• Journal of Advanced Marine Engineering and Technology
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• 제28권7호
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• pp.1111-1122
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• 2004

An idea to suppress the self-excited combustion oscillation was applied to the flames. The characteristics of unsteady combustion were examined and the unsteady combustion was 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 this 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 oscillation. Symptoms of self-excited combustion oscillation were also studied in order to predict the onset of combustion oscillation before it proceeded to a catastrophic failure For the purpose, the unique measures to observe the onset of self-excited combustion oscillations based on the careful statistics of fluctuating properties in flames, such as pressure or emission of OH radicals, have been proposed.

• 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.

• Journal of Mechanical Science and Technology
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• 제18권10호
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• pp.1859-1868
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• 2004

Monitoring of OH chemiluminescence through an optical fiber was demonstrated to be a useful method in detecting self-excited combustion oscillations. OH chemiluminescence intensity detected by the optical fiber showed mostly excellent agreement with those obtained by high speed CCD camera measurements when combustion oscillations were strong. Symptoms of self-excited combustion oscillation were also studied in order to predict the onset of combustion oscillation before it proceeded to a catastrophic failure. For the purpose, we have found and proposed unique measures to tell the onset of self-excited combustion oscillations based on the careful statistics of fluctuating properties in flames, such as pressure or emission of OH radicals.

• 전자공학회논문지C
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• 제35C권3호
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• pp.90-96
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• 1998

The self-excited oscillation is the phenomenon which can be observed in the systems composed of nonlinear elements. The phenomenon is of fundamental importance in nonlinear systems and, as far as the design of a nonlinear system is concerned, it should be considered along with the stability analysis. In this paper, the oscillation of a system controlled by a static nonlinear fuzzy controller is theoretically addressed. First, the describing functionof a static fuzzy controller is derived and then, based on the derived describing function, self-excited oscillation of the system controlled by a static fuzzy controller is predicted. To obtain the describing function of the static fuzzy controller, a simple struture is assumed for the fuzzy controller. Finally, computer simulation is included to show an example where the describing function given in the paper is used to predict the self-excited oscillation of a fuzzy-control system.

• 한국연소학회지
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• 제6권2호
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• pp.8-14
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• 2001

The effects of unsteady combustion are experimentally studied using forced pulsating mixture supply. It was shown that unsteady combustion used in this experiment plays an important role in controlling self-excited combustion oscillations. It may also have desirable performances, from a practical point of view, such as high combustion load, augmented heat transfer, reduced pollutant emissions and so on. We examined the characteristics of unsteady combustion driven by forced pulsating mixture supply in a small duct-combustor with a rearward-facing step. Further, we found its influence on the onset of self-excited combustion oscillations, the possibility of suppressing self-excited combustion oscillations and the reason why the self-excited combustion oscillation was suppressed using the forced pulsating mixture supply, comparing with the steady mixture supply.

• 전자공학회논문지C
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• 제35C권5호
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• pp.41-49
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• 1998

This paper deals with the self-excited oscillation of a system that is controlled by a dynamic nonlinear fuzzy controller. The self-excited oscillation can be observed in the systems composed of nonlinear elements and its analysis is as important as that of stability in the design of nonlinear systems. by using the frequency transfer function analysis known as the describing function method in nonlinear control theory, the oscillation is theoretically predicted. First, the describing function of a dynamic fuzzy controller is derived and then, based on the derived describing fuction, self-excited oscillation of the system controlled by a dynamic fuzzy controller is predicted. To obtain the describing function of the dynamic fuzzy controller, a simple structure is assumed for the fuzzy controller.

• 산업기술연구
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• 제23권A호
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• pp.29-33
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• 2003

This paper proposed methods of filament preheating to extend a fluorescent lamp life. The ballast for the fluorescent lamp can be classified into two main groups magnetics and electronics. The electronic ballast is lighter and smaller than the magnetic ballast and it can dim up and down. There are two ways to start the fluorescent lamp in the electronic ballast: rapid start and instant start. Also there are two methods of the driving inverter self excited oscillation and force excited oscillation. The rapid starting is different from the instant starting in that the rapid start is preheating the filament before the steady state. If there is a preheating process before the lamp ignition, the life of the fluorescent lamp can be increased. This paper presented the preheating methods for self excited oscillating system and force excited oscillating system.

• Environmental Engineering Research
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• 제9권6호
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• pp.256-268
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• 2004

• 에너지공학
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• 제13권3호
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• pp.205-213
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• 2004

본 연구에서는 고가인 고속도 CCD카메라가 아닌 비교적 간단한 광파이버 시스템을 이용한 자려진동연소 발생에 관한 검출과, 진동연소가 발생하기 전에 이를 미리 예견할 수 있는 통계학적 수법에 관해 조사를 하였다. 먼저 자려진동연소의 발생시에 사용될 수 있는 광파이버의 유용성이 검증되었다. 광파이버에 의해 검출되어진 OH 라디칼 자발광 강도는 고속도 CCD카메라에 의해 얻어진 값과 강한 자려진동연소가 발생할 때에 거의 일치를 하였다. 자려진동연소가 발생하면 시스템과 연소기기에 손상을 가하게 된다. 이러한 피해가 발생하기 전에 자려진동연소의 발생 징후를 미리 포착하려는 시도를 하였다. 이를 위해 압력과 OH라디칼 자발광과 같은 화염에서의 변동성분께 대한 통계학적 처리를 이용하여 자려진동연소의 발생을 예견할 수 있는 독특한 수법에 관해 조사를 하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 F
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• pp.2505-2507
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• 1999

This paper presents novel self excited DC-DC converters such as Buck-boost type, Buck type and also non-inverting Buck-boost type. The proposed converters has the following advantages: simple topology, small number of circuit components, easy control methode. Therefore, these converters are suitable for the portable appliances with battery source. Theoretical analysis and experimental results for SOW class Buck-boost type self oscillation DC-DC converter have been obtained, which demonstrate the high efficiency and good performance.