• Tribology and Lubricants
• /
• 제28권2호
• /
• pp.47-55
• /
• 2012

Generally, to product multi-grade oil like engine oil, a sort of mineral base oil is mixed with a fundamental additive package liquid and a polymer liquid as viscosity index improver in order to improve the lubricating property of base oil. That is, engine oil is the mixture of more than two fluids. Specially, a polymeric type liquid cannot be seen as the linear viscosity like Newtonian fluids. In this research, by using the governing equation describing non-Newtonian hydrodynamic lubrication related with the mixture of incompressible fluids based on the principle of continuum mechanics, it will be compared the bearing performance between the mixture of each liquid to be blended and multi-grade engine oil as a single fluid in a high speed hydrodynamic journal bearing. Further, it is to be found the way estimating the performance of the blended multi-grade engine lubricant in a journal bearing in advance before blending by using the physical properties of mineral base oil, fundamental additive liquid and polymer liquid of viscosity index improver. So, it can be reduced the number of trial and error to get the wanted lubricant by selecting the proper volume fraction of each liquid to satisfy the expected performance and estimating in advance the performance of various multi-grade oils before blending. Therefore, it can be shorten the developing time and saved the developing cost.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제15권2호
• /
• pp.78-83
• /
• 2007

An experimental study has been carried out to analyze the thermal stability and to estimate the lifetime of refrigerating lubricants. PAG and POE oil are considered as test oils in this study. The viscosity of PAG and POE oil was measured by the vibration type viscometer while temperature is varied periodically in the range of $0^{\circ}C{\sim}100^{\circ}C$. In order to estimate lifetime of PAG and POE oil with temperature, the viscosity was measured while the test temperature of oils was maintained continuously at $180,\;200\;and\;220^{\circ}C$. The lifetime of oils is estimated as the decrease in viscosity change by 15%. The results indicate that the reduction rates of viscosity of PAG and POE oil are less than 5% after 510 temperature variation cycles. However, when the oils are kept at high temperature, it is found that the lifetimes of PAG oil is seen to be 244, 177 and 89 hours at the test temperature of $180,\;200\;and\;220^{\circ}C$, respectively, where as the lifetimes of POE oil are estimated to be 1,744, 1,007 and 334 hours at the temperature of $180,\;200\;and\;220^{\circ}C$, respectively. Thus, the lifetime of POE oil is found to be much longer than that of PAG oil. The lifetime correlations of PAG and POE oil are also obtained by Arrhenius's equation method in this paper.

• 한국식품과학회지
• /
• 제46권3호
• /
• pp.295-302
• /
• 2014

본 연구에서는 저장 온도 및 기간에 따른 계란의 물리화학적 특성 변화를 관찰하고 이들과 신선도 및 전체적인 기호도 간의 상관관계 분석 및 최적 회귀모형 도출을 통한 적정 품질 지표를 규명하고자 하였다. 물리화학적 평가지표 중 중량감소율의 경우 저장온도가 증가할수록 유의적으로 증가하였으며, 비중, Haugh unit, 난황계수 및 난백계수의 경우 저장 온도가 증가할수록 유의적으로 감소하는 경향을 나타내었다. 난황의 경우 저장기간 및 온도에 따라 pH 값이 큰 차이를 나타내지 않은 반면, 난백의 경우 저장에 따라 pH가 증가하는 경향을 나타내었다. 난황점도의 경우에는 저장 기간에 따라 유의적으로 감소하였으며, 특히 저장 온도가 높아질수록 더 빠르게 감소하였다. 반면 난백점도, 색도 및 TBARS 값의 경우 저장 온도와 기간에 따라 큰 차이를 보이지 않았다. 상관분석 결과 신선도에 있어서는 중량감소율, Haugh unit, 난황계수, 난백계수, 난백 pH가 매우 밀접한 관련성을 나타내었고, 전체적인 기호도에 있어서는 중량감소율, Haugh unit, 난황계수, 난백계수가 매우 밀접한 관련성을 나타내었다. 상관분석 결과를 이용하여 회귀분석을 하였는데, 신선도와 전체적인 기호도 모두 중량감소율, 비중, 난황 pH 및 난황점도가 전체 모형의 89%를 나타내는 선형 회귀식이 도출되었다.

