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축류 팬의 공력 성능과 소음 성능을 향상시키기 위한 케이싱 펜스의 적용
박근태(Keuntae Park),최해천(Haecheon Choi),최석호(Seokho Choi),사용철(Yongcheol Sa) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
A casing fence is a newly proposed casing treatment to enhance the aerodynamic and aeroacoustic performances of the axial flow fan that exhausts air into the atmosphere for cooling and ventilation. In the present study, the fence is applied on the shroud near the trailing edge of an axial flow fan used in an outdoor unit of an air conditioner operating at the design condition. The Reynolds number of the fan is 547,000 based on the radius of the blade tip and the tip velocity. We simulate turbulent flows and acoustic fields in the fan using large eddy simulation (LES) coupled with Ffowcs-Williams Hawkings (FW-H) equations. From the numerical simulations with the casing fence, the efficiency of the fan is increased by about 9.5% and the propagating noise is reduced by 0.5dB (A) compared with those without the fence. The fence decreases backflows induced by the tip-leakage vortex near the casing, suppressing the circumferential development of the tip-leakage vortex from the previous blade to the next blade. Also, it reduces the double-leakage tipclearance flow generated at the trailing edge of the blade tip. As a result, the blockage effect by the leakage flow is reduced and the efficiency is increased, and pressure fluctuations on blade surfaces due to the tip-leakage vortex are reduced, resulting in a reduction of the propagating noise.
유체-구조 연성해석을 이용한 능동/수동 유동제어방식이 결합된 고하중 축류 팬의 성능특성 연구
마상범,김광용,최재호,이원석 한국수소및신에너지학회 2017 한국수소 및 신에너지학회논문집 Vol.28 No.1
An investigation on aerodynamic performance of a highly-loaded axial fan has been conducted to find the effects of tip injection and casing groove on aerodynamic performance in this study. Three-dimensional Reynolds-averaged Navier-Stokes equations with k-ε turbulence model were used to analyze the fluid flow in the fan with Fluid-Structure Interaction (FSI) analysis. The hexahedral grid was used to construct computational domain, and the grid dependency test drew the optimal grid system. FSI analysis was also carried out to predict the deformation of rotor and stator blades, and the effect of deformation on the aerodynamic performance of axial fan was analyzed compared to the performance predicted without FSI analysis.
저소음형 축류 팬 개발을 위한 수치해석 연구PartⅡ : 팬의 주파수 별 음압 분포
남현택,전유선,김진택,이철형,선광명,이승로 한국기계기술학회 2020 한국기계기술학회지 Vol.22 No.2
PartI of this paper identified the location and size of the noise sources from the axial flow fans, and partII based on that, identified the magnitude of sound pressure from the case and the blade according to frequency in the range of 2200 Hz to 5000 Hz. The equation of Lighthill was used for calculation. Generally, when measuring noise, the analytical area was extended more than 1m from the outlet of the fan. To eliminate the effects of backflow coming from the rear of the fan, the analytical area was extended a little longer than 1m. From the results of the analysis, high noise occurs in the low frequency area, and the lower noise becomes in the high frequency area. The maximum sound pressure generated in the range of 2000Hz~5000Hz is 65dB at a distance of 1m and 82dB at the outlet of the fan. Noise of the fan mainly occurred around the blade and guide, and the noise decreased as the frequency increased between 2200Hz and 3400Hz, but the noise increased as the frequency increased between 3800Hz and 5000Hz.
전완호(W.H. Jeon),박창환(C.H. Park) 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.2
The Present work describes the prediction method for the unsteady flow field and the aeroacoustic noise of an axial fan which has 3 blades with high sweep angle. Unsteady Reynolds-averaged Navier-Stokes(URANS) and large eddy simulation(LES) numerical approaches were adopted for prediction of unsteady flow field around the axial fan. Ffowcs-Williams and Hawkings equation with dipole assumption was used to calculate the aeroacoustic sound generated from the axial fan. Although both URANS and LES offer good estimates of the overall sound spectrum including blade pass frequency, LES produces more accurate and reliable results especially for the prediction of broadband and tonal noise at high frequency range. Through fast Fourier transform(FFT) analysis of noise source strength, the noise source of tonal peak at 750Hz is identified as the vortex separation at 1/4 position of the blade tip. It is also found that the noise source of broadband peak between 1200Hz and 1400Hz is located from center of tip to trailing edge.
