• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.153-156
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• 2014

This study was aimed to assess combustion stability for coaxial swirl injector and FOOF impinging injector which would be candidates in liquid rocket engine combustors. Simulating combustion tests under atmospheric condition have been conducted by gaseous oxygen and the mixture of methane and propane, using two actual injectors. By analyzing the measured dynamic pressure signals, we have evaluated the combustion stability margin of both injectors by drawing a stability map.

• 한국연소학회지
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• 제22권1호
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• pp.46-52
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• 2017

High-frequency combustion instabilities may occur during the development of feasible engine combustors. These instabilities can result in irreparable damages to the wall of combustors or the degradation of engine performance. So, it is essential to identify injectors that have high stability characteristics during the early stages of development. The objective of present study was to assess the stability of coaxial injectors and an impinging injector with different recess lengths in order to develop stable injectors optimally. Stability margin was evaluated based on the distance from operating condition to the unstable regions. A simulating combustion test method was used to analyze the stability of injectors. A small-scale combustion chamber was designed to simulate the first tangential acoustic mode of the actual combustor. Gaseous oxygen and a mixture of methane and propane were used as simulant propellants to satisfy their flow similarity to the actual propellants of a combustor in a liquid rocket combustor. The results indicated that injectors having small recess lengths showed relatively large combustion stability margins. For the injectors of large recess lengths, instability regions with large and super-large amplitude oscillations were observed. Thus, injector with shorter recess lengths had a higher stability than that of longer one due to the different mixing processes.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2013년도 제46회 KOSCO SYMPOSIUM 초록집
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• pp.117-119
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• 2013

Combustion stability margin of a model gas turbine has been assessed by utilizing damping ratios of measured dynamic pressure data. It is known that acoustic oscillations in combustion chambers can be described as a superposition of nonlinearly interacting oscillators. Based on this theoretical background, CSMA (Combustion Stability Margin Assessment) code has been developed. The code has been employed into a model gas turbine combustion experiment, focused on the combustion instability, to show its capability to determine the damping ratio of measured dynamic pressure and further to assess combustion stability margin of the experiment, and turned out that the code works well.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.395-402
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• 2007

Homogeneous Charge Compression Ignition (HCCI) shows great potential for low $NO_x$ emission but is hampered by the problem of no direct method to control the combustion process. Therefore, HCCI combustion becomes unstable easily, especially at lower and higher engine load. This paper presents a method to achieve diesel-fueled HCCI combustion, which involves directly injecting diesel fuel into the cylinder before the piston arrives at top dead center in the exhaust stroke and adjusting the valve overlap duration to trap more high temperature residual gas in the cylinder. The combustion stability of diesel-fueled HCCI combustion and the effects of engine load, speed, and valve overlap on it are the main points of investigation. The results show that: diesel-fueled HCCI combustion has two-stage heat release rate (low temperature and high temperature heat release) and very low $NO_x$ emission, combustion stability of the HCCI engine is worse at lower load because of misfire and at higher load because of knock, the increase in engine speed aids combustion stability at lower load because the heat loss is reduced, and increasing negative valve overlap can increase in-cylinder temperature which aids combustion stability at lower load but harms it at higher load.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.257-263
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• 2006

액체로켓엔진 연소기는 연소성능 및 연소안정성 분야에 있어서 높은 신뢰도를 가져야 한다. 특히, 추진제의 혼합을 담당하는 분사기는 이 신뢰도를 결정짓는 중요한 요소이다. 연소안정성 관점에서 수행된 본 연구는 모델 상사 기법을 이용하여 동축 와류 분사기의 연소안정성 특성을 평가하였다. 또한 연소안정성 증대를 위해 사용하는 배플의 경우 축방향 길이 및 간극 변화로부터 나타나는 효과를 검토하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.240-246
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• 2005

현재 개발 중에 있는 30-tonf-class 실물형 액체로켓연소기는 이미 설계검증을 위해 수차례의 연소시험이 이루어졌으며 그 결과 높은 연소효율을 얻었다. 연소성능과 더불어 액체로켓연소기의 중요한 또 하나의 요소는 바로 연소안정성이다. 연소안정성에 대한 평가시험은 개발하고자 하는 액체로켓연소기의 연소불안정 발생 빈도를 파악하는 시험으로서 액체로켓연소기 개발시 꼭 확인해야하는 시험이라 할 수 있다. 펄스건을 이용한 스테인레스 스틸 재질의 임시 배플이 장착된 실물형 연소기의 연소안정성 평가시험은 성공적으로 수행되었으며 그 결과 우수한 연소안정성 특성을 얻었다. 시험결과는 다음 호기의 실물형 연소기 배플 설계에 활용될 예정이다.