• Tribology and Lubricants
• /
• 제5권2호
• /
• pp.48-54
• /
• 1989

The effects of angular misalignment, coning and the temperature difference between the primary seal ring and the seal seat on the pressure distribution in mechanical face seals are analyzed. The modified Reynolds equation for the temperature dependent viscosity was solved by a finite difference approximation and Gauss-Seidel method. It is shown that the amplitude of pressure is significantly affected by the misalignment of the seals and a large temperature difference between the rotor and the stator.

• 호남수학학술지
• /
• 제36권4호
• /
• pp.755-766
• /
• 2014

In the discrete formulation of the bubble stabilized Legendre Galerkin methods, the system of equations includes the artificial viscosity term as the parameter. We investigate the estimation of this parameter to get the optimal solution which minimizes the maximum error. Some numerical results are reported.

• 대한수학회지
• /
• 제37권3호
• /
• pp.339-358
• /
• 2000

Let be a bonded domain in N with smooth boundary . In this paper, we consider the existence of solutions of the following problem: (1.1)-div{} - + = , , , , , , where q > 1, p$\geq$1, $\delta$>0, , the Laplacian in N and is a positive function like as .

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1995년도 하계학술대회 논문집 C
• /
• pp.1404-1406
• /
• 1995

In this paper, argon gas was used for numerical analysis of an arc in a cutting plasma torch driven by constant current. We established nozzle-constricting type torch domain and calculated steady state characteristics of argon arc plasma using the control volume method(CVM). For simplicity, we assumed that the flow field is laminar and the local thermodynamic equilibrium(LTE) prevails in all domain regions. We also neglected cathode-fall and anode-fall effects. Considering magnetic pinch effect and viscosity effect, we solved the momentum equation. Voltage drop in the arc column due to input current was calculated from the temperature field obtained by the energy balance equation.

• 설비공학논문집
• /
• 제7권2호
• /
• pp.329-340
• /
• 1995

Basic refrigeration effect and efficiency of a thermoacoustic refrigerator is studied. The refrigerator model for numerical simulation is composed of half wavelength resonator and appropriate stack of plate. Theoretical model for thermoacoustic refrigeration suggested by Swift et. al is adapted for numerical calculation. The model contains arbitrary viscosity effect of the gas filled in the resonator. The wave equation is integrated by using 4-th order Runge-Kutta algorithm to give pressure distribution along the stack of plate. Heat flux and COP are also calculated based on the energy flux equation. By analyzing the numerical simulation results, optimum values of design parameters for thermoacoustic refrigerator are obtained.

• International Journal of Automotive Technology
• /
• 제6권4호
• /
• pp.421-427
• /
• 2005

This work analyzes the behaviors of aerated lubricant in the gap between con-rod bearing and journal. It is assumed that the film formation with aerated lubricant is influenced by the two major factors. One is the density characteristics of the lubricant due to the volume change of lubricant for the formation of bubbles and the other is the viscosity characteristics of the lubricant due to the surface tension of the bubble in the lubricant. These two major factors surprisingly increase the load capacity in some ranges of bubble sizes and densities. Modified Reynolds' equation is developed for the computation of fluid film pressure with the effects of aeration ratio in the lubricant. From the calculated load capacity by solving modified Reynolds' equation, journal locus is computed with Mobility method after comparing it with the applied load at each time step. The differences of journal orbits between aerated and pure lubricants are shown in the computed results.

• Ocean Systems Engineering
• /
• 제1권3호
• /
• pp.207-222
• /
• 2011

A stabilized incompressible smoothed particles hydrodynamics (ISPH) method is utilized to simulate free falling rigid body into water domain. Both of rigid body and fluid domain are modeled by SPH formulation. The proposed source term in the pressure Poisson equation contains two terms; divergence of velocity and density invariance. The density invariance term is multiplied by a relaxed parameter for stabilization. In addition, large eddy simulation with Smagorinsky model has been introduced to include the eddy viscosity effect. The improved method is applied to simulate both of free falling vessels with different materials and water entry-exit of horizontal circular cylinder. The applicability and efficiency of improved method is tested by the comparisons with reference experimental results.