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작은 안내 깃이 붙은 원심형 임펠러의 소음 특성에 대한 연구
전완호,Jeon, Wan-Ho 한국유체기계학회 2001 한국유체기계학회 논문집 Vol.4 No.1
Centrifugal fans are widely used in industrial practices but the noise generated by these machines causes one of the most serious problems. In general, the centrifugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cutoff in the easing. However, only a few researches have been carried out on predicting the noise because of the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal fan, and to calculate the effects of small vanes that are attached in original impeller - Splitter impeller. We assume that the impeller rotates with a constant angular velocity and the flow field around the impeller is incompressible and inviscid. So, a discrete vortex method (DVM) is used to model the centrifugal fan and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The splitter impeller changes the acoustic characteristics as well as performance. Two-splitter type impeller and splitter impeller which splitter locates in jet region are good for acoustic characteristics.
전완호,Jeon, Wan-Ho 한국유체기계학회 2004 한국유체기계학회 논문집 Vol.20 No.3
In this paper, we identify the noise source and the path of a chiller. This chiller is newly developed for R-l34a refrigerant and 250 RT cooling capacity. The measured overall SPL of the developed turbo-chiller is about 100 dBA. Due to the high rotating speed of the centrifugal impeller, the nun noise source of the chiller is the blade passing frequency and its higher harmonics of the centrifugal impeller. This generated soundpropagates through the duct, and then transmits and radiates to the outer field. From the experiment, it is found that the high frequency noise is mostlytransmitted and radiated through the elbow duct, but the low frequency noise is transmitted and vadiated through the condenser wall. Therefore applying the absorbing material is an effective way of reducing the high and low frequency noise simultaneously. Measurement results show that the application of the sound absorbing material to the elbow duct reduced the overall sound pressure level by 4 dB compared to the 9 dBA reduction for the case of full enclosure. In order to control the generated noise, a dissipativetype silencer is also designed and tested. The silencer reduced the radiated noise about 7.5 dBA.
원심홴의 설계 변수가 홴의 성능과 소음에 미치는 영향의 수치적 연구
전완호,이덕주,Jeon, Wan-Ho,Lee, Duck-Joo 한국유체기계학회 1999 한국유체기계학회 논문집 Vol.2 No.3
Centrifugal fans are widely used and the noise generated by these machines causes one of the most serious problems. In general, the centrifugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cutoff in the casing. However, only a few researches have been carried out on predicting the noise due to the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal fan and to calculate the effects of rotating velocity, flow rate, cut-off distance and the number of blades and its effects on the noise of the fan. We assume that the impeller rotates with a constant angular velocity and the flow field around the impeller is incompressible and inviscid. So, a discrete vortex method (DVM) is used to model the centrifugal fan and to calculate the flow field. The force of each element on the blade is calculated with the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The cut-off distance is the most important factor effecting the noise generation. Acoustic pressure is proportional to 2.8, which shows the same scaling index as the experimental result. In this paper, the cut-off distance is found to be the dominant parameter offecting the acoustic pressure.
전완호,정기훈,이덕주,Jeon, Wan Ho,Chung, Ki Hoon,Lee, Duck Joo 한국유체기계학회 2000 한국유체기계학회 논문집 Vol.3 No.2
The present work describes the prediction method for the unsteady flow field and the acoustic pressure field of a ducted axial fan. The prediction method is comprised of time-marching free-wake method, acoustic analogy, and the Kirchhoff-Helmholtz BEM. The predicted sound signal of a rotor is similar to the experiment one. We assume that the rotor rotates with a constant angular velocity and the flow field around the rotor is incompressible and inviscid. Then, a time-marching free-wake method is used to model the fan and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The newly developed Helmholtz-Kirchhoff BEM lot thin body is used to calculate tile sound field of the ducted fan. The ducted fan with 6 blades is analysed and the sound field around the duct is calculated.
전완호(Wan-Ho Jeon),김창준(Chang-Joon Kim),류호선(Ho-Seon Rew) 한국유체기계학회 2001 유체기계 연구개발 발표회 논문집 Vol.- No.-
A new method to calculate the aeroacoustic pressure of a centrifugal fan was developed. The fan consists of an impeller, diffuser and circular casing. Due to the high rotating velocity and the small gap between the impeller and diffuser, the centrifugal fan makes very high noise level at BPF and its harmonic frequencies. The aeroacoustic pressure is calculated acoustic analogy. In this paper, only dipole term is considered in the equation. The acoustics generated by moving impeller and stationary diffuser is calculated separately. The unsteady flow field data is calculated by the vortex method. The predicted acoustic pressure agrees very well to the measured data. The difference of the two is smaller than 3㏈A.
재생형 블로워에서 발생하는 비정상 유동과 유동 소음 특성에 관한 연구
전완호(Wan-Ho Jeon),임태균(Tae-Gyun Lim),이경근(Kyoung-Keun Lee),장춘만(Choon-Man Jang),이상문(Sang-Moon Lee) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.4
This paper shows the characteristics of the unsteady flow field and aeroacoustic noise of a regenerative blower. Three-dimensional Navier-Stokes equations were applied as a numerical solution to analyze the unsteady flow field with static pressure fluctuation on the impeller and an the casing. For computational study, it was predicted that the upper part of outlet region and the tips of blades are dominant aeroacoustic noise sources in the regenerative blower. The measurement data of sound camera indicates that the dominant noise source of the regenerative blower appears in the outlet region. In this study, the position of noise source and the characteristic of noise by using numerical solution were predicted and validated through comparison between experimental data and computational ones. It is represented as fundamental data which are able to be used to reduce the noise in a regenerative blower.
에어컨 실외기 내 축류팬 유동소음 예측을 위한 수치해석적 연구
전완호(Won-Ho Jeon),이여해(Yeohae Lee),임태균(Tae-Gyun Lim),박준철(Jun-Churl Park),Gaku Minorikawa 한국소음진동공학회 2016 한국소음진동공학회 학술대회논문집 Vol.2016 No.4
The current study investigates the aeroacoustic noise characteristics of two axial flow fans in outdoor unit of air conditioner by performing CFD (Computational Fluid Dynamics) simulation and CAA (Computational Aeroacoustics) method. The predicted aeroacoustic noise and the performances, obtained respectively from CAA and CFD results about axial flow fans, are in good agreement with the experimental results. Deviation of overall SPL (Sound Pressure Levels) between CAA results and the experimental ones represents 5% approximately, and follows qualitatively the trend within the relationship. Additionally, using CFD and CAA data helped to design the low noise fan because it can visualize regions that can be improved. As a result, overall SPL reductions of 2 dBA occurred. It is indicated that the overall SPL of existing model is 67.92 dBA and new model is 65.91 dBA respectively based on the CFD results. Therefore, CFD and CAA method can help the fan designer to design low noise axial flow fan.