• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1548-1553
• /
• 2003

The design of a high speed axial piston pump for hydrostatic transmission systems requires specific understanding on where and how much its internal frictional and flow losses are generated. In this study, the frictional loss of a bentaxis type hydraulic piston pump was analyzed in order to find out which design factors influence the mechanical efficiency most significantly. To this end, the friction coefficients of the sliding components were experimentally identified by a specially constructed tribometer. Applying them to the three-dimensional dynamic model of the pump presented by Doh and Hong [1], the friction torques generated by the sliding components such as piston head , bearing and valve plate were theoretically computed. The accuracy of the computed results was confirmed by the comparison with the experimentally measured mechanical efficiency. In this paper, it is shown that the viscous friction on the valve plate and the drive shaft bearing is the primary sources of the frictional losses of the bent-axis type pump, while the friction forces on the piston contribute to them only slightly.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.5
• /
• pp.670-677
• /
• 1999

An analysis of generation and growth of multicomponent particles has been carried out to predict the size and composition distributions of particles generated in the Modified Chemical Vapor Deposition(MCVD) process. In MCVD process. scale-up of sintering and micro-control of refractive index may need the Information about the size and composition distributions of $SiO_2-GeO_2$ particles that are generated and deposited. The present work solved coupled steady equations (axi-symmetric two dimensions) for mass conservation, momentum balance. energy and species(such as $SiCl_4$, $GeCl_4$, $O_2$, $Cl_2$) conservations describing fluid flow. heat and mass transfer in a tube. Sectional method has been applied to obtain multi-modal distributions of multicomponent aerosols which vary in both radial and axial directions. Chemical reactions of $SiCl_4$ and $GeCl_4$ were included and the effects of variable properties have also been considered.

• Proceedings of the Korea Water Resources Association Conference
• /
• 1993.07a
• /
• pp.483-490
• /
• 1993

This paper presents the results of a study conducted to improve the understanding of the characteristics of cylindrical capsule flow in a pipeline by taking into account of the effect of capsule density uniformity. The effect of capsule density variation in the axial direction was studied both experimentally and analytically. The experiments were xonducted in a 190mm diameter straight pipe 18m long. The velocity, tilt of capsules and the gap between the capsule bottom and the pipe bottom were measured under various conditions. In order to interpret the data on the various capsule density conditions, the stability index given in the dimensionless numberwas introduced. The motion of capsules in pipelines is strongly affected by the stability of the capsules characterized by the stability index. The experiments conducted proved that the stability index is a valid criterion for explaining and correlating data on the capsule motion and the capsule density uniformity.

• Journal of the Korean Society of Combustion
• /
• v.7 no.2
• /
• pp.62-68
• /
• 2002

To investigate statistics of flamelet in a turbulent premixed flame and to obtain components of their burning velocities in a vertical plane above a pipe-flow burner, the local motion of flamelets with respect to gas are measured by specially arranged diagnostics, composed of an electrostatic probe with four identical sensors and a two-color four-beam LDV system. With this technique, the three-dimensional local flame- front-velocity vector is measured by the electrostatic probe for the first time, and simultaneously the axial and radial components of the local gas-velocity vector in a vertical plane above the vertically oriented burner are measured by the LDV system. Two components of burning velocities of planar flamelets can be obtained from these results and are found to be distributed over different directions and to range in magnitude from nearly zero to a few times the planar, un strained adiabatic laminar burning velocity measured in the unburnt gas. It may be concluded from these results that turbulence exerts measurable influences on flamelets and causes at least some of them to exhibit increased burning velocity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.705-709
• /
• 2002

The spacer grids in nuclear fuel assembly locate and align the fuel rods with respect to each other. They provide axial and lateral restraint against an excessive rod motion mainly caused by coolant flow. It is understood that each rod Is supported by multiple spacer grid. In such a case, it is important to determine spacer grid span so as to avoid resonance between the natural frequency of the fuel rods and excitation frequency. Actually dynamic characteristics of the fuel rods can be improved by assigning adequate spacer grid locations. When a dynamic performance of the structure is to be improved, design sensitivity analysis plays an important role as like many structural redesign problems. In this work, a shape design concept, different from conventional design, was applied to the problem. According to the theory shape can be a design parameter and optimal shape design can be found. This study concentrates on eigenvalue design sensitivity of the fuel rod supported by multiple spacer grids to determine optimal spacer grids positions.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.3
• /
• pp.303-315
• /
• 1998

