초음속 제트에서의 유동 특성 및 소음 예측에 관한 연구

임동화(Dong-Hwa Lim),최종수(Jong-Soo Choi),고영성(Young-Sung Ko) 한국항공우주학회 2007 韓國航空宇宙學會誌 Vol.35 No.1

본 논문에서는 초음속 제트로부터 유발되는 소음의 특성을 실험적으로 분석하고, 기존의 소음예측식을 사용하여 비교해 봄으로서 예측식의 적용가능 범위를 살펴보았다. 실험을 위하여 제작된 초음속제트 발생장치의 출구마하수를 측정하기 위하여 정체실의 온도, 압력과 함께 피토 튜브를 이용하였고, 결과를 쉐도우 그래프 가시화 방법을 사용하여 얻은 결과와 비교하였다. 제트소음의 스펙트럼을 관찰한 결과, 불완전 팽창의 제트 유동에서 발생하는 충격파 관련 소음인 광대역 소음과 스크리치 톤 소음의 경향이 나타는 것을 확인 할 수 있었다. 아음속 조건에서는 큰 난류 구조에 의해 발생되는 난류 혼합 소음에 의하여 흐름방향으로 강한 방향성을 나타내었고, 초음속 조건에서는 충격파 관련 소음이 흐름의 상류 방향으로도 강하게 전파됨을 확인 하였다. 그리고 제트 엔진의 소음 예측 프로그램인 ARP876D 코드를 이용하여 실험에서 측정한 스펙트럼과 비교해 본 결과 아음속 영역에서보다는 초음속 영역에서 더 좋은 결과를 보였다. In this paper the acoustic signature from a supersonic nozzle is measured and compared to the result of a program developed for a gas turbine noise prediction. In order to measure the jet Mach Number, the pressure and temperature at the settling chamber was measured along with pressures from a pitot-tube placed near the exit. The results are also compared to the ones obtained with a shadow graph technique. Jet noise produced by an imperfectly expanded jet contains shock associated noise, which consist of broadband noise and screech tone noise. For subsonic condition, the directivity is dominant to the downstream direction due to turbulence mixing noise. For supersonic conditions, however, the directivity is dominant toward upstream direction due to shock associated noise. The comparison with a jet exhaust noise prediction code shows good agreement at supersonic conditions but needs to be improved at subsonic speeds.

유도무기의 제트소음 분석을 통한 발사환경에서의 소음지도 작성

김상민(Sang Min Kim),박웅(Woong Park),하재현(Jae Hyoun Ha) 한국소음진동공학회 2011 한국소음진동공학회 학술대회논문집 Vol.2011 No.10

Noise map is drawn up under launch environment through analyzing jet noise of guided weapon in this research. This has an important significance in terms of having an opportunity to look at influence of noise which is caused by guided weapon in the surrounding environment. In this paper, the magnitude of jet noise that was measured by using microphone and the result of numerical analysis that was gained by using ENPro which is environment noise prediction program are shown. At this point estimation of noise source was based on ISO 9613. Finally noise map derived from results mentioned above will become useful material when setting safety guide for protecting hearing loss of operator of weapon system in the future.

노즐 출구 형상에 따른 아음속 제트 유동의 소음 저감에 대한 실험적 연구

배주현(Juhyun Bae),이규호(Kyuho Lee),공병학(Byunghak Kong),김민우(Minwoo Kim),이수갑(Soogab Lee) 한국소음진동공학회 2011 한국소음진동공학회 학술대회논문집 Vol.2011 No.10

Experimental analysis has been carried out on noise reduction of subsonic jet flow with chevron nozzle to investigate relationships between geometry variation of chevron nozzles and jet noise reduction. Including base nozzle, seven nozzles are tested at Mach number 0.9. Parametric variables are chevron count, chevron length, and chevron shape. From these experiment, the more chevron count increase, the more jet noise reduction gain. Varying the chevron length, short chevron nozzle increase the jet noise at certain direction all the more. Chevron shape is also considered as important factor to reduce the jet noise.

고차 수치기법을 이용한 비정상 제트 플품 해석

안명환(Myeong Hwan Ahn),이덕주(Duck Joo Lee) 한국항공우주학회 2016 한국항공우주학회 학술발표회 논문집 Vol.2016 No.4

초음속 제트와 같이 고속으로 흐르는 유동에서 발생하는 소음은 구조물에 음향하중으로 작용하며 그 소음원은 잘 파악하는 것이 중요하다. 본 연구에서는 고차의 수치기법을 이용하여 속도가 없는 지유장으로 흐르는 마하수 2의 3차원 초음속 제트에 대한 유동해석을 진행하며 이를 파악해보고자 하였다. Norum과 Seiner의 실험적 데이터를 통해 노즐 출구의 조건을 입력해 주었으며, 이를 이용한 계산 결과를 실험데이터 및 S. -C. Lo 등의 수치결과와의 비교를 통해 검증하였다. 또한 검증을 위한 시간평균압력 데이터 뿐만 아니라 압력변동 데이터를 같이 고찰한 결과 소음원이 제트 중심축에서는 충격파 구조가 파괴되면서, 제트 전단층에서는 유동의 불안정으로 인해 전방부터 후방까지 넓게 분포하고 있음을 알 수 있었다. The noise from high-speed flows such as supersonic jet affects structures as the acoustic loading. Therefore, it is important to understand strength and distribution of noise sources. In this paper, the analysis of jet flow of Mach number two with no external flow is conducted on there dimensions by using high-order numberical scheme, Nozzle exit conditions are similar to Norum & Seiner’s data, and the results are compared with experimental and S. -C. Lo et al.’s numerical results. In addition, not only the averaged but also the fluctuated pressure data are shown for realizing positions of noise sources. Consequently, noise sources along the jet center mainly distribute after the destruction of shock cells, whereas those along the shear layer spread on the wider region than the jet center.

