ISO 6834:2022

INTERNATIONAL ISO
STANDARD 6834
First edition
2022-10
Plain bearings — Thermo-
hydrodynamic lubrication design
charts for circular cylindrical bearings
under steady-state conditions
Paliers lisses — Diagrammes de conception de la lubrification
thermo-hydrodynamique des paliers cylindriques circulaires dans des
conditions de régime permanent
Reference number
© ISO 2022
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols, units and abbreviated terms . 1
5 Basis of calculation, assumptions, and preconditions . 5
5.1 Assumptions and preconditions . 5
5.2 ISOADI THL model . 6
5.2.1 General . 6
5.2.2 Generalized Reynolds equation . 6
5.2.3 Energy equation for lubricant film temperature distribution . 7
5.2.4 Formula for lubricant film thickness . 7
5.2.5 Formula for axial contraction ratio of lubricant streamlet . 8
5.2.6 Temperature-viscosity relationship . 8
5.2.7 Zero net heat flow method for journal surface temperature. 8
5.2.8 Formula for mixing temperature . 8
5.2.9 Balance of bearing load and lubricant film reaction force . 9
5.3 Boundary conditions . 9
5.3.1 Pressure distribution of lubricant film . 9
5.3.2 Temperature distribution of lubricant film . 9
5.4 Basis of calculation . 9
6 Design charts .10
6.1 General . 10
6.2 Input of design charts . 12
6.3 Axes of design charts .13
6.4 Read of design charts. 13
6.5 Conversion of modified dimensionless values from design charts to dimensional
ones . 13
7 Calculation procedure.14
Annex A (informative) Calculation examples .16
Bibliography .24
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 123, Plain bearings, Subcommittee SC 8,
Calculation methods for plain bearings and their applications.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv
Introduction
The calculation procedure specified in ISO 7902-1:2020 is useful to calculate the performance of
hydrodynamic plain journal bearings with a circular cylindrical shape. This procedure, however,
does not specify the maximum bearing temperature, which is one of the most important bearing
characteristics. The reason for this is that ISO 7902-1:2020 is based on the Reynolds equation which
assumes a constant lubricant film temperature. Therefore, the calculation procedure requires some
numerical iteration before the effective dynamic viscosity in the lubricant film is converged.
This document provides a calculation procedure for the maximum bearing temperature and the
effective dynamic viscosity in the lubricant film of oil-lubricated and statically loaded hydrodynamic
plain journal bearings with a circular cylindrical shape, without any complicated numerical analysis and
iterative calculation. The basic formulae contain the energy equation and the formula of temperature-
viscosity of the lubricant to obtain the maximum bearing temperature. Since the results already satisfy
the energy balance, no iterative calculation is required.
For the reason given above, the effective dynamic viscosity in the lubricant film obtained by the
procedure in this document can also be a good input data for ISO 7902-1:2020. Annex A shows an
example of how the calculated results serve to provide input data for ISO 7902-1:2020.
v
INTERNATIONAL STANDARD ISO 6834:2022(E)
Plain bearings — Thermo-hydrodynamic lubrication
design charts for circular cylindrical bearings under
steady-state conditions
1 Scope
This document specifies a calculation procedure for the maximum bearing temperature and effective
dynamic viscosity in the lubricant film of oil-lubricated and statically loaded hydrodynamic plain
journal bearings with a circular cylindrical shape, angular span Ω of 360° and width ratio B* of 0,5
to 1,5 under fluid lubrication regime. The bearing characteristics are obtained by design charts from
four dimensionless numbers which are calculated from bearing dimensions, operating conditions and
viscosity characteristics of the lubricant.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 4378-1, Plain bearings — Terms, definitions, classification and symbols — Part 1: Design, bearing
materials and their properties
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4378-1 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
streamlet
axially separated stream of lubricant flow at bearing clearance where the gap increases in the rotational
direction
4 Symbols, units and abbreviated terms
Symbols and units are defined in Figure 1 and Table 1. Abbreviated terms are defined in Table 2.
Figure 1 — Illustration of symbols
Table 1 — Symbols and their designations
Symbol Designation Unit
B Bearing width m
* *
B Width ratio (B = B/D) 1
C Bearing radial clearance (C = R − R ) m
R R J
c Specific heat of the lubricant J/(kg·K)
p
D Inside diameter of journal bearing m
D Journal diameter m
J
E Function of relative dynamic viscosity of the lubricant 1
E Function of relative dynamic viscosity of the lubricant 1
e Eccentricity between journal and bearing axis m
e Eccentricity in the horizontal direction between journal and bearing axis m
h
e Eccentricity in the vertical direction between journal and bearing axis m
v
*
Relative heat energy of lubricant at the exit of the gap 1
e
F Bearing load N
F Function of relative dynamic viscosity of the lubricant 1
F Function of relative dynamic viscosity of the lubricant 1
F Function of relative dynamic viscosity of the lubricant 1
h Local lubricant film thickness m
* *
h Relative local lubricant film thickness (h = h/C ) 1
R
-1
N Rotational frequency of the rotor s
O Centerline of circular cylindrical bearing 1
B
O Centerline of journal 1
J
NOTE 1 S number is frequently referred to as Sommerfeld number. See References [4] to [6].
[1]
NOTE 2 In ISO 4378-5, β is defined as the attitude angle or the temperature viscosity coefficient. In ISO 7902-1:2020, β is
defined as the attitude angle. However, in this document, the attitude angle and the temperature viscosity coefficient are
represented by φ and β, respectively, to avoid confusion due to duplication.
TTabablele 1 1 ((ccoonnttiinnueuedd))
Symbol Designation Unit
Pe Peclet number (Pe = Ccρω/ λ ) 1
R p
p Local lubricant film pressure Pa
* * 2
p Relative local lubricant film pressure [p = pψ /(η ω)] 1
Lubricant side flow rate leaking out of one of the bearing side ends due to
Q m /s
sf
hydrodynamic pressure
Lubricant side flow rate parameter leaking out of one of the
...