Pressure effect on NO emission in methane/air lean-premixed flames

박성우 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6

Nitrogen oxides (NO x ) from combustion system are one of major pollutants which causes photochemical smog and ozone layer depletion. The interest in lean-premixed combustion has increased to reduce NO x emissions in the industrial gas-turbine as a suitable reduction strategy. The present study investigates methane/air premixed flames with a detailed chemical kinetic model to better understand the pressure effect on NO x formation. A detailed chemical kinetic model is developed by merging AramcoMech 3.0 and recently proposed nitrogen chemistry. The proposed mechanism is first validated against experimental data, including laminar flame speed, ignition delay times, and NO concentration in premixed flames at various pressures. Freely propagating methane/air lean-premixed flames are simulated over a pressure range 1-20 atm and equivalence of 0.5, 0.55 and 0.6. Prompt NO formation is dominant within a narrow heat release region and thermal NO production pathways lead to the total NO formation in the postflame zone. Prompt NO formation rate increases between 1 and 5 atm and then decreases with further increasing pressure due to pressure dependent NCN formation rates. On the other hand, the formation rate of NO in the postflame zone increases monotonically as pressure increases.

Investigation of NO_(x) and CO Formation in Lean Premixed Turbulent Combustion with Methane - Air

Hong, Myung-Seok 조선대학교 에너지.자원신기술연구소 2001 에너지·자원신기술연구소 논문지 Vol.23 No.1

희박 예혼합 가스터빈 연소기 설계에서 NO_(x) 생성과 혼합전달 분위기와의 관계는 매우 중요하다. 본연구에서는 이문제를 위해 메탄-공기의 예혼합으로 작동되는 고압제트 교반 반응기의 NO_(x) 생성에 관해 연구하였다. 실험은 체류시간 (0.5~4.Oms), 압력 (3.0, 4.7, 6.5 atm) 입구온도 (344~573K)의 효과에 대해 중점을 두었다 연소온도는 가장 짧은 체류시간의 1815±5K에서 가장 긴 체류시간의 1910±30K 까지 변화한다. NO_(x) 발생량은 중간의 체류시간에서 가장 낮으며 가장 긴 체류시간에서 높은 값이 나타났다. 압력과 입구온도가 증가하면 NO_(x) 농도는 감소하는 경향이 있다. 연소반응기 내의 농도분포를 두 부분으로 가정하였는데 (1) CO의 농도가 높게 나타나는 비평형반응 지역 (2) 후 화염 지역이다. NO_(x)의 생성은 강력한 비평형 연소반응 지역에 집중되어 있다. 담켈러수 범위는 0.06≤Da≤1 이고 층류연소속도에 대한 난류강도비의 범위는 28≤u´/S₂≤356이며 이는 높은 강도로 연소가 일어나고 있음을 나타내고 있다. 실험 결과는 두 부분으로 나누어 분석하였으며. 화염의 구조와 크기에서 측정된 값과 일치하는 상세 화학 모델을 확립하고, 난류연소 속도와 화염두께의 관계를 이용하여 독립적으로 이 모델을 검증하였다. 이 모델에 의해 NO_(x)의 생성은 비평형 화염지역의 조건과 크기에 의해 지배되고 있음을 알 수 있었다. 또한 이 모델은 NO_(x) 생성에 대해서 잘 교반된 연소는 짧은 체류시간의 상태에서 얻어졌다. The relation between NO_(x) formation and the mixing/transport environment is very importance to the design of lean-premixed gas turbine combustors, but it is not understood completely. In the present research, this problem is studied in NO_(x) formation in a high-pressure jet-stirred reactor operating on lean-premixed methane/air. These experiments focus on the effects of residence time(0.5~4.0ms), pressure(3.0, 4.7, and 6.5 atm), and inlet temperature (344~573K). The combustion temperature varies from 1815±5K at the lowest residence times to 1910±30K at the largest residence times. The NO_(x) is lowest at intermediate residence times, reaching higher values at the extremes. Increasing pressure and inlet temperature tend to reduce NO_(x) concentrations. Concentration profiling in the reactor suggests two zones. (1) a highly non-equilibrium reaction zone defined by high CO concentrations, and (2) a post-flame zone. The NO_(x) formation is concentrated in the region of strongly non-equilibrium combustion chemistry. The Damkohler number is 0.06≤Da≤1, and the ratio of turbulent intensity to laminar burning velocity is 28≤u ´ /SL≤356, indicating the combustion occurs in the high intensity. The experimental are interpreted using a two-environment, detailed chemistry mode1 in which the size and structure of the flame environment are established by matching the measured data, and which is independently verified using turbulent flame velocity and thickness correlations. The modeling suggests NO_(x) formation is controlled by both the specific conditions in the non-equilibrium zone and by the size of the zone. The modeling also suggests the unique case of well-stirred combustion for NO_(x) is obtained at low residence time conditions.

