• Tribology and Lubricants
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• v.19 no.5
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• pp.292-297
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• 2003

The fundamental fluid mechanics associated with the rotation of a smooth plane disk enclosed within a cylindrical chamber have been studied experimentally. In order to acquire systematic information pertinent to this problem torque and friction loss data were obtained over a wide range of disk Reynolds numbers for axial clearance-disk radius ratio H/R from 0.025 to 0.2 and radial tip gap-disk radius ratio s/R from 0.021 to 0.105. Loss analysis of hard disk drive (HDD) is presented to describe the contribution of windage loss of a rotating disk. The minimum loss form factor of HDD can be obtained from this analysis at each operation conditions.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.159-165
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• 2001

The fundamental fluid mechanics associated with the rotation of a smooth plane disk enclosed within a cylindrical chamber have been studied experimentally. In order to acquire systematic information pertinent to this problem torque and friction loss data were obtained over a wide range of disk Reynolds numbers for axial clearance-disk radius ratio H/R from 0.025 to 0.2 and radial tip gap-disk radius ratio s/R from 0.021 to 0.105. Loss analysis of hard disk drive(HDD) is presented to describe the contribution of windage loss of a rotating disk. The minimum loss from factor of HDD can be obtained from this analysis at each operation conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.596-604
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• 2011

To improve the total efficiency of centrifugal compressor, it is necessary to reduce the disk friction loss, which is defined as the power loss. In this study, the disk friction loss due to the axial clearance and the surface roughness effect is analyzed and proposed the new empirical equation for the reduction of the disk friction loss. The rotating reference frame technique and the 2-equation k-${\omega}$ SST model using commercial CFD code FLUENT is used for the steady-state analysis of the centrifugal compressor impeller. According to CFD results, the disk friction loss of the impeller is more affected by the surface roughness than the change of the axial clearance. For the minimization of the disk friction loss on the centrifugal compressor impeller, the magnitude of the axial clearance should be designed to the same size compare with theoretical boundary layer thickness and the surface roughness should be minimized.

• Tribology and Lubricants
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• v.23 no.4
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• pp.156-161
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• 2007

The friction test using disk-on-pad type was carried out and regression analysis with friction parameters was applied fur wear loss presumption of motorcycle break disk. The wear loss has an effect on the frictional factor such as applied load, sliding speed, and number of ventilated disk hole. However, it is difficult to know the mutual relation of these factors on wear loss of motorcycle break disk. From this study, the result was shown that the regression analysis equation containing 4 elements were constructed and this equation had a trust of 95% in wear loss presumption of motorcycle break disk. It is possible to apply for another automobile parts.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.4
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• pp.15-21
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• 2007

The effect of manufacturing parameters on friction characteristics of motorcycle break system was studied using a disk-on-pad type friction tester. Such parameters conditions have an effect on the frictional factor such as number of ventilated disk hole, applied load, sliding speed, and sliding distance. However, it is difficult to know the mutual relation of these factors. In this study, the friction characteristics using design of experiment containing 4 elements were investigated for an optimal condition for the best motorcycle break system employing regression analysis method. From this study, the result was shown that the applied load in frictional factors was the most important, next to sliding speed, number of ventilated disk hole.

• The KSFM Journal of Fluid Machinery
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• v.10 no.4
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• pp.21-28
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• 2007

The ratio of disk friction loss in a centrifugal pump is very large for the total pump loss in the range of very low specific speed. Therefore, impeller radius should be shortened to increase the pump efficiency because the disk friction loss is proportional to the fifth power of impeller radius. In order to compensate the decreased head by the shortened impeller radius, vane angle at impeller outlet should be increased. However, as the vane angle at impeller outlet becomes larger, performance instability occurs at low flow rate regions. In this study, J-Groove is adopted to suppress the performance instability and detailed examination is performed for the influence of the J-Groove on the pump performance. The results show that J-Groove gives good effect on the suppression of performance instability. Moreover, as J-Groove increases pump head considerably, the pump size can be smaller for head requirements.

