• Tribology and Lubricants
• /
• v.36 no.2
• /
• pp.82-87
• /
• 2020

In thrust bearings, the thrust collar and bearing surface need to be parallel to each other to ensure that all pads share the same load. In rotating machines, the shaft system cannot achieve perfect alignment. Misalignment of the thrust collar results in some pads supporting a higher load than others and excessive loads being placed on some pads. Consequently, high loads and high temperatures may occur in the bearing. Thus, in this study, we aim to analytically evaluate the performance of a misaligned non-equalizing direct lubricated tilting pad thrust bearing. We define the oil film thickness of the misaligned thrust bearing using the Byrant angle. Additionally, we calculate the pressure distribution and temperature distribution of the thrust bearing using the generalized Reynolds equation and energy equation. The design limit of the thrust bearing is defined by the load and temperature. Therefore, we evaluate the allowable misalignment angle as the limit of the maximum load and temperature. The analysis results demonstrate that an increase in the speed and load corresponds to a smaller allowable misalignment angle. However, as this is not the same for all thrust bearings, evaluating the allowable misalignment angle at each thrust bearing is essential.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.21 no.5
• /
• pp.61-70
• /
• 2017

Robust thrust distribution method of solid DACS is researched. For the case of the system which has higher number of actuation nozzles than the degree of freedom of thrust to be controlled, the robust thrust allocation law which accommodate the abnormal operation is suggested. Assuming the situation that some nozzles are uncontrollable, the error between nozzle throat area command and response can be calculated. The error is used for realtime reshaping of weighting matrix. From the weighting effect, the nozzle which operated abnormally has low responsibility for the command then, the thrust error is reduced. The suggested algorithm is verified by the simulation of abnormal operation condition of DCS and ACS nozzle respectively.

• 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.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.4
• /
• pp.69-75
• /
• 2003

The ideal thrust function is used to determine the local thrust of supersonic combustor. Method of thrust determination from measured pressures are applied to the Mach 2.5 model supersonic combustor. In this application, measured pressures from the experiments in the University of Michigan are used to determine the local thrust of supersonic combustor. Marginal results of local thrust are obtained and discussed. Combustion and wedge affect thrust distributions in the upstream region significantly. The thrust determination from pressure measurements can be a simple, feasible and applicable method, especially when thrust stand is not available.

• Proceedings of the KIEE Conference
• /
• 1997.11a
• /
• pp.6-9
• /
• 1997

The study is analyzed the thrust fon:e of moving type Linear DC Motor(MM-LDM). The MM-LDM consists of a stator (platen) and mover (forcer). One of the method for calculating tile thrust of an MM-LDM is to analyze the energy gradient which is determined by the distribution of magnet flux. However, this method is very difficult when used to calculate the thrust force of this kind of LDM. The stored energy in the MM-LDM can be obtained by measuring the self-inductance and mutual-inductance of equivalent circuit of the MM-LOM and this energy gradient gives the thrust. The calculation of thrust force included in this motor shows that the mutual inductance has large influence on the generation of thrust force.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.60 no.1
• /
• pp.80-86
• /
• 2024

We analyzed the performance of hubless rim propellers based on the number of blades, maintaining a fixed pitch ratio and expanded area ratio, using computational fluid dynamics (CFD). Thrust coefficient, torque coefficient and efficiency according to the number of blades were analyzed. In addition, the pressure distribution on the discharge and suction sides of the blade was analyzed. As the advance ratio increases, the thrust coefficient decreases. The highest thrust was shown when the advance ratio was lowest. For the three, four, five and six-blades, the torque coefficient tended to decrease as the advance ratio increased. In the case of seven and eight-blades, the torque coefficient tended to increase as the advance ratio increased. The maximum efficiency was found when the advance ratio was 0.8. When the three-blade, it showed high efficiency at all advance ratios. A high pressure distribution was observed at the leading edge of the discharge blade, and a low pressure distribution was observed at the trailing edge. Applying a hubless rim-driven thruster with the three-blade can generate higher thrust and increase work efficiency.

• Journal of Ocean Engineering and Technology
• /
• v.28 no.6
• /
• pp.500-507
• /
• 2014

This study aimed at conducting a flow analysis of the pressure distribution, discharge flow rate, and consequent thrust force according to the rotational speed of a three-dimensional screw propeller, and then investigating the effect of the rotational speed on the characteristics of the screw propeller by varying the relevant speed (3200, 2400, 1600, 800 rpm). In particular, the computational domain was considered by the analysis in the blades and outlet chamber, using boundary conditions. The difference between the minimum and maximum pressures was 5.5 MPa under the given conditions. The discharge flow rate at this pressure difference was on the level of 1956.67 kg/s, as a thrust force of 47083.7 T(N) was obtained. This study showed that the discharge flow rate linearly increased with the rotational speed, proportional to the RPM, while the thrust force was gradually and steadily increased with the relevant speed. In addition, it was proved that the occurrence of cavitation under the given conditions was closely related to the decrease in the durability of the screw propeller because the thrust force depends on the speed.

• 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.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.19 no.6
• /
• pp.98-104
• /
• 2015

Excessive thrust acting on the rotor of pump can cause the damage of pump or the decrease of pump lifetime. Therefore, for ensuring the safety of LOX pump of a liquid rocket engine, the thrust of pump rotor is estimated by similarity tests. Axial thrust is indirectly measured by an axial thrust measurement unit positioned outside pump. Radial thrust is calculated based on pressure distribution of volute scroll. As a result, axial and radial thrust are increased when the flowrate of pump decreases. However, both thrusts do not affect the stability of pump rotor since their values are not large.

• Structural Engineering and Mechanics
• /
• v.20 no.3
• /
• pp.313-334
• /
• 2005

The paper presents a new approach for the analysis of slope stability that is based on the numerical solution of a differential equation, which describes the thrust force distribution within the potential sliding mass. It is based on the evaluation of the thrust force value at the endpoint of the slip line. A coupled approximation of the slip and thrust lines is applied. The model is based on subdivision of the sliding mass into slices that are normal to the slip line and the equilibrium differential equation is obtained as the slice width approaches zero. Opposed to common iterative limit equilibrium procedures the present method is straightforward and gives an estimate of slope stability at the value of the safety factor prescribed in advance by standard requirements. Considering the location of the thrust line within the soil mass above the trial slip line eliminates the possible development of a tensile thrust force in the stable and critical states of the slope. The location of the upper boundary point of the thrust line is determined by the equilibrium of the upper triangular slice. The method can be applied to any smooth shape of a slip line, i.e., to a slip line without break points. An approximation of the slip and thrust lines by quadratic parabolas is used in the numerical examples for a series of slopes.