• Journal of Advanced Marine Engineering and Technology
• /
• v.22 no.6
• /
• pp.800-808
• /
• 1998

In this study the thermal stress distribution and deformantion characteristics resulting from the nonuniform temperature fields of the cylinder block of a light 3-cylinder 4-stroke gasoline engine were analyzed using the 3-dimensional finite element method. The temperature distributions req-uisite for the thermoelastic behavior alalysis were obtained from the steady-state heat conduction analysis performed on the basis of experimental data. in order to examine the effect of a ceramic material the cylinder liner was replaced by the silicon nitride($Si_{3}N_{4}$) and its thermal behaviors were compared with those of the original block.

• Journal of Korea Foundry Society
• /
• v.22 no.4
• /
• pp.192-199
• /
• 2002

Dimensional defects of castings are mainly due to the stresses and strains caused by a nonuniform temperature distribution and phase transformation during solidification and cooling, and by mechanical constraint between the mold and casting. It is, however, nearly impossible to trace movements of the casting and mold during solidification and cooling by experimental measurements for castings with complex shape. Two and three dimensional deformation analyses of the casting and the mold were performed using commercial finite element code, MARC. It was possible to calculate deformation and temperature distribution in the casting and mold simultaneously. Cooling curves of the casting obtained by calculation were close to that measured in the field since it was possible to treat latent heat evolution of the casting which could be divided into two parts, primary and eutectic parts. Mold bent inward just after pouring due to the temperature gradient across the mold thickness, and mold returned to its previous position with time. Plastic deformation occurred at the part of the casting where solidification was slow.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.9
• /
• pp.82-88
• /
• 2006

In order to effectively reduce thermal loads on regenerative cooled walls, fuel cooling injectors and film cooling devices have often been employed. The present study has established a numerical methodology for prediction of performance and near-wall temperature distribution taking into account the nonuniform mixing due to these additional cooling devices. A correction procedure for main propulsive parameters has also been proposed based on comparison between prediction and experimental data. Under the computational framework of this study, the predicted results were in good agreement with hot-firing test data for a 30 tonf-class full-scale combustor at the design and off-design conditions. As a consequence, the present numerical method is expected to be useful for design and evaluation of regenerative cooled liquid rocket thrust chambers.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.309-312
• /
• 2000

Nonuniform temperature distribution due to hydration heat induces thermal stress in mass concrete. At early ages, such thermal stress may induce thermal cracks which can affect on the durability ad safety of the structure. Steel fiber reinforced concrete may be useful when a large amount of energy has to be absorbed, when a high tensile strength and reduced cracking are desirable, of an improvement of thermal conductivity is desirable. In LG IPP Project, the upper part(50cm) of turbine foundation was replaced with steel fiber reinforced concrete to reduce the thermal crack induced by hydration heat. It was shown that the thermal crack control could be successfully achieved by steel fiber reinforced concrete.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.9 no.4
• /
• pp.10-17
• /
• 2001

The performance of a radiator is generally determined using a wind tunnel, in which the air velocity is uniform. However, when it is installed in a car, the distribution of the air velocity becomes nonuniform due to front-end openings, cross members, and horns etc., resulting in lower performance. In this study, several underhood flow simulations have been first performed to get flow rates and velocity distributions over the radiator. Secondly heat release rates are calculated by both a performance curve and a radiator model. Finally, using an engine cooling system simulator, radiator-top-tank temperature is predicted and the variations of heat release rate and radiator-top-tank temperature with nonuniformity of air velocity distributions are analyzed. The results show that the current engine cooling model successfully accounts for the nonuniformity effects that should be considered for higher accuracy in predicting engine cooling performance.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.1
• /
• pp.53-61
• /
• 1997

The performance characteristics of magnetic fluid seals are studied numerically as a function of working gap, pole width, angle of pole sharpening, and shaft speed. The temperature distribution of a magnetic fluid seal with multiple tooth is investigated as a function of the contact fraction of magnetic fluids at the periphery of pole tooth using a finite element method. The most significant design parameter of a magnetic fluid seal is the working gap between the pole pieces and the rotating shaft. The result shows that with increasing the working gap, the friction torque decreases radically. The practical working gap for the pole pieces with triangular tooth zone profile is 0.2-0.4mm. The FEM results indicate that the optimal filling of a magnetic fluid between the pole pieces and the shaft is very important due to the accumulations of nonuniform friction heating within the pole pieces, which may interfere the magnetic circuit flow.

