• 제목/요약/키워드: Self-oscillation

검색결과 137건 처리시간 0.026초

Experimental Studies on Self-Oscillation of a Swirl Coaxial Injector

  • Kim, Dongjun;Wonho Jeong;Jihyuk Im;Youngbin Yoon
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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    • pp.228-233
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    • 2004
  • The spray and acoustic characteristics by the self-oscillation of a swirl coaxial injector were experimentally studied. The self-oscillation of a swirl coaxial injector is defined as pressure and flowrate oscillations by a time-delayed feedback between liquid and gas phase and has strong influences on atomization and mixing processes. Hence the occurrence and effect of the self-oscillation are measured using shadow photography technique, acoustic test and PDPA. The occurrence of self-oscillation largely depends on the injection conditions, such as pressure drop of liquid phase and relative momentum ratio. From the experimental results, self-oscillation occurs when the momentum of gas phase is enough large and the smaller the pressure drop of liquid phase is, the better self-oscillation occurs at the same momentum ratio. The self-oscillation is also affected by injector geometries, increasing the recess length results in the expansion of self-oscillation region and the increase of sound pressure level. The self-oscillation of a swirl coaxial injector accompanies a high intensity scream and this scream may provide harmful disturbances to combustion processes. Self-oscillation leads to strong changes in the drop size distribution and smoothly varies the slope of radial SMD distribution.

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자려 연소진동에 관한 연소제어와 징후의 검출 (Combustion Control and Symptom Detection on Self-excited Combustion Oscillation)

  • 양영준
    • 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.

비대칭 자기 진동에 대한 PID 자동동조 알고리듬 (PID Autotuning Algorithm with an Asymmetric Self-oscillation)

  • 오승록
    • 전기전자학회논문지
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    • 제6권2호
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    • pp.128-135
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    • 2002
  • 선형 플랜트의 극한 이득과 주기를 찾기 위해 포화함수를 이용하여 자기 진동을 발생 시켰다. 포화함수 사용으로 극한이득과 주기의 정확성을 높였다. 발견한 극한 이득과 극한 주기는 PID 제어기 값을 구하는데 사용하였다. 정적인 부하 왜란 등이 있는 경우 비대칭 진동이 발생할 수 있다. 발생하는 비대칭 자기 진동을 분석하였고 분석결과로부터 극한 이득과 주기를 찾는 방법을 제안하였다.

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Symptoms of Self-excited Combustion Oscillation and their Detection

  • Yang, Young-Joon;Akamatsu, Fumiteru;Katsuki, Masashi;Bae, Suk-Tae;Kim, Si-Pom
    • 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.

Characteristics of Self-excited Combustion Oscillation and Combustion Control by Forced Pulsating Mixture Supply

  • Yang, Young-Joon;Fumiteru Akamatsu;Masashi Katsuki;Lee, Chi-Woo
    • 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.

묘사함수를 이용한 퍼지 제어 시스템의 자기진동 현상의 예측 - 정적 경우 (The Prediction of Self-Excited Oscillation of a Fuzzy Control System Based on the Describing Function - Static Case)

  • 김은태;노흥식;김동연;박민용
    • 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.

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Fabry-Perot 레이저의 자기궤환 레이저 발진을 이용한 색분산 측정법 (Dispersion measurement technique based on a self-seeding laser oscillation of a Fabry-Perot laser)

  • 윤기홍;송재원;김현덕
    • 한국광학회지
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    • 제15권2호
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    • pp.104-108
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    • 2004
  • 폐경로를 통한 Fabry-Perot 레이저의 자기궤환 레이저 발진(self-seeding laser oscillation)을 이용하여 구조가 간단하고 경제적인 색분산(chromatic dispersion) 측정법을 제안하였다. 저가의 Fabry-Perot 레이저를 이용하여 광펄스들을 생성하고, 광섬유를 통해 전송되는 광펄스들 사이의 군속도 차(group delay difference)를 Fabry-Perot 레이저의 자기궤환 발진 현상을 통해 감지함으로써 광섬유의 색분산계수를 측정할 수 있도록 하였다. 제안된 측정법에 따라 구현된 측정 장치는 고가의 상용 계측기와 비슷한 수준의 색분산계수 측정 정확도를 제공하고, 재현성은 0.5%보다 좋음을 실험적으로 검증하였다.

바이쿼드 RC 필터의 자가 발진을 이용한 필터 교정 (Filter Calibration using Self Oscillation of Biquad RC Filter)

  • 안덕기;황인철
    • 전기학회논문지
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    • 제59권5호
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    • pp.1005-1009
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    • 2010
  • This paper presents a digitally-controlled filter calibration technique for biquad RC filter using self oscillation. The biquad RC filter is converted to a fully-differential ring oscillator by changing its resistor connections, where the oscillation frequency reflects the cut-off frequency. The proposed calibration circuit measures the oscillation frequency by counting with a fixed higher-frequency clock and then tunes it to a desired frequency with a digital frequency-locked loop including a PI controller. Because the proposed circuit directly measures the cut-off frequency of the filter itself and calibrates it with the small area digital circuits, the area and the power consumption are much small compared with conventional works. When it is implemented in a 65nm CMOS process, the calibration circuit except the filter consumes the area of 80um X 50um and power consumption is 443uA at 1.2 V supply voltage.

묘사함수를 이용한 퍼지 제어시스템의 자기진동 현상의 예측-동적 경우 (The prediction of self-excited oscillation of a fuzzy control system based on the describing function dynamic case)

  • 김은태;노흥식;권철;김동연;박민용
    • 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.

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진동하는 층류예혼합화염의 불안정성에 관한 연구 (A study of Instability on Oscillating Laminar Premixed Flames)

  • 이원남
    • 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.

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