• 설비공학논문집
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• 제29권6호
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• pp.306-315
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• 2017

This study introduces a software for real-time assessment of combustion stability for utility gas turbines. The software was written with LabView, and implemented the time-domain kurtosis as a parameter to proactively access the instantaneous combustion stability during operation of the industrial gas turbine. The simple time-domain assessment algorithm incorporated in the software is advantageous over conventional frequency-domain signal processing of dynamic pressure signal since it reduces the computational cost, thereby making the algorithm more appropriate for real-time monitoring of combustion stability. Benchmark data obtained from a model gas turbine combustor were used for the reproducibility test of the software. The assessment obtained from the software agreed well with previously published results, indicating that incorporation of the software could enhance the performance of systems monitoring the combustion stability for gas turbines during power generation.

• 한국추진공학회지
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• 제13권5호
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• pp.15-20
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• 2009

분사기 배열 및 벽면 냉각 방식이 다르게 설계된 30톤급 재생냉각 두 연소기에 대한 연소시험이 수행되었다. 본 논문에서는 연소시험 결과 중 연소안정성에 대한 내용을 분석, 제시하였다. 연소안정성 평가를 위해 압력 섭동의 크기 및 SRT 결과를 검토하였으며, 두 연소기 모두 연소안정성 측면에서 매우 만족스러운 결과를 얻을 수 있었다. 압력 섭동의 RMS 값은 연소실 압력 대비 3% 미만의 값을 나타내었으며, SRT 결과에서도 외부 가진에 의한 압력 peak의 감쇠시간은 기준 감쇠시간의 10% 정도로 짧게 나타났다. 막냉각이 적용된 연소기의 경우 벽면 냉각용 분사기가 최외곽 열에 배치된 연소기에 비해 압력 섭동의 RMS 값이 감소하는 결과를 보였다.

• Journal of Mechanical Science and Technology
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• 제20권6호
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• pp.874-881
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• 2006

Combustion stability characteristics in actual full-scale combustion chamber of a rocket engine are investigated by experimental tests with the model (sub-scale) chamber. The present hot-fire tests adopt the combustion chamber with three configurations of triplet impinging-jet injectors such as F-O-O-F, F-O-F, and O-F-O configurations. Combustion stability bound-aries are obtained and presented by the parameters of combustion-chamber pressure and mixture (oxidizer/fuel) ratio. From the experimental tests, two instability regions are observed and the pressure oscillations have the similar patterns irrespective of injector configuration. But, the O-F-O injector configuration shows broader upper-instability region than the other configurations. To verify the instability mechanism for the lower and upper instability regions, air-purge acoustic test is conducted and the photograph or the flames is taken. As a result, it is found that the pressure oscillations in the two regions can be characterized by the first impinging point of hydraulic jets and pre-blowout combustion, respectively.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.67-75
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• 2002

A study to investigate the influence of combustion chamber shape, especially piston top face configuration, on the combustion stability is presented with CFD analysis and single cylinder GDI engine test. Initial configuration of the piston bowl was designed with CFD analysis and further parametric studies of the design factors on the piston top face were carried out through the single cylinder GDI engine test. It was found that both the geometry of piston top face and the compression ratio have great influences on the combustion stability. Of interest is that the design factors of the GDI piston to prevent mixture diffusion out of the piston bowl have important roles for the stable combustion at the stratified mixture condition. Also the relationship between spray impingement and flow pattern in a GDI piston bowl should be considered to design an optimal bowl configuration for stable stratified combustion.