Lattice-Boltzmann Method를 이용한 이중구조팬의 공력소음 해석 및 저감

Abstract

최근 가전제품에 팬 블레이드의 허브측과 팁측이 서로 다른 형태를 갖는 이중구조팬이 등장하고 있다. 각 제조사들은 이러한 이중구조팬이 고압, 고유량, 저소음이라 주장하지만 이를 뒷받침할 만한 근거 자료나 연구결과는 아직 미비한 상태이다. 본 연구에서는 전산해석을 수행하여 이중구조팬의 소음원과 소음특성을 규형하기 위해 Band pass filter와 dBmap을 활용하였다. 전산해석에는 LBM(Lattice Boltzmann Method)를 이용한 비정상 전산해석을 수행하였으며 전산해석 결과의 검증을 위하여 KS B 6311에 따른 팬의 성능시험과 KS B 6361에 따른 팬의 소음시험을 수행하였다. 그 결과 전산해석결과와 매우 유사한 경향성을 갖는 것을 확인하였다. 전산해석 결과 이중구조팬은 일반적인 팬처럼 단일의 BPF(Blade Passing Frequency)를 갖는 것이 아니라 내부팬과 외부팬 각각의 BPF가 서로 다른 음역대에서 나타나는 것을 확인 하였다. 주된 소음원으로는 외부팬의 깃끝, 내부팬과 외부팬을 구분짓는 링, 내부팬의 뒷전인 것을 확인하였다. 내부팬 뒷전에서 발생하는 소음을 저감하고자 선행 연구들에 의해 소음저감 방법 중 하나로 알려진 톱니형 뒷전(Serrated Trailing Egde)을 내부팬에 적용하여 블레이드의 구속와류에 의해 발생하는 뒷전에서의 와류흘림이 억제 또는 분산되어 광역소음뿐만 아니라 팬의 토크도 저감되는 것을 확인하였다.| Efforts have been undertaken in last years to better understands noise reduction in fan applications. As one method, the developments of dual type combined fan have been pushed strongly by home appliance manufacturers. the dual type combined fan is known for higher pressure, mass flow, lower noise characteristics. However, no detailed discussions of the its performance regarding noise reduction have been provided. In this paper, aeroacoustics characteristics of the fan was studied using Computational Fluid Dynamics, and Band pass filter, dBmap were used to find out noise-sources. Unsteady simulation or calculation was conducted using LBM. KS B 6311 and KS B 6361 were referred to validate the CFD result, and the results between CFD and experiments had similar tendency. As the result, the dual type combined fan had the different BPF between the inner fan and outer fan unlike general fan. Tip of outer fan, ring, trailing edge of inner fan were the main noise-sources. Serrated Trailing Edge was applied at the inner fan to reduce the noise of trailing edge, and this method has used in many references. Finally, broadband noise and torque were reduced by controlled and dispersed vortex-shedding, which is generated by the bound vortex of blades.; Efforts have been undertaken in last years to better understands noise reduction in fan applications. As one method, the developments of dual type combined fan have been pushed strongly by home appliance manufacturers. the dual type combined fan is known for higher pressure, mass flow, lower noise characteristics. However, no detailed discussions of the its performance regarding noise reduction have been provided. In this paper, aeroacoustics characteristics of the fan was studied using Computational Fluid Dynamics, and Band pass filter, dBmap were used to find out noise-sources. Unsteady simulation or calculation was conducted using LBM. KS B 6311 and KS B 6361 were referred to validate the CFD result, and the results between CFD and experiments had similar tendency. As the result, the dual type combined fan had the different BPF between the inner fan and outer fan unlike general fan. Tip of outer fan, ring, trailing edge of inner fan were the main noise-sources. Serrated Trailing Edge was applied at the inner fan to reduce the noise of trailing edge, and this method has used in many references. Finally, broadband noise and torque were reduced by controlled and dispersed vortex-shedding, which is generated by the bound vortex of blades.