• 한국연소학회지
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• 제12권4호
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• pp.22-30
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• 2007

The NOx emission characteristics were studied in an oscillating combustion burner equipped with a specially designed proportioning valve. The effects of various parameters on the NOx emission which are important in oscillating combustion were investigated. Also, the effects of coincident application of flue gas recirculation(FGR) were evaluated. The results show that oscillating combustion is an efficient tool for reducing NOx in the burner. Up to 53% of NOx reduction could be acquired in low frequency and small duty ratio conditions. The coincident application of FGR further reduced the NOx emission up to 74%. Thus, this study assured that oscillating combustion technology with FGR could be a fascinating method for NOx reduction in industrial burners.

• 한국연소학회지
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• 제14권3호
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• pp.37-44
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• 2009

An experimental study was conducted to reduce NOx emission in RT(radiant tube)burner by using oscillating combustion processes in RIST. A solenoid valve gives the various oscillating conditions, such as oscillation frequency, duty ratio of fuel flow. In this study, we used commercial software, CFD-ACE+ to predict combustion and NOx emission characteristics for various experimental oscillation conditions. The effect of oscillation frequency and duty ratio on NOx emission will be discussed in terms of flow field, temperature and equivalence ratio distributions in detail.

• 한국연소학회지
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• 제9권3호
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• pp.36-43
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• 2004

The flame patterns were investigated in an oscillating combustion burner equipped with a specially designed proportioning valve. The proportioning valve is driven by a solenoid and has an elastomer part which controls the valve opening area. For characterizing the valve, nozzle exit velocities were measured with a hot wire anemometry. The flame patterns were investigated by direct photographing methods using a high speed camera and a digital camera. The results show that the nozzle exit velocities could be controlled diversely and rapidly changed, so the valve seemed appropriate for the oscillating combustion burner application. Mushroom shape and highly wrinkled structure were typical features of the flames in the oscillating combustion burner. As the oscillating intensity of the fuel flow increased, the flame length was shortened.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제29회 KOSCI SYMPOSIUM 논문집
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• pp.130-137
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• 2004

The flame patterns were investigated in an oscillating combustion burner equipped with a proportioning valve. The proportioning valve is driven by a solenoid and has an elastomer part which controls the valve opening area. For characterizing the valve, nozzle exit velocities were measured with a Hot Wire Anemometry. The flame patterns were investigated by direct photographing methods using a high speed camera and a digital camera. The results show that the nozzle exit velocities could be controlled diversely and rose up and fell down abruptly, so the valve seemed appropriate for the application for the oscillating combustion burner. Mushroom shaped and highly wrinkled flames were a typical features of the oscillating combustion burner. As the oscillating intensity of the fuel flow increased, the flame length was shortened.

• 대한기계학회논문집B
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• 제32권2호
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• pp.100-106
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• 2008

An experimental study was carried out in a small-scale test furnace to investigate the performance, such as $NO_X$ emission, enhancement of heat transfer, uniformity of temperature, and etc, of oscillating combustion applied in radiant tube burner system. A premixed type burner and a cyclic oscillating control valve were designed and used. The fuel, used commercial LPG in this study, was only oscillated using the cyclic oscillating control valve. As oscillating combustion was applied in radiant tube burner system, it is found that $NO_X$ emission, compared to no oscillation, could be reduced by 38% at $90{\sim}120rpm\;(1.5{\sim}2.0Hz)$. However, as oscillating frequency was increased, effect of abatement of $NO_X$ emission is gradually reduced. From the measurement of furnace heating time from $100^{\circ}C$ to $720^{\circ}C$, heat transfer is increased by 11.5% at the oscillation of 120rpm. Temperature distribution of radiant tube surface is more uniform at oscillation of 120rpm with decrease of the peak temperature and increase of low temperature. From these results, it is confirmed that oscillating combustion is useful in radiant tube burner system.

• 대한기계학회논문집B
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• 제35권5호
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• pp.539-545
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• 2011

맥동연소기술을 적용한 산업용 복사관버너의 연소특성을 살펴보기 위해 실규모 (120,000 kcal/h) 산업용 복사관버너 설비를 사용하여 실험실 및 현장 테스트를 수행하였다. 제철부생가스를 사용하는 산업용 복사관버너의 3 가지 종류를 하나의 W 형 복사관이 장착된 실험설비에서 실험하였다. W 형 복사관이 다수 사용되는 대형 설비를 이용하여 장기운영 실험을 실시하였다. 맥동연소기술을 적용한 기실험설비들을 대상으로 성능향상 및 배가스조절 측면에서 다양한 실험조건으로 테스트를 진행 하였다. 맥동연소기술의 적용가능성 평가를 위해 NOx 저감 및 효율향상을 분석하였다. 맥동연소기술의 적용결과 에너지 절감, 복사관 수명 향상 및 생산성 향상 등이 얻어짐을 확인할 수 있었다. 최고의 성능 및 배가스 조절을 얻기 위한 최적의 운전조건이 각 버너별로 결정되었다.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1219-1226
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• 2017

This paper presents the hybrid stepping machine for linear oscillating generators. The focus of the work is the suggestion of the improved model through the comparison of proposed models ; new flux concentrating PMs mover of the hybrid stepping generator is proposed based on the symmetrical and non-symmetrical stator cores of the surface mounted PMs mover, and non-slanted PMs and slanted PMs of the flux concentrating PMs mover. It is achieved using equivalent magnetic circuit considering leakage elements. Finally, this study suggests new hybrid stepping structure of linear oscillating generator.

• 한국연소학회지
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• 제13권4호
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• pp.8-15
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• 2008

When a circular cylinder is placed at the center of a slot burner nozzle, once stable Woflhard-Parker type laminar lean premixed flame is changed to an oscillating flame with self-induced noise. The wrinkled flame surface showed the same pattern and frequency of the Karman vortex street at the downstream of a circular cylinder. The interaction of flame with Karman vortex street is observed to be responsible for flame oscillation. The measured flame oscillation frequency is very similar to the estimated Karman vortex shedding frequency based on the St-Re relationship of the flow past circular cylinder, which could be considered as a strong evidence for the interaction between laminar pre-mixed flame and a Karman vortex street. As Reynolds number increases oscillation frequency decreases and the self-induced noise level increases as well as the flame front is more severly wrinkled. This result suggests that the flame/vortex interaction becomes more active at higher Re.

• 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.

• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1820-1831
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• 2003

Characteristics of self-excited combustion oscillation are experimentally studied using confined premixed flames stabilized by a rearward-facing step. A new idea to suppress combustion oscillation was applied to the flames. The characteristics of unsteady combustion were examined, which is driven by forced pulsating mixture supply that can modulate its amplitude and frequency. The self-excited combustion oscillation having weaker flow velocity fluctuation intensity than that of the forced pulsating supply can be suppressed by the method. The effects of the forced pulsation amplitude and frequency on controlling self-excited combustion oscillations were also investigated comparing with the steady mixture supply. The unsteady combustion used in this experiment plays an important role in controlling self-excited combustion oscillations, and it also exhibits desirable performances, from a practical point of view, such as high combustion load and reduced pollutant emissions of nitric oxide.