• Journal of the Korean Vacuum Society
• /
• v.17 no.5
• /
• pp.400-407
• /
• 2008

In this study, Two dimensional spatial profile of electromagnetic field for capacitively coupled plasma source is calculated. Based on one dimensional fluid equation, spatial profile for the axial direction of electric field and conduction current density is firstly calculated. The two dimensional spatial profile for the electromagnetic field is calculated from solution of Maxwell equation that is expanded to power series for ${\omega}r/c$ into the radial direction.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1991.06a
• /
• pp.50-54
• /
• 1991

This paper shows the effect of axial profile on the elastohydrodnamic lubrication (EHL) behavior of axially profiled cylindrical roller. For two different type of profiles which have nearly similar elastostatic pressure distribution, the EHL results show large differences. Especially the difference in film shape is larger than that of pressure distribution. Therefore, the magnitude of the minimum film thickness should be a major criteria to design the axial profile of the roller and a new design procedure is presented which take into account the minimum film thickness as well as the pressure distribution.

• Journal of Mechanical Science and Technology
• /
• v.16 no.8
• /
• pp.1154-1164
• /
• 2002

Losses on the turbine consist of the mechanical loss, tip clearance loss, secondary flow loss and blade profile loss etc.,. More than 60 % of total losses on the turbine is generated by the two latter loss mechanisms. These losses are directly related with the reduction of turbine efficiency. In order to provide a new design methodology for reducing losses and increasing turbine efficiency, a two-dimensional axial-type turbine blade shape is modified by the optimization process with two-dimensional compressible flow analysis codes, which are validated by the experimental results on the VKI turbine blade. A turbine blade profile is selected at the mean radius of turbine rotor using on a heavy duty gas turbine, and optimized at the operating condition. Shape parameters, which are employed to change the blade shape, are applied as design variables in the optimization process. Aerodynamic, mechanical and geometric constraints are imposed to ensure that the optimized profile meets all engineering restrict conditions. The objective function is the pitchwise area averaged total pressure at the 30% axial chord downstream from the trailing edge. 13 design variables are chosen for blade shape modification. A 10.8 % reduction of total pressure loss on the turbine rotor is achieved by this process, which is same as a more than 1% total-to-total efficiency increase. The computed results are compared with those using 11 design variables, and show that optimized results depend heavily on the accuracy of blade design.

• The KSFM Journal of Fluid Machinery
• /
• v.3 no.2 s.7
• /
• pp.7-14
• /
• 2000

For a given axial turbine blade, reverse design method is developed to improve blade efficiency, optimize blade profile, or repair parts etc. In this process, design parameters for designing axial turbine blade are induced. The induced design parameters are as follows; ellipse at leading edge, radios of trailing edge, axial chord, tangential chord, wedge angle at the inlet, and unguided turning angle. Suction and pressure surfaces of turbine blade are described by cubic polynomials. Two sample blades we chosen and their blade profiles are measured at the mean radius. Values of design parameters for sample blades are obtained by the reverse design method. Re-designed blade profiles using calculated design parameters are compared with the measured data, and they show good agreement. So, the developed design method could be applied to design general turbine blades. Various blade shapes are designed, and they show that designed blade profiles can be adjusted by controlling design parameters.

• Tribology and Lubricants
• /
• v.23 no.5
• /
• pp.187-194
• /
• 2007

The profile of the roller in the axial direction is the main design factor in order to increase endurance life against the contact fatigue due to the stress concentration along the edge of the roller. Even under the elas-tohydrodynamic lubrication (ehl) conditions, the stress concentration along the edge of the roller greatly worsens the fatigue life both for the roller and contacting body. In this study, roller contacts of finite axial length are studied for the film thickness and pressure of ehl. For the real contact behaviors under the ehl conditions, multigrid and multi-level method is applied so that much higher loading conditions can be investigated. Several axial profiles of roller are investigated to verify how both ehl film and pressure are generated and some of them are recommended for the ehl contact condition.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.2
• /
• pp.243-253
• /
• 1999

The dual reciprocity boundary element method (DRBEM) is used to solve the Graetz problem of laminar flow inside circular duct. In this method the domain integral tenn of boundary integral equation resulting from source term of governing equation is transformed into equivalent boundary-only integrals by using the radial basis interpolation function, and therefore complicate domain discretization procedure Is completely removed. Velocity profile is obtained by solving the momentum equation first and then, using this velocities as Input data, energy equation Is solved to get the temperature profile by advancing from duct entrance through the axial direction marching scheme. DRBEM solution is tested for the uniform temperature and heat flux boundary condition cases. Local Nusselt number, mixed mean temperature and temperature profile inside duct at each dimensionless axial location are obtained and compared with exact solutions for the accuracy test Solutions arc in good agreement at the entry region as well as fully developed region of circular duct, and their accuracy are verified from error analysis.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.420-423
• /
• 2008

