• 한국항공우주학회지
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• 제47권10호
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• pp.720-727
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• 2019

하이브리드 로켓 연소의 저주파수 연소불안정은 고체연료의 열적지연(Thermal Lag)과 경계층 유동 변화에 의한 열전달 진동의 공진에 의해 발생한다. 본 연구는 연료 표면 근처의 경계층 유동의 교란이 어떤 물리적 과정에 의해 발생하여 연소불안정으로 발달하는지를 실험적으로 확인하였다. 특히 산화제의 스월 분사는 연소 안정화에 매우 큰 기여를 하므로 스월 강도를 증가시키며 경계층의 변화와 연소불안정의 발생과정을 연구하였다. 경계층 섭동을 확인하기 위하여 연소 유동장을 가시화하였고 이미지에 대한 POD(Proper Orthogonal Decomposition) 분석을 시도하였다. 스월 강도가 증가할수록 500Hz 대역 고주파수 p', q'의 결합이 약해지며 열적지연과 유사한 주파수 특성을 갖는 Rayleigh Index의 섭동 발생도 약해져 경계층 진동의 발생이 점차 감소하는 것을 관찰하였다. 따라서 고주파수 p', q'의 주기적인 결합에 의한 축 방향 경계층 진동이 나타나면 열적지연 주파수와 공진에 의한 연소불안정이 발생함을 확인하였다.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.153-159
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• 2007

The performance of a direct-injection type diesel engine often depends on the strength of air flow in the cylinder, shape of combustion chamber, the number of nozzle holes, etc. This is of course because the process of combustion in the cylinder was affected by the mixture formation process. In the present paper, high speed photography was employed to investigate the effectiveness of holes penetrated from the bottom of cavity wall to piston crown for some more useful utilization of air. The holes would function to improve mixing of fuel and air by the increase of air flow in the cylinder. The results obtained are summarized as follows, (1) Activated first of the combustion by shorten of ignition timing and rapid flame propagation (2) Raised the combustion peak pressure, more close to TDC the formation timing of peak pressure.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.191-193
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• 2012

The use of diesel engines has recently increased due to the need for internal combustion engines with a high thermal efficiency and low harmful exhaust gas. The PCCI(premixed charged compression ignition) technology has been studied specifically to simultaneously reduce NOx and PM. While the PCCI means has the merit of reducing NOx and PM, control of the combustion phase is difficult. In this study, Flame visualization was then performed with an endoscope system in order to compare combustion flame characteristics in an commercial diesel engine.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.126-130
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• 2003

하이브리드 로켓은 기존의 고체, 액체 로켓에 비하여 많은 이점을 가지고 있다. 본 연구에서는 lab-scale의 하이브리드 모터를 설계 및 제작하여 regression rate의 증진 방안을 모색하고자 하였다. 산화제 유량의 변화에 따라 연소실 압력을 측정하여 추력을 계산하였으며, 연소과정의 가시화를 통해 근사적 regression rate를 측정하였다. 또한 하이브리드 로켓 시험 중 발생할 수 있는 문제점과 해결방안도 제시하였다.

• 한국분무공학회지
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• 제15권3호
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• pp.150-156
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• 2010

Ethanol has properties of a lower setting point, higher oxygen contents, lower cetane numbers, and also higher volatility compared to biodiesel. Thus, biodiesel fuel can be improved in the fluidity of blending fuel and exhaust emissions by blended ethanol fuel. This research aims to understand combustion characteristics of biodiesel-ethanol blending fuel inside a constant volume chamber. High speed camera was applied to visualize the physics of development of combustion processes, and combustion pressure and exhaust emissions were measured at several blending ratios of ethanol and biodiesel fuel. This information may contribute to improve the performance of biodiesel engine and reduce emissions in future.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.101-104
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• 2012

In this work, in-cylinder pressure measurements and high-speed direct imaging of the flame were performed in an optically accessible single cylinder diesel engine with premixed charge compression ignition combustion and a narrow injection angle. The results show that the frequency ranges of pressure ringing were 8.35 to 9 kHz and 12..2 to 13.1 kHz. The frequencies of the flame movement were shown as 8.7 kHz and 13 kHz. It was found that there is a direct relationship between the pressure ringing and the flame movement.

• 한국연소학회지
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• 제8권3호
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• pp.31-37
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• 2003

The objective of this work is to investigate the effect of swirl, injection pressure and pilot injection on D.I.Diesel combustion by using a transparent engine system. The test engine is equipped with common rail injection system to obtain high pressure and to control injection timing and duration. In this study, the combustion analysis and steady flow test were conducted to estimate the heat release rate from in-cylinder pressure and pilot injection was investigated by using LII technique. As the results, high injection pressure was found to shorten ignition delay as well as enhance peak pressure and heat release rate was greatly affected by injection timing and pilot injection. In addition, the results showed that the period of soot formation corresponded to the diffusion flame.

• 한국자동차공학회논문집
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• 제3권2호
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• pp.136-145
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• 1995

The aim of this study is to gain a better understanding of the effect of a flow motion on the flame development by means of an optically-accessible constant-volume combustion chamber and the visualization technique of a combustion flame. At first, the characteristics of a flame propagation are investigated in the combustion field of the two kinds of flow conditions such as a quiescent and a flowing condition, and methane-air mixture is used as fuel. Then the same investigation is performed in two flow configurations : bulk flow motion type and turbulence generating type. In this study, the combustion phenomena are analyzed by measuring the combustion pressure, flame propagation speed, mean velocity, turbulent intensity, and mass fraction burned.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.193-196
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• 2015

Combustion of low concentration VOC in inert gas around the flammability limit has been experimentally studied. Streams of nitrogen and propane mixture with various compositions and flow conditions were treated by a turbulent partially-premixed pilot flame. HC and CO contents in exhaust gas measured and the flow patterns were visualized. The results suggested that there exists an optimal mixture velocity range for efficient combustion treatment for each flow condition and composition of the mixture.

• 한국추진공학회지
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• 제15권4호
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• pp.35-40
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• 2011

희박 예혼합 가스터빈에서 발생되는 연소 불안정 현상의 메커니즘을 규명하기 위하여 입구 속도 변동에 대한 열발생 변동을 정량화한 화염 전달 함수가 실험적으로 규현되었다. 이를 위하여 실제 가스터빈과 유사한 형태를 갖는 모형 연소기가 제작되었으며, 열발생율의 측정을 위한 가시화 연소기가 장착되었다. 또한 흡기 속도의 변조를 위하여 가변 속도 모터 및 유량 제어 장치가 설계되었고, 이러한 장치들을 통하여 입구 속도 변동이 열발생율의 진폭에 미치는 영향 및 화염 구조의 변화를 실험적으로 계측하였다. 실험 결과 화염 전달 함수는 당량비와 같은 운전 조건과 더불어 속도 섭동 조건에 대하여도 크게 의존하며, 화염의 길이와 섭동파 파장의 비율을 의미하는 Strouhal 수에 의하여 일반화될 수 있었다.