• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.873-876
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• 2011

In this research, a Helmholtz resonator was applied to the thermo-acoustic environment that has thermal gradient using Rijke tube. The thermo-acoustic instability was invoked by a Rijke tube which use a DC power supplier and a Blower. A target instability frequency was appeared by the Rijke tube. A preliminary experiment on damping characteristics of the resonator in the thermo-acoustic environment was performed and compared with the room temperature experiment data.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.610-613
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• 2010

A horizontal Rijke tube with an electric heating part is a convenient system for studying the thermo acoustic instability. In this work, horizontal Rijke tube is manufactured to investigate and compare damping characteristics of Helmholtz resonator under unsteady heat release and room temperature conditions. We obtained basic data using the Helmholtz resonator which is used as passive damper under the thermo acoustic instabilities.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.47-50
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• 2011

A Rijke tube which has an electric heater and a flow controller was designed and thermo-acoustic instability was induced by the Rijke tube. The thermo-acoustic instability was damped by a resonator and the damping characteristics were investigated and compared to room temperature acoustic test. Results show that decay time of the thermo-acoustic condition was increased by about 40% compared to that of room temperature acoustic test.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2524-2529
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• 2008

The thermal system like a combustion chamber is believed to experience a significant instability problem with vibration in case that the thermal energy or the acoustic energy are transformed into a different form through a relevant path. This study deals with a numerically- predicted, Thermoacoustic instability in a Rijke tube by using a non-linear model for a heat source. The heating part where the energy transformation occurs actively is modeled after simulating two-dimensional cylinder case with constant surface temperature, and a nonlinear model that accounts for the transfer function of magnitude- and phase-characteristics is properly implemented so as to be dependent on the pulsation strength in the tube. The heat source model is observed to result in equivalent Thermoacoustic instabilities in the Rijke tube except low flow-rate cases in which the natural convection is dominant.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.809-813
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• 2010

For the purpose of developing a modeling technique for reduced-order dynamics of thermoacoustic instability, we constructed an electrically heated Rijke tube and measured the pressure oscillation inside the tube. Analysing the measured pressure data showed that the instability generated three major oscillation modes, among which the first mode frequency quite well matches the result from a rough acoustic analysis. As a continuing research, a data-based modeling technique for the thermoacoustic instability will be developed in the near future.

• Journal of Mechanical Science and Technology
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• v.20 no.6
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• pp.905-913
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• 2006

The instability curve of a Rijke tube system was obtained accurately by following different paths of heat power and flow-rate for three regions and by defining its locus from the criterion based on the measured sound pressure levels. The unstable limits in the region of flow-rate lower than that at the minimal power are compared with previous data. To observe the effect of turbulence on the unstable limits, inflow turbulence was introduced by placing a bundle of circular cylinders upstream of the heating part ($50). The large-amplitude inflow fluctuation may delay the transition of the chamber acoustic mode to the unstable Bone even at a sufficient power.

• The Journal of the Acoustical Society of Korea
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• v.29 no.8
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• pp.491-496
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• 2010

Thermoacoustic power generation by a spiral heater in the Rijke tube was analyzed numerically. In the analysis, variables were normalized by the angular frequency of the sound and the thermal diffusivity of the air. The effect of the heater wire diameter d, the spacing between wires P-d, and the air-current velocity $U_0$, upon the power generation was obtained and discussed. When the spacing is broad enough, the normalized velocity is $U_0{\approx}0.8$ and the diameter is $d{\approx}4$ for the maximum power generation. With decrease of the spacing, however, the power generation increases more than 5 times and becomes maximum around $d{\approx}2$, $P-d{\approx}3$. And the velocity $U_0{\approx}0.8$ for the maximum power generation is almost independent of the wire spacing.

• The Journal of the Acoustical Society of Korea
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• v.30 no.5
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• pp.249-254
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• 2011

Inquiring activities on the acoustic phenomena have been carried out by using a sound card installed in a personal computer. A sound card is cheaper and more accessible to the students than the precision equipment such as a function generator or an oscilloscope. The students record the sounds from various acoustic phenomena to the sound card. Then they analyze the frequency spectrums of that sounds by using a program. Inquired phenomena include beat by two tuning forks, sound from Rijke tube, pouring sound, breaking of a wine glass and pop-up sound of a wine bottle. Through these activities students perform quantitative analysis of various phenomena due to superposition, resonance and standing wave.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.555-561
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• 2012

The Hilbert Huang Transform (HHT) technigue with Empirical Mode Decomposition (EMD) is one of the time-frequency domain analysis methods and it has several advantages such that analyzing non-stationary and nonlinear signal is possible. However, there are shortcomings in detecting near-range of frequencies and added noise signals. In this paper, to analyze characteristics of each method, HHT and Short-Time Fourier Transform (STFT) effective in dealing with stationary signals are compared. And with thermoacoustic instabilities signals from a Rijke tube test, HHT and the improved HHT with Ensemble Empirical Mode Decomposition (EEMD) are compared. The results show that the improved HHT is more appropriate than the original HHT due to the relative insensitivity to noise. Therefore it will result in more accurate analysis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.676-684
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• 1990

This study is on the pulsating combustion of premixed gas in a Rijke type combustor made of a honeycomb flame holder in a tube. Modelling for the onset condition of the oscillation is made by the ratio of the acoustic power generation based on the analysis of heat transfer to the power loss due to the thermoviscous dissipation and radiation. Experiment is performed for the characteristics of acoustic, thermal and combustion. It is shown that the theoretical modelling for the oscillation may be used as a limit condition. And the combustion analysis for the acoustic power generation is needed for better prediction of the onset condition. Experimental result shows that, by pulsation, the flame length is shortened and the flame temperature is decreased with increase in the heat transfer coefficient. The NO$_{x}$ concentration in the exhaust gas is significantly reduced by pulsation and the concentration of unburned hydrocarbon shows a little increase.e.