1、BSI Standards PublicationBS ISO 7902-1:2013Hydrodynamic plain journalbearings under steady-state conditions Circularcylindrical bearingsPart 1: Calculation procedureBS ISO 7902-1:2013 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 7902-1:2013.The UK participat
2、ion in its preparation was entrusted to TechnicalCommittee MCE/12, Plain bearings.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its cor
3、rectapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 82561 3ICS 21.100.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strateg
4、y Committee on 30 November 2013.Amendments issued since publicationDate Text affectedBS ISO 7902-1:2013 ISO 2013Hydrodynamic plain journal bearings under steady-state conditions Circular cylindrical bearings Part 1: Calculation procedurePaliers lisses hydrodynamiques radiaux fonctionnant en rgime st
5、abilis Paliers circulaires cylindriques Partie 1: Mthode de calculINTERNATIONAL STANDARDISO7902-1Second edition2013-11-01Reference numberISO 7902-1:2013(E)BS ISO 7902-1:2013ISO 7902-1:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2013All rights reserved. Unless otherwise spe
6、cified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or
7、ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 7902-1:2013ISO 7902-1:2013(E) ISO 2013 All rights reserved iiiContents PageForeword iv
8、1 Scope . 12 Normative references 13 Basis of calculation, assumptions, and preconditions 14 Calculation procedure 35 Symbols and units . 56 Definition of symbols . 66.1 Load-carrying capacity 66.2 Frictional power loss . 96.3 Lubricant flow rate . 106.4 Heat balance . 116.5 Minimum lubricant film t
9、hickness and specific bearing load .136.6 Operational conditions 146.7 Further influencing factors 15Annex A (normative) Calculation examples .17Bibliography .32BS ISO 7902-1:2013ISO 7902-1:2013(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national
10、standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International
11、 organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for
12、 its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/dir
13、ectives.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the
14、 Introduction and/or on the ISO list of patent declarations received. www.iso.org/patents.Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.The committee responsible for this document is ISO/TC 123, Plain bearings, Subcommit
15、tee SC 4, Methods of calculation of plain bearings.This second edition cancels and replaces the first edition (ISO 7902-1:1998), which has been technically revised.ISO 7902 consists of the following parts, under the general title Hydrodynamic plain journal bearings under steady-state conditions Circ
16、ular cylindrical bearings: Part 1: Calculation procedure Part 2: Functions used in the calculation procedure Part 3: Permissible operational parametersiv ISO 2013 All rights reservedBS ISO 7902-1:2013INTERNATIONAL STANDARD ISO 7902-1:2013(E)Hydrodynamic plain journal bearings under steady-state cond
17、itions Circular cylindrical bearings Part 1: Calculation procedure1 ScopeThis part of ISO 7902 specifies a calculation procedure for oil-lubricated hydrodynamic plain bearings, with complete separation of the shaft and bearing sliding surfaces by a film of lubricant, used for designing plain bearing
18、s that are reliable in operation.It deals with circular cylindrical bearings having angular spans, , of 360, 180, 150, 120, and 90, the arc segment being loaded centrally. Their clearance geometry is constant except for negligible deformations resulting from lubricant film pressure and temperature.T
19、he calculation procedure serves to dimension and optimize plain bearings in turbines, generators, electric motors, gear units, rolling mills, pumps, and other machines. It is limited to steady-state operation, i.e. under continuously driven operating conditions, with the magnitude and direction of l
20、oading as well as the angular speeds of all rotating parts constant. It can also be applied if a full plain bearing is subjected to a constant force rotating at any speed. Dynamic loadings, i.e. those whose magnitude and direction vary with time, such as can result from vibration effects and instabi
21、lities of rapid-running rotors, are not taken into account.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the late
