• 한국유체기계학회 논문집
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• 제3권4호
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• pp.44-51
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• 2000

The present study has been conducted to design the high efficiency centrifugal compressor for a R134a turbo-chiller. The centrifugal compressor consists of an impeller with splitters, two vaneless diffusers, a low-solidity vaned diffuser and a volute. A cycle analysis program for a turbo-chiller was developed to obtain compressor design parameters and requirements. We have designed the high efficiency centrifugal compressor by applying the repeated design procedure including a meanline design, a 3D geometry generation and fluid dynamic loading calculations.

• 한국정밀공학회지
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• 제23권2호
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• pp.122-128
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• 2006

This study focuses on a performance improvement of the vent silencer using acoustic analysis. Since the vent silencer is generally used for a high level shock noise, it should be designed to reduce a wide frequency band noise. In the designing stage of the vent silencer, structural shapes of diffuser and splitter are the most significant design parameters. Effects of modifying the original structure of the diffuser and the splitter are analyzed and evaluated. From the results, It is found that the diffuser with two pipes and double-step structure more effectively reduces a wide frequency band noise but the increment of the number of splitters is not desirable.

• 한국추진공학회지
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• 제13권5호
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• pp.21-28
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• 2009

본 연구는 초음속 축소형 디퓨저의 설계 및 시동 특성에 영향을 주는 변수를 파악하기 위하여 상온의 공기와 질소 가스를 사용하여 실험을 수행하였다. 1차 노즐의 목 면적의 변화, 1차 노즐 전단의 압력 변화, 디퓨저 길이와 직경의 비($L_d/D_d$) 그리고 디퓨저의 팽창부 유 무에 따른 디퓨저의 시동 특성을 알아보았다. 실험 결과 1차 노즐의 직경이 감소할수록 디퓨저 시동압력은 증가하였으며, 디퓨저의 예측 모델과 비교하여 90~98%의 장치 효율을 확인하였다. 또한 $L_d/D_d$가 8.4이상인 디퓨저와 팽창부의 유 무에 관계없이 디퓨저는 정상적으로 시동하였다. 본 실험 결과는 실물형 고고도 환경 모사 장치의 개발에 있어서 기초 자료로 활용될 것이다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.142-148
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• 1998

Recently for the impressive gains of performance and efficiency over vaneless diffuser with apparently little or no loss in flow range, the use of LSVD(Low Solidity Vaned Diffuser) is well recommended. The experiments on the effect of the vane turning angle variation(positive, negative, zero) with other design parameters fixed on the performance and flow range were carried out. Diffuser with zero turning angle has the best characteristics in terms of performance and efficiency and The FFT results show the different frequency characteristics due to the vane turning angle in low flow range.

• 대한기계학회논문집B
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• 제39권5호
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• pp.435-441
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• 2015

본 연구에서는 원심압축기 임펠러와 디퓨져 블레이드 형상을 반응표면법과 다목적 유전알고리즘 기법을 사용하여 최적설계 연구를 수행하였다. 임펠러와 디퓨져의 블레이드 선단과 후단의 각도와 두께를 3 구간으로 나누어 설계변수로 적용하였으며 수치해석은 상용코드인 ANSYS CFX 를 사용하였다. 실험계획법 중 많이 사용되는 중심합성계획을 이용하여 총 45 개의 설계점에 대한 값을 계산하였다. 계산된 결과를 바탕으로 반응표면을 생성하였으며 반응표면은 최적형상의 임펠러와 디퓨져를 선정하는데 이용하였다. 최적설계의 전 과정은 ANSYS DX 를 사용하였으며, 최적화의 결과로 원심압축기의 주요 성능변수인 등엔트로피 효율과 압력회복계수가 각각 0.3%, 5% 향상된 임펠러와 디퓨져 블레이드 형상을 제시하였다.

• 한국유체기계학회 논문집
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• 제2권2호
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• pp.74-80
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• 1999

Recently, impressive gains of performance and efficiency with apparently little or no loss in flow range have been seen with the use of LSVD(Low Solidity Vaned Diffuser) over vaneless diffuser. Experiments of the effects of the vane turning angle variations(positive, negative, zero), with the other design parameters fixed, on the performance and flow range were carried out. Diffusers with a zero turning angle have the best characteristics in terms of performance and efficiency and the FFT results show different frequency characteristics due to vane turning angles in low flow range.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.15-20
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• 2006

Despite the fact that UFAD (Under Floor Air Distribution) systems have many benefits and are being applied in the field in increasing numbers, there is a strong need for an improved fundamental understanding of several key performance features of these systems. This study numerically investigates the effect of design parameters on the performance of UFAD, especially focused on thermal comfort. The design parameters considered in this study include supplied air temperature, supplied flow rate, diffuser shape, swirl, diffuser location, and floor-to-floor height. Also this study has compared UFAD with over head system, on the point of thermal comfort by evaluating PMV using radiative mean temperature, which shows how inadequate the evaluation of thermal comfort can be when radiation is neglected. Until now, the radiative temperature has been the missing link between CFD and thermal comfort, but the present study paves the way for overcoming this weakness.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.604-608
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• 2004

Experimental study was conducted to increase the oxygen transfer efficiency of air diffusers in clean water. By measuring the bubble size from the bubbly two-phase flow visualization with several air diffusers the size of air bubbles near the top surface of aeration tank seems to be independent on the diffuser types. Considering design parameters for the better breakup of larger bubbles around the air diffusers, advanced conceptual air diffusers using nozzle-type throat showing the higher oxygen transfer efficiencies were made.

• 대한기계학회논문집B
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• 제39권8호
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• pp.645-651
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• 2015

본 논문은 중앙구동 이젝터의 유량비에 미치는 설계변수의 영향에 대한 연구를 목적으로 한다. 중앙구동 이젝터의 설계변수는 구동노즐 출구 단면적 및 거리비, 디퓨저 출구 단면적비로 설정하였다. 실험장치는 가변노즐 이젝터, 전동 모터-펌프, 구동유체 저장수조, 제어판넬 그리고 고속 카메라 시스템으로 구성하였다. 유량비는 실험변수에 따라 측정되는 유입 공기량과 구동유체인 물의 유량을 이용하여 도출하였다. 유량비는 구동노즐 거리비와 혼합관 길이비가 커지면 증가하는 반면에, 구동노즐 면적비와 디퓨저 출구 면적비가 커지면 감소하였다.

• KSTLE International Journal
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• 제3권2호
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• pp.101-109
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• 2002

This paper presents the fabrication and performance inspection of a peristaltic micropump by flow simulation. The valve-less micropump using the diffuser/nozzle is consists of base plate, mid plate, top plate and connection tubes fur inlet and outlet. In detail, the base plate is composed of two diffuser nozzles and three chambers, the mid plate consists of a glass diaphragm for the volumetric change of the pumping chamber. The inlet and outlet tubes are connected at the top plate and the actuator fur pressing the diaphragm is located beneath the top plate. The micropump is fabricated on the silicon wafer by DRIE (Deep Reactive ion Etching) process. The pumping performances are tested by the pneumatic test rig and compared with the simulated results fur various dimensions of diffuser nozzles. The pumping characteristics of the micropump by the volumetric change at the pumping chamber is modeled and simulated by the commercial software of FLOW-3D. The simulated results shows that reverse flow is the inherent phenomena in the diffuser nozzle type micropump, but it can be reduced at the dual pumping chamber model.