MADAN MOHAN MALAVIYA UNIVERSITY OF TECHNOLOGY

GORAKHPUR

HYDRODYNAMIC JOURNAL BEARINGS

Presented By:-Shiv Prasad 1204240048

Shubham Shukla 1204240050

Suraj Gupta 1204240054

Swapnil Jain 1204240055

Swati Srivastava 1204240056

Swati Singh 1204240057

Vareesh Pratap 1204240058

CONTENTS

Introduction

Terminology

Causes of failure

Assumptions

Problem statement

Design procedure and calculation

Graphs

Applications

Conclusion

References

INTRODUCTION Bearings are machine elements that constrain

relative motion and reduce friction between

moving parts to only the desired motion.

In sliding contact bearing, surface of the shaft

slides over surface of the bush.

In order to reduce frictional resistance, wear

and to carry away the heat generated, a layer

of fluid i.e. lubricant is provided.

TERMINOLOGY

D= diameter of bearing

d= diameter of journal

l= length of bearing

c= radial clearance

e= eccentricity

h0 = minimum oil film

thickness.

ε= eccentricity ratio= e-

c

CAUSES OF FAILURE

Lubricant failure due to high operating

temperature.

Corrosion

Excessive loading

Misalignment

Improper mounting

Fig1: Failure chances in percentage of

a hydrodynamic bearing [2]

ASSUMPTIONS

The bearing is subjected to static loads

only.

Bearing is assumed to be made of babbitt

material.

Lubricant carried away all the heat

generated during the operation.

The lubricant obeys Newton's law of

viscous flow.

The pressure is constant throughout the

film thickness.

The flow is one dimensional, i.e. the side

leakage is neglected.

The lubricant is incompressible.

The viscosity is constant throughout the

film.

There is continuous supply of lubricant.

No dynamic forces acting on both shaft

and bearing.

l=d

c=0.001r

h0 /c=0.6

PROBLEM STATEMENT

To design a full hydrodynamic journal bearing

with the following specification for high speed

machine tool application:[1]

• Journal diameter= 75mm

• Radial load=10kN

• Journal speed = 1440rpm

• Minimum oil film thickness=22.5microns

• Inlet temperature=400C

• Bearing material= Babbitt

Determine the length of the bearing and select a

suitable oil for this application.

DESIGN PROCEDUREAND CALCULATION

Given: W=10kN, N=1440rpm, d=75mm,

h0= 22.5 microns, T= 40˚C

STEP 1: Length of bearing

For machine tool application , the

permissible bearing pressure, p=2N/mm²

l=W/(p*d) = 10000/(2*75) = 66.67mm

l/d= 66.67/75 =0.89 ≈1(standard value)

l=d=75mm

STEP 2: Selection of lubricant

p=W/(l*d)

=10000/(75*75)

= 1.78N/mm²

c=0.001r

=0.001*37.5

=0.0375mm

l/d=1 and h0/c = 0.0225/0.0375=0.6( high

speed application)

From table[1], for the above values,

S=0.264,

(r/c)f=5.79,

Q/(r*c*n*l)=3.99,

n=1440/60

=24rps

S=(r/c)²(µn/p)

0.264=(1000)²(µ*24/1.78)

µ=19.58cP

∆t={8.3p(CFV)}/(FV)

= (8.3*1.78*5.79)/3.99

= 21.44˚C

We know that,

Average temperature=Ti + (∆t/2)

= 40+(21.44/2)

=50.72˚C

RESULT :

1) Length of bearing= 75mm

2)The viscosity of SAE-10 oil is 22cP at 50˚C

.So we select SAE-10 oil for this application from

the graph.

Fig 2: Viscosity temperature

relationship[9]

Fig 3: Variation between h0 and

frequency of rotation N [1],[6]

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35 40 45 50

h0(m

icro

n)

-->

Ns (Revolution per second) -->

µ= 12.9 cP µ = 18.9 cP µ = 27.52 cP

Fig 4: Variation between temperature

and frequency of rotation N[1]

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70

Tem

pe

ratu

re (

°C)

-->

Ns (Revolution per second) -->

Ti Tmax Tavg

Fig 4:Variation between maximum load

with frequency of rotation[8]

APPLICATIONS

Crankshaft bearings in petrol and diesel

engine

Turbines

Centrifugal pumps

Rope conveyors

Large electric motors

CONCLUSION

From the graph it can be concluded

that it is in agreement with a numerical

solution. Further it can be used to

select lubricating oil for a particular

speed and permissible limit of

temperature rise.

REFERENCES1. Bhandari V B , “Design of machine element” McGraw-Hill

third edition 2014

2. Thakar Dutt “Bearing failure its causes and countermeasures” 2014

3. Pickering Steve, “ Tribology of journal bearing subjected to boundary and mixed lubrication” Department of mechanical & industrial engineering Northeastern university 2011

4. “Bearing failure causes and curses” by Wilcoxon Research

5. Temiz Vedat “sliding contact bearing” 1995

6. http://www.viscopedia.com/viscosity-tables/substances/iso-viscosity-classification/

7. http://www.engineeringtoolbox.com/iso-grade-oil-d_1207.html

8. tribolab.mas.bg.ac.rs/radovi/2005_02.pdf

9. https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB4QFjAA&url=http%3A%2F%2Ffaculty.ksu.edu.sa%2Fessam%2FDocuments%2FME301chapter12.pdf&ei=G7IZVZeHDYKjuQTPyIDADg&usg=AFQjCNHG1H5YGbDUxgWliwf43TtosWRA1A