• Title/Summary/Keyword: Combustion Conditions

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Study on Mechanism of Combustion Instability in a Dump Gas Turbine Combustor (모형가스터빈 연소기내 연소불안정성에 대한 연구)

  • Lee, Jong-Ho;Lee, Yeon-Ju;Jeon, Chung-Hwan;Jang, Yeong-Jun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.9
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    • pp.1284-1291
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    • 2002
  • Combustion instabilities are an important concern associated with lean premixed combustion. Laboratory-scale dump combustor was used to understand the underlying mechanisms causing combustion instabilities. Experiments were conducted at atmospheric pressure and sound level meter was used to track the pressure fluctuations inside the combustor. Instability maps and phase-resolved OH chemiluminescence images were obtained at several conditions to investigate the mechanism of combustion instability and relations between pressure wave and heat release rate. It showed that combustion instability was susceptible to occur at higher value of equivalence ratio (>0.6) as the mean velocity was decreased. Instabilities exhibited a longitudinal mode with a dominant frequency of ∼341.8 Hz, which corresponded to a quarter wave mode of combustor. Heat release and pressure waves were in-phase when instabilities occurred. Rayleigh index distribution gave a hint about the location where the strong coherence of pressure and heat release existed. These results also give an insight to the control scheme of combustion instabilities. Emission test revealed that NOx emissions were affected by not only equivalence ratio but also combustion instability.

Catalytic Combustion Characteristics of Hydrogen-Air Premixture in a Millimeter Scale Monolith Coated with Platinum (밀리미터 스케일 촉매 연소기에서의 수소-공기 예혼합 가스의 촉매 연소 특성)

  • Choi, Won-Young;Kwon, Se-Jin
    • Journal of the Korean Society of Combustion
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    • v.10 no.1
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    • pp.20-26
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    • 2005
  • In the present study, catalytic combustion of hydrogen-air premixture in a millimeter scale monolith coated with Pt catalyst was investigated. As the combustor size decreases, the heat loss increases in proportion with the inverse of the scale of combustion chamber and combustion efficiency decreases in a conventional type of combustor. Combustion reaction assisted by catalyst can reduce the heat loss by decreasing the reaction temperature at which catalytic conversion takes place. Another advantage of catalytic combustion is that ignition is not required. Platinum was coated by incipient wetness method on a millimeter scale monolith with cell size of $1{\times}1mm$. Using this monolith as the core of the reaction chamber, temperatures were recorded at various locations along the flow direction. Burnt gas was passed to a gas chromatography system to measure the hydrogen content after the reaction. The measurements were made at various volume flow rate of the fuel-air premixture. The gas chromatography results showed the reaction was complete at all the test conditions and the reacting species penetrated the laminar boundary layer at the honeycomb and made contact with the catalyst coated surface. At all the measuring locations, the record showed monotonous increase of temperature during the measurement duration. And the temperature profile showed that the peak temperature is reached at the point nearest to the gas inlet and decreasing temperature along the flow direction.

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Effect of Reentrant Type Bowl Geometry on Combustion Characteristics in Diesel Engine -Effect of Aspect Ratio(Bowl Diameter/Bowl Depth)- (리엔트런트형 연소실 형상이 디젤기관의 연소특성에 미치는 영향 -연소실 형상비(Bowl직경/Bowl깊이)의 효과-)

  • Kwon, J.B.;Kim, H.S.;Kwon, I.K.;Oh, K.J.
    • Journal of ILASS-Korea
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    • v.1 no.4
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    • pp.54-62
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    • 1996
  • Effect of reentrant type bowl geometry on combustion characteristics was investigated in a D.1.diesel engine. The main factor was the aspect ratio (Bowl Diameter/Bowl Depth) of bowl of combustion chamber, and the measured data include the cylinder pressure, engine performance and emissions of the engine using the 4 kinds of the combustion chamber. Experimental results indicate that the effect of dc/H and nozzle protrusion are relatively small and there exists an optimum dc/H according to the combustion conditions. It is also found that the smoke emission is quite sensitive the overall combustion time where the 90 percentage of the combustion heat is released. The smoke mission increases by shortening the 90% combustion time while it decreases by delaying the 90% combustion time.

