1D 네트워크 모델을 이용한 항공용 가스터빈 연소기에서의 음향장 해석

표영민,박희호,정승채,김대식 한국추진공학회 2019 한국추진공학회지 Vol.23 No.2

The present work suggests a numerical approach using a thermoacoustic network model for the eigenvalue calculation of thermoacoustic instability problems in an aero gas turbine combustor. The model is developed based on the conservation laws for mass, momentum, and energy between acoustic network elements with an area change. Acoustic field in a practical aero gas turbine combustor which has a complicated flow path is analyzed using the current model. The predictive capabilities of the current modeling approach are compared with the acoustic characteristics calculated using Helmholtz solver based on 3D finite element method(FEM). 본 연구에서는 항공용 가스터빈의 연소실에서의 연소불안정 해석을 위한 고유값 도출을 목적으로 하는 1D 네트워크 모델을 개발하였다. 모델은 면적 변화가 있는 음향 네트워크 요소들 사이의 각종 지배방정식을 통하여 개발되었고, 이를 이용하여 현재 개발 중인 복잡한 유로 형상을 갖는 실제 항공용 가스터빈 연소기에서의 음향장 해석에 적용되었다. 본 모델을 통하여 도출된 음향장 해석 결과는 3차원유한요소해석 기반의 헬름홀츠 솔버의 계산 결과와 비교하였다.

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.

Numerical investigation on combustion instability modeling in a lean premixed gas turbine combustor combining finite element analysis with local flame transfer function

표영민,김대식,김성구,차동진 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.11

The present work suggests a numerical approach using an FEM (finite element method) code for the eigenvalue calculation of the thermoacoustic combustion instabilities coupling with the local flame transfer function in a generic lean premixed combustor. The URANS (unsteady Reynolds average Navier-Stokes) simulation shows a good agreement in capturing steady and unsteady flame geometries with the measurement in the literature. Also, global and local parameters of flame responses to acoustic velocity fluctuations undergo quantitatively similar changes in prediction and in the experiment. The numerically determined flame transfer function and gas properties are incorporated in an in-house Helmholtz solver to compute eigenvalues of the target combustor. In the solver, the Helmholtz equation is discretized with a Galerkin FEM on a multi-dimensional hybrid unstructured mesh. The nonlinearity related with the heat release source term is treated with an iterative methodology, and the large scale eigenvalue calculation is performed using the shift-invert approach available in the ARPACK (ARnoldi PACKage) library. The predictive capabilities of the current modeling approach are validated against the measured mode frequency and instability growth rate. In addition, the prediction results show the effect of spatiallydistributed heat release on the thermoacoustic model accuracy.

3D FEM 해석기법을 이용한 실제 항공용 가스터빈 연소기에서의 열음향 해석

표영민(Yeongmin Pyo),박희호(Heeho Park),정승채(Seungchai Jung),김대식(Daesik Kim) 한국추진공학회 2019 한국추진공학회 학술대회논문집 Vol.2019 No.5

환형 가스터빈 연소기에서 네트워크 모델을 이용한 연소불안정 해석

표영민(Yeongmin Pyo),윤명곤(Myunggon Yoon),김대식(Daesik Kim) 한국추진공학회 2018 한국추진공학회지 Vol.22 No.3

화염전달함수의 위상차를 이용한 시간지연 분석

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.

가스터빈 연소기에서의 음향 네트워크 해석 모델 개발

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.

AHP기법을 이용한 건설노동생산성 저하요인 분석에 관한 연구

이상범,표영민 대한건축학회지회연합회 2007 대한건축학회연합논문집 Vol.9 No.1

Usually, processing whole project or a part of frame work delays due to acceleration, changing orders, management, characters of projects, overtime, worker crowding, early occupation in the field of construction. Through a whole project, these factors cause decreasing construction labor-productivity which is the most dependent in business of construction. These kind of decreasing of construction labor-productivity cause many negative effects, just as extension of time, increasing cost in project of construction. Regardless of characters of construction or decreasing labor-productivity, extension of time is a incident which needs acceleration, also it cause a high possibility of claim and dispute. The productivity has just a broad meaning in business of construction. That's why it's difficult to apply in the field of construction. Especially, factors increasing or decreasing labor-productivity is defined by analysis of working as qualitative and outlined evaluation. However, study of the each factor decreasing construction labor-productivity analysis has not researched, because of difficulty of systematic measurement and management. The existed studies about management of productivity are just focused on estimation of productivity, not on evaluation of productivity. It was true that I couldn't examine clearly about the analysis of how much important per each the factor which have influence on labor-productivity because of the characteristic as qualitative that the labor productivity have. On this study, I tried to get the factors decreasing of labor-productivity with gathering opinions of panels of expert's studies about the factors decreasing of labor-productivity on project of construction through Delphi method and I evaluated the result factors as quantitatively and subjectively about importance of factors decreasing construction labor-productivity analysis, using AHP Method by Saaty. Also, using Delphi and AHP method, I suggest substantiated method qualitative factors are measured by quantitative criteria.

건설 프로젝트에서 D-virus가 안전에 미치는 영향에 관한 기초적 연구

송진우,표영민,진유나,이상범,김정길 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.2

Construction site has contributed to construction productivity improvement by utilizing information, simplification, and standardization concept. Also it has contributed to quality and productivity improvement by standardizing design and construction process, using them to a fair decision-making process by organizing diverse data in construction process. However, construction process has diverse variables and uncertain case due to particularity in construction. These parts have an effect on construction process. To use unorganic construction information and knowledge properly has become the factor to project success. Therefore, this study analyzes that D-virus of the uneasy factors has an effect on safety control of construction industry. That is to say, aim of the study is to suggest the solution to remove those after confirming for these factors to have certain effect in construction process through fact finding survey and retesting the factors of D-virus to refer in business management in a constructive position.