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박이선(I-Sun Park),손채훈(Chae Hoon Sohn) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
Acoustic behavior in gas turbine combustor with acoustic resonator is investigated numerically by adopting linear acoustic analysis. Helmholtz-type resonator is employed as acoustic resonator to suppress acoustic instability passively. The tuning frequency of acoustic resonator is adjusted by varying its length. Through harmonic analysis, acoustic-pressure responses of chamber to acoustic excitation are obtained and the resonant acoustic modes are identified. Acoustic damping effect of acoustic resonator is quantified by damping factor. As the tuning frequency of acoustic resonator approaches the target frequency of the resonant mode to be suppressed, mode split from the original resonant mode to lower and upper modes appears and thereby complex patterns of acoustic responses show up. Considering mode split and damping effect as a function of tuning frequency, it is desirable to make acoustic resonator tuned to broad-band frequencies near the maximum frequency of those of the possible upper modes.
박이선(I Sun Park),김철진(Chul Jin Kim),손채훈(Chae Hoon Sohn),백강수(Kang Su Paik) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The spontaneous ignition of coal stockpiles causes a serious economic and safety problem. It occurs in a coal stockpile when heat generated within the pile is not emitted quickly to the environment and air is entrained to the pile. In this study, numerical approach of computational fluid dynamics (CFD) is employed to simulate the ignition process. There are several parameters affecting the process such as air flow rate, coal porosity, chemical reaction rate, and initial temperature. The numerical results are compared with the experimental results and it is found that the reasonable ignition time is predicted numerically. The present numerical simulation can be used to predict temperature in the coal stockpile, the position of hot spots, and their transient behavior.
액체 로켓엔진 분사기의 음향감쇠 효과에 관한 수치적 연구
박이선(I-Sun Park),손채훈(Chae-Hoon Sohn) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.5
기체-액체형 분사기를 사용하는 고성능 로켓엔진을 위하여 공명기로서의 분사기의 역할을 연구하였다. 단일 분사기가 장착된 연소기에서의 음향 거동을 상온 선형 음향해석을 통해 조사하였다. 음향감쇠 효과는 분사기 길이에 따른 감쇠인자를 통해 정량화되었다. 계산 결과, 분사기는 음향 감쇠에 있어 큰 역할을 하며, 최적의 분사기 길이는 감쇠시키고자 하는 음향 주파수에 대한 반파장 길이에 해당함을 알 수 있었다. 배플이 장착된 연소기에서, 상온 조건과 실제 연소 상황의 조건을 설정하여 각 조건에 대해서 배플길이에 따른 최적 분사기 길이의 변화를 계산하여 제시하였다. The role of the injector as an acoustic resonator is studied for the high performance rocket engine adopting the gas-liquid scheme injector. Acoustic behavior in the combustor with single injector is investigated numerically adopting linear acoustic analysis for cold condition. Acoustic-damping effect of the injector is evaluated by damping factor as a function of the injector length. From the numerical results, it is found that the injector can play a significant role in acoustic damping and the optimum length of the injector corresponds to half of a full wavelength of the longitudinal mode with the acoustic frequency to be damped in the chamber. In baffled chamber, the optimum lengths of the injector are calculated as a function of baffle length for both cold and hot conditions.
이중 블레이드 팬이 장착된 진공청소기 흡입 노즐내 유로 유동 소음 및 팬 성능 해석
박이선(I Sun Park),손채훈(Chae Hoon Sohn),이성철(Sung Cheol Lee),오장근(Jang Keun Oh) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Rotary performance and flow resistance induced by each element in suction nozzle of a vacuum cleaner with a double-blade rotary fan are investigated numerically and its relation with flow-induced noise and rotary performance is examined. Flow resistance and vorticity in suction nozzle are calculated and it is found that they are closely related with flow-induced noise. Gap between double blades, adoption of cross-flow fan, enlargement of flow inlet area, and optimization of blade number are tested for noise reduction. Finally, the effects of each method are verified experimentally. It is found that several combinations of the proposed methods can be adopted for noise reduction although the degree of reduction is not much.
이중 블레이드 팬이 장착된 진공청소기 브러쉬의 유동소음 특성
박이선(I Sun Park),손채훈(Chae Hoon Sohn),오장근(Jang Keun Oh) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.2
진공청소기 브러쉬의 소음원인과 소음특성에 관하여 고찰하였다. 먼저, 소음원인을 분석하기위해서 수치해석 결과를 토대로 유동저항을 분석하였다. 그 결과 청소기 브러쉬 소음의 주요 원인은 팬회전에 의한 톤소음이 아니고, 브러쉬 내부의 유체역학적인 특성에 의한 유동저항 증가로 인해서 발생하는 유동소음임을 알 수 있었으며, 그 타당성을 무향실에서 음향파워 측정 실험을 통해서 확인하였다. 다음으로, 소음측정 실험을 통해서 브러쉬의 최적 설계를 통해 저감할 수 있는 최대 소음저감 한계가 4㏈A 임을 확인하였다. 팬 블레이드 개수, 공기 흡입구 확장에 따른 소음 특성을 분석하였고, 이로부터 소음저감 한계가 너무 작아서 팬 블레이드 개수, 공기 흡입구 확장에 따른 소음 저감량이 2 ㏈A 이내로 작은 것을 알 수 있었다. The characteristics of noise generation in the suction nozzle of a vacuum cleaner are analyzed numerically and experimentally. First, the flow resistance induced by each element in the suction nozzle of a vacuum cleaner with a double-blade rotary fan is investigated numerically and its relation with flow-induced noise and suction performance is examined in an anechoic room. The flow resistance and vorticity in the suction nozzle are calculated, and it is found that they are closely related to flow-induced noise and that the upper limit of noise reduction is only 4 ㏈A. This upper limit can be achieved by changing the design of the brush nozzle. Two methods for noise reduction by enlargement of flow-inlet area and by optimization of the number of blades are tested. Finally, the effects of each method are verified experimentally.