• 한국유체기계학회 논문집
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• 제2권1호
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• pp.50-55
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• 1999

The performance of a centrifugal fan depends on the dimensional parameters of impeller, such as the inlet and exit diameter, area ratio, relative flow angles to the blade, and the number of blades. These design parameters, however, are inter-related, so it is very difficult to identify the effect of each parameter on the fan performance. In this experimental study the effects of the design parameters on the performance of a small centrifugal impeller being used for vacuum cleaners are investigated. A total of 30 shrouded impellers with 120mm diameter were tested and the results were non-dimensionalized to compare their performance.

• 한국유체기계학회 논문집
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• 제9권4호
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• pp.43-48
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• 2006

In this study, the effect of flow settling means on the performance of fan tester were numerically investigated by using a computational fluid dynamics(CFD). The airflow rate was calculated from the pressure differential across a flow nozzle in the measuring plane and the flow settling means were generally installed in the chamber of the fan tester to provide proper airflow patterns ahead of the measuring plane. The predicted nozzle differential pressures with uniform inlet velocities were compared with the values of the ANSI/AMCA 210-99 to verify the performance of the commercial CFD code CFX 5.6. The influence of flow settling means on the measurement of airflow rate in a fan tester were discussed with various porosities and inlet jet velocities. The results obtained show that the proper band of porosities exist to meet the AMCA standard in a specified inlet jet velocity.

• 한국유체기계학회 논문집
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• 제6권1호
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• pp.66-71
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• 2003

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 하계학술발표대회
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• pp.43-43
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• 2005

• 한국유체기계학회 논문집
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• 제2권3호
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• pp.45-51
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• 1999

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.

• 대한기계학회논문집B
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• 제25권10호
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• pp.1281-1292
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• 2001

Experiments were done for the comparison of performance and flow characteristics between a two -stage axial flow fan and a counter-rotating axial flow fan. Each stage of the two -stage axial flow fan used fur the present study has an eight bladed rotor and thirteen slater blades. The front and the rear rotor of the counter - rotating axial flow fan have eight blades each and are driven by coaxial counter ro latins shafts through a gearbox located between the rear rotor and the electric motor. Both of the two axial fan configurations have identical rotor blades and the same operating condition fur the one -to-one comparison of the two. Performance curves of the two configurations were obtained and compared by varying the blade pitch angles and axial gaps between the blade rows. The fan characteristic curves were obtained following the Korean Standard Testing Methods for Turbo Fans and Blowers (KS B 6311). The fa n flow characteristics were measured using a five-hole probe by a non-nulling method. The velocity profiles between the hub and tip of the fans were measured and analyzed at the particular operating condition s of peak efficiency, minimum and maximum pressure coefficients. The peak efficiency of the counter-rotating axial fan was improved about 2% respectively, compared with the two stage axial fan. At the minimum pressure coefficient point of the two stage axial fan, the fan inlet flow patterns show that axial velocity highly decreased in the vicinity of the blade tip region. Also, the reverse flow took place at the blade tip.

• 농업과학연구
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• 제19권1호
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• pp.97-102
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• 1992

동력경운기(動力耕耘機) 탑재용(搭載用) 디젤 기관(機關)은 정격출력(定格出力)에 작업(作業)할 때 과열(過熱)되어 농민(農民)들은 작업(作業) 시작전(始作前)에는 필(必)히 냉각수(冷却水)를 보충(補充)해야 하는 것으로 알고있다. 따라서 기관(機關)이 과열(過熱)되는 것을 해결(解決)하기 위해서는 냉각(冷却)시스템의 개선(改善)이 이루어져야 되는데 이를 위해서는 냉각(冷却)시스템의 기초적(基礎的)인 실험(實驗) 자료가 필요(必要)하다. 기관(機關)의 생산(生産)은 외국(外國)과의 기술(技術) 제휴(提携)에 의하여 제작(製作)하고 있어 자료(資料)가 부족(不足)한 실정(實情)이므로 적합(適合)한 설계(設計)를 위해서는 현재(現在)의 기관(機關)에 사용(使用)되고 있는 냉각(冷却)홴, 라디에타등(等) 냉각장치(冷却裝置)에 대한 실험(實驗)을 실시(實施)하였다. 그 결과(結果)를 요약(要約)하면 다음과 같다. 1. 동력경운기(動力耕耘機) 탑재용(搭載用) 7.5kW 디젤기관(機關)의 정격출력시(定格出力時)에 냉각(冷却)홴의 효율(效率)은 49.9%로 비교적(比較的) 양호(良好)하였다. 2. 기관(機關)의 정격출력(定格出力)(상용회전(常用回轉))시(時) 홴의 소요동력(所要動力)은 최대(最大) 0.5kW이었다. 3. 기관(機關)의 정격출력(定格出力)(상용회전(常用回轉))시(時) 홴의 송풍량(送風量)은 $12.9m^3/min$이었다. 4. 기관(機關)의 정격출력(定格出力)(상용회전(常用回轉))시(時) 홴의 송풍정압(送風靜壓)은 29.8mmHg이었다.

• 에너지공학
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• 제15권4호
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• pp.235-242
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• 2006

본 연구는 공기 열원 열펌프의 성능 향상을 위한 연구로써 제상 방법으로 고온냉매 우회방법을 사용하고 내부열교환기를 장착한 열펌프 시스템의 성능을 ISO5151의 표준제상 조건에서 실험하였다. 실험은 고온냉매 우회방법과 가장 일반적인 제상 방법인 시간주기 제상방법을 비교하였으며 착상 발생 후 압축기 출구의 고온냉매를 실외기 입구로 우회시킬 때 실외기 홴 속도를 정상속도에 대하여 0%, 30%, 60%, 90%로 변화 시키면서 열펌프의 성능변화를 관찰하였다. 연구결과 210분의 열펌프 가동시간 동안 고온냉매 우회방법은 시간주기 제상방법 보다 $2.2{\sim}6%$ 높은 평균 성능계수를 나타냈으며 고온냉매 우회방법에서는 실외기의 홴 속도가 60%일 때 가장 좋은 성능계수와 난방용량을 나타냈다.

• 한국소음진동공학회논문집
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• 제20권1호
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• pp.51-57
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• 2010

This paper presents temperature control of engine cooling system using a controllable magnetorheological(MR) fan clutch. An appropriate size of MR fan clutch is devised and modeled on the basis of Bingham model. Subsequently, an optimization to determine design parameters such as width of housing is undertaken by choosing the reciprocal of the controllable torque as an objective function. Under consideration of spatial limitation, design parameters are optimally determined using finite element analysis. A sliding mode controller is then designed to control the angular velocity of the MR fan clutch using experimentally determined parameters. The designed controller is experimentally implemented and control performances of the MR fan clutch system are evaluated.

• 한국유체기계학회 논문집
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• 제13권3호
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• pp.24-29
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• 2010

Axial fans for an air-conditioning unit are designed to equip the system with an expected flow-rate and low noise level by applying the blade design method of multi-sectioning and local camber generation. In this study, the distributions of chord length, stagger angle, and camber angle are globally and locally determined for the given specific speed, which is considered to be relatively high. The mock-up fans are observed to satisfy the aerodynamic performance and the noise level for the system simultaneously and discussed in terms of local flow patterns related to the emitted noise.