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A Study on the Ultra Lean Combustion Characteristics of the BMW N53 GDI Engine (BMW N53 직접분사식 가솔린 엔진의 초희박 연소특성에 관한 연구)

  • Kim, Hong-Suk;Oh, Jin-Woo;Kim, Sung-Dea;Park, Chul-Wong;Lee, Seok-Whan;Jeong, Young-Il
    • Transactions of the Korean Society of Automotive Engineers
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    • v.19 no.6
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    • pp.82-89
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    • 2011
  • Ultra lean combustion with stratified air-fuel mixture is one of the methods that can improve fuel economy of gasoline engines. The aim of this study is to show that how much fuel economy is improved and what are differences in engine control of the ultra lean combustion compared with stoichiometric combustion. In this study, the BMW N53 GDI engine, which is one of ultra lean combustion GDI engines introduced in the market recently, was tested at various engine operating conditions. Results indicated that fuel consumption rates were improved by 11.9~25.8% by the ultra lean combustion compared with stoichiometric combustion. It was also found that multiple fuel injection, multiple spark, early intake valve opening, and large vlave overlap duration were the features of the ultra lean combustion for combustion stability and emission improvement.

Influences of Environmental Conditions and Refractory Organic Matters on Organic Carbon Oxidation Rates Measured by a High Temperature Combustion and a UV-sulfate Methods (다양한 환경요인과 난분해성 유기물에 따른 고온산화 및 UV산화방식 총 유기탄소 산화율 변화)

  • Jung, Heon-Jae;Lee, Bo-Mi;Lee, Keun-Heon;Shin, Hyun-Sang;Hur, Jin
    • Journal of Korean Society on Water Environment
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    • v.32 no.1
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    • pp.98-107
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    • 2016
  • This study examined the effects of environmental conditions and the presence of refractory organic matter on oxidation rates of total organic carbon (TOC) measurements based on high temperature combustion and ultraviolet-sulfate methods. Spectroscopic indices for prediction of oxidation rates were also explored using the UV spectra and fluorescence excitation-emission matrix (EEM) of humic acids. Furthermore, optimum TOC instrument conditions were suggested by comparing oxidation rates of a standard TOC material under various conditions. Environmental conditions included salts, reduced ions, and suspended solids. Salts had the greatest influence on oxidation rates in the UV-sulfate method. However, no effect was detected in the high temperature combustion method. The UV-sulfate method showed lower humic substance oxidation rates, refractory natural organic matter, compared to the other methods. TOC oxidation rates for the UV-sulfate method were negatively correlated with higher specific-UV absorbance, humification index, and humic-like EEM peak intensities, suggesting that these spectroscopic indices could be used to predict TOC oxidation rates. TOC signals from instruments using the UV-sulfate method increased with increasing chamber temperature and increasing UV exposure durations. Signals were more sensitive to the former condition, suggesting that chamber temperature is important for improving the TOC oxidation rates of refractory organic matter.

Characterization of the Effect of the Inlet Operating Conditions on the Performance of Lean Premixed Gas Turbine Combustors

  • Samperio, J.L.;Santavicca, D.A.;Lee, J.G.
    • Journal of the Korean Society of Combustion
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    • v.9 no.3
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    • pp.10-18
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    • 2004
  • An experimental study of the effect of operating conditions on the behavior of a lean premixed laboratory combustor operating on natural gas has been conducted. Measurements were made characterizing the pressure fluctuations in the combustor and the flame structure over a range of inlet temperatures, inlet velocities and equivalence ratios. In addition the fuel distribution at the inlet to the combustor was varied such that it was an independent parameter in the experiment. Inlet temperature, inlet velocity and equivalence ratio were all found to have an effect on the stability characteristics of the combustor. The nature of this effect, however, depended on the fuel distribution. For example, with one fuel distribution the combustor would become unstable when the temperature was increased, whereas with a different fuel distribution the combustor would become unstable when the temperature was decreased. Similarly, the operating conditions had an effect on the flame structure. For example the intensity-weighted center of mass of the flame was found to move closer to the center body as either the temperature or equivalence ratio increased. It was interesting and somewhat surprising to note, however, that as the location of the center of mass changed with operating conditions it did so by moving along a line of constant flame angle.

