• Journal of Sensor Science and Technology
• /
• v.23 no.4
• /
• pp.266-271
• /
• 2014

Chemical sensors are used in various industrial facilities such high-risk and prevent the leakage of substances, important in life and environmental protection and the safe use of industry, used for management. In particular, high-temperature environments such as power generation equipment of the rotating part due to leakage generated by the various oil, power plants Shut Down, fire, work environment (exposure to various chemical solution and gas leak) and various water, air and soil pollution causes. Thus, over the long term through various channels such as crops and groundwater contamination caused by the slow, serious adverse effect on the ecosystem. In this paper, synthetic lube oil and high pressure hydraulic fluid leakage and immediately detect a new Printed Electronic implementation of technology-based film-type sensors, and its performance test. Thus, industrial accidents and environmental pollution and for early detection of problems, large accidents can be prevented. Experimental results of the synthetic lube oil and high pressure hydraulic fluid solution after the contact time depending on the experiment and the oil solution of the sensor material of the conductive porous PE resistance value by a chemical reaction could be confirmed that rapid increase. Also implemented in the film-type oil sensor electrical resistance change over time of the reaction rate and the synthetic lube oil is about 2 minutes or less, the high pressure hydraulic fluid is less than about 1 minute was. Therefore, more high-pressure hydraulic fluid such as a low volatility synthetic lube oils are the resistance change and the reaction rate was confirmed to be the slowest.

• Tribology and Lubricants
• /
• v.16 no.5
• /
• pp.341-350
• /
• 2000

The study reported in this paper deals with the development for parametric investigation of the influence of the rheological properties of the lubricant in the thermohydrodynamic (THD) film conditions which occur in slider and journal bearings. A parametric investigation based on a Bingham model with a shear yield stress which best fit the experimental pressure is performed for predicting the thickness of the shear Bone in lubricating films with fixed geometry between the stationary and moving surfaces. The results suggest that the shear yield stress for the lubricating film is proportional to the pressure developed in the film within the range of the investigated cases and the shear zone thickness which is of the same order of magnitude as that obtained by the empirical formula is significantly smaller than the fluid film thickness in the lubrication zone.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2002.10b
• /
• pp.381-382
• /
• 2002

The Fluid film between the valve plate and the cylinder block was measured by use of a gap sensor and the mercury-cell slip ring unit under real working conditions. During the operating periods, experiments with discharge pressure, revolution speed, and valve geometry was carried out for the fluid film on the valve plate. To investigate the effect of the valve shape, we designed two valve plates each having a different shape; the first valve plate was a plane valve plate. while the second valve plate was a spherical valve plate. It was noted that these two valve plates observed different aspects of the fluid film characteristics between the cylinder block and the valve plate. The leakage flow rate and the shan torque were also investigated in order to clarify the difference between these two types of valve plates. From the results of this study. we found that the spherical valve plate estimated good fluid film patterns and performance more than the other valve plate in oil hydraulic axial piston pumps.

• Tribology and Lubricants
• /
• v.19 no.3
• /
• pp.167-177
• /
• 2003

The study deals with the development of a thermohydrodynamic (THD) computational procedure for evaluating the pressure, temperature and velocity distributions in fluid films with very rough geometry. A parametric investigation is performed to predict the bearing behaviors in the lubricating film having the absorbed layers and their interfaces determined by the rough surfaces with Gaussian distribution. The layers are expressed as functions of the standard deviations of each surface to characterize flow patterns between both the rough sur-faces. The velocity variations and the heat generation are assumed to occur in the central (shear) zone with the same bearing length and width. The coupled effect of surface roughness and shear zone dependency on hydrodynamic pressure and temperature has been found in non-contact mode. The procedure confirms the numerically determined relationship between the pressure and film gap on condition that its roughness magnitude is smaller than the fluid film thickness.

• Tribology and Lubricants
• /
• v.2 no.1
• /
• pp.61-68
• /
• 1986

Effects of the ram-pressure on the THD-performance of pivoted pad thrust bearings are investigated experimentally. A sector-shaped tilting pad thrust bearing and a rotating disk are used. Temperature distribution on the disk surface as well as on the pad surface, distribution of the pressure generated within the fluid film, and the film thickness are measured continuously in the circumferential direction after thermal equilibrium is established. The ram-pressure is proportional to the mean pressure of oil film and to the rotational speed of the disk and affects the maximum pressure and the pressure distribution. The temperature rise on the mating surface of the disc and the pad, contacting with the oil film, is proportional to to the bearing load and the disk speed. The ram-pressure and the temperature rise on the disk surface are dominant factors that affect the THD-performance of pivoted pad thrust bearings.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.1912-1915
• /
• 2007