This present work is to find optimum design of a NACA65 axial fan blade with weighted average surrogate model. The numerical analysis by Reynolds-average Navier-Stokes equations with shear stress turbulence(SST) is discretized by finite volume approximations and solved on hexahedral grids for flow analysis. The blade aerodynamic shape is modified by six design variables for the optimization. The blade profile as well as stacking line is modified to enhance blade total efficiency. Six design variables, airfoil maximum camber, maximum camber location, leading edge radius, trailing edge radius, lean angle at 50% span and lean angle at 100% span, are selected for blade profile to enhance the total efficiency. The PBA model which is basically weighted average of the basis surrogates is used to find the optimal design in the design space from the constructed response surface model for the objective function. By the optimization, the total efficiency is increased by 1.4%.

• Steel and Composite Structures
• /
• v.45 no.5
• /
• pp.653-663
• /
• 2022

This study reports the results of a series of tests of pultruded glass fiber reinforced polymer (P-GFRP) box section composite profile columns, geometrically similar with/without concrete core, containing 0-1-2-3% steel fiber, with different lengths. The recycled steel wires were obtained from waste tyres. The effects of steel fiber ratio on the collapse and size effect of concrete filled P-GFRP columns under axial pressure were investigated experimentally and analytically. A total of 36 columns were tested under compression. The presence of pultruded profile and steel wire ratio were selected as the primary variable. The capacity of pultruded profiles with infilled concrete are averagely 9.3 times higher than the capacity of concrete without pultruded profile. The capacity of pultruded profiles with infilled concrete are averagely 34% higher than that of the pultruded profiles without infilled concrete. The effects of steel wire ratio are more pronounced in slender columns which exhibit buckling behavior. Moreover, the proposed analytical approach to calculate the capacity of P-GFRP columns successfully predicted the experimental findings in terms of both pure axial and buckling capacity.

• Journal of the Korean Vacuum Society
• /
• v.8 no.2
• /
• pp.172-179
• /
• 1999

The axial distributions of plasma density in a helical resonator plasma with the external magnetic field have been measured using Langmuir probes. Net RF power is set to 200W and chamber pressure is varied from 0.4 mTorr to 100mTorr there are three kinds of eternal magnetic field structure applied on the helical resonator plasma. One is a uniform magnetic field, the second is a positive gradient magnetic field and the third is a negative gradient magnetic field. In the three magnetic field structures, the negative gradient magnetic field is found to show the highest increase in plasma density on the substrate compared with other magnetic structures. Plasma density profile in helical resonator is well consistent with electromagnetic field pattern obtained by computer simulation. It is also found that axial magnetic fields do not affect plasma density distribution in the plasma reactor region, but induce the increase of plasma density in the process chamber region. In order to avoid the nonuniformity of radial density profile, weak magnetic fields under 100G are applied.

• Structural Engineering and Mechanics
• /
• v.72 no.1
• /
• pp.43-60
• /
• 2019

This paper presents a finite element model which can simulate the axial compression behavior of steel reinforced recycled concrete (SRRC) filled square steel tube columns using the ABAQUS software. The analytical model was established by selecting the reasonable nonlinear analysis theory and the constitutive relationship of material in the columns. The nonlinear analysis of failure modes, deformation characteristics, stress nephogram, and load-strain curves of columns under axial loads was performed in detail. Meanwhile, the influences of recycled coarse aggregate (RCA) replacement percentage, profile steel ratio, width thickness ratio of square steel tube, RAC strength and slenderness ratio on the axial compression behavior of columns were also analyzed carefully. It shows that the results of finite element analysis are in good agreement with the experimental results, which verifies the validity of the analytical model. The axial bearing capacity of columns decreased with the increase of RCA replacement percentage. While the increase of wall thickness of square steel tube, profile steel ratio and RAC strength were all beneficial to improve the bearing capacity of columns. Additionally, the parameter analysis of finite element analysis on the columns was also carried out by using the above numerical model. In general, the SRRC filled square steel tube columns have high bearing capacity and good deformation ability. On the basis of the above analysis, a modified formula based on the American ANSI/AISC 360-10 was proposed to calculate the nominal axial bearing capacity of the columns under axial loads. The research conclusions can provide some references for the engineering application of this kind of columns.