Effect of the Unmixedness of Fuel and Air on the Pressure Fluctuations in a Model Gas Turbine Combustor

본 연구는 연소기술연구센터 (CERC)와 미쓰비시 중공업 (Mitsubishi Heavy Industries, Ltd.)의 연구비 지원에 의해 수행되었습니다

Effect of Helmholtz Resonator on the Pressure Fluctuation of Low-frequency

본 연구는 연소기술연구센터 (CERC)와 미쓰비시 중공업의 연구비 지원에 의해 수행되었습니다

An Effect of Pressure Fluctuations of a Combustion Chamber on the Modulation of Equivalence Ratio in the Channel of the Burner

In order to understand the phenomena of combustion instability, an experimental study was conducted at the moderate pressure and ambient temperature conditions. The flame behavior and the pressure fluctuations were measured in a dump combustor. Various types of combustion modes occurred in accordance with the equivalence ratio and the fuel supplying conditions. The fluctuation of pressure, heat release and equivalence ratio were measured by piezoelectric pressure sensor, high speed Intensified Charge Coupled Device (HICCD) camera and gas chromatography respectively. Two representative modes were self-excited pressure oscillations at the resonance of combustion chamber (200Hz) and instabilities related to the modulated fuel flow rate through the fuel holes (10Hz). It is found that, especially in an unchoked fuel flow condition, the modulation of the fuel flow rate affects the characteristics of flame behavior and pressure fluctuations in a lean premixed flame.본 연구는 연소기술연구센터(CERC)와 BK21 그리고 미쓰비시 중공업(Mitsubishi Heavy Industries, Ltd.)의 연구비 지원에 의해 수행되었습니다

An experimental study on the instability of lean premixed turbulent combustion induced by thermo-acoustics

본 연구는 연소기술연구센터(CERC)와 BK21의 연구비 지원에 의해 수행되었다

Numerical Simulation of the Effect of Pressure Fluctuation on the Modulation of Equivalence Ratio at the Fuel Injection Hole

In gas turbine technology, the flame stability is inherently greater in conventional diffusion type combustion over a wider range fuel to oxidizer ratio. However, premixed type combustion which has narrow flame stability region, is widely used due to environmental reason. It has been observed in experiments that combustion instability of low frequency (${\sim}10Hz$) results from the modulation of equivalence ratio at fuel injection hole when a pressure fluctuation propagates upwards along the channel of the burner under an unchoked fuel flow condition. In this study, a commercial program was used to determine how the fuel flow rate changed with respect to the pressure, velocity of the fuel flow and the mass fraction in a choked and an unchoked condition. The calculation focuses on the upstream of the dump plane to know how the forced pressure with the fuel injection conditions affects the modulation of the equivalence ratio. Therefore, it is found that pressure fluctuation leads to oscillation of mass flow rate and then results in equivalence ratio modulation under the unchoked fuel flow condition.연소기술연구센터(CERC), BK2

An Experimental Study on the Combustion Characteristics with Hydrogen Enrichment in a Dump Combustor

본 연구는 연소기술연구센터(CERC)와 BK21의 연구비 지원에 의해 수행되었습니다

An Experimental Study of Pressure Fluctuations and Equivalence Ratio Fluctuations in a Dump Combustor

본 연구는 연소기술연구센터 (CERC)와 미쓰비시 중공업의 연구비 지원에 의해 수행되었습니다

A study on the instability of combustion in a model gas turbine combustor

학위논문(박사) - 한국과학기술원 : 기계공학전공, 2008. 8., [ xv, 160 p. ]본 연구에서는 실제 가스터빈 연소기를 모사한 덤프형태의 모델 연소기를 사용하여, 혼합실 (mixing chamber)을 이용한 완전 예혼합 (fully premixed) 조건과 연소실 바로 직전에서 산화제 유동쪽으로 연료를 분사하는 부분 예혼합 (partially premixed) 조건으로 실험장치를 구현하였다. 부분 예혼합되는 경우는 하류의 압력변동에 영향을 받지 않는 초우크 연료유동 (choked fuel flow: 이하 “초우크 조건”으로 표기함) 조건과 압력변동에 영향을 받는 언초우크 연료유동 (unchoked fuel flow: 이하 “언초우크 조건”으로 표기함) 조건으로 구별하여 실험함으로써 열발생률 변동을 초래하는 당량비 변동을 연료유량의 변조에 의한 당량비 변동과 연료와 공기 혼합기의 혼합정도 (unmixedness)에 의한 당량비 변동으로 구분하였다. 또한 유동에 의해 생성된 재순환영역의 와동 효과도 고려하여, 열발생률 변동의 원인이 연소 불안정성에 어떤 영향을 미치는지를 밝히고자 한다. 그리고, 가스터빈 제작자와 운전자에 의해 심각하게 보고되고 있는 저주파수 (~10 Hz) 대역의 연소 불안정성에 대한 발생 메커니즘을 규명하고, 그 발생 메커니즘을 뒷받침할 만한 실험적, 수치해석적 결과를 정량적으로 도출하고, 특히 저주파수 대역의 연소 불안정성을 효과적으로 감쇄하거나 그 운전영역을 좁힐 수 있는 실용적인 방법으로 버너의 혼합기가 유동하는 채널 (channel)에 헬름홀츠 공진기 (Helmholtz resonator)를 부착하거나, 연료 분사구 입구에 헬름홀츠 공진기를 부착하여 그 효과와 성능을 확인하고자 한다. 이를 위해 실험과 수치계산을 통해 저주파수 대역의 불안정한 연소모드의 발생영역을 좁힐 수 있는 구체적인 방안을 제안하고자 한다. 궁극적으로 본 연구를 통해 가스터빈과 같은 실용 연소기에서 발생하는 불안정한 연소모드의 발생 및 증가, 지속, 감소기구를 관찰하여, 이러한 현상에 관한 원인을 명확히 밝히고, 제어할 수 있는 방법을 모색하고자 한다.한국과학기술원 : 기계공학전공

Numerical Simulation of Self-excited Combustion Oscillation in a Dump Combustor with Bluff-body

Combustion instability has been considered as very important issue for developing gas turbine and rocket engine. There is a need for fundamental understanding of combustion instability. In this study, combustion instability was numerically and experimentally investigated in a dump combustor with bluff body. The fuel and air mixture had overall equivalence ratio of 0.9 and was injected toward dump combustor. The pressure oscillation with approximately 256Hz was experimentally obtained. For numerical simulation, the standard k-ε model was used for turbulence and the hybrid combustion model (eddy dissipation model and kinetically controlled model) was applied. After calculating steady solution, unsteady calculation was performed with forcing small perturbation on initial that solution. Pressure amplitude and frequency measured by pressure sensor is nearly the same as those predicted by numerical simulation. Furthermore, it is clear that a combustion instability involving vortex shedding is affected by acoustic-vortex-combustion interaction. The phase difference between the pressure and velocity is π/2, and that between the pressure and heat release rate is in excitation range described by Rayleigh, which is obvious that combustion instability for the bluff body combustor meets thermoacoustic instability criterion.본 연구는 연소기술연구센터(CERC)와 BK21 의 연구비 지원에 의해 수행 되었습니다