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Comparison of Combustion and Emission Characteristics of Propane and n-butane in a Stratified DISI Engine (성층연소 직분식 엔진에서의 propane과 n-butane의 연소 및 배기특성 비교)

  • Joo, Yongjoon;Jung, Jinyoung;Bae, Choongsik
    • 한국연소학회:학술대회논문집
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    • 2014.11a
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    • pp.97-100
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    • 2014
  • The combustion and emission characteristics of propane and n-butane which are the main components of LPG were compared with gasoline. The experiment was performed in a stratified DISI engine under lean combustion conditions. Mixtures of propane and n-butane wre more homogeneous because propane and n-butane have better evaporation characteristics. As a result, combustion speeds of n-butane and propane were slower, and emission levels of NOx and PM were lower. However, in spite of better evaporation, PM from propane was higher.

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Numerical Study of Flame Structures and Conditional Statistics in Turbulent Spray Jet Combustion (난류분무제트연소에서의 화염구조와 조건평균 통계에 대한 수치적 연구)

  • Seo, Jaeyeob;Huh, Kang Y.
    • Journal of the Korean Society of Combustion
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    • v.17 no.3
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    • pp.46-52
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    • 2012
  • 3D DNS is performed for n-heptane spray turbulent jet combustion. Diesel-like conditions are considered including single and multiple injections. Conditional statistics are obtained for multiple Lagrangian flame groups of sequentially evaporating fuel. Each fuel group represents the conditional statistics of an independent Lagrangian flame group. Sequentially evaporating fuel goes through different histories and residence times over the ignition delay period. Multiple flame groups are required for accurate description of combustion of a spray jet that goes through a long injection duration or multiple injections.

Linear Stability Analysis in a Gas Turbine Combustor Using Thermoacoustic Models (열음향 해석 모델을 통한 가스터빈 연소기에서의 선형 안정성 분석)

  • Kim, Daesik
    • Journal of the Korean Society of Combustion
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    • v.17 no.2
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    • pp.17-23
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    • 2012
  • In this study, thermoacoustic analysis model was developed in order to predict both eigenfrequencies and initial growth rate of combustion instabilities for lean premixed gas turbine combustors. As a first step, a model combustor and nozzle were selected and analytical linear equations for thermoacoustic waves were derived for a given combustion system. Then, methods showing how the equations can be used for analysis of the combustion instability were suggested. It was found that the prediction results showed a good agreement with the measurements. However, there were some limitation in growth rate predictions, which were related with over-simplification of flame structure, acoustic boundary conditions, and temperature distribution in the combustor.

A Study on Sprny and Combustion Characteristics by Temperature of Biodiesel Fuel (바이오디젤 연료온도에 따른 분무 및 열소특성에 관한 연구)

  • Baik, Doo-Sung;Lee, Seang-Wock
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.1
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    • pp.152-157
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    • 2008
  • The biodiesel becomes one of the favorite alternative fuel applied to diesel engines. This research aims to understand the physics of spray and combustion characteristics of a biodiesel fuel in a constant volume chamber. For spray visualization, biodiesel was injected into a combustion chamber and a high speed camera was applied at various combustion conditions. To investigate heat-release rates and flame propagations, spark was ignited on a hydrogen fuel for the premixed combustion and then biodiesel was injected directly. In addition, parametric study was made by various geometries of combustion chambers and temperatures of fuels and injection pressures. This technology may contribute to improve the performance of bio-diesel engine and reduce emissions in future.