Numerical simulation of structure and no formation of turbulent lean-premixed flames in gas turbine conditions

강성모,김용모,이관수 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.12

This study numerically investigates the detailed structure and NO formation in atmospheric and high-pressure leanpremixed flames. Parallel unstructured-grid finite-volume method (FVM) has been developed to maintain the geometric flexibility and computational efficiency for the solution of the physically and geometrically complex flows. In order to realistically represent the complex turbulence-chemistry interaction of high-pressure lean-premixed turbulent flames encountered in gas turbine combustors, a flamelet model based on the level-set approach has been adopted. Special emphasis is given to the effects of pressure and equivalence ratio on the flame front location and NO formation, as well as the dimensionless parameters including turbulent Reynolds number, Re, Damköhler number, Da, and Karlovitz number, Ka in the lean-premixed gas turbine-like situations. Numerical results obtained in this study suggest that the level-set approach in the context of parallel unstructured-grid FVM is capable of realistically simulating the detailed structure and NO formation in the atmospheric and high-pressure lean-premixed flames.

고압 완전혼합반응기(PSR)내의 메탄-공기 희박 예혼합 연소의 NO<SUB>x</SUB> 생성에 관한 모델링 연구

박정규(Jungkyu Park),김현(Hyun Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

In this study the predictions of NOx in methane-air lean premixed combustion in HP-PSR were carried out by using GRI mech 3.0 and Zeldovich, nitrous oxide, prompt, and NNH NO formation mechanism. Also the comparison of the prediction to HP-JSR experimental data of Rutar for the validation of the model. This study concerns about the importance of the chemical pathways. The chemical pathway most likely to form the NO in lean-premixed combustion was investigated. Results obtained with the 4 different NO mechanisms are compared.

화학 반응기 모델을 이용한 희박 예혼합 메탄-공기 연소의 NOx 생성 경로 연구

이보람(Bo Rahm Lee),박정규(Jung Kyu Park),이민철(Min Chul Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

In this study the predictions of NOx in methane-air lean premixed combustion in JSR were carried out with GRI 3.0 methane-air combustion mechanism and Zeldovich, nitrous oxide, prompt, and NNH NO formation mechanism by using CHEMKIN code. The information from CFD modeling for combustor is analyzed and represented as an arrangement of reactor elements. The results are compared to the JSR experimental data of Rutar for the validation of the model. The chemical pathway most likely to form the NO in methane-air lean-premixed combustion was investigated. The results obtained with the 4 different NO mechanisms for residence time(2-4㎳) and pressure(3, 4.7, 6.5 atm) are compared and discussed.

희박 예혼합 메조스케일 다중노즐 수소 화염의 곡률 분포

이태송(Taesong Lee),김규태(Kyu Tae Kim) 한국연소학회 2021 한국연소학회지 Vol.26 No.1

Local structures of lean fully-premixed hydrogen-air flames in a mesoscale multinozzle array were studied in a tunable combustion test facility, using instantaneous OH PLIF measurements and subsequent image processing techniques. We observe that under thermoacoustically stable conditions, pure hydrogen flame ensemble takes on a conical structure and they are stabilized in isolation without strong flame-to-flame interactions. Under unstable conditions, however, marked flame front deformation and cusp formation occur due to high amplitude velocity fluctuations. Our curvature calculation results reveal that the probability density function distribution is characterized by a positive average value, meaning that the formation of convex contours is more pronounced in lean-premixed pure hydrogen combustion environment.

이중선회 가스터빈 연소기의 희박-예혼합 화염에 관한 실험적 연구

조준익(Junik Jo),이기만(keeman Lee) 한국자동차공학회 2013 한국자동차공학회 지부 학술대회 논문집 Vol.2013 No.5-1

The purpose of this experimental study is the lean-premixed flame characteristics of dual swirl gas turbine combustor with laboratory scale base. The fuel used here is methane and the varied parameters include in the swirl number and the equivalence ratio of the pilot and main fuel streams in dual swirl combustor configuration. In this study, the stability curves of a dual swirl flame with heat release ratio and heat release rate are proposed. It is found that the blowout and flashback limits are plotted in stability map and flashback mechanism which caused the flame to be entrained into the premixed central recirculation zone is attributed to the combustion induced vortex breakdown(CIVB).

연소장치에서 발생하는 고주파 연소 불안정 특성

서성현(Seonghyeon Seo) 한국연소학회 2012 한국연소학회지 Vol.17 No.1

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.

연소 장치들에서의 동적 연소 특성

서성현(Seonghyeon Seo) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.42

Dynamic characteristics of combustion occurring in various combustion devices have been extensively studied for a long time 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 a 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 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.

화학 반응기 네트워크 모델을 이용한 희박 예혼합 가스터빈 연소기에서의 예측 NOx

이보람(Borahm Lee),이도용(Doyong Lee),박정규(Jungkyu Park),이민철(Minchul Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

Development of prediction methods for NOx emission is very important for the modern combustion system design. This study shows the development and application of chemical reactor network(CRN) for the methane-air lean-premixed combustion. The CRN development is based on results from CFD analysis for a test gas turbine combustor. The predictions of NOx in methane-air lean premixed combustion are carried out by using CHEMKIN code with GRI 3.0 methane-air combustion mechanism. The calculated results are compared with experimental data for a validation of the CRN. The effect of various loads and atmosphere temperature on NOx emissions are investigated.