• Tribology and Lubricants
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• v.39 no.2
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• pp.76-80
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• 2023

This paper describes an experimental investigation of the effect of cooling flow rate on gas foil thrust bearing (GFTB) performance. In a newly developed GFTB test rig, a non-contact type pneumatic cylinder provides static loads to the test GFTB and a high-speed motor rotates a thrust runner up to the maximum speed of 80 krpm. Force sensor, torque arm connected to another force sensor, and thermocouples measures the applied static load, drag torque, and bearing temperature, respectively, for cooling flow rates of 0, 25, and 50 LPM at static loads of 50, 100, and 150 N. The test GFTB with the outer radius of 31.5 mm has six top foils supported on bump foil structures. During the series of tests, the transient responses of the bearing drag torque and bearing temperature are recorded until the bearing temperature converges with time for each cooling flow rate and static load. The test data show that the converged temperature decreases with increasing cooling flow rate and increases with increasing static load. The drag torque and friction coefficient decrease with increasing cooling flow rate, which may be attributed to the decrease in viscosity and lubricant (air) temperature. These test results suggest that an increase in cooling flow rate improves GFTB performance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.3 s.246
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• pp.278-286
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• 2006

Experiments were conducted to estimate the performance of drag force type vertical axis wind turbine with an opening-shutting rotor. It was operated by the difference in drag force generated on both sides of the blades. The rotational speed was measured by a tachometer in a wind tunnel and the tunnel wind speed was measured by using a pilot-static tube and a micro manometer. The performance test for a prototype was accomplished by calculating power, power coefficient, torque coefficient from the measurement of torque and rpm by a dynamometer controller. Various design parameters, such as the number of blades(B), blade aspect ratio(W/R), angle of blades$(\alpha)$ and drag coefficient acting on a blade, were considered for optimal conditions. At the experiment of miniature model, maximum efficiency was found at N=15, $\alpha=60^{\circ}$ and W/R=0.32. The measured test variables were power, torque, rotational speed, and wind speeds. The data presented are in the form of power and torque coefficients as a function of tip-speed ratio V/U. Maximum power was found in case of $\Omega=0.33$, when the power and torque coefficient were 0.14 and 0.37 respectively. Comparing model test with prototype test, similarity law by advance ratio for vertical axis wind turbine was confirmed.

• Journal of Biosystems Engineering
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• v.27 no.5
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• pp.371-380
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• 2002

The objectives of this study were to analyze gear rattle in a power drive line using its dynamic model and to derive design guidelines to eliminate it. A 72 degrees of freedom model of power driveline of an agricultural tractor was developed and proved to be valid fer predicting the collision characteristics of gears in mesh, which may determine whether or not the gear rattle will occur. Using the model the effects on the rattle of drag torque, backlash, mass moment of inertia, transmitting torque were analyzed. Increasing drag torque or decreasing mass moment of inertia reduced gear rattle. The gears transmitting power do not develop rattles. It was also found that a large amount of rattle is likely to be developed by the change gears placed at the end of idle shafts. Increasing the drag torque to such change gears may be the most effective way of reducing the gear rattle in a tractor driveline.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.30-41
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• 1995

Gear rattle is a source of vibration and noise in automotive gearbox casing and generally occurs at or near system resonant frequencies. The neutral gear rattle of the gearbox. is affected by the stiffness and hysteresis torque in the clutch disk and drag torque determining balancing point of the clutch disk operating range. The experiment is carried out in the pre-damper type clutch and a manual transmission of a automobile equipped for inline four-sylinder four-cycle 1.5L MPI engine and the computer simulation is executed by 5th order Runge-Kutta method. The results of the simulation analysis and experimental studies show the dynamic behavior of clutch and a phenomenon of the neutral gear rattle with respect to drag torque and torsional characteristics of the clutch.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.897-898
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• 2013

• Fibers and Polymers
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• v.4 no.4
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• pp.161-168
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• 2003

