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열-음향에 의한 난류희박 예혼합연소의 불안정성에 관한 실험적 연구
홍정구(Jung Goo Hong),이민철(Min Chul Lee),신현동(Hyun Dong Shin) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
The combustion instability acts as a serious obstacle for the lean premixed combustion of gas turbine and even causes the fatal damage to the combustor and whole system. In this experiment, the pressure fluctuation is highly related to the stabilizing position of flame and fuel injection location. The fuel injection location is connected with the convection time of the fresh mixture, which is important time scale to refresh the mixtures near the flame stabilization location. The flame is extremely unstable when the alternative stabilization occurs and bulk mode frequency (~10Hz) of pressure fluctuation is observed in this condition. It was found that the convection time scale of the fresh reactant coincided with the time scale of the bulk mode fluctuation. Hence this phenomenon results from the local equivalence ratio change caused by the pressure fluctuation induced by thermo-acoustic effects.
커먼레일 디젤 인젝터의 분사압력과 분위기압력에 따른 분무 특성
홍정구(Jung Goo Hong),구건우(Kun Woo Ku),김준희(Jun Hee Kim),이충원(Choong Won Lee) 한국자동차공학회 2012 한국자동차공학회 지부 학술대회 논문집 Vol.2012 No.4
본 연구에서는 디젤 인젝터의 거시적 분무특성을 실험적으로 알아 보았다. 커먼레일 디젤 인젝터의 본사를 위해 보쉬 커먼레일 시스템을 사용하였다. 본 연구를 위한 대상 인젝터는 6-hole 보쉬 디젤 인젝터였다. 다양한 분사 조건에서 디젤 인젝터의 거시적 분무특성인 분무도달거리 및 분무각을 측정하였다. 본 연구에 따르면, 인젝터의 분사압력이 높을수록 분무달거리는 증가 하였다. 또한 동일 분사압력에서 분사되는 곳의 분위기 압력이 증가 할수록 분무도달거리는 감소하였고, 분무각은 증가하였다. In this study, we conducted the experimental study to investigate the macroscopic spray characteristics with a CRDI injector. A Bosch common rail system has been equipped for this study. We used a Bosch injector with 6 holes for nozzle in this study. The spray tip penetration and sprat angle was measured with the various test conditions. According to this study, the spray tip penetration increased with increase of the injection pressure. Furthermore, as the ambient pressure increase, the spray tip penetration decreased and the spray angle increased although the injection pressure was same.
헬름홀츠 공진기에 따른 버너내의 음향장에 관한 수치해석
홍정구(Jung Goo Hong),조한창(Han Chang Cho),신현동(Hyun Dong Shin) 한국연소학회 2007 KOSCOSYMPOSIUM논문집 Vol.- No.-
A study was performed to understand self-excited pressure fluctuations in the lean premixed flames and to evaluate the effect of Helmholtz resonator on the pressure fluctuations. As low-frequency pressure fluctuations have been reported to cause fatal damage to the combustor and the entire system, Helmholtz-type resonators, which reduce the damage by low-frequency pressure fluctuation in the combustor, are attached to the channel of unburned mixture flow. It is found that the range of low-frequency pressure fluctuations of flame mode 2 is narrowed by the attachment of Helmholtz resonators. From this result, if Helmholtz-type resonators are applied to actual gas turbine combustor, it is confirmed that Helmholtz resonators attached on the fuel discharge hole are also effective for narrowing the range of flame mode 2
연료와 공기의 혼합정도가 모델 가스터빈 연소기내의 압력변동에 미치는 영향
홍정구(Jung Goo Hong),신현동(Hyun Dong Shin) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Combustion instability is a serious obstacle for the lean premixed combustion of gas turbines, and can even cause fatal damage to the combustor and the entire system. Thus, improved understanding of the mechanisms of combustion instability is necessary for designing and operating gas turbine combustors. In this study, in order to understand the instability phenomena, an experimental study was conducted in a rearwardstep dump combustor with LPG and air. The fluctuations of pressure and heat release were measured by piezoelectric pressure sensor and High speed Intensified Charge Coupled Device (ICCD) camera respectively. Various types of combustion modes occurred in accordance with the equivalence ratio and the fuel supplying conditions. The unmixedness of the fuel and air can be controlled by changing the mixing distance (Lf<SUB></SUB>uel). It is found that the unmixedness of the fuel and air affects the characteristics of flame behavior and pressure fluctuations in a lean premixed flame.
당량비 변동과 와동이 덤프연소기내의 연소 불안정성에 미치는 영향
홍정구(Jung Goo Hong),이민철(Min Chul Lee),이은도(Uen Do Lee),오광철(Kwang Chul Oh),신현동(Hyun Dong Shin) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The combustion instability of turbulent flames, together with the emission of combustion products, is the most important problem of the gas turbine combustor. Thus improved understanding of mechanisms of combustion instability is necessary for the design and operation of gas turbine combustors. In this study, we investigated the cause of the combustion instability in a rearward-step dump combustor with respect to the fuel flow modulation choked fuel flow, unchoked fuel flow and fully premixed mixture flow. We observed various types of combustion instabilities with respect to the variation of equivalence ratio, fuel flow conditions and fuel injection location. We found that the pressure fluctuation of turbulent combustion in a lab-scale combustor is highly related to the vortex structure and the equivalence ratio fluctuations due to fuel flow modulation and unmixedness of the fuel and air.
덤프연소기내의 압력 변동과 당량비 변동에 관한 실험적 연구
홍정구(Jung Goo Hong),곽영태(Young Tae Guahk),오광철(Kwang Chul Oh),신현동(Hyun Dong Shin) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
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 fluctuations of pressure and equivalence ratio were measured by piezoelectric pressure sensor and gas chromatography respectively. Two representative modes were self-excited pressure oscillations at the resonance of combustion chamber (200 ㎐) and instabilities related to the modulated fuel flow rate through the fuel holes (10 ㎐). 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.
미립화 및 분무장치 1 : 타원형 노즐의 내부유동 구조가 액주분열에 미치는 영향
홍정구 ( Jung Goo Hong ),구건우 ( Kun Woo Ku ),이충원 ( Choong Won Lee ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-
An experimental study was conducted to investigate the atomization characteristics of a circular nozzle and elliptical nozzles of small diameter (0.5mm) under the high injection pressure (1MPa~9MPa). Furthermore, num erical simulations were attempted to investigate the internal flow structure in the circular and elliptical nozzles. This study showed that the disintegration characteristics of the liquid jet of elliptical nozzles were much differ ent from those of the circular nozzle. In the case of the circular nozzle, the surface of liquid jet was much smooth near the nozzle exit under the injection pressures of this study. But, in the case of the elliptical nozzles, surface waves on liquid jet have been generated and grown with increase of the injection pressure. As a result, surface breakup was observed with the increase of injection pressure because a rough column surface caused by growth of surface wave is disintegrated to ligament as the relative velocity between the liquid jet and ambient air increases. Furthermore, the numerical simulations informed that the internal flow structure of elliptical nozzle was quite different from that of the circular nozzle. The internal flow structure of the elliptical nozzle in hydraulic flip was reattached to the orifice wall of the minor axis unlike the flow in the circular nozzle which is detached from orifice wall. It has been concluded that the internal flow structure of the elliptical nozzle has influence on the disintegration characteristics of the liquid jet issued from the elliptical nozzle.