• 한국전산유체공학회:학술대회논문집
• /
• 2011.05a
• /
• pp.112-116
• /
• 2011

In this paper, a preconverter of MCFC for an emergence electric power supplier is numerically simulated to increase the hydrogen production from natural gas (methane). Commercial code is used to simulated the porous catalyst with user subroutine to model three dominant chemical reactions which are Stream Reforming(SR), Water-Gas Shift(WGS), and Direct Stram Reforming(DSR). To get 10% fuel conversion rate in preconverter. the required external heat flux is supplied from outer wall of preconverter. The calculated results show that very nonuniform temperature distribution and chemical reaction happen near the wall of preconverter. These phenomena can be explained by the low heat conductivity of porous catalyst and the endothermic reforming reaction.

• Nuclear Engineering and Technology
• /
• v.29 no.3
• /
• pp.186-195
• /
• 1997

When asymmetric thermal-hydraulic conditions occur between cold legs, the core inlet temperature will be nonuniform if the coolant is not mixed perfectly in the lower plenum. These uneven core inlet conditions may induce the change in core power distribution. Thus realistic prediction of thermal mixing is important in such abnormal conditions. In this study, reactor internals, which are scaled down as to conserve the flow area ratio, are set up in the model of KORI Unit 1 with the scaling factor of 1/710 by volume and coolant temperatures are measured beneath the lower core plate. Based on experimental results, the ability of COMMIX-1B code to simulate the coolant mixing phenomena in the lower plenum is estimated. The results show that complete mixing never occurs in any conditions and the mixing pattern is characterized according to the plant type.

• Steel and Composite Structures
• /
• v.32 no.6
• /
• pp.821-832
• /
• 2019

An analysis on thermal buckling and postbuckling of composite laminated plates reinforced with a low amount of graphene platelets is performed in the current investigation. It is assumed that graphaene platelets are randomly oriented and uniformly dispersed in each layer of the composite media. Elastic properties of the nanocomposite media are obtained by means of the modified Halpin-Tsai approach which takes into account the size effects of the graphene reinforcements. By means of the von $K{\acute{a}}rm{\acute{a}}n$ type of geometrical nonlinearity, third order shear deformation theory and nonuniform rational B-spline (NURBS) based isogeometric finite element method, the governing equations for the thermal postbuckling of nanocomposite plates in rectangular shape are established. These equations are solved by means of a direct displacement control strategy. Numerical examples are given to study the effects of boundary conditions, weight fraction of graphene platelets and distribution pattern of graphene platelets. It is shown that, with introduction of a small amount of graphene platelets into the matrix of the composite media, the critical buckling temperature of the plate may be enhanced and thermal postbuckling deflection may be alleviated.

• Journal of Welding and Joining
• /
• v.4 no.2
• /
• pp.30-39
• /
• 1986

In manufacturing of pipe walls for boiler units, distortion can result in pipe-web-pipe joints from the nonuniform expansion and contraction of the weld metal and the adjacent base metal during heating and cooling cycle of the welding process. In this study, the stresses and strains during longitudinal welding of the plate-to-pipe joint were investigated. Using the method of successive elastic solution, longitudinal stresses and strains during and after welding were calculated from the information of temperature distributions obtained by Rosenthal's equations. In order to confirm the validity of the numerical results, the temperature and residual stress distributions were measured and compared with the calculated results. In spite of some assumptions, the one-dimensional analytical results of residual stresses were in fairly good agreement with the experimental ones. The residual stresses due to welding of plate-to-pipe joints are tensile near the weld line and compressive in the base metal as in the welding of plates. the amount and distribution of residual stresses were deeply dependent on the heat input ratio of the plate and pipe.