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마이크로 가스터빈용 스월-예혼합 버너의 선회 유동 특성 분석
주해지,조주형,황정재,김민국,김한석,이원준 대한기계학회 2019 大韓機械學會論文集B Vol.43 No.12
Swirl-premixed burners have been gaining considerable interest in low-emission gas turbines. The wellpremixed combustion of fuel and air reduces thermal NOx emissions by inhibiting the local high temperature spots. If the fuel and air are poorly mixed, however, the benefit of premixed combustion may diminish. The recirculation zone generated by a swirler acts as an aerodynamic flame holder for flame stability. In this study, we investigated the characteristics of a swirl-premixed burner to identify how the swirl intensity affects the fuel/air mixing, recirculation flow field, flame shapes, and NOx emissions. The numerical results show that the swirl intensity influences the radial pressure gradient in the burner and, subsequently, the fuel penetration depth, leading to a change in the unmixedness, which quantifies degree of fuel/air mixing. A comparison of the unmixedness with the measured NOx emissions shows that NOx production was decreased by enhanced mixing. The strongly swirled flow augmented the recirculation flow rate, which moved the flame base toward the more upstream side and changed the flame shape from ‘V’ to ‘M’. 최근 저공해 연소기 개발 추세인 스월-예혼합 버너는 균일하게 예혼합된 연료와 공기를 hot-spot 생성 없이 연소함으로써 thermal NOx 발생을 최소화하고, 화염 안정성을 향상시키기 위해 재순환 유동이 flame holder 역할을 하는 버너이다. 본 연구에서는 마이크로 가스터빈 연소기용 스월-예혼합 버너의 기본 설계를 수행하고 CFD 해석과 실험을 통해 버너의 선회 유동 및 연소 특성을 분석하였다. 특히, 선회 강도 변화가 연료/공기 혼합 정도(unmixedness) 및 재순환 유동, 화염 형상, NOx 배출 특성 등에 미치는 영향을 분석하였다. 선회 강도 증가는 버너 내부에 반경 방향으로 압력 구배를 형성하고 연료의 penetration 특성을 변화시킴으로써 unmixedness와 NOx 배출량에 영향을 주었다. Unmixedness 값은 CFD를 통해 정량적으로 계산하였으며 실험으로 계측된 NOx 배출량과 상관관계를 고찰한 결과, 연료/공기 혼합도가 향상될 때 NOx 배출량이 감소하는 경향성을 보였다. 또한, 선회 강도 증가로 재순환 유량이 증가하면서 화염의 부착 위치가 노즐의 상류로 이동하였으며 화염 형상은 V-flame에서 M-flame으로 변화하는 현상을 보였다.
연료와 공기의 혼합정도가 모델 가스터빈 연소기내의 압력변동에 미치는 영향
홍정구(Jung Goo Hong),신현동(Hyun Dong Shin) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Combustion instability is a serious obstacle for the lean premixed combustion of gas turbines, and can even cause fatal damage to the combustor and the entire system. Thus, improved understanding of the mechanisms of combustion instability is necessary for designing and operating gas turbine combustors. In this study, in order to understand the instability phenomena, an experimental study was conducted in a rearwardstep dump combustor with LPG and air. The fluctuations of pressure and heat release were measured by piezoelectric pressure sensor and High speed Intensified Charge Coupled Device (ICCD) camera respectively. Various types of combustion modes occurred in accordance with the equivalence ratio and the fuel supplying conditions. The unmixedness of the fuel and air can be controlled by changing the mixing distance (Lf<SUB></SUB>uel). It is found that the unmixedness of the fuel and air affects the characteristics of flame behavior and pressure fluctuations in a lean premixed flame.
최민성,성연모,원명준,박예슬,김민국,최경민,김덕줄 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.48 No.-
Numerical analysis of lean-premixedflames is utilized to investigate the correlation between turbulenceand combustion, fuel–air mixing, and NOx emission using three types of micro gas turbine combustors. Swirlflows generating vortex breakdown andflow recirculation contributing to mixing uniformity areimproved by interaction of burners. Mixing plays an important role inflame dynamics and NOx emissionby means of the unmixedness parameter. To discuss the correlation betweenflame characteristics andvorticity structures, progress variable c is introduced. Theflame stability is enhanced by ring-shaped,large-scale vorticity structures, and air–fuel mixing is increased by momentum and kinetic energy.
