(Device and method for gas-wiping zincgalvanized steel sheet)

본 발명은 용융금속 욕조(浴槽)를 통과한 용융도금강판을 서로 이격된 한 쌍의 에어나이프 사이로 통과시켜 분사 제트에 의해 용융금속을 일정량 제거할 수 있는 용융도금강판의 가스 와이핑 장치에 관한 것으로서, 특히 에어나이프의 상측에서 분사되는 중심제트를 이용하여 용융도금강판에 부착된 용융금속을 제거하도록 하고, 하측에서 분사되는 안내제트를 이용하여 중심제트의 유동을 안정화시키면서 충돌 제트 영역의 유동장을 균일하게 함으로써, 분사 제트의 에너지 손실을 줄이면서 용융금속의 제거 능력을 향상시킬 수 있고, 아울러 용융도금강판에 발생되는 표면 얼룩무늬 현상을 방지할 수 있는 효과를 얻을 수 있는 용융도금강판의 가스 와이핑 장치 및 방법에 관한 것이다

Device for preventing an edge-overcoating in zincgalvanized steel sheet

본 발명에 따른 용융도금강판의 단부 과도금 방지장치는 용융금속 욕조(浴槽)를 통과한 용융도금강판을 소정거리 이격된 한 쌍의 에어나이프 사이로 통과시켜, 분사 제트에 의해 용융금속이 박막의 도금층으로 제거되도록 하되, 상기 용융도금강판이 관통하는 제1대향영역에는 충돌제트가 형성되고, 상기 용융도금강판의 양단의 제2대향영역에는 비 충돌제트가 형성되어 와류가 방지되는 것을 특징으로 한다.본 발명은 용융도금강판이 통과되지 않는 에어나이프의 제2대향영역에는 코안다 효과(Coanda Effect)에 의하여 제트의 진행방향이 유도되도록 노즐출구에 접하는 실린더를 부착시킴으로써, 제2대향영역에서 두 분사제트의 충돌이 방지되도록 하고, 이로 인하여 용융도금강판 단부에서의 비정상(非正常) 와동이 방지되는 효과를 달성할 수 있으며, 결과적으로 용융도금강판 양단에서의 과도금현상이 발생되지 않는 균일한 품질의 제품을 제공하게 되는 효과를 얻을 수 있다

Analysis of Turbulent Gas-Particle Suspension Flows in a Venturi

A "two-fluid" equation model has been applied for predicting gas-solid suspension flows through a Venturi tube. In the "two-fluid"equation model, the bulk motion of the particles is considered as a continuum whose governing equation is obtained by averaging the conservation equations over a volume and expressing the equations in differential forms. Closure of the time-mean equations is achieved by modeling the turbulent correlations with an extended mixing-length theory. Proposed closure model is found to aptly simulate the dependency of the static pressure drop on the particle size, flow rate and the loading ratio.d the loading ratio

Experimental Study on the Turbulent Flow Field in a Sudden Expansion-Contraction Pipe Joint

The flow structure in a sudden expansion-contraction joint in a pipe is experimentally investigated. The turbulent velocity field is measured by using a single channel LDV system. Mathematical relations between forward-scattered signals from incident beams at three different angles permit measurements of Reynolds stress components, u2, v2 and uv. The static wall pressure distribution in the streamwise direction is also measured by tapping a number of small pressure holes in the expansion-joint wall. The expansion-joint length(L) to step height(H) ratios were L/H=5.45, 10.9 and 16.4. For the cases, L/H=5.45 and 10.9, the flows turn out to have cavity-like flow structure, whereas in the last case, L/H=16.4, the mean flow reattaches at about the distance 10.5 times the difference in radii of two pipes from the sudden expansion, and shortly later re-separates again to reach the exit of the expansion-joint. The profiles of the Reynolds normal stresses, u2 and v2, and the shear stress, -uv, are discussed in details in comparison with those of other axisymmetric sudden expansion flows

An Experimental Study of Turbulent Uniform Shear Flow in a Nearly Two-Dimensional 90 Curved Duct (1) Mean Flow Field

An experimental study is made in a nearly two-dimensional 90° curved duct to investigate the effects of interaction between streamline curvature and mean strain on turbulence. The initial shear at the entrance to the curved duct is varied by an upstream shear generator to produce five different shear conditions; a uniform flow(UF), a positive weak shear(PW), a positive strong shear(PS), a negative weak shear(NW) and a negative strong shear(NS). With the mean field data of the case UF, variations of the momentum thickness, the shape factor and the skin friction over the convex(inner) surface and the concave(outer) surface are scrutinized quantitatively in-depth. It is found that, while the pressure loss due to curvature is insensitive to the inlet shear rates, the distributions of wall static pressure along both convex and concave surfaces are much influenced by the inlet shear rates

Experimental Study on Local Convective Mass Transfer From a Circular Cylinder in Uniform Shear Flow

A naphthalene sublimation technique based on the heat/mass transfer analogy is used to investigate the circumferential mass transfer from a circular cylinder in an approaching uniform shear flow. Experiments are performed in a wind tunnel (450*450m $m^{2}$ with a shear flow generator which is specially manufactured for generating variable shear rates(S). The effects of an approaching shear flow are correlated with mass transfer coefficients. It is found that the local mass transfer rate on a circular cylinder is characterized with the shear parameter $K^{d}$ defined as Sd/ $U^{c}$ , where d is the radius of cylinder and $U^{c}$ is the approaching velocity at the center of cylinder. The angle on the corresponding to minimum Sherwood number is approximately proportional to the shear parameter on an upper and down number is approximately proportional to the shear parameter on an upper and down circular cylinder (0< $K^{d}$ <0.132). Changes on the averaged mass transfer rate are not significant for small $K^{d}$ , which are slightly proportional to K$d^{2}$ but the local mass transfer rates are significantly changed with the approaching shear flow

Comparative Study between the Centered Scheme and the Upwind Scheme for a Shock-Wave/Turbulent-Boundary-Layer Interaction

A comparative study of three different centered schemes (Beam-Warming, SIAF and LU-SGS) and an upwind scheme in computing the shock-wave/turbulent-boundary-layer interaction phenomena is made over a two-dimensional compression corner. The Baldwin-Lomax mixing length model is adopted to dosed the turbulent shear stress in the mass-averaged, two-dimensional compressible Navier-Stokes equations. Computations are performed for a Mach number of 2.90 with the Reynolds number Reδ (based on the incoming boundary layer thickness) of 1.6×106 for α=16 ramp. The upwind scheme is found to yield oscillation-free solutions around the shock while all of the centered schemes give oscillatory solutions. The present study leads us to believe that any centered difference scheme using scalar artificial dissipation should be suspect in predicting the shock-wave/turbulent-boundary-layer interaction problem