# Journal Bearing Pressure-Fed

Hydraulic portion of pressure-fed journal bearing

Orifices

## Description

The Journal Bearing Pressure-Fed block simulates the hydraulic portion of a pressure-fed journal bearing, shown in the following illustration.

The lubricant under pressure p is pumped into the circumferential groove at the center of the bearing. The groove divides the bearing into two half-bearings. The lubricant exits through the end grooves located at a distance l from the central groove. The model is intended to be used in lubrication system simulation to assess the flow consumption through the pressure-fed journal bearing. The flow regime is assumed to be laminar due to very small clearances between the journal and the bushing.

The flow rate is computed using the Hagen-Poiseuille equation (see [1]):

`$q=\frac{\pi pr{c}^{3}}{3\mu l}\left(1+1.5{\epsilon }^{2}\right)$`

where

 q Volumetric flow rate p Pressure differential across the bearing r Journal radius c Radial clearance at neutral position μ Dynamic viscosity l Length of the half-bearing ε Relative eccentricity, ε = e / r e Eccentricity or journal deflection from the central position

The journal radial displacement, which controls the bearing eccentricity, is imported through the physical signal port J. Connections A and B are hydraulic conserving ports associated with the bearing inlet and outlet, respectively. The block positive direction is from port A to port B. This means that the flow rate is positive if it flows from A to B and the pressure differential is determined as $p={p}_{A}-{p}_{B}$. Positive signal at the physical signal port J increases the eccentricity and is limited to the radial clearance of the bearing.

## Basic Assumptions and Limitations

The flow regime is assumed to be laminar due to small clearances.

## Dialog Box and Parameters

The radius of the journal. The parameter must be positive. The default value is `0.05` m.

The radial clearance between the journal and the bushing at neutral position. The parameter must be positive. The default value is `2e-4` m.

Bearing half-length

The length of the half-bearing, that is, the distance between each of the end grooves and the central groove. The parameter must be positive. The default value is `0.025` m.

## Global Parameters

Parameters determined by the type of working fluid:

• Fluid density

• Fluid kinematic viscosity

Use the Hydraulic Fluid block or the Custom Hydraulic Fluid block to specify the fluid properties.

## Ports

The block has the following ports:

`A`

Hydraulic conserving port associated with the bearing inlet.

`B`

Hydraulic conserving port associated with the bearing outlet.

`J`

Physical signal port that controls the journal deflection.

## References

[1] Shigley, J., C. Mischke, and R. Budynas. Mechanical Engineering Design. New York: McGraw-Hill, 2004.