• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
• /
• pp.705-710
• /
• 2004

In the present study, a transient incompressible viscous turbulent flow is simulated for the automotive torque converter with moving mesh technique. For the analysis, entire torque converter flow passages are modeled. Computed torque ratio, capacity factor and efficiency show a good agreement with the experiment data. The flow instabilities characterized by back-flow and wake etc. appeared in some cascade passages are shown to be Propagating along tangential direction. These flow patterns are mainly influenced by the pump and turbine blade passing and can't be predicted through conventional steady simulation with a mixing plane approach. The understanding of the unsteady flow characteristics in a torque converter achieved in the present study may lead to the optimal design of a torque converter.

• 한국유체기계학회 논문집
• /
• 제9권5호
• /
• pp.36-41
• /
• 2006

In the present study, a transient incompressible viscous turbulent flow is simulated for the automotive torque converter with moving mesh technique. For the analysis, entire torque converter flow passages are modeled. Computed torque ratio, capacity factor and efficiency show a good agreement with the experiment data. The flow instabilities characterized by back-flow and wake etc. appeared in some cascade passages are shown to be propagating along tangential direction. These flow patterns are mainly influenced by the pump and turbine blade passing and can't be predicted through conventional steady simulation with a mixing plane approach. The understanding of the unsteady flow characteristics in a torque converter achieved in the present study may lead to the optimal design of a torque converter.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2006년도 PARALLEL CFD 2006
• /
• pp.87-89
• /
• 2006

• 동력기계공학회지
• /
• 제14권2호
• /
• pp.28-33
• /
• 2010

In this research, cascade liquefaction process was simulated using two-staged direct expansion with inter-cooler. Evaporated gaseous refrigerant which has low pressure and temperature from the inter-cooler is mixed with gaseous refrigerant from outlet of 1st compressor, and flows into 2nd compressor. Therefore this prevents superheating compression. Compressor work of process which includes inter-cooler to all cycles shows the lowest value of 338.68 MW and it is lower 16.34% than that of basic process. Refrigeration capacity shows decreasing tendency as applied inter-cooler and that of process which includes inter-cooler to all cycles shows the lowest value of 449 MW. COP was increased when the inter-cooler was applied, and process which includes inter-cooler to all cycles shows highest value of 1.33. It shows that COP was increased because decrement of compressor work by applying inter-cooler was higher than decrement of refrigeration capacity.

• 한국항공우주학회지
• /
• 제35권2호
• /
• pp.143-148
• /
• 2007

액체 추진 로켓을 구동하는 충동형 터빈은 크기가 작고 가벼워야 하며 큰 출력을 발생시켜야 한다. 충동형 터빈은 초음속 조건에서 작동되기 때문에 유동 특성이 매우 복잡하여 성능 예측은 주로 수치해석에 의존해 왔다. 그러나 신뢰성을 확보하기 위하여는 해석결과를 실험으로 검증하는 과정이 필요하다. 본 연구에서는 설계에 사용되는 주요 변수들의 영향을 확인하기 위하여 회전하는 3차원 축류 터빈을 2차원 형상으로 모사하여 실험하였다. 먼저 노즐 출구에서의 마하수를 측정하였으며, 이론적인 노즐 추력식을 유도하여 터빈 블레이드에 작용하는 깃하중을 계산하였고 측정된 결과와 비교하였다. 또한 추력 계수를 구하고 이를 통해 터빈 출력을 예측하여 설계 요구 조건의 타당성을 확인하였다

• 한국유체기계학회 논문집
• /
• 제13권1호
• /
• pp.42-51
• /
• 2010

Many different types of fan have been applying to various industrial fields. Fan design methods are much different depending on the types of fan, operating conditions, and connecting parts at the inlet or exit of the fan etc. In this study, design methods for an axial-type suction fan are studied. This fan discharges the air in the relative static pressure of -285Pa to the atmosphere with the flow rate of $960m^3/min$. For three-dimensional blade design, three different design methods were applied, such as the free vortex method, the exponential method, and the cascade method. In the cascade method, the blade loading along the radial direction was obtained from the lift coefficient which was necessary to obtain the pressure rise on a fan rotor. This method is different from the free vortex and the exponential method which control the strength of the vortex. The fan performance prediction was conducted using the CFD with three different inlet ducts. The best fan performance was obtained when the fan was designed by using the cascade method. The designed fan using the exponential method showed better performance compared to a fan designed using the free vortex method. However, the fan performance was changed depending on the installed inlet ducts. So, an efficient fan can be designed with the adjustment of design variables on the basis of the flow structures within the fan as well as the fan design procedure.

