Characteristic Analysis of Water Lubricated Plain Journal Bearing under Transient Load

Transient load has a huge impact on the life and stability of water-lubricated bearings. In this paper work, CFD software is used to analyse the dynamic characteristic of water lubricated bearings under different transient loads of 500N, 1000N, 2000N and 3000N. The water film pressure contour distribution at different transient time was given. The time-varying relationships between the different transient loads with bearing forces, the journal displacement, the maximum value of water film pressure as well as the minimum value of water film thickness are obtained. The results show that with the increase of transient load, the effective bearing area of dynamic water pressure film decreases, and the maximum pressure increases. The bearing forces, the journal displacement, the maximum value of water film pressure as well as the minimum value of water film thickness will increase fast.

Theoretical and Experimental Investigation on Air Film Pressure Field Characteristics of Aerostatic Thrust Bearing

This paper studied the air film pressure field (AFPF) characteristics of aerostatic thrust bearing, in which we proposed the measurement equipment for the 2D AFPF and successfully verified the theoretical simulation results. The experimental results agreed well with the theoretical results. However, in the area between the distribution circle of orifice to the air film outlet boundary, the experimental air film pressure (AFP) was slightly higher than the theoretical one. While for the area between the distribution circle of orifice and the center of the bearing, it showed the opposite law. Besides, the increase ratio of the AFP was close to that of the external load with its increase.

Numerical Study of Single Pad Externally Adjustable 120° Pad Bearing Using Fluid Structure Interaction

High-speed turbomachinery like turbine generators and marine propulsion systems uses special fluid film bearing called externally adjustable pad bearing due to their great advantages. The principal feature of this bearing is to alter the radial clearance and film thickness along the circumferential direction to improve the bearing performance parameters. In the present study, the effect of radial and tilt adjustment of 120° pad both in upward (or negative) and downward (or positive) direction on the bearing performance is predicted for various eccentricity ratios using the CFD technique. Later the influence of fluid film pressure on the bearing pad is examined using the FSI technique. Furthermore, the effect of eccentricity ratio on the bearing performance and also on pad structure is also analyzed using CFD coupled FSI analysis. The solution technique of the present numerical analysis is validated with the already published literature and the results are in good agreement. The numerical results suggest that for bearing with negative radial and negative tilt adjustment, bearing performance is superior compared to the other adjustments. However, the structural deformation is also significant for the negative radial and negative tilt adjustment. It is also observed that pad deformation increases with the increase in eccentricity ratio as there has been a rise in fluid film pressure.

Multi-sensor recognition of human pressure

At present, skin pressure ulcers are a common problem in the care of bedridden patients. Solving this problem usually involves turning the patient over regularly, which requires a lot of manpower and material resources. This paper designs a human body pressure recognition model, which can solve the problem of human pressure ulcers very well in combination with intelligent nursing beds. This paper collects the bone data of the human body by using the Kinect sensor, and then processes the collected data. The film pressure sensor is used to collect the pressure information of the human body, and the pressure information is matched with the bone data of the human body, so as to obtain the pressure of the corresponding part of the human body, and judge the current posture of the human body through the pressure information. When the pressure of the compression part of the human body reaches the threshold, the intelligent nursing bed automatically turns over to reduce the pressure of the compression part of the human body.

Effects of axial motion and couple stress on lubrication performances of ship stern shaft

Increasingly prominent marine oil pollution problems highlight the importance of environmentally friendly lubricants in a ship. According to the actual navigation environment, the couple stress effect of environmentally friendly lubricants and axial motion of stern shaft is considered to establish a new hydrodynamic lubrication model, and finite difference method and Simpson integral method have been utilized to solve film pressure and bearing carrying capacity, respectively. Various performance characteristics were obtained for a range of couple stress parameters, misalignment angles and rotation speeds. The results show that axial motion and couple stress have opposite effects on film distribution, the minimum film thickness decreases with the increasing of axial velocity while the maximum film pressure significant reduce as couple stress parameter grows. The axial position corresponding to the maximum pressure is reduced from 0.51 to 0.49 m as axial velocity enhances from 0 to 0.8 m/s while couple stress parameter is 0, but nearly remains the place while couple stress is considered. Meanwhile, couple stress lubricants effectively restrain friction of journal caused by hydrodynamic effect, and the decreasing amplitude is nearly independent of axial velocity.

Effects of Surface Roughness and Supply Inertia on Steady Performance of Hydrostatic Thrust Bearings Lubricated with Non-Newtonian Fluids

The objective of present theoretical analysis is to study the combined effects of surface roughness and fluid inertia (including the inertia of the fluid in the supply region) on the steady performance of stepped circular hydrostatic thrust bearings lubricated with non-Newtonian pseudoplastic fluids using Rabinowitsch stress-strain model. To account for the effects of surface roughness, the classical Christensen theory of rough surface has been taken. Analytic expressions for film pressure in bearing regions have been established for radial and circumferential patterns of roughness. Numerical results for film pressure, load carrying capacity and lubricant flow rate has been plotted and analysed. Due to surface roughness and fluid inertia in overall regions, significant improvement in performance properties have been observed.

Tribological study of multi-scale textured parallel sliding contacts by considering a mixed lubrication regime and mass conservation condition

Surface texturing is a viable technique to enhance the tribological performance of sliding interacting contacts. Single-scaled surface textures exhibit better tribological performance only at hydrodynamic lubrication regime (fluid film pressure) but not in mixed lubrication regime where fluid film pressure and asperity contact pressure co-exists. In most of the machinery with the increase in load and/or decrease in speed, there is a shift of lubrication regime from hydrodynamic to mixed lubrication. To address this, the present work proposed a multi-scale (a combination of shallow and deep) textures concept. A numerical model is developed to study its effect on the tribological characteristics of parallel sliding contacts by considering mixed lubrication regime and mass-conservative cavitation condition. It has been observed that multi-scaled textures exhibit superior results in comparison with single-scaled textures. Moreover, improved tribological characteristics are observed when shallow surface textures are placed first towards the fluid inlet flow.

An analysis method of pressure characteristic for cylindrical intershaft gas film seal considering centrifugal expansion, rotor misalignment, and precession

To improve the weaknesses of large leakage and wear of dual-rotor intershaft labyrinth seal in aero-engines, the cylindrical gas film seal of metal rubber with a compliant feature is proposed to substitute this conventional seal. According to the dual-rotor operating condition, an analysis method of gas film pressure is presented considering the complex condition of rotor tilt, centrifugal expansion effect, and rotor circular precession. The characteristics of gas film pressure distribution are computed and comparisons are conducted in a complex operating state that the tilt rotor is in forward/backward circular precession under a homodromous/counter-rotating condition with/without the influence of centrifugal expansion. Besides, the formation mechanism of the gas film pressure caused by rotor rotational direction and circular precession direction is revealed. Also, the influence of rotor speed and seal ring speed on gas film pressure is analyzed when the rotor is tilted. The results indicate that for the dual-rotor cylindrical gas film seal with high rotating speed, the rotor tilt and centrifugal expansion effect have significant influence on the gas film pressure distribution, and the rotors’ rotational direction as well as rotor circular precession direction determines the maximum gas film pressure distribution area. The maximum pressure under a homodromous condition with backward precession is the highest; the maximum pressure under a homodromous condition with forward precession is the lowest. The former is 1.33% and 1.68% higher than the latter, respectively, with/without consideration of centrifugal expansion. The study method, which is generally suitable for the cylindrical gas film seal with single-rotor/dual-rotor, lays the foundation of performance analysis under complex operating conditions.