An investigation of the dimensionless torque in the newly developed cone drum twister texturing mechanism is reported. The cone drum twister is one of the outer surface contacting friction-twisting devices in false-twist texturing. In this cone drum twister, a filament yam passes over the surface of the cone drum that rotates by the passing yarn without a special driving device. This research is composed of the theoretical analysis of the false twisting mechanism and the experimental analysis at room temperature. The equations have been derived which shows interrelationship of the conical angle of cone drum, the wrapping angle, the drag angle, and the yam helix angle. Theoretical values of dimensionless torque were calculated and were compared with the experimental results. It is shown that, as the conical angle and the projected wrapping angle increased, the dimensionless torque also increased. But the conical angle was reached to ${30.75}^{\circ}C$, the dimensionless torque decreased.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.166-174
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• 2008

Recently, the automotive industry has been developing rapidly. With the progress parts of the automobile components need high quality and the reliability. Among them, braking unit is essential device, and acquire the reliability through the performance test of brake. This study was aimed to design the performance-test-bench to measure the drag torque which has effect on caliper in braking unit. In this progressive technology, it is vital importance to use hydraulic and pneumatic, and to combine test bench with instrumentation engineering technology. This system to construct the design of hydraulic and pneumatic circuit, interface technique between sensors and personal computer, data acquisition and display design, and integrated control are very important technology. Moreover, reliable data are obtained through vacuum system and hydraulic and pneumatic system by using of booster and brake master cylinder which are actually applied to automobile. Then, data signal detector sensors for speed, pressure and torque is attached on this system. Therefore, in this study, we designed a performance-test-bench by and we also made an total control system using personal computer which is more progressive and flexible method than existing PLC control.

• Journal of Energy Engineering
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• v.29 no.1
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• pp.34-43
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• 2020

A study has been done for self-starting torque of vertical axis wind turbine blade. It is especially concentrated to evaluate the torque coefficient before starting rotation. Two different aerofoils(AMI903 and AMI904) are proposed to benchmark the possible best blade(supercritical airfoil) for self-starting performance. Torque coefficients in the tangential direction of rotation are given with respect to the angle of attack in terms of drag coefficient and lift coefficient. Torque coefficient shows that the effect of Reynolds number is minimal. The thicker blade(AMI904) between two different proposed airfoils has bigger torque coefficient, which is attributed to lower lift coefficient and higher drag coefficient.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.4
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• pp.10-16
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• 2007

A rubber seal for wheel bearing which has been mainly applied to car wheel supporting device is required to have both high sealing performance and drag torque. Because of severe operational conditions like infiltration of mud or splashed water, the importance of rubber seal which is aimed for leakage prevention of grease and effective blocking of foreign substances has been increasing continuously. The sealing performance of this seal depends on several factors such as materials of seal, friction conditions of contact regions and geometry of seals and so on. We have focused on the effects of geometric characteristics such as the angle of main lip, interference between lip edge and inner metallic ring. In this study, the optimization of geometric variables was performed using the finite element analysis. For the sake of finite element analysis, uniaxial tensile tests were conducted and several constants for Mooney-Rivlin's equation were obtained. According to the results of this study, mock-up bearing was made. To verify this study, drag torque and mud spray test were preformed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.488-496
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• 1991

Dynamic chanracterisitcs and control of a submerged working robot manipulator have been investigated for articulated type robot manipulator with three revoluted joints. A dynamic equation of the manipulator has been derived. The dynamic equation includes not only mass matrix, centrifugal and Coriolis terms and gravity terms but also added mass, buoyant force and drag force terms, which are important terms for underwater motion description. A series of simulations using computed torque method have been performed for the cases of straight and circular trajectory motion controls. The results of this study show that the dynamic characteristics of the submerged working robot manipulator are very different from that of the manipulator which works in air. The influences of added mass, buoyant force and drag force terms to the total required torques have been discussed as distribution ratios to the total required torques.