Analytical Investigation of Roller Skew and Tilt in a Spherical Roller Bearing

The objective of this investigation was to analytically investigate the performance of a spherical roller bearing operating under various loading and speed combinations. In order to achieve the objective, a full six degree of freedom spherical roller bearing dynamic model was developed. The model was corroborated with results in open literature. An adaptive slicing method was developed to optimize the accuracy and computational effort of the roller force, skew, and tilt calculations. A comprehensive roller-race contact analysis in terms of slip velocity and contact area was then carried out to identify how bearing load and inner race speed variations change slip velocity and skew at the roller-race contact. The results from this investigation demonstrate that roller skew increases with inner race speed, while the roller tilt remains relatively constant. The inner race speed and roller slip velocity correlate well, which causes the traction force to increase and therefore produce greater skew. Skew and tilt angles also increase with applied axial load. However, at a certain load the skew angle begins to decrease.

Assessing the Potential Replacement of Mineral Oil with Environmentally Acceptable Lubricants in a Stern Tube Bearing: An Experimental Analysis of Bearing Performance

This study compares the performance of a plain bearing, with a similar structure to a tail shaft stern bearing, lubricated with either mineral oil or an environmentally acceptable lubricant (EAL). The main characteristic of the bearing is its length/diameter ratio of <1. Measurements are carried out with the bearing operating under loads from 0.5 to 1 MPa and seven speeds ranging from 1 to 11 rev/s. The bearing lubricated with either mineral oil with a viscosity grade of 100 or an environmentally acceptable lubricant (EAL) with a viscosity grade of 100 or 150 is investigated according to the ISO standard. Bearing wear is simulated by increasing the clearance circle by 0.1 mm. According to the results obtained, the use of an EAL in place of mineral oil does not cause significant changes in the bearing performance, regardless of the value of the clearance radius. The pressure distribution in the oil film, bearing load carrying capacity, eccentricity and friction coefficient have similar values for the entire load and speed ranges considered, and the discrepancies in the results are within the range of the measurement errors. Only an increase in EAL viscosity causes significant changes in bearing performance and these changes comply with the general theory of lubrication.

Effects of Ship Propulsion Shafting Alignment on Whirling Vibration and Bearing Temperature Response

Ship’s propulsion shafting is one of the main sources of ship vibration and noise. The shafting, whirling vibrations, and alignment are important factors that affect the comfort, stability, and reliability during a ship’s navigation. However, the mechanism of the interacting of the both factors is not fully revealed. In this paper, the effect of shafting alignment on whirling vibration and the bearing temperature response is studied by experiment. The test scheme is designed reasonably according to the theoretical analysis. The results show that the horizontal component of the shafting whirling vibration can be effectively reduced by adjusting the shafting alignment state while the vertical component is not. The shafting axis balancing position (SABP) slightly moves upward in high speed, which should be considered in the dynamic alignment design of the shafting, especially for the high-speed shafting. Little ABSB (the angle between the shafting centre line and the No. 1 bearing centre line) is beneficial to the stable operation of shafting, while appropriately increasing the ABSB and bearing load is beneficial to reducing the shafting whirling vibration. By balancing the relationship between bearing load and ABSB, the performance of whirling vibration and bearing temperature response can be optimized.

Method for calculating the sliding bearing of a piston engine and compressor

A one-dimensional model for calculating the sliding bearing of a piston engine and compressor is proposed. The results of approximation of the graphs by analytical dependences of the relative eccentricity on the bearing load coefficient for different values of the ratio of the working length of the bearing to the diameter of the crankshaft journal are presented in the form of exponential functions. Keywords: sliding bearing, heat balance, piston compressor, piston engine, friction [email protected]; [email protected]; [email protected]

Assessment of Rotor Stability for Steam Turbine Considering Labyrinth Seal Characteristics of Fluid Destabilization Force and Vibrational Frequency Effect of Bearing Coefficients