Choi, Minsung,Sung, Yonmo,Won, Myungjun,Park, Yeseul,Kim, Minkuk,Choi, Gyungmin,Kim, Duckjool Elsevier 2017 Journal of industrial and engineering chemistry Vol.48 No.-
<P><B>Abstract</B></P> <P>Numerical analysis of lean-premixed flames is utilized to investigate the correlation between turbulence and combustion, fuel–air mixing, and NO<SUB>x</SUB> emission using three types of micro gas turbine combustors. Swirl flows generating vortex breakdown and flow recirculation contributing to mixing uniformity are improved by interaction of burners. Mixing plays an important role in flame dynamics and NO<SUB>x</SUB> emission by means of the unmixedness parameter. To discuss the correlation between flame characteristics and vorticity structures, progress variable <I>c</I> is introduced. The flame stability is enhanced by ring-shaped, large-scale vorticity structures, and air–fuel mixing is increased by momentum and kinetic energy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We study a numerical analysis of a lean-premixed flames in a micro gas turbine combustor. </LI> <LI> The large eddy simulation model is adopted to predict unsteady turbulent motions of methane-air premixed flames. </LI> <LI> The effect of the interaction of the between burners has a larger impact on the mixing process. </LI> <LI> A lower local equivalence ratio of the between burners produces a lower temperature distribution, reducing thermal NO<SUB>x</SUB> formation. </LI> <LI> The flame stability is enhanced by ring-shaped large scale coherent vorticity structures. </LI> <LI> Air–fuel mixing is also increased by strong momentum and high kinetic energy with low NO<SUB>x</SUB> emission. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
모형 가스터빈 연소기에서 NOx 배출량에 미치는 압력 및 비혼합도 효과 분석
왕위엔강,박순빈,손채훈 한국연소학회 2023 한국연소학회지 Vol.28 No.3
Pressure effects on NOx emission in a gas turbine combustor are numerically investigated in the present study. Initially, fully premixed flame condition with air and fuel injection at the combustor inlet is examined. Increasing pressure leads to a 0.08% rise in flame temperature and a significant 30% increase in NOx emissions. Technically premixed flame condition is then conducted. NOx emissions rise from 1.3 to 3 bar but decline beyond 3 bar due to combined pressure and mixing effects. Applying the NOx emission calibration formula, which accounts for pressure-induced changes while eliminating mixing influence, reveals a direct link between increased pressure and higher NOx emissions.
박덕봉(Deok Bong Park),조봉국(Bong Kug Cho),장영준(Young June Chang),전충환(Chung Hwan Jeon) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Lean premixed combustors are effective for significant NOx reductions compared to convectional gas turbine combustor. The objective of this research is to characterize the effects of the Unmixedness of fuel-air and equivalence ratio on the NOx emission in a lean premixed combustor. Experiments were conducted in a dump combustor at one atmosphere using commercial grade methane. At the same swirler angle of 45°, the degree of fuel-air mixing was varied from 0, 50, 100 and equivalence ratio ranged from 0.5 to 0.8. Inlet temperature on the first and second experimental condition was 570K. The resalts show when the degree of fuel-air is increased, NOx emission is decreased at the constant equivalence ratio. When equivalence ratio is increased, NOx emission is increased. Finally, an increase of the inlet temperature leads to NOx emission decrease.
마이크로 가스터빈용 스월-예혼합 버너의 선회 유동 특성 분석
주해지(Hae-ji Ju),조주형(Ju Hyeong Cho),황정재(Jeongjae Hwang),김민국(Min Kuk Kim),김한석(Han Seok Kim),이원준(Won June Lee) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
Swirl-premixed burners have been gaining considerable interest in low-emission gas turbines. The well-premixed combustion of fuel and air reduces thermal NOx emissions by inhibiting the local high temperature spots. If the fuel and air are poorly mixed, however, the benefit of premixed combustion may diminish. The recirculation zone generated by a swirler acts as an aerodynamic flame holder for flame stability. In this study, we investigated the characteristics of a swirl-premixed burner to identify how the swirl intensity affects the fuel/air mixing, recirculation flow field, flame shapes, and NOx emissions. The numerical results show that the swirl intensity influences the radial pressure gradient in the burner and, subsequently, the fuel penetration depth, leading to a change in the unmixedness, which quantifies degree of fuel/air mixing. A comparison of the unmixedness with the measured NOx emissions shows that NOx production was decreased by enhanced mixing. The strongly swirled flow augmented the recirculation flow rate, which moved the flame base toward the more upstream side and changed the flame shape from ‘V’ to ‘M’.
주해지,조주형,황정재 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.11
This study numerically investigates the flow and combustion characteristics of a swirl-premixed burner with a curved vane swirler (i.e., curved type) to reduce the pressure loss of the burner nozzle with a conventional vane swirler (i.e., flat type). For the curved type swirler, the pressure loss is decreased by 35 % due to the inhibition of flow separation at the vane, and NO X emission is reduced by 69 % because fuel-air mixing is enhanced at the flame front, leading to more uniform fuel distribution toward downstream. In addition, the characteristics of the jet penetration are analyzed because the jet behavior is crucial to fuel-air mixing. The jet trajectory in non-swirling flow can be reasonably predicted by a conventional formula, but it is difficult to predict the jet trajectory in swirling flow by this formula because of the effect of a radial pressure gradient formed by the swirling flow.