다중노즐에서의 초음속 제트 소음에 대한 수치해석

고성호(Sungho Ko),곽영균(Youngkyun Kwack),한승열(Seungyeul Han) 한국유체기계학회 2009 유체기계 연구개발 발표회 논문집 Vol.2009 No.-

Numerical studies were performed to analyze effect of nozzle number on supersonic jet noise. When the nozzle of antitank guided missile(ATGM) exhausts a plume, the supersonic blast wave is created and makes a complicated flux and supersonic jet noise. The method of similarity modelling is used to analyze the supersonic jet noise of multiple nozzle jets as well as a single nozzle jet. Numerical results show that the sound pressure level of multiple nozzle jet is lower than that of a single nozzle jet.

초음속 제트유동의 소음특성에 관한 실험적 연구

권용훈(Yonghun Kweon),임채민(Chaemin Lim),靑木俊之(Toshiyuki Aoki),김희동(Heuydong Kim) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-

The present paper describes an experimental work to investigate a transonic resonance in supersonic jet that is discharged from a convergent-divergent nozzle with a design Mach number of 2.0. Whenthe conver-gent-divergent nozzle runs at low nozzle pressure ratios, the shock wave occurs within the divergent section of the nozzle. The transonic resonance of a jet flow is generated by an emission of strong acoustic tones due to the unsteadiness of the shock. In the present study, the nozzle pressure ratio is varied to obtain the super-sonic jets which are operated in the range between 1.0 and 7.8. A high-quality Schlieren optical system is used to visualize the flow field of supersonic jets. In order to specify the flow resonance of a jet, acoustic measure-ments are performed to obtain the overall sound pressure level and noise spectra. The acoustic characteristicsof transonic resonance are compared with those of jet screech tones. The results obtained show that the transonic resonance is different in characteristics from jet screech tones. It is also found that unlike screech frequency, the transonic resonance frequency somewhat increases with increasing the nozzle pressure ratio, and the transonic resonance takes place in two stages.

Effect of Mesh Screen Device on Over-Expanded Supersonic Jet Noise

Yong-Hun Kweon(권용훈),Jae-Hyung Kim(김재형),Chae-Min Lim(임채민),Toshiyuki Aoki(靑木俊之),Heuy-Dong Kim(김희동) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

This paper describes an experimental work to investigate the effect of mesh screen device on the jet structure and acoustic characteristics of over-expanded supersonic jet. The mesh screen device is placed into the supersonic jet stream. In order to perturb mainly the initial jet shear layer, the hole is perforated in the central part of the mesh screen. The diameter of the perforated hole and the location of mesh screen device are varied. A Schlieren optical system is used to visualize the flow fields of supersonic jet without and with the mesh screen device. Pitot pressure measurement is carried out to obtain the pressure distribution in the jet flow. Acoustic measurement also is performed to obtain the OASPL and noise spectra. The results obtained show that the jet structure and the jet noise control effectiveness is strongly dependent upon the diameter of the perforated hole and the location of the mesh screen device in the jet stream. Provided that the mesh screen device is placed at the location to perturb effectively the initial shear layer, the present control method is effective in suppressing the supersonic jet noise.

소음 저감 장치를 통한 공압 시스템 배기 소음 분석

안민형(Min-Hyeong Ahn),이승열(Seoung-Ryeol Lee),김지훈(JiHun Kim),신동준(Dong-Jun Shin),유재영(JaiYoung Ryu) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

Pneumatic systems are devices that use compressed air to transmit and control power, which are used in pneumatic artificial muscles and cause loud noises. The exhaust noise characteristics of pneumatic systems with or without noise reduction devices were experimentally analyzed. The noise reduction device mimicked the shark gill structure, exhausting the compressor pressure from the initial 8 bar to the final 2 bar, and varying the measurement position according to the angle and distance for close noise analysis. When equipped with a noise reduction device for non-uniformly dense porous cells, the noise reduction effect was approximately 18 dB compared to when the device was not present. Noise reduction devices for homogeneous porous cells showed little reduction in exhaust rate compared to non-uniform porous cell devices, and noise was reduced by about 20 dB compared to those without devices.

초음속 제트의 스크리치 톤에 관한 실험적 연구

임채민(Chae-Min LIM),권용훈(Yong-Hun KWEON),?木俊之(Toshiyuki AOKI),김희동(Heuy-Dong KIM) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

The effects of nozzle-lip thickness on the relationship between screech tone and broadband shock-associated noise were experimentally investigated using a convergent-divergent nozzle with a design Mach number of 2.0. Overall sound pressure levels (OASPL) and noise spectra were obtained at far-field locations. Schlieren optical system was used to visualize the flow-fields of supersonic jets. A baffle plate was installed at the exit of the nozzle and its size was varied to obtain different nozzle-lip thicknesses. Experiment was carried out over a wide range of nozzle pressure ratios from 2.0 and 18.0, which corresponds to over- and underexpanded conditions. The results obtained clearly show that the screech tones are influenced by the nozzle-lip thickness. It is found that the screech tone and its peak amplitude are strongly dependent on whether the jet is over-expanded and under-expanded at the nozzle exit.

Control of the Supersonic Jet Noise Using a Wire Device

권용훈(Yong Hun Kweon),임채민(Chae Min Lim),靑木俊之(Toshiyuki Aoki),김희동(Heuy Dong Kim) 한국가시화정보학회 2004 한국가시화정보학회 학술발표대회 논문집 Vol.- No.-