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오재응,이승종,이상환,이동익,김철환,Oh, J.E.,Yi, S.J.,Lee, S.H.,Lee, D.I.,Kim, C.H. 대한설비공학회 1995 설비공학 논문집 Vol.7 No.1
Axial fans are very useful cooling devices being widely used in many electric and industrial machinery. However those are often accompanying annoying noise. Many efforts have been devoted in order to reduce the fan noise. In this study, the procedure was devided into two major parts in considering effects of design parameters of axial fan concerned with noise ; the fan theory and the Fukano's fan noise study. By using the fan theory we defined stagger angle, camber angle, blade inlet and outlet angle for studying low noise fan. Then the effects of such angles on the flow rate and static pressure were investigated. By using the Fukano's fan noise theory, the relations of the chord length, the rotational speed and the number of blades vs. fan noise are investigated.
지표면상을 전파하는 소음의 초과감쇠 산정방법에 관한 연구
오재응,김동규,임동규,Oh, J.E.,Kim, D.G.,Yim, T.K. 한국음향학회 1988 韓國音響學會誌 Vol.7 No.2
본 연구는 소음전파에 대한 옥외실험과 축적 음향모형실험에 의해서 지표면에 의한 초과감쇠 특징을 밝힌 것으로써, 옥외실험에 의한 소음전파감쇠는 음향출력이 큰 소형엔진을 사용하여, 거리감쇠로부터 산출한 실측의 초과감쇠와 Log(D/(Hs+Hr))의 관계를 확인했다. 그 결과 소음전파감쇠는 풍향, 주파수에 따라 다르며 직선회귀 된다는 것을 알 수 있었다. 그리고, 지표면상의 초과감쇠치는 통기저항을 이용해서 Log(D/Hs+Hr))을 파라미터로써 구할 수 있었고, 가장 적당한 통기저항$\sigma$는 실측의 초과감쇠치와 임의의 $\sigma$에 대한 $L=-20Log\mid1+(r_1/r_2)Qexp(ik, \bigtriangleup r)\mid$ 식의 평균자승 오차가 가장 적어질 때 결정된다. 모형의 지표로써 축척 1/40의 모형실험으로, 큰 무향실내에서 거리감쇠의 측정을 한 결과, 실측치와의 대응이 충분하다는 것을 확인했다. This study is to explain the characteristic of excess attenuation on the ground through the outdoors experiment about noise propagation and the reduced model experiment of acoustic. The outdoors experiment on the attenuation of noise propagation was tried with the small engine that had large acoustic output, and then it was conformed that there was relationship between the excess attenuation calculated by measurement from distance attenuation and Log(D/(Hs+Hr)). As a result, it was found that the attenuation of noise propogation depended upon the direction of the wind and frequency and was regressed in a straight line. And the numerical values of excess attenuation on the ground could be calculated by regarding Log(D/(Hs+Hr)) as a parameter with an airing resistance $\sigma$. It was found that when the mean square error between the excess attenuation calculated by measurement and the value calculated by a fomula $L=-20Log\mid1+(r_1/r_2)Qexp(ik, \bigtriangleup r)\mid$ about optional $\sigma$ was least, the optimal decision of u was made. As the characteristic of model is the model experiment on a reduced scale of 1 to 40, It was conformed that it corresponds enough with the measurement value with measuring the distance attenuation in the large anecoic chamber.
다차원스펙트럼 해석법을 이용한 엔진방사소음 규명에 관한 연구
오재응(J.E.Oh),백문열(M.Y.Beck),김준우(J.W.Kim),김진동(J.D.Kim) 한국자동차공학회 1993 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
With the advance of the standard of living, the demand on automobile goes beyond the simple transportation equipment. therefore the interior noise reduction has been the important factor for improvement of ride quility. Noise during idling is transmitted by the vibration of engine mount is a major vehicle characteristic determining occupant comfort In the present research two approaches for noise source identification based on theory for multiiple-input system have been investigated. The concepts of the frequency response function and the multi-dimensional spectral analysis were used to estimated the spectra of the noise source that were accounted for in the multiple-input model.<br/>
[論文] 음향인텐시티법을 이용한 4기통 가솔린 엔진의 소음원 검출에 관한 연구
오재응(J.E.Oh),박호(H.Park),이완익(W.I.Lee),조진호(J.H.Cho) 한국자동차공학회 1989 오토저널 Vol.11 No.1
본 연구에서는 음향 인텐시티법을 가솔린 엔진에 직접 적용하여, 각각의 중심주파수별 음향 인텐시티 음답특성을 1/3 옥타브 밴드로 구하였고,오버을 레벨 및 최대 인텐시티레벨을 갖는 중심주파수에서의 음향 인텐시티 방사특성을 등고선 및 3차원 표시로 나타내었다. 또한 그 결과를 분석 및 고찰하여 엔진의 중요 소음원을 검출하므로서 이 수법이 소음대책에 유효하다는 것을 검증하였다.<br/> 연구 결과, 오버올 레벨에서는 아이들링 상태의 경우 엔진 전면부에서, 2.000rpm 상태의 경우 엔진 우측부에서 가장 높은 읍향 인텐시티가 방사되었으며, 최대 인텐시티레벨을 갖는 중심주파수에서는 오일팬과 홉ㆍ배기매니홀드가 100Hz에서 가장 높은 음향 인텐시티를 나타내었다. Acoustic intensity method is applied to a 4-cylinder gasoline engine in order to identify the noise sources and the response characteristics. Acoustic intensity is analyzed by 1/3 octave band filter for each center frequency. Radiational characteristics of acoustic intensity at overall and the maximum intensity level are represented by using the contour and three-dimensional plot. It is verified that this method is effective to the assessment of engine noise.<br/> It can be found that the maximum intensity is radiated from the front side of the engine under idling condition and the right side of it under 2,000 rpm running with no loading condition at overall level, and also that the maximum intensity is radiated from the oil pan and the intake and exhaust manifold at the center frequency of 100 Hz.<br/>
[論文] 자동차 배기계의 동특성 규명 및 행거 최적위치의 결정
오재응(J.E.Oh),임동규(D.G.Im),이정윤(J.Y.Lee),조준호(J.H.Cho),김만복(M.B.Kim) 한국자동차공학회 1992 오토저널 Vol.14 No.3
As automobile industry develope, design techniques to satisfy light weight and high efficiency in automobile parts is demanded. In this study modal analysis is performed using transfer matrix method to identify dynamic characteristics of exhaust system. It is estimated the theoretical transfer function by Pestel-Leckey method and the mode shapes in 3-D graphic. the validity of developed program is verified by comparing with the experimental results of exhaust system. Estimated modal parameters (natural frequency, vibrational mode. transfer function) are in accord with the experimental results. From the developed program, we can predict a location of the hanger which is determined by the lowest RMS value point, when displacement is given as an input at the engine side. We can find that attachment of spring modelled hanger at the hanger location bring vibration level down.