22、st edition of the referenced document (including any amendments) applies.ISO 3448, Industrial liquid lubricants ISO viscosity classificationISO 7902-2:1998, Hydrodynamic plain journal bearings under steady-state conditions Circular cylindrical bearings Part 2: Functions used in the calculation proce
23、dureISO 7902-3, Hydrodynamic plain journal bearings under steady-state conditions Circular cylindrical bearings Part 3: Permissible operational parameters3 Basis of calculation, assumptions, and preconditions3.1 The basis of calculation is the numerical solution to Reynolds differential equation for
24、 a finite bearing length, taking into account the physically correct boundary conditions for the generation of pressure:+=+()xhpxxhpzuuhxJB336 (1)The symbols are given in Clause 5.See References 1 to 3 and References 11 to 14 for the derivation of Reynolds differential equation and References 4 to 6
25、, 12, and 13 for its numerical solution. ISO 2013 All rights reserved 1BS ISO 7902-1:2013ISO 7902-1:2013(E)3.2 The following idealizing assumptions and preconditions are made, the permissibility of which has been sufficiently confirmed both experimentally and in practice.a) The lubricant corresponds
26、 to a Newtonian fluid.b) All lubricant flows are laminar.c) The lubricant adheres completely to the sliding surfaces.d) The lubricant is incompressible.e) The lubricant clearance gap in the loaded area is completely filled with lubricant. Filling up of the unloaded area depends on the way the lubric
27、ant is supplied to the bearing.f) Inertia effects, gravitational and magnetic forces of the lubricant are negligible.g) The components forming the lubrication clearance gap are rigid or their deformation is negligible; their surfaces are ideal circular cylinders.h) The radii of curvature of the surf
28、aces in relative motion are large in comparison with the lubricant film thicknesses.i) The lubricant film thickness in the axial direction (z-coordinate) is constant.j) Fluctuations in pressure within the lubricant film normal to the bearing surfaces (y-coordinate) are negligible.k) There is no moti
29、on normal to the bearing surfaces (y-coordinate).l) The lubricant is isoviscous over the entire lubrication clearance gap.m) The lubricant is fed in at the start of the bearing liner or where the lubrication clearance gap is widest; the magnitude of the lubricant feed pressure is negligible in compa
30、rison with the lubricant film pressures.3.3 The boundary conditions for the generation of lubricant film pressure fulfil the following continuity conditions: at the leading edge of the pressure profile: pz10,()= ; at the bearing rim: pzB, =()=20; at the trailing edge of the pressure profile: pzz20()
31、=, ; ()=pzz20, .For some types and sizes of bearing, the boundary conditions may be specified.In partial bearings, if Formula (2) is satisfied:pipi22()41,3R,DCeff(for example as a result of high peripheral speed), higher loss coefficients and bearing temperatures shall be expected. Calculations for
32、bearings with turbulent flow cannot be carried out in accordance with this part of ISO 7902.4.7 The plain bearing calculation takes into account the following factors (starting with the known bearing dimensions and operational data): the relationship between load-carrying capacity and lubricant film
33、 thickness; the frictional power rate; the lubricant flow rate; the heat balance.All these factors are mutually dependent.The solution is obtained using an iterative method; the sequence is outlined in the flow chart in Figure 1.For optimization of individual parameters, parameter variation can be a
34、pplied; modification of the calculation sequence is possible.5 Symbols and unitsSee Figure 2 and Table 1.Minimum lubricant film thickness, hmin:hmin= ()DDeDJ0,512 (5)where the relative eccentricity, , is given by =eDDJ2(6)Ifpipi22 1,2 m/skVAa=+712 (19)(See References 3 and 14.)Should the area of the
35、 heat-emitting surface, A, of the bearing housing not be known exactly, the following can be used as an approximation: for cylindrical housingsADDDB=()+2422pipiHHH(20) for pedestal bearingsAHBH=+piH2(21) for bearings in the machine structureADB=()15 20to (22)whereBHis the length of the axial housing