• 폴리머
• /
• 제35권6호
• /
• pp.574-579
• /
• 2011

자동차 선도장 강판을 위한 핵심 응용기술로서 3-롤코팅 공정을 연구하였다. 본 연구를 위한 3-롤코팅은 저장조로부터 코팅액을 끌어 올리는 pick-up롤, 적절한 코팅 두께로 계량시키기 위한 계량롤, 강판에 직접 코팅시키기 위한 applicator 롤로 구성되어 있다. 전단담화의 유변물성을 갖는 고분자 도료의 코팅 유동 특성과 코팅 운전 영역을 pickup 롤과 계량롤 사이의 속도비와 간격 등의 공정조건과의 상관관계를 통해 고찰하였다. 안정한 코팅 영역에서, 간격이 크거나 속도비가 작을수록 코팅 두께는 증가하였다. 또한, ribbing과 cascade라는 불안정성은 각각 속도비가 낮고 높을 때 관찰되었다. 특히, 속도비가 낮을때, ribbing의 파장과 심각도가 증가함을 확인하였다.

• 대한기계학회논문집
• /
• 제10권5호
• /
• pp.751-757
• /
• 1986

본 연구에서는 준 3차원 유동에서 문제가 되는 B-B 유동만을 대상으로 하고 여기에 두개의 유동함수를 이용해서 수치계산한다. 이 방법의 정당성을 입증하기 위해 계산결과를 이론해와 비교하고 또 실제유동과의 관계를 보기 위해 실험결과와도 비교하여 또 실제유동과의 관계를 보기 위해 실험결과와도 비교하여 Wu에 의한 정상 비점성 유동의 준3차원적 수치계산방법의 유효성을 제시한다.

• 대한기계학회논문집B
• /
• 제28권3호
• /
• pp.315-323
• /
• 2004

An electrical cascade impactor is a multi-stage impaction device to separate airborne particles into aerodynamic size classes using particle charging and electrical detection techniques. A Faraday cage and an aerosol charger, which are basic components of the electrical cascade impactor, were designed and evaluated in this study. The low-level current response of the Faraday cage was investigated with changing particle size and air flow rate by using sodium chloride (NaCl) particles. The response of the prototype Faraday cage was very similar to that of a commercial aerosol electrometer (TSI model 3068) within ${\pm}$5% for singly-charged particles. The response linearity of the prototype Faraday cage could be extended up to flow rate of 30 L/min. For the performance evaluation of the aerosol charger the monodisperse liquid dioctyl sebacate (DOS) particles, with diameters of 0.1∼0.8$\mu\textrm{m}$, were generated using spraying from an atomizer followed by evaporation-condensation process. Typical performance parameters of the aerosol charger such as P$.$n, wall loss, and elementary charges per particle were evaluated. The performance of the prototype aerosol charger was found to be close to that of the aerosol charger used in an electrical low pressure impactor (ELPI, Dekati).

• 한국전산유체공학회지
• /
• 제1권1호
• /
• pp.19-25
• /
• 1996

A multiblock grid generation has been developed to be reliably used for a Navier-Stokes simulation of the turbomachinery flow-fields A multiblock structure simplifies the creation of structured H-grids about complex turbomachinery geometries and facilitate the creation of a grid in the tip flow region. The numerical algorithm adopts the combination of the algebraic and elliptic method to create the internal grids efficiently and quickly. The grid refinement process is enhanced by developing strategies to utilized Bezier curves and splines along with weighted transfinite interpolation technique and by formulating the grid-imbedding method for the viscous boundary-layer meshes. For purposes of illustration, the grid generator is applied to the high turning turbine rotor blades. Two different types of computational grids are provided to be compared with respect to the grid adaptation to the flow simulations. Extension to three-dimensions was done to show the possibility of its application to the tip-flow simulations. The grid quality of the multiblock structure is good in the passages, with gloval orthogonality and adequate smoothness.