The disjoining pressure is critical in modeling the transport phenomena in small scales. They are very useful in characterizing the non-continuum effects that are not negligible in heat and mass transports in the film of less than submicro-scales. We present he disjoining pressure of thin film absorbed on solid substrate using Molecular Dynamics Simulation (MD). The disjoining pressure with respect to the film thickness is accurately calculated in the resolution of a molecular scale. The characteristics of the pressure are discussed regarding the molecular nature of the fluid system like molecular diameter and intermolecular interaction. Also, the MD results are compared with those based on the macroscopic approximation of the slab-like density profile. Significant discrepancy is observed when the effective film thickness is less than several molecular diameter

• The KSFM Journal of Fluid Machinery
• /
• v.19 no.4
• /
• pp.13-18
• /
• 2016

The various film cooling hole shapes have been proposed for effective external cooling of gas turbine blade. In this study, the film cooling effectiveness by three different hole shapes (cylindrical hole, $15^{\circ}$ angle anti-vortex hole, 30-7-7 fan-shaped hole) were examined experimentally. Pressure Sensitive Paint (PSP) technique was used to measure the film cooling effectiveness. The coolant to mainstream density ratio was 1.0 and three blowing ratios of 0.5, 1.0, and 2.0 were considered. Results clearly showed that the effect of hole shape on the distribution of film cooling effectiveness. For the cylindrical hole case, the film cooling effectiveness decreased remarkably as the blowing ratio increased due to the jet lift off. Because of large hole exit area and low coolant momentum, the 30-7-7 fan-shaped hole case showed the highest film cooling effectiveness at all blowing ratio, followed by the anti-vortex hole case.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11a
• /
• pp.304-311
• /
• 2001

This research numerically analyzes the dynamic characteristics of a coupled journal and thrust hydrodynamic bearing due to its groove location which has the static load due to the weight of a rotor in the axial direction and the dynamic load due to its mass unbalance in the radial direction. The Reynolds equation is transformed to solve a plain member rotating type of journal bearing(PMRJ), a grooved member rotating type of journal bearing (GMRJ), a plain member rotating type of thrust bearing (PMRT) and a grooved member rotating type of thrust bearing (GMRT). FEM is used to solve the Reynolds equations in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors, such as whirl radius or floating height of a rotor, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. This research shows that the groove location affects the pressure distribution in the fluid film and consequently the dynamic performance of a HDD spindle system.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.6
• /
• pp.52-58
• /
• 2014

In the present work, design optimization of film-cooling hole array on the pressure side of high pressure turbine nozzle was conducted. There are four rows of fan-shaped film cooling holes on the nozzle pressure side surface and each row has a straight array of holes in the spanwise direction for baseline model. For design optimization, hole distributions in streamwise and spanwise directions for three rows of holes except first row are parameterized as a 2nd-order shape function. Three-dimensional compressible RANS equations are used for flow and thermal analysis around the nozzle surface and optimization technique using Design of Experiment, Kriging surrogate model and Genetic Algorithm is used. The results shows that averaged adiabatic wall temperature at the whole nozzle surface decreases about 2.7% and averaged film cooling effectiveness at the pressure side of nozzle increased about 8.2%.

• Tribology and Lubricants
• /
• v.28 no.1
• /
• pp.12-18
• /
• 2012

This application study of a swash-plate type axial piston pump was concerned about the lubrication characteristics between cylinder barrel and valve plate which are the main rotating body and its opposite sliding part respectively. A computer simulation was implemented to assess bearing and sealing functions of the fluid film between cylinder barrel and valve plate. A numerical algorithm was developed to facilitate simultaneous calculations of dynamic cylinder pressure, 3 degree-of-freedom barrel motions considering inertia effect, and fluid film pressure assuming full fluid film lubrication regime. Central clearance, tilt angle, and azimuth angle of the rotating body were calculated for each time step. Surface waviness was found to be an influential factor due to the small fluid film thickness which can appear in flat land bearings. Five surface lays which can form on the lubrication surface in accordance with machining process were defined and analyzed using the simulation tool. Oil leakage flow and frictional torque in the fluid film between cylinder barrel and valve plate were also calculated to discuss in the viewpoint of energy loss. The simulation results showed that in actual sliding conditions proper surface non-flatness can make a positive effect on the energy efficiency and reliability of the thrust bearing.