• Journal of Auto-vehicle Safety Association
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• v.7 no.3
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• pp.19-24
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• 2015

Brake pads are a component of disc brake system of automobile and consist of steel backing plates and friction material facing the disk brake rotor. Due to the repeated sliding forces and torque in vehicle braking, friction performance of brake pads are ensured. Futhermore, the brake pad is one of major tuning components in aftermarket, mechanical characteristics of the brake pad are necessary to evaluate for establishing the certification standards of tuning components. This study had performed the five specimen tests for friction coefficients and wear loss rates according to the SAE test specification. Using the instrumented indentation method, yield strength and tensile strength were measured. Friction coefficients, 0.386 - 0.489, and wear loss rates, 1.0% - 3.7% are obtained. The range of yield strength and tensile strength are 21.4 MPa - 105.3 MPa and 39.5 MPa - 176.4 MPa respectively.

• The KSFM Journal of Fluid Machinery
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• v.15 no.5
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• pp.32-36
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• 2012

The positive displacement pump and the regenerative pump are widely used in the range of low specific speed, $n_s{\leq}100$[rpm, m3/min, m]. The positive displacement pump is not suitable for miniaturization and operation in high rotational speed. The regenerative pump has a problem with large leakage flow and low efficiency. While the centrifugal pump has advantages of high efficiency, miniaturization and high rotational speed, efficiency drops sharply with decrease in specific speed. Therefore the purpose of this study is to design a new type of centrifugal pump that has advantages of centrifugal pumps in operation in low specific speed. The name of this new type of pump was called 'Pipe type centrifugal pump', since the flow path through the impeller is simple circular pipe. Due to the simple shape of impeller, the manufacturing process is simple and cost is low. There is strong jet flow at the outlet of the impeller. This jet induces flow path loss, meridional dynamic pressure loss and mixing loss. Large disk friction makes the efficiency be limitted in the range of low specific speed. Even though the loss and the low efficiency, 'Pipe type centrifugal pump' represents stable performance, affordable pressure ratio and efficiency better than that of other low specific speed pumps.

• The KSFM Journal of Fluid Machinery
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• v.10 no.2 s.41
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• pp.46-53
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• 2007

An improved performance characteristics analysis model of a regenerative pump is proposed in the present paper. For its low characteristic speed, a regenerative pump generates high head with low flow rate. However, the efficiency is fairly low due to the skin friction between impeller and casing. Also, the complexity of its internal flow pattern makes prediction of performance characteristics difficult. In the present research, a one-dimensional analysis model was improved with consideration of disc friction loss, minor loss, and modified flow length, and the result was proven to be close in range with the results from experiments.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.6_2
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• pp.917-926
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• 2020

Friction mechanisms is a very important role in the industrial machinery. However, many experiments have been conducted to reduce the loss of energy resources and parts used due to friction because the friction force adversely affects parts, efficiency, noise, and the like of the power unit. Therefore, in this study, the friction coefficient according to the characteristics of the lubricant was measured to find out which Grease Lubricant maintains the low friction coefficient without being most affected by external conditions. A total of five grease lubricants were tested in this study: GHP CAL 301, GHP EP 2, GHP KG 10, GHP HPG 2, and GHP HTG 2. And the friction coefficient was conducted by changing the load conditions (2, 4, 6, 8, 10N) and rotational speed (24, 48, 67, 86, 105, 124, 143, 162vrpm) using a pin-on-disk wear test system. Also, duty number were calculated. As a result, it was confirmed that in all grease lubricants, the speed did not significantly affect the friction coefficient, and it was confirmed that in all lubricants, the size of the friction coefficient decreased as the load increased from a small load to a large load. In addition, it was determined from the experimental results that GHP EP 2 is the most suitable as a grease lubricant and GHP CAL 301 is not the most suitable.