• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1399-1406
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• 1988

Flow behaviors of the open channel type flow with its geometric boundary conditions being similar to that of the Multi-Stage-Flash evaporator were studied qualitatively by measuring the velocity distribution. Without a baffle, the flow was in the shape of a simple submerged plane wall jet. At the downstream of this flow, the jet boundary made sharp curve toward the free surface ; this is because the entrainment of the ambient liquid is restricted by the free surface boundary, similar to the Coanda effect. According to the experimental results the level of the free surface appeared to be the most important parameter. The flow with a baffle was in much complicated shape ; especially the recirculating region at the downstream free surface was detected according to the experimental conditions imposed. Inlet liquid velocity, heights of the liquid level and the baffle, and the opening heights of sluice gate of the entrance were the most important parameters in the baffle flow.

• Advances in aircraft and spacecraft science
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• v.9 no.5
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• pp.415-431
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• 2022

Secondary flows have a huge impact on losses generation in modern low pressure gas turbines (LPTs). At design point, the interaction of the blade profile with the end-wall boundary layer is responsible for up to 40% of total losses. Therefore, predicting accurately the end-wall flow field in a LPT is extremely important in the industrial design phase. Since the inlet boundary layer profile is one of the factors which most affects the evolution of secondary flows, the first main objective of the present work is to investigate the impact of two different inlet conditions on the end-wall flow field of the T106A, a well known LPT cascade. The first condition, labeled in the paper as C1, is represented by uniform conditions at the inlet plane and the second, C2, by a flow characterized by a defined inlet boundary layer profile. The code used for the simulations is based on the Discontinuous Galerkin (DG) formulation and solves the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the Spalart Allmaras turbulence model. Secondly, this work aims at estimating the influence of viscosity and turbulence on the T106A end-wall flow field. In order to do so, RANS results are compared with those obtained from an inviscid simulation with a prescribed inlet total pressure profile, which mimics a boundary layer. A comparison between C1 and C2 results highlights an influence of secondary flows on the flow field up to a significant distance from the end-wall. In particular, the C2 end-wall flow field appears to be characterized by greater over turning and under turning angles and higher total pressure losses. Furthermore, the C2 simulated flow field shows good agreement with experimental and numerical data available in literature. The C2 and inviscid Euler computed flow fields, although globally comparable, present evident differences. The cascade passage simulated with inviscid flow is mainly dominated by a single large and homogeneous vortex structure, less stretched in the spanwise direction and closer to the end-wall than vortical structures computed by compressible flow simulation. It is reasonable, then, asserting that for the chosen test case a great part of the secondary flows details is strongly dependent on viscous phenomena and turbulence.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.405-408
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• 2005

A theoretical analysis is developed for an annular injection type supersonic ejector having a second-throat downstream under the assumption that the Fabri-chocking is placed in mixing chamber. Non-mixing theory is applied to formulate secondary flow pressure in the region between inlet of the mixing chamber and Fabri-chocking. To describe the shock standing at the inlet of the mixing chamber, two dimensional oblique shock relations are used and it is assumed that the shock affects only primary flow at Fabri-chocking plane. In conclusion, it agrees well with experiments in case of small contracting angle of mixing chamber, under 4degrees.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.2
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• pp.267-278
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• 1996

Steady, laminar, forced convection flow and heat transfer in the entrance region of an internally finned circular duct with a finite thermal conductivity has been analyzed numerically. The problem under investigation is a three-dimensional boundary layer problem, and is solved by employing a marching-type procedure which involves solution of a series of 2-dimensional elliptic problems in the cross-stream plane. Two types of inlet hydrodynamic conditions are considered : (a) uniform velocity flow and (b) fully developed flow. From the above inlet conditions, the effects of the fin height(h), fin number(N) and conductivity ratio($k_r$) on the flow and thermal characteristics are investigated. The numerical results show that the height and number of fins, and ratio of the solid to fluid thermal conductivity have pronounced effect on the solution. Considering pressure drop, optimized dimensionless fin height is 0.4.

• Journal of Environmental Science International
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• v.23 no.6
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• pp.1151-1156
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• 2014

The photocatalytic decomposition characteristics of single n-pentane, n-pentane mixed with methyl ethyl ketone (MEK), and n-pentane mixed with ethyl acetate (EA) by cylindrical UV reactor installed with $TiO_2$-coated perforated plane were studied. The effects of the residence time, the inlet gas concentration, and the oxygen concentration were investigated. The removal efficiency of n-pentane was increased with increasing the residence time and the oxygen concentration, but decreased with increasing the inlet concentration of n-pentane. The photocatalytic decomposition rates of single n-pentane, n-pentane mixed with MEK, and n-pentane mixed with EA fitted well on Langmuir-Hinshelwood kinetics equation. The maximum elimination capacities of single n-pentane, n-pentane mixed with MEK, and n-pentane mixed with EA were obtained to be $465g/m^3{\cdot}day$, $217g/m^3{\cdot}day$, and $320g/m^3{\cdot}day$, respectively. The presence of coexisting MEK and EA vapor had a negative effect on the photocatalytic decomposition of n-pentane and the negative effect of MEK was higher than that of EA.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.600-605
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• 2012