36、;DHis the length of the outside diameter of the housing;H is the length of the total height of the pedestal bearing.6.4.2 Heat dissipation via the lubricantIn the case of force-feed lubrication, heat dissipation is via the lubricant:PcQT Tth,L ex en=() (23)For mineral lubricants, the volume-specific
37、 heat is given by:cx=()18 1063,/JmK (24)From the heat balance, it follows thatPPth fthamb,= 12 ISO 2013 All rights reservedBS ISO 7902-1:2013ISO 7902-1:2013(E)for pressureless-lubricated bearings andPPth fthL,= for pressure-lubricated bearings.This gives bearing temperature, TB(see Reference 15), an
38、d lubricant outlet temperature, Tex(see Reference 15). The effective film lubricant temperature with reference to the lubricant viscosity isa) in the case of pure convection: Teff= TBb) in the case of heat dissipation via the lubricant: Teff= TL= 0,5 (Ten+ Tex)At high peripheral speed, it is possibl
39、e to select, instead of these mean values, a temperature which lies nearer to the lubricant outlet temperature. The values calculated for TBand Texshall be checked for their permissibility by comparison with the permissible operational parameters, Tlim, given in ISO 7902-3.In the sequence of calcula
40、tions, at first only the operational data Tambor Tenare known, but not the effective temperature, Teff, which is required at the start of the calculation. The solution is obtained by first starting the calculation using an estimated temperature rise, i.e.a) TB,0 Tamb= 20 Kb) Tex,0 Ten= 20 Kand the c
41、orresponding operating temperatures, Teff. From the heat balance, corrected temperatures, TB,1or Tex,1, are obtained, which, by averaging with the temperatures previously assumed (TB,0or Tex,0), are iteratively improved until the difference between the values with index 0 and 1 becomes negligibly sm
42、all, for example 2 K. The condition then attained corresponds to the steady condition. During the iterative steps, the influencing factors given in 6.7 shall be taken into account. As a rule, the iteration converges rapidly. It can also be replaced by graphical interpolation in which, for calculatin
43、g Pth,fand Pth,ambor Pth,L, several temperature differences are assumed. If the heat flows Pth,amb= f (TB) or Pth,L= f (Tex) are plotted, then the steady condition is given by the intersection of the two curves (see Figure A.1).6.5 Minimum lubricant film thickness and specific bearing loadThe cleara
44、nce gap, h, in a circular cylindrical journal bearing with the shaft offset is a function given by:hD=+()05 1,coseff(25)starting with =1, in the widest clearance gap (see Figure 1).The minimum lubricant film thicknesshD=()05 1, eff(26)shall be compared with the permissible operational parameter, hli
45、m, specified in ISO 7902-3.The specific bearing load:pFDB= (27)shall be compared with the permissible operational parameter, plim, specified in ISO 7902-3. ISO 2013 All rights reserved 13BS ISO 7902-1:2013ISO 7902-1:2013(E)6.6 Operational conditionsShould the plain bearing be operated under several,
46、 varying sets of operating conditions over lengthy periods, then they shall be checked for the most unfavourable p , hmin, and TB. First, a decision shall be reached as to whether or not the bearing can be lubricated without pressure and whether or not the heat dissipation by convection suffices. Th
47、e most unfavourable thermal case shall be investigated, which, as a rule, corresponds to an operating condition at high rotary frequency together with heavy loading. If, for pure convection, excessive bearing temperatures occur, which even by increasing the dimensions of the bearing or of the surfac
48、e area of the housing to their greatest possible extent cannot be lowered to permissible values, then force-feed lubrication and oil cooling are necessary.If an operating condition under high thermal loading (low dynamic lubricant viscosity) is followed directly by one with high specific bearing loa
49、d and low rotary frequency, this new operating condition should be investigated while keeping the thermal condition from the preceding operating point.The transition to mixed friction is due to contact of the roughness peaks of the shaft and bearing under the criteria for hlimspecified in ISO 7902-3, whereby deformation is also to be taken into account. A transition eccentricity:ueff=12hDlim(28)and a transition Som