Accurate evaluation of the rotor stability is important for increasing the performance of the Steam Turbines. This paper discusses the important factors (such as destabilization force, bearing coefficient) for the evaluation of rotor stability. The destabilization force which varies with the type of seal suggests that seal shape plays an important role. In the past, several researchers have studied the fluid destabilization force both numerically and experimentally and prediction of the same can be done fairly accurately by applying CFD techniques. The characteristics of the fluid destabilization force can be accurately evaluated by investigating the sensitivity of parameters such as clearance and swirl velocity for each seal type using CFD. In the case of partial admission operation in which the bearing load changes (such as control stage of steam turbines), the frequency ratio effect on bearing coefficients is higher in the case of light-load (Sommerfeld number is large) than in the case of high-load (Sommerfeld number is small). In order to estimate the frequency ratio effects due to varying load accurately, an experimental study and analytical study were carried out. As a result of comparison of the test results to analytical results, the test results are in good agreement with thermo-elastic-hydrodynamic-lubrication (TEHL) analysis which considers deformation of pad obtained by 3D-FEM. The evaluation of rotor stability at each bearing load by partial admission (example: Governing Valve test) is in agreement with the field data of steam turbine. For new designs and modification designs, this assessment considering the characteristics of each parameter is effective for improving the quality of rotor design.

Simulation Study of Composite Materials Directional Pipe Based on Visual Prototype

When the flexible deformation of composite materials directional pipe which influences the movement of rocket projectile is considered, the visual prototype is a good approach that calculates the course of rocket projectile launch. In this thesis, the mechanical model of bearing load of composite materials directional pipe is established, and the theory and arithmetic of calculation are expatiated. After the simulation model is established and simulation calculation is done, not only the needed data and results are gained, but also the movement principles of rocket projectile in directional pipe and the dynamic mechanical capabilities of FRP directional pipe are held.

Numerical and experimental studies on the thermal and static characteristics of multi-leaf foil thrust bearing

Foil bearing is considered to be a promising supporting technology in high-speed centrifugal machinery. Due to the high-speed shearing effect in the viscous lubricant film, heat generation could not be ignored. In this paper, a thermo-elastic model of the multi-leaf foil thrust bearing is proposed to predict its thermal and static characteristics. In the model, modified Reynolds equation, energy equation, and Kirchhoff equation are solved in a coupling way. The contact area between the foil and welding plate is taken into account. Besides, the effect of cooling air on the bearing temperature is investigated. The ultimate load capacity and transient overload failure process of the bearing is analyzed and discussed. The effect of rotation speed on the bearing temperature is more obvious than that of the bearing load. The bearing temperature drops obviously by introducing the cooling air, and the cooling effect is improved with the supply pressure. The transient overload failure of the bearing occurs when the bearing load exceeds the ultimate value.

A Numerical Model for the Analysis of the Bearings of a Diesel Engine Subjected to Conditions of Wear and Misalignment

In the present work, a numerical model is developed to investigate the influence of wear and misalignment on the bearings of a stationary diesel engine. The model implemented considers the effects of surface wear on the bearing, cavitation effects, and surface roughness. For the numerical analysis, changes in the surface roughness of , , and are defined, and changes in the bearing load of 50%, 75%, and 100%. The results demonstrated that increasing the surface roughness intensifies the bearing wear, which represents 18% and 140% of the bearing clearance for the roughness of and , respectively. Additionally, the surface roughness causes a considerable increase in the bearing wear rate. The results described a maximum wear rate of . In general, increasing the bearing load by 25% doubles the hydrodynamic pressure conditions increases friction force by 33%, and reduces lubrication film thickness by 12%. The analysis of the angle of deflection, and , shows that the moment and the degree of misalignment tend to increase significantly with the increase in the magnitude of the angle . Negative angles of deflection, , produce a greater increase in the degree of misalignment and the moment. This implies a greater chance of contact with the bearing surface. In conclusion, the proposed methodology serves as a reliable tool to simultaneously evaluate key parameters on the tribological behavior of bearings that further extend their endurance and minimize wear damage.