Performance of a noncircular 2-lobe multirecess
hydrostatic journal bearing with wear
Satish C. Sharma, Vikas M. Phalle and S.C. Jain
Department of Mechanical and Industrial Engineering, Indian Institute of Technology Roorkee, Roorkee, India
Abstract
Purpose – Noncircular journal bearings are used in industry because of their simplicity, efficiency and low cost. During the life time of a machine, these
are required to be operated over a number of years and are submitted to several stops and starts. As a result, the bush becomes progressively worn out
and the bearing performance changes. The purpose of this paper is to study theoretically the influence of wear on the performance of a non-circular
2-lobe four-pocket multirecess hybrid journal bearing system.
Design/methodology/approach – The Reynolds equation governing the flow of lubricant in the clearance space of a non-circular 2-lobe multirecess
worn hybrid journal bearing system has been solved using FEM along with appropriate boundary conditions. The defects caused by wear are centered
on the load line and range from 10 per cent to 50 per cent of the bearing radial clearance.
Findings – The numerically simulated results based on a Newtonian lubricant and the steady state flow field system have been presented in terms of
maximum fluid film pressure, minimum fluid film thickness, lubricant flow rate, direct fluid film stiffness and damping coefficients and stability threshold
speed margin. The paper demonstrates that, for the bearing configurations studied, the bearing behavior is clearly affected by wear. The numerically
simulated results indicate that for an offset factor of
d
¼ 1.2, the value of
h
min
reduces by 21.21 per cent at
d
w
¼ 0.5.
Originality/value – The presented results have valuable data in case of 2-lobe four pocket hybrid journal bearing compensated with constant flow
valve restrictor. The paper outcomes are sure to be of interest for researchers and useful for bearing designers.
Keywords Wear, Physical properties of materials, Lubricants, Flow, Noncircular hybrid journal bearing, Constant flow valve, Multirecess
Paper type Research paper
Nomenclature
a
b
¼ bearing land width (mm)
c ¼ radial clearance (mm)
e ¼ eccentricity (mm)
h ¼ fluid film thickness (mm)
p ¼ pressure (N mm
2 2
)
t, g ¼ time (s), acceleration due to gravity
(m s
2 2
)
x, z ¼ horizontal and vertical coordinates
measured from steady state equilibrium
position of journal center (mm)
C
1
¼ c ¼ clearance due to circumscribed circle on
the bearing (mm)
C
2
¼ clearance due to inscribed circle on the
bearing (mm)
L ¼ bearing length (mm)
R
J
, R
L
, R
b
¼ radius of journal, lobe and bearing
X, Y, Z ¼ Cartesian coordinates
X
J
, Z
J
¼ coordinates of steady state equilibrium
journal center from geometric centre of
bearing
Greek symbols
u
¼ angle of inter-recess land width
l
¼ aspect ratio (L/D)
m
¼ dynamic viscosity of lubricant (N sm
2 2
)
m
r
¼ dynamic viscosity of lubricant at reference
temperature and pressure (N sm
2 2
)
r
¼ density of lubricant (kg mm
2 3
)
v
J
¼ journal rotational speed (rad s
2 1
)
v
I
¼ (g/c)
1/2
(rad s
2 1
)
v
th
¼ threshold speed (rad s
2 1
)
O
J
, O
Li
¼ journal centre, lobe centre
p
s
¼ lubricant supply pressure
Q
c
¼ flow rate for constant flow valve restrictor
Non-dimensional parameters
a
b
¼ land width ratio (a
b
/L)
C
i;j
¼ damping coefficients, C
ij
c
3
=
m
R
4
J
,
(i, j ¼ 1, 2)
F ¼ ðF=p
s
R
2
J
Þ
F
0
¼ ðF
0
=p
s
R
2
J
Þ
F
x
;
F
z
¼ ðF
x
; F
z
=p
s
R
2
J
Þ
h ¼ h/c
h
min
¼ minimum fluid film thickness (
h
min
=c)
x ¼ x/c
z ¼ z/c
p ¼ p/p
s
Q ¼ Q(
m
/c
3
p
s
)
S
ij
¼ stiffness coefficients, S
ij
c=p
s
R
2
J
,
(i, j ¼ 1, 2)
t ¼ tðc
2
p
s
=
m
R
2
J
Þ
W
o
¼ external load (W
o
=p
s
R
2
J
)
X
J
¼ X
J
/c
Z
J
¼ Z
J
/c
X
i
L
;
Z
i
L
¼ ðX
i
L
; Z
i
L
Þ=c
(
a
,
b
) ¼ circumferential, axial coordinates (X, Y)/R
J
1 ¼ eccentricity ratio (e/c)
d
w
¼ nondimensional wear depth (
d
w
/c)
The current issue and full text archive of this journal is available at
www.emeraldinsight.com/0036-8792.htm
Industrial Lubrication and Tribology
64/3 (2012) 171– 181
q Emerald Group Publishing Limited [ISSN 0036-8792]
[DOI 10.1108/00368791211218704]
171