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항공용 가스터빈 연소기에서의 혼합기 노즐 형상의 단순화가 음향장 해석 결과에 미치는 영향
표영민,홍수민,김대식,Pyo, Yeongmin,Hong, Sumin,Kim, Daesik 한국분무공학회 2019 한국액체미립화학회지 Vol.24 No.2
A 3D FEM (Finite Element Method) based Helmholtz solver has been commonly used to characterize fundamental acoustic behavior and investigate dynamic instability features in many combustion systems. In this approach, a geometrical simplification of the target system has been generally made in order to reduce computational time and cost because a real combustor and fuel nozzle have a very complicated flow passage. The feasibility of these simplifications is quantitatively investigated in a small aero gas turbine nozzle in term of acoustic characteristics. It is found that the simplification in a nozzle geometry during the 3D FEM analysis process has no great influence on the acoustic modeling results, while the calculation complexity can be improved for a similar modeling accuracy.
표영민 ( Yeongmin Pyo ),김지환 ( Jihwan Kim ),김대식 ( Daesik Kim ) 한국액체미립화학회 2016 한국액체미립화학회지 Vol.21 No.2
Main purpose of the current paper is to show results of time lag analysis using phase information of flame transfer function in order to predict combustion instabilities in a gas turbine combustor. The flame transfer function (FTF) is modeled using a commercial Computational Fluid Dynamics (CFD) code (Fluent). Comparisons of the modeled flame shapes with the measured ones were made using the optimized heat transfer conditions and combustion models. The FTF modeling results show a quite good agreement with the measurement data in predicting the phase delay (i.e. time lag). Time lag analysis results using the phase of FTF shows better combustion instability prediction accuracy than using time lag calculated from the steady state flame length.
환형 가스터빈 연소기에서 네트워크 모델을 이용한 연소불안정 해석
표영민(Yeongmin Pyo),윤명곤(Myunggon Yoon),김대식(Daesik Kim) 한국추진공학회 2018 한국추진공학회지 Vol.22 No.3
Combustion instabilities are caused by the feedback relationship between heat release perturbations and acoustic pressure oscillations in the combustor. Studies on the combustion instability in an annular combustor have recently received great attention due to the enhanced NOx requirement in aero-engines. In this study, a thermoacoustic network model was developed in order to calculate the acoustic characteristics for various modes in the annular combustor. The network model is combined with flame transfer function(FTF) in order to calculate the stability of the combustor. Numerical results are compared with measurement data.
표영민(Yeongmin Pyo),이석주(Seokju Lee),김대식(Daesik Kim) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-3
Lean premixed gas turbine combustors were successful in meeting current NOx emission regulations. However, these have been found to be susceptible to comvustion instability. The combustion instabilites result from the feedback relationship between heat release perturbations and acoustic pressure oscillations in the combustor. Therefore, the acoustic characteristics in the system are the key parameters in determining combustion instability behavior in the gas turbine combustors. In this study, in order to predict acoustic field correlated by combustion driven oscillations, in-house thermoacoustic network model was developed. The model is based upon physical conservation equations and 1-D acoustic theory, and provide information on the frequency and initial growth rate for the combustion instability. The prediction results show a good agreement with measurements under the selected combustion system and operating conditions. Also, it was found that the change in a system length influenced the longitudinal instability characteristics such as mode shape and frequencies.
네트워크 모델을 이용한 환형 가스터빈 연소기에서의 연소불안정 해석
표영민(Yeongmin Pyo),윤명곤(Myunggon Yoon),김대식(Daesik Kim) 한국추진공학회 2017 한국추진공학회 학술대회논문집 Vol.2017 No.5
희박 예혼합 연소기는 NOx 배출 규제를 만족시키지만, 연소불안정 현상을 야기하는 단점을 갖고 있다. 이때 연소불안정 현상은 연소기 내부에서 열발생 섭동과 음향 압력 섭동 사이의 피드백 관계로부터 도출된다. 특히 항공용 엔진에 대한 배출 가스 규제가 강화되면서, 환형 연소기에서의 연소불 안정 연구에 대한 관심이 크게 증가하고 있다. 본 연구에서는 환형연소기에서의 길이방향 및 환형 방향의 모드까지 계산할 수 있는 열음향 네트워크 모델을 개발 및 사용하였고, 이때 연소 모델은 화염전달함수를 적용하였다. 이와 같은 네트워크 모델을 사용하여 벤치마킹한 환형연소기의 실험데이터와 비교 분석하여 연소불안정 해석을 진행하였다. Lean premixed combustion was successful in meeting current NOx emission regulations. However, these often leads to combustion instability. This phenomena results from the feedback relationship between heat release perturbations and acoustic pressure oscillations in the combustor. Researches on the combustion instability in an annular combustor have recently received great attention due to the enhanced NOx requirement in aero-engines. In this study, the thermoacoustic network model has been developed in order to calculate the acoustics for longitudinal as well as circumferential modes in the annular combustor. The combustion model in the network model is calculated by flame transfer function(FTF). Numerical and analytical results are compared to an measurement data.
연소응용 기술 : 상용 CFD 코드를 이용한 국부화염전달함수 모델링
김지환 ( Jihwan Kim ),표영민 ( Yeongmin Pyo ),김대식 ( Daesik Kim ) 한국액체미립화학회 2015 한국액체미립화학회 학술강연회 논문집 Vol.2015 No.-
The present paper describes a methodology to improve the accuracy of prediction of heat release information that it is very important parameter in a thermoacoustic instability models. Most combustion instability models use the flame transfer function(FTF) to determine heat release fluctuations. However, previous studies for FTF measurements assume that the flames are so thin that they are treated "acoustically compact", or heat release characteristics have no significant deviations through the flames. So, the current studies introduce a concept of the local FTF in order to quantitatively and qualitatively analyze the heat release distribution through the flames. Commercial CFD code(FLUENT) is used for model a local FTF. The results show that when the flame length is not acoustically compact the model prediction calculated using the local FTF is better than the prediction made using the global FTF. Therefore, the calculated local FTF has very high accuracy in predicting gain and phase in a mode combustor, comparing with the measured reference data.
엄준식(Junsik Eom),표영민(Yeongmin Pyo),김사량(Sa Ryang Kim),김대식(Daesik Kim) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.5
In this study, the effect on the flow in the combustor was numerically simulated when the velocity magnitudes at the gas turbine combustor inlet were varying with time. The time delay of velocities on the combustion chamber due to the variation of inlet velocity was observed while there was no time delay on the nozzle. These results will be useful to study and design the combustor.