1. Grooving Effects in Circular Step Thrust Bearings
M. Mahbubur Razzaque and M. Zakir Hossain
Department of Mechanical Engineering, BUET

2. Background
In circular step thrust bearings fluid film is maintained by external pressure.
are used for high load applications.
Ps >> Po Po
Load
Bearing
Step
4th IMEC, 31 December 2004, IEB, Dhaka.

3. Background Grooves on a bearing surface may modify its performance.
For other types of bearings, optimum groove design guidelines are available in literature.
But no studies have yet been reported on the effect of grooving on the performance of a circular step thrust bearing.
4th IMEC, 31 December 2004, IEB, Dhaka.

4. Objectives To study how grooves on the step modify
the flow field
the load capacity
To identify the optimum groove & step geometry
Step
Recess
4th IMEC, 31 December 2004, IEB, Dhaka.

5. Methodology Narrow groove theory If we make grooves extremely small …
Flow
Narrow groove
Wide groove
Actual pressure
Smooth pressure
If we make grooves
extremely small …
smooth pressure will closely approximate
the actual pressure
4th IMEC, 31 December 2004, IEB, Dhaka.

6. Smooth pressure distribution
For the step region rs ri ro W r Ps Po
For the recess region
There 4 unknowns and 4 b.c.s are required
4th IMEC, 31 December 2004, IEB, Dhaka.

7. Smooth pressure distribution
2 BC s come from rs ri ro W r Ps Po
The remaining 2 conditions are
obtained from the requirements
of flow and pressure continuity
at the step
4th IMEC, 31 December 2004, IEB, Dhaka.

8. Smooth pressure distributionrs ri ro W r Ps Po
Grooved Nongrooved
Ps = 1.5 kPa, r = 850 kg/m3, 1800 rpm, ro = 5 cm, rs = 0.05ro
4th IMEC, 31 December 2004, IEB, Dhaka.

9. Load bearing capacity Nondimensional load bearing capacity:
With appropriate substitution, this equation
can be reduced to Dowson[1961]’s equation
for nongrooved circular step thrust bearings.
4th IMEC, 31 December 2004, IEB, Dhaka.

10. Load bearing capacity……
Effect of groove
Inertia parameter
S = 0
4th IMEC, 31 December 2004, IEB, Dhaka.

11. Load bearing capacity……
Load vs. step location: effect of inertia
Inertia parameter
S = 0
S = 2
Load curves
Intersects
At radius ratio
0.45
4th IMEC, 31 December 2004, IEB, Dhaka.

12. Conclusions
A simple analytical equation is derived for estimating the load capacity of a circular step thrust bearing.
Load bearing capacity may be increased by suitable inclination of grooves
With an increase in inertia load capacity increases only if the step radius > half of the bearing radius.
In a wider step, no increase in load capacity is possible with increase of inertia.
4th IMEC, 31 December 2004, IEB, Dhaka.

13. Thanks !
4th IMEC, 31 December 2004, IEB, Dhaka.