Numerical and experimental studies on a heat pipe with two heat sources have been performed to investigate the operating characteristics. Numerical analysis was performed based on the cylindrical two-dimensional incompressible laminar flow for the vapor space and the conjugate heat transfer for the entire heat pipe. Experimental study with a 0.45 m length copper-water heat pipe was also performed to validate the numerical modeling for the heat input range from 29 W to 47 W on each heater. As results, the temperature profiles at the outer wall for the single active heat source as well as the temperature profiles for the switching operation between two heat sources are suggested. Due to the axial conduction, it is found that the temperature drop between the evaporator and the condenser appears small when the heat source closer to the condenser is turned on. For the switching operation in the present study, the transient time is about 700s and the temperatures at the locations of both heat source are same in 130s after switching.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.5 s.98
• /
• pp.586-594
• /
• 2005

In this paper, we studied about the effects of the rotating cantilever pipe conveying fluid with a moving mass. The influences of a rotating angular velocity, the velocity of fluid flow and moving mass on the dynamic behavior of a cantilever pipe have been studied by the numerical method. The equation of motion is derived by using the Lagrange's equation. The cantilever pipe is modeled by the Euler-Bernoulli beam theory. When the velocity of a moving mass is constant, the lateral tip-displacement of a cantilever pipe is proportional to the moving mass and the angular velocity. In the steady state, the lateral tip-displacement of a cantilever pipe is more sensitive to the velocity of fluid than the angular velocity, and the axial deflection of a cantilever pipe is more sensitive to the effect of a angular velocity. Totally, as the moving mass is increased, the frequency of a cantilever pipe is decreased in steady state.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.19 no.3
• /
• pp.23-28
• /
• 2011

To secure basic data for intake port design, effects of a port masking on the part load performance were investigated in a 4 valve SI engine. For this purpose, 9 kinds of masking, which have different shapes and masking ratio, are applied to the engine intake system. The characteristics of the performance were estimated through mixture response test at various engine load and speed. The results show that NOx emission, one of indexes for stratification, increases considerably in spite of retarded spark timing due to the stratification which is caused by unequal flow distribution between the two intake ports. The mechanism of stratification by masking is different from axial stratification and the fuel entering through masked port plays a very important role in this stratification process. In conclusion, the port masking method could be easily applied to engine intake system and be very effective for inducing the stratified charging without the change of port design.

• Journal of Animal Environmental Science
• /
• v.20 no.4
• /
• pp.155-160
• /
• 2014

This study was researched for use by data for the improvement of ventilation system of optimum environmental control systems. The ventilation system for windowless swine housing was installed negative pressure system that circular pipe duct for inlet was installed on the ceiling and axial flow fan for exhaust was installed on the sidewall. The temperatures in the pen was measured using infrared thermography camera and thermocouple with data-logger. The temperature measurement points was selected by infrared thermography camera is alley (G), inlet (A), front-upper (B), front-lower (C), rear-upper (D), rear-lower (E), forward fan (F). The temperature measured at those selected points for temperature distribution was $28^{\circ}C$ that was maintained setting temperature in suitably. The temperature deviations of F point and A~E points in windowless swine housing was less then average $0.5^{\circ}C$. The result of air velocity of measured points was suitable to the breeding of pigs.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.5 no.2
• /
• pp.287-301
• /
• 2013

The present paper deals with the problems of yaw angle effects on podded propulsor performance. The study aims at providing insights on characteristics of podded propulsors in azimuthing condition. In this regard, a wide numerical simulation that concerned yaw angle effect measurement on podded propeller performance was performed. The Reynolds-Averaged Navier Stokes (RANS) based solver is used in order to study the variations of hydrodynamic characteristics of podded propulsor at various angles. At first, the propeller is analyzed in open water condition in absence of pod and strut. Next flow around pod and strut are simulated without effect of propellers. Finally, the whole unit is studied in zero yaw angle and azimuthing condition. Structured and unstructured mesh techniques are used for single propeller and podded propulsor. The performance curves of the propeller obtained by numerical method are compared and verified by the experimental results. The characteristic parameters including the torque and thrust of the propeller, the axial force and side force of unit are presented as function of velocity advance ratio and yaw angle. The results shows that the propeller thrust, torque and podded unit forces in azimuthing condition depend on velocity advance ratio and yaw angle.