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권영필,서기원,Kwon, Y.P.,Suh, K.W. 대한설비공학회 1992 설비공학 논문집 Vol.4 No.2
The objective of this paper is to study experimentally on the noise characteristics of supersonic jet from multihole orifice in the range of jet pressure from $at_g$ to $at_g$ in the reverberation room. At first, the single orifice jets are investigated for various hole diameter from 3.8mm to 10mm. Through the noise spectrum, the turbulent mixing noise and the shock associated noise is analyzed. The noise for confined jets into a tube of diameter 30mm or 90mm with length 2m is investigated in comparision with that for the free jets. The sound power level is measured and compared with thoretical models for free jet. At second, multihole orifice jets are investigated to study the effect of multijet on noise reduction. The spectrum and power level of multijets are measured and compared with single jets. The multi-jets in a confined pipe are also investigated. It is found that the noise spectrum is significantly altered by increasing the number of jet with decrease in jet diameter and also by confining the jet into tube.
권영필,이주원,이동훈,Kwon, Y.P.,Lee, J.W.,Lee, D.H. 대한설비공학회 1997 설비공학 논문집 Vol.9 No.2
A strong combustion-driven sound from a surface burner made of a perforated metal fiber plate for premixed gas was investigated to clarify the physical mechanism of its generation. A simple model was developed for the acoustic power generation in terms of the heat transfer response function and the acoustic impedance of the burner. The acoustic impedance of the perforated metal fiber placed on the open exit was measured and the heat release response of the burner to the oscillating flow associated with the acoustic disturbance was expressed in terms of a response function. It was found that the power is generated by the heat release in response to the downstream particle velocity, in contrast to the upstream velocity in the case of the Rijke oscillation driven by a heater placed in the lower half of a columm with upstream flow. The measured frequencies of the oscillation were in agreement with the estimated resonance frequencies and their excitation was varied with the combustion conditions. For the same fuel rate, the excited frequency increases with the air ratio if it is low but decreases with the ratio if not so low. Such frequency characteristics were explained by assuming a heat release response function with a time constant and it was shown that the excited frequency decreases as the time constant increases.
권영필(Y. P. Kwon),이동훈(D. H. Lee),방정환(J. H. Bang) 한국자동차공학회 1992 오토저널 Vol.14 No.6
This study is on the performance of the perforated tube muffler when it operates as an exhaust silencer with through-flow, steady or pulsating. Theoretical estimation of the insertion loss was made by means of transfer matrix and by using the impedance equation for the perforated tube obtained for the case of low-speed steady through-flow. Experiment was performed for the measurement of the insertion loss at two flow conditions. The one is a steady flow supplied by blow-down of a compressed air reservoir and the other is a pulsating flow from the exhaust pipe of an idling diesel engine.<br/> The effect of the through-flow velocity and steadiness on the muffler performance was obtained. By comparing the theoretical prediction with the experimental result, the validity of the impedance equation in the theoretical model was discussed. It has been found that steadiness as well as magnitude of the through-flow has a significant effect on the perlormance of the perforated tube muffler. Especially, the self-noise due to the pulsating flow in the engine exhaust system must be taken into account for the prediction of the muffler performance.
권영필(Y.P. Kwon),현길학(G.H. Hyun),이동훈(D.H. Lee),서기원(G.W. Suh) 한국자동차공학회 1990 오토저널 Vol.12 No.5
The object of this study is to develop the computer program to predict the transmission loss of a perforated tube muffler with mean flow, and to investigate the influence of porosity and<br/> mean flow on the performance of the muffler. '<br/> The numerical model is made by dividing the muffler into small segments and estimating the transfer matrices for each segment. The computer program is developed for the calculation of the transmission loss of a through-or cross-flow perforated muffler.<br/> The experiment is performed for the measurement of the transmission loss and/or the pressure drop for various porosity and flow velocity. From the comparison between computation and experiment, it is known that the numerical model agrees well with the experimental result. The effect of porosity and flow velocity on the acoustic performance and the flow resistance of a muffler is presented.