Wide Chord 팬에서 Stacking Line이 공력 성능에 미치는 영향
마상범(Sang-Bum Ma),김광용(Kwang-Yong Kim),이원석(Wonsuk Lee),최재호(Jaeho Choi),김용련(Yeong-Ryeon Kim) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.5
본 연구에서는 다단 천음속 Wide Chord 팬 첫 단 동익에서의 Stacking Line이 공력 성능에 미치는 영향에 대한 수치적 연구가 수행되었다. 천음속 Wide Chord 팬의 유동장을 해석하기 위해 3차원 Reynolds-averaged Navier-Stokes 방정식과 SST Reattachment Modification 난류모델을 사용하였다. 계산영역은 회전방향으로 주기조건을 부여하여 단일 유로로 구성하였고, 정렬 격자계를 사용하여 격자계를 구성하였으며 격자의존성 테스트를 통하여 최적의 격자수를 선정하였다. Stacking Line은 기준 형상의 동익 전연부 팁 부분을 기준으로 회전 방향 혹은 회전반대 방향으로 설정하였고, 각 형상의 설계 회전 속도와 탈설계 회전 속도에서 공력 성능을 기준모델의 성능과 비교분석하였다. In this research, an investigation on aerodynamic performance of a multi-stage transonic wide chord fan with various stacking lines has been conducted. To analyze fluid flow in the transonic wide chord fan, three-dimensional Reynolds-averaged Navier-Stokes equations with SST Reattachment Modification turbulence model were used as governing equations. A passage of the transonic wide chord fan was used to construct computational domain and the optimal grid system was selected through a grid dependency test. The stacking line of first rotor was set to forward or backward toward rotation axis at tip leading edge, and the aerodynamic performances of these models were compared with that of the reference model at design and off-design speeds.
설계 조건에서 작동하는 축류 팬 주위 익단 누설 유동의 큰 에디 모사
박근태(Keuntae Park),최해천(Haecheon Choi),최석호(Seokho Choi),사용철(Yongcheol Sa) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
An axial fan with a shroud generates complicated vortical structures by the interaction of the axial flow with the fan blades and duct near the blade tips. Large eddy simulation (LES) is performed for flow through a forward-swept axial fan, operating at the design condition of Re = 547,000 based on the radius of blade tip and the tip velocity. The present study predicts the mean values of the flow and head coefficients quite well as compared with the experimental measurements. It is found that two unsteady vortical structures are formed near the blade tip: the tip leakage vortex (TLV) and vortex ropes. The TLV is initiated near the leading edge, develops downstream, and impinges on the pressure surface of the next blade, where the pressure fluctuations and turbulence intensity become high. Vortex ropes are initiated at the aft part of the blade and they merge with TLV.
MPI 일방향통신을 이용한 축류 팬 주위 소음해석 병렬프로그램 최적화
권오경 ( Oh-kyoung Kwon ),박근태 ( Keuntae Park ),최해천 ( Haecheon Choi ) 한국정보처리학회 2018 정보처리학회논문지. 컴퓨터 및 통신시스템 Vol.7 No.3
Recently, noise reduction in an axial fan producing the small pressure rise and large flow rate, which is one type of turbomachine, is recognized as essential. This study describes the design and optimization techniques of MPI parallel program to simulate the flow-induced noise in the axial fan. In order to simulate the code using 100 million number of grids for flow and 70,000 points for noise sources, we parallelize it using the 2D domain decomposition. However, when it is involved many computing cores, it is getting slower because of MPI communication overhead among nodes, especially for the noise simulation. Thus, it is adopted the one-sided communication to reduce the overhead of MPI communication. Moreover, the allocated memory and communication between cores are optimized, thereby improving 2.97x compared to the original one. Finally, it is achieved 12x and 6x faster using 6,144 and 128 computing cores of KISTI Tachyon2 than using 256 and 16 computing cores for the flow and noise simulations, respectively.