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음향 인텐시티 기법을 이용한 복잡한 진동-음향계의 방사 음장에 대한 음원 탐색에 관하여
강승천,이정권 한국음향학회 2002 韓國音響學會誌 Vol.21 No.8
본 연구에서는 진동-음향계에서 방사되어 생성된 일반 근접장에서 음향 인텐시티 기법을 이용해 소음원을 파악하는 방법의 문제점에 관하여 논한다. 이를 위해 자동차나중장비의 엔진실을 모사하는 3차원 구조물 모델을 고려한다. 실제 상황과 유사하도록 모델에는 음원들이 복잡한 형상의 표면에 상호 연관성이 있는 또는 없는 형태로 분포한다. 즉, 음원들은 음향학적으로 단단한 상자들에 의해 형성된 좁은 공간으로 연결되어 있다. 따라서 반사가 심한 음장에 면한 표면에 배치되어 있으며, 전체 구조의 바닥 부분은 하부의 바닥과 작은 틈새만큼 떨어져 있다. 음향 경계요소법을 이용하여 근접 음장과 내부 음장의 인텐시티를 계산한다. 주어진 음원들간의 상대적 위상, 주파수, 위치에 따른 효과를 조사하였고, 그 결과를 등인텐시티선도, 벡터도 및 에너지 유선으로 표현하였다. 현장에서 종종 행해지는 바와 같이, 예를들어 엔진룸 상부에서 인텐시티를 측정하여 음원을 조사하는 것과 같은, 반사장이 강한 음장에서 음향 인텐시티 기법을 적용하여 음원탐색을 시도할 경우 가짜 음원이 검색될 수 있음을 보였다. 이와 같은 음장에서 정확한 결과를 얻기 위해서는, 음원탐색 수행 전에 음장의 리액티비티에 대한 조사가 먼저 필요하며, 측정을 시행하기 전에 음장의 리액티비티를 없애거나 대폭적으로 줄이는 작업이 선행되어야 할 것이다. In this paper, the problems in identifying the noise sources by using the sound intensity technique are dealt with for the general radiated near-field from vibro-acoustic sources. For this purpose, a three-dimensional model structure resembling the engine room of a car or heavy equipment is considered. Similar to the practical situations, the model contains many mutually coherent and incoherent noise sources distributed on the complicated surfaces. The sources are located on the narrow, connected, reflecting planes constructed with rigid boxes, of which a small clearance exists between the whole box structure and the reflecting bottom. The acoustic boundary element method is employed to calculate the acoustic intensity at the near-field surfaces and interior spaces. The effects of relative source phases, frequencies, and locations are investigated, from which the results are illustrated by the contour map, vector plot, and energy streamlines. It is clearly observed that the application of sound intensity technique to the reactive or reverberant field, e.g., scanning over the upper engine room as is usually practiced, can yield the detection of fake sources. For the precise result for such a field, the field reactivity should be checked a priori and the proper effort should be directed to reduce or improve the reactivity of sound field.
불연속 양단 자유보(미사일 모델)의 최대추진력에 관한 연구
박영필,강승천 연세대학교 산업기술연구소 1985 논문집 Vol.17 No.1
In this study, the dynamic stability of a launch vehicle with non-uniform mass and bending stiffness distributions is analyzed. The launch vechile is idealized as a free-free Euler-Bernoulli beam subjected to a controlled constant follower force. For the study, finite element model is formulated through the extended Hamilton's principle. The effects of the fuel consumption on the dynamic stability behavior of the launch vehicle is studied for various gains and locations of the direction control sensor.
강승천(SungChon Kang),노병후(Byunghoo Rho) 한국자동차공학회 1994 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Noise is the weak point of diesel engine even though it has been used in many commercial and industrial vehicles, construction equipments and ships because of the superiority of thermal efficiency. In this research the several reduction techniques for light duty diesel engine are studied. Noise reduction by the vibration isolation, change of material, reduction of gear backlash and modification of piston and cylinder block is analyzed.<br/>
김태규(Tae-Kyu Kim),이웅건(Woong-Gun Lee),강승천(Sung-Chon Kang),이동인(Dong-In Lee) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The major purpose of this study is to find optimized Injector nozzle's hole-number, hole-hyd.flow and injection pressure, injection-timing in order to achieve their NOx reduction targets while minimizing smoke and fuel economy penalty. The tests were performed on a 6 ℓ Common Rail Diesel Engine to use commercial-vehicle, excavator, wheel-loader, fork-lift truck. In this study, two case of injector nozzle's hole-number(#7, #8) and three case of injector nozzle's hole-hyd.flow(Standard, +7%, -7%) were tested for their relation of NOx, BSFC, smoke by changing injection-pressure, injection-timing. From the test, we find that injector nozzle's hole-number, #8 and hole-hyd.flow, Standard are optimized at this engine. And we find engine performance and emission trend by changing injection-pressure and injection-timing.
조영진(Youngjin Cho),원준희(Junhee Won),박준영(Junyoung Park),강승천(Sungchun Kang),이동인(Dongin Lee) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
It is well known that two representative method to satisfy the EURO4 emission regulation. The one is the EGR system that reduces NOx in an engine by using EGR and PM by OPF. But this system has disadvantages of fuel efficiency and requirement for larger engine cooling capacity. The other is SCR system that reduces NOx in exhaust gas by dosing reagent (urea water solution) into exhaust gas. And the SCR system needs to decrease PM by optimization of fuel combustion. The SCR system has advantages of fuel efficiency and good durability of engine. Recently as the price of oil (diesel) goes up, the commercial vehicle drivers are more concerned about the fuel economy. So the European major manufacturer of commercial vehicle adopted the SCR system because of the above mentioned advantages. And this study focused on the development of EURO4 engine and commercial vehicle equipped with SCR system.