong prediction of fuel leakage through the reaction zone, is examined and the Zel#dovich-Linan kinetics is introduced as an alternative to meet the needs of modern combustion analysis, where the detailed chemical structure of flame is demanded.

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Large Eddy Simulation of Turbulent Premixed Flame Behavior with Dynamic Subgrid G-Equation Model (Dynamic Subgrid G-방정식을 적용한 난류 예혼합 화염의 LES 해석)

  • Park, Nam-Seob;Kim, Man-Young
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.11
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    • pp.57-64
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    • 2005
  • Large Eddy Simulation (LES) of turbulent premixed combustion flow is performed by using the dynamic subgrid scale model based on -equation describing the flame front propagation. After introducing the LES governing equations with dynamic subgrid scale (DSGS) model newly introduced into the -equation, the turbulent premixed combustion flow over backward facing step is analyzed to validate present formulation. The calculated results can predict the velocity and temperature of the combustion flow in good agreement with the experiment data.

The Low-NOx Characteristics of Premixed Lean-Burn Gas Turbine Combustor (예혼합 희박연소 가스터빈 연소기의 저 NOx 특성)

  • Pae, H.S.;Ahn, K.Y.;Park, J.I.;Ahn, J.H.;Kim, Y.M.
    • 한국연소학회:학술대회논문집
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    • 1999.10a
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    • pp.201-207
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    • 1999
  • The combustion characteristics for the low NOx 50 kW-class gas turbine combustor have been experimentally investigated. In order to achieve the premixing and the lean burn combustion, the geometries of the primary zone including premixed chamber were modified from conventional combustor. The centerline profiles of CO and NO concentration, and temperature were measured for the premixed combustors with or without dilution holes in the liner. The effects of the pilot fuel injection rate and air dilution on flame stabilization and pollutant (CO, NO) emission are discussed in detail.

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Flame Dynamic Response to Inlet Flow Perturbation in a Turbulent Premixed Combustor (난류 예혼합 연소기에서의 흡입 유동 섭동에 대한 화염의 동적 거동)

  • Kim, Dae-Sik
    • Journal of the Korean Society of Combustion
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    • v.14 no.4
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    • pp.48-53
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    • 2009
  • This paper describes the forced flame response in a turbulent premixed gas turbine combustor. The fuel was premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. To impose the inlet flow velocity, a siren type modulation device was developed using an AC motor, rotating and static plates. Measurements were made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The test results showed that flame length as well as geometry was strongly dependent upon modulation frequency in addition to operating conditions such as inlet velocity. Convection delay time between the velocity perturbation and heat release fluctuations was calculated using phase information of the transfer function, which agreed well with the results of flame length measurements. Also, basic characteristics of the flame nonlinear response shown in the current test conditions were introduced.

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