In this paper, the acoustic performance of a shipboard large-sized room unit is studied. The room unit is a kind of rectangular absorptive chamber with a partition whose surface absorptive material with fabric skin is attached to. The room unit has one inlet and three outlet. At the inlet, a plane damper is installed to control the flow rate. The acoustic performance of a prototype room unit is measured using a HVAC mock-up. It is shown that its insertion loss is comparable with that of a commercially-used room unit but the developed room unit generates flow noise higher than the other one. The major source of flow noise is analyzed by NADS-R, the noise analysis program for room unit. Cone-shaped dampers are proposed to be used as the damper of a room unit to reduce flow noise. It is shown that the cone-shaped damper decrease flow noise remarkably.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.5
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• pp.468-473
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• 2012

In this paper, the acoustic performance of a shipboard large-sized room unit is studied. The room unit is a kind of rectangular absorptive chamber with a partition whose surface absorptive material with fabric skin is attached to. The room unit has one inlet and three outlets. At the inlet, a plane damper is installed to control the flow rate. The acoustic performance of a prototype room unit is measured using a HVAC mock-up. It is shown that its insertion loss is comparable with that of a commercially-used room unit but the developed room unit generates flow noise higher than the other one. The major source of flow noise is analyzed by NADS-R, the noise analysis program for room unit. Cone-shaped dampers are proposed to be used as the damper of a room unit to reduce flow noise. It is shown that the cone-shaped damper decrease flow noise remarkably.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.308-312
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• 1999

Developed the model equations which calculate roll force, roll power during hot rolling in real time. The variables which mainly effect on the roll force, roll power are shape factor, reduction, roll diameter, roll velocity, strip inlet temperature, carbon content of strip and strip-roll contact friction coefficient. Among these variables roll diameter, roll velocity, inlet temperature, carbon content and friction coefficient can be excluded in interpolated model equation by introducing equation of die force(F'), power(p') of the frictionless uniform plane strain compression which can be calculated without iteration. At the case of coulomb friction coefficient of 0.3, we evaluated coefficient of polynomial equations of {{{{ { F} over {F' } }}}}, {{{{ { Pf} over {Pd }, { Pd} over {P' } }}}} from the result of finite element analysis using interpolation. It was found that the change of values of {{{{ { F} over {F' }, { P} over {P' } }}}} with the friction coefficient tend to straight line which slope depend only on shape factor. With these properties, developed model equations could be extended to other values of coulomb friction coefficient. To verify developed roll force, roll power model equation we compared the results from these model equation with the results from these model equation with the results from finite element analysis in factory process condition.

• Plant Journal
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• v.6 no.2
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• pp.62-69
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• 2010

The stability of coal pulverizer in the 800 MW coal-fired plants is vital to maintain their performance. Thus, this study analyzed the uneven abrasion of the deflector and coal spillage due to the air velocity maldistribution in the vane wheel of a bowl-type pulverizer as it is a possible cause for problems of facility using pulverized coal. In addition, air flow in the underbowl of a bowl-type pulverizer was studied to check air velocity maldistribution in the vane wheel using numerical method. In an attempt to correct the maldistribution of air velocity, air flow of the modified duct vane was studied as enlarging the length of the duct vanes installed at the air inlet duct of the pulverizer and increasing the angle of inclination. It was found that modified duct vane make the velocity distribution at the vane wheel uniform. formed by the duct vanes installed at the air inlet duct of the pulverizer and swirling flow is the major factor in making the velocity distribution of vane wheel exit uniform. This can prevent the uneven abrasion of the deflector, which is one of the components inside the pulverizer and coal spillage.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.150-156
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• 2008

A program based on a 2-D CFD code has been developed to simulate a gas turbine engine. 2-D Navier-Stokes implicit code with $k-\omega$ turbulent model is used in compressor and turbine. Lumped method chemical equilibrium code with 10 species of molecular is applied to combustor with assuming perfect mixture and 100% combustion efficiency at constant pressure state. Fluid properties are shared on interfaces between engine components. Compressor supplies outlet temperature and pressure to combustor. At the same time, combustor also carries temperature and pressure to turbine. The back pressure of compressor outlet is transferred by inlet pressure of turbine. Unsteady phenomena in rotor-stator are covered by mixing-plane method. The running condition of engine can be determined only by given the inlet condition of compressor, the outlet condition of turbine, equivalence ratio and rotating speed.