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음향 경계 조건이 가스터빈 연소기에서의 연소불안정에 미치는 영향
임재영(Jaeyoung Lim),김대식(Deasik Kim),김성구(Seong-Ku Kim),차동진(Dong Jin Cha) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.5
본 연구는 유한요소해석 기반의 Helmholtz solver인 ASCI3D를 사용하여 예혼합 가스터빈 연소기에서 연소불안정 현상과 관련된 주요 결과들을 예측하였다. 해석 결과 실험 결과와 비교할 때 일반적인 불안정 특성 예측에는 성공하였으나, 불안정 구간이 나타나는 영역을 다소 과대 예측하는 경향이 발견되었다. 이를 개선하기 위한 노력으로 반사계수가 불안정 특성에 미치는 영향이 분석되었다. 결과로부터 반사계수는 불안정 특성에 큰 영향을 미치고, 정확한 예측 결과를 얻기 위해서는 정확한 음향 경계조건의 정의가 필수적인 것으로 나타났다. This study predicts the basic characteristics of combustion instabilities in a gas turbine lean premixed combustor using ASCI3D code which is a FEM(Finite Element Method)-based Helmholtz solver. The prediction results show the good agreement with the measured data in modeling the overall combustion instability features, however, the code is found to overpredict the unstable conditions. As one of the efforts to improve the model accuracy, the effects of acoustic boundary conditions on the instability growth rate are analyzed. As a result, it is shown that the acoustic reflection coefficient has a great impact on the instability and the prediction accuracy can be enhanced by defining the precise acoustic conditions.
연소응용 기술 : Helmholtz solver를 이용한 연소불안정 예측 기법 소개
임재영 ( Jaeyoung Lim ),김대식 ( Deasik Kim ),김성구 ( Seong-ku Kim ),차동진 ( Dong Jin Cha ) 한국액체미립화학회 2015 한국액체미립화학회 학술강연회 논문집 Vol.2015 No.-
Lean premixed combustion system has been used to meet strengthened NOx emission regulations. However, it can be easily affected by combustion instability. This paper introduces a FEM(Finite Element Method)-based Helmholtz solver developed to predict numerically longitudinal combustion instability. The results such as complex valued eigenfrequency and acoustic pressure field can predict resonant frequency, growth rate and modal shape for acoustic modes.
유한요소법을 이용한 부분 예혼합 가스터빈 연소기에서의 연소불안정 모델링
장세구 ( Segu Jang ),김대식 ( Deasik Kim ),주성필 ( Seongpil Joo ),윤영빈 ( Youngbin Yoon ) 한국액체미립화학회 2018 한국액체미립화학회지 Vol.23 No.1
The current study has developed an in-house 3D FEM code in order to model thermoacoustic problems in a gas turbine combustion system and compared calculation results of main instability characteristics with measured ones from a lab-scale partially-premixed combustor. From the comparison of calculation results with the measured data, the current model could successfully capture the harmonic longitudinal instability frequencies and their spatial distributions of the acoustic field as well as the growth rate of self-excited modes.
음향 경계 조건이 가스터빈 연소기에서의 연소불안정에 미치는 영향
임재영(Jaeyoung Lim),김대식(Deasik Kim),김성구(Seong-Ku Kim),차동진(Dong Jin Cha) 한국추진공학회 2015 한국추진공학회지 Vol.19 No.4
This study predicts the basic characteristics of combustion instabilities in a gas turbine lean premixed combustor using ASCI3D code which is a FEM(Finite Element Method)-based Helmholtz solver. The prediction results show the good agreement with the measured data in modeling the overall combustion instability features, however, the code is found to overpredict the unstable conditions. As one of the efforts to improve the model accuracy, the effects of acoustic boundary conditions on the instability growth rate are analyzed. As a result, it is shown that the acoustic reflection coefficient has a great impact on the instability and the prediction accuracy can be enhanced by defining the precise acoustic conditions.
윤명곤(Myung-Gon Yoon),김진아(Jina Kim),김대식(Deasik Kim) 한국추진공학회 2016 한국추진공학회지 Vol.20 No.3
In this paper we propose a new frame transfer function model describing the variations of a heat release rate in response to an external flow oscillation in gas turbine systems. A critical difference of our model compared to the so-called n-τ model which has been widely used for a prediction of combustion instability (CI), is that our model is able to describe a nonlinear relation between phase and frequency. In contrast, the phase part of the n-τ model is a pure time delay and thus the phase should be a linear function of frequency, which is inconsistent with many experimental results of real combustion systems. For an illustration, our new model is applied to experimental data and the effect of phase nonlinearity is investigated in the context of combustion instability.