• 대한기계학회논문집B
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• 제31권4호
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• pp.357-366
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• 2007

The present study investigated local heat/mass transfer characteristics on the surface of the rotating turbine blade with various incidence angles. The experiments are conducted in a low speed annular cascade with a single stage turbine. The blade has a flat tip with the mean tip clearance of 2.5% of the blade chord. A naphthalene sublimation method is used to measure detailed mass transfer coefficient on the blade. At design condition, the inlet Reynolds number is $Re_c=1.5{\times}10^5$ which results in the blade rotation speed of 255.8 rpm. Also, the effect of off-design condition is examined with various incidence angles between $-15^{\circ}$ and $+7{\circ}$. The results indicated that the incidence angle has significant effects on the blade surface heat transfer. In mid-span region, the laminar separation region on the pressure side is reduced and the laminar flow region on the suction side shrinks with increasing incidence angle. Near the tip, the effect of tip leakage flow increases in span wise and axial directions as the incidence angle decreases because the tip leakage flow is formed near the suction side surface. However, the effect of tip leakage flow is reduced with positive incidence angle.

• Journal of Advanced Marine Engineering and Technology
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• 제20권3호
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• pp.74-81
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• 1996

The wave washer springs are widely used in non-return valves of fluid, especially in air check valves to confirm the rapid shut-off of valve propers. The stiffness of wave washer springs used in suction and exhaust valves of reciprocating air compressor play an important role on efficiency of the compressor. If the stiffness of the spring is too high, the pressure differences necessary to open the valves become high and the volumetric efficiency of cylinder decreasse. If the stiffness of the spring too low, the valve can not be closed rapidly and the inverse flow of air can take place. So, the optimum stiffness of valve spring is very important and it will be very helpful that the stiffness of wave washer springs to be used in suction and exhaust valves can be calculated in design stage of air compressor. In this paper the formula for calculating the spring constant of wave washer spring is introduced using bending and torsion theory of frames. The experiments are also carried out to measure the spring constants of several samples. It is proven that the calculated spring constants of wave washer springs are coincided well with measured values and that the formula presented in this paper for calculating the spring constants of wave washer spring is very useful for design of valves used in reciprocating air compressor.

• 유기물자원화
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• 제18권3호
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• pp.77-86
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• 2010

본 연구에서는 간접흡입식 풍력선별기의 모델에 대하여 폐기물의 선별특성을 전산유체역학적인 방법으로 고찰하여 폐기물 모델에 대한 적정한 항력계수 및 흡입풍속에 대한 결과를 얻었다. 개발중인 풍력선별기는 송풍기를 설치하여 공기를 사이클론 후단에서 흡입하는 방식으로 선별 폐기물이 송풍기 회전차를 통과하지 않는 특징이 있으며, 흡입구의 특성 및 배관의 압력손실이 선별효율에 큰 영향을 미칠 수 있다. 풍력선별기를 이용한 폐기물을 선별하기 위해서는 폐기물의 공기역학적 특성에 대한 사전연구가 필수적이다. 비닐의 경우 약 0.8~1.0 내외의 항력계수를 적용하는 것이 타당하며, 캔은 압축여부에 따라 차이가 있으나 0.2~0.7의 범위에 있다. 풍력선별기의 흡입유속에 따른 선별효율은 약 25~26 m/s의 흡입유속에서 가장 높은 효율을 얻었다. 흡입구의 형상, 이송덕트의 배관방법에 따라 압력손실이 발생하여 흡입유속이 변화하므로 표준화를 통해 적절한 설계가 가능하도록 지속적인 연구가 필요하다.

• 한국유체기계학회 논문집
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• 제2권3호
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• pp.24-29
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• 1999

The ASME strainers have been newly installed at the suction side of each reactor coolant pump to get rid of the foreign materials which may damage the pump impeller or interfere with the coolant path of fuel flow tube or primary plate type heat exchanger. The strainer was designed in accordance with ASME SEC. III, DIV. 1, Class 3 and the structural integrity was verified by seismic analysis. The screen was designed in accordance with the effective void area from the result of flow analysis for T-type strainer. After installation of the strainer, it was confirmed through the field test that the flow characteristics of primary cooling system were not adversely affected. The pressure loss coefficient was calculated by Darcy equation using the pressure difference through each strainer and the flow rate measured during the strainer performance test. And these are useful data to predict flow variations by the pressure difference.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1670-1675
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• 2004

A thermal vapor compressor in which the subsonic/supersonic flow appears simultaneously, has been accurately designed through the CFD analysis for the various shape parameters such as the primary nozzle shape, converging duct shape. mixing tube diameter, and so on. The performance of the developed thermal vapor compressor has been experimentally verified to be installed in a Multi Effect Desalination(MED) plant as an important element, In this paper, the experimental results for Various boundary conditions(motive pressure, suction pressure, and discharge pressure) are presented in comparing with CFD results. The two results show a good agreement with each other within 3.5 % accuracy with regard to the entrainment ratio.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.48-53
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• 2001

A centrifugal fan design code was developed and included in $DasignFan^{TM}$. This program generates forward -curved and backward-curved bladed centrifugal fan data. With the inverse design concept used in the code, the period of designing a fm, which has given aerodynamic performance with minimal acoustic noise, is significantly shortened.. A centrifugal fan design code, developed in this study and included in $DasignFan^{TM}$, predicts the aerodynamic performance by using mean-line analysis and various loss models. In the period of design a lift force distribution between pressure side and suction side of blade is calculated. And then it is used to calculate steady loading noise from the impeller.

• Journal of Advanced Marine Engineering and Technology
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• 제36권2호
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• pp.286-293
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• 2012

본 연구에서는 설계유량 $16m^3/h$에서 설계효율 90%와 설계양정 20m의 성능을 보이며, 3,500rpm 고정회전수로 작동하는 원심펌프 임펠러를 대상으로 단상류 유동해석을 수행하였다. 임펠러는 A.J. Stepanoff 경험식에 근거로 설계되었다. 단상류 해석의 경우, 설계유량에서 88.8%와 19.4m의 효율과 양정 결과를 보여주었고, 그 결과는 설계값과 상당히 일치하였다. 다상류 해석은 다양한 NPSH 조건하에서 수행되었으며, NPSH가 8.79m 일 때, 블레이드 부압면 근처에서 캐비테이션개시가 관찰되었다. 본 연구에서 설계된 임펠러의 필요흡입헤드는 대략 6.5m이며, 이 값 이상의 입구압력조건하에서 원심펌프는 작동되어야 할 것으로 판단된다.

• 한국추진공학회지
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• 제23권1호
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• pp.52-60
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• 2019

본 연구에서는 수치해석을 활용하여 여러 개의 이젝터로 구성된 병렬형 이젝터의 성능과 구조에 대한 특성을 확인하였다. 병렬 이젝터의 설계는 단일 이젝터와 동일한 설계 변수(질량 흡입비, 압축비, 팽창비)를 사용하였다. 해석 결과에 의하면, 병렬형과 단일 이젝터의 작동 질량 흡입비의 비가 같을 경우에는 성능에 있어 큰 차이를 보이지 않았으나, 시스템의 크기가 작아지는 이점이 있음을 확인하였다. 또한, 동일 성능의 이젝터를 병렬로 배치하였을 때는 질량 흡입비가 단일 보다 감소하여 더 낮은 압력을 구현하는 것을 확인하였다. 해석 결과를 종합하면 병렬형 이젝터 성능은 단일 이젝터와 크게 다르지 않으나, 병렬형 이젝터 구성에 따라서는 크기와 작동에 이점이 있음을 확인하였다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.335-338
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• 2006

A Numerical study of the cavitation within a centrifugal pump is carried out using CFD commercial code, FLUENT. The objective of this study is to predict the onset of cavitation within the pump blade and the degradation in the pressure rise due to the generation and transport of vapor. A pump designed for the study is a six bladed, one-circular arc impeller design suggested by A.J. Stepanoff et al. The Steady-state calculations are performed for a wide range of flow rate without the cavitation to investigate the pump performance. The design head and efficiency show a very good agreement with the numerical results at the design flow rate. After the validation with the numerical results, the pump performance and the onset of cavitation within the blade is predicted by changing NPSH at the design flow rate.

• International Journal of Fluid Machinery and Systems
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• 제7권1호
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• pp.28-33
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• 2014

In order to research the relationship between the tip clearance and leakage flow of centrifugal compressor, a high speed centrifugal compressor was investigated by using CFD. A numerical study on the effect of four different rotor tip clearance sizes of centrifugal compressor, which were 0.5times, 1 times, 1.5times and 2.0times of the design tip clearance, was carried out. Efficiency and pressure ratio curves were obtained under different mass flow. The reasons of the clearance vortex and the factors of vortex size were analyzed. The result indicated that with the increase of tip clearance size, the performance of the compressor changed obviously, the performance parameters such as efficiency and pressure ratio tended to decrease obviously. While, the leakage flow does not always lead to leak vortex. The strength of the vortex increased with the tip clearance. The size of leak vortex was affected by the pressure difference between the suction side and the pressure side of blade tip.