1、BSI Standards Publication BS ISO 7902-1:2013 Hydrodynamic plain journal bearings under steady- state conditions Circular cylindrical bearings Part 1: Calculation procedureBS ISO 7902-1:2013 BRITISH STANDARD National foreword This British Standard is the UK implementation of ISO 7902-1:2013. The UK p
2、articipation in its preparation was entrusted to Technical Committee MCE/12, Plain bearings. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsib
3、le for its correct application. The British Standards Institution 2013. Published by BSI Standards Limited 2013 ISBN 978 0 580 82561 3 ICS 21.100.10 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard was published under the authority of the Standa
4、rds Policy and Strategy Committee on 30 November 2013. Amendments issued since publication Date Text affectedBS ISO 7902-1:2013 ISO 2013 Hydrodynamic plain journal bearings under steady-state conditions Circular cylindrical bearings Part 1: Calculation procedure Paliers lisses hydrodynamiques radiau
5、x fonctionnant en rgime stabilis Paliers circulaires cylindriques Partie 1: Mthode de calcul INTERNATIONAL STANDARD ISO 7902-1 Second edition 2013-11-01 Reference number ISO 7902-1:2013(E)BS ISO 7902-1:2013ISO 7902-1:2013(E)ii ISO 2013 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2013 All ri
6、ghts reserved. Unless otherwise specified, 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
7、either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandBS ISO 7902-1:2013ISO 7902-1:2013(E) ISO 2013 All r
8、ights reserved iii Contents Page Foreword iv 1 Scope . 1 2 Normative references 1 3 Basis of calculation, assumptions, and preconditions 1 4 Calculation procedure 3 5 Symbols and units . 5 6 Definition of s ymbols . 6 6.1 Load-carrying capacity 6 6.2 Frictional power loss . 9 6.3 Lubricant flow rate
9、 .10 6.4 Heat balance .11 6.5 Minimum lubricant film thickness and specific bearing load .13 6.6 Operational conditions14 6.7 Further influencing factors 15 Annex A (normative) Calculation examples .17 Bibliography .32BS ISO 7902-1:2013ISO 7902-1:2013(E) Foreword ISO (the International Organization
10、for Standardization) is a worldwide federation of national 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 t
11、he right to be represented on that committee. International 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 pro
12、cedures used to develop this document and those intended for 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 editor
13、ial rules of the ISO/IEC Directives, Part 2. www.iso.org/directives. 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 ide
14、ntified during the development of the document will be in the 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 respons
15、ible for this document is ISO/TC 123, Plain bearings, Subcommittee 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 Hydro
16、dynamic plain journal bearings under steady-state conditions Circular 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 ST ANDARD ISO 7902-1:
17、2013(E) Hydrodynamic plain journal bearings under steady-state conditions Circular cylindrical bearings Part 1: Calculation procedure 1 Scope This part of ISO 7902 specifies a calculation procedure for oil-lubricated hydrodynamic plain bearings, with complete separation of the shaft and bearing slid
18、ing surfaces by a film of lubricant, used for designing plain bearings 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
19、 deformations resulting from lubricant film pressure and temperature. The 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 continuo
20、usly driven operating conditions, with the magnitude and direction of loading 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 directio
21、n vary with time, such as can result from vibration effects and instabilities of rapid-running rotors, are not taken into account. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated ref
22、erences, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3448, Industrial liquid lubricants ISO viscosity classification ISO 7902-2:1998, Hydrodynamic plain journal bearings under steady-state conditions Ci
23、rcular cylindrical bearings Part 2: Functions used in the calculation procedure ISO 7902-3, Hydrodynamic plain journal bearings under steady-state conditions Circular cylindrical bearings Part 3: Permissible operational parameters 3 Basis of calculation, assumptions, and preconditions 3.1 The basis
24、of calculation is the numerical solution to Reynolds differential equation for a finite bearing length, taking into account the physically correct boundary conditions for the generation of pressure: (1) The symbols are given in Clause 5. See References 1 to 3 and References 11 to 14 for the derivati
25、on of Reynolds differential equation and References 4 to 6, 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
26、experimentally and in practice. a) The lubricant corresponds 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 lubrican
27、t. Filling up of the unloaded area depends on the way the lubricant 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
28、are ideal circular cylinders. h) The radii of curvature of the surfaces 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 t
29、he bearing surfaces ( y-coordinate) are negligible. k) There is no motion 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 w
30、idest; the magnitude of the lubricant feed pressure is negligible in comparison 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: ; at the bearing rim:
31、; at the trailing edge of the pressure profile: ; . For some types and sizes of bearing, the boundary conditions may be specified. In partial bearings, if Formula (2) is satisfied: 2 2 (2) then the trailing edge of the pressure profile lies at the outlet end of the bearing: (3) 3.4 The numerical int
32、egration of the Reynolds differential equation is carried out (possibly by applying transformation of pressure as suggested in References 3, 11, and 12) by a transformation to a differential formula which is applied to a grid system of supporting points, and which results in a system of linear formu
33、lae. The number of supporting points is significant to the accuracy of the numerical 2 ISO 2013 All rights reservedBS ISO 7902-1:2013ISO 7902-1:2013(E) integration; the use of a non-equidistant grid as given in References 6 and 13 is advantageous. After substituting the boundary conditions at the tr
34、ailing edge of the pressure profile, integration yields the pressure distribution in the circumferential and axial directions. The application of the similarity principle to hydrodynamic plain bearing theory results in dimensionless magnitudes of similarity for parameters of interest, such as load-c
35、arrying capacity, frictional behaviour, lubricant flow rate, and relative bearing length. The application of magnitudes of similarity reduces the number of numerical solutions required of Reynolds differential equation specified in ISO 7902-2. Other solutions may also be applied, provided they fulfi
36、l the conditions laid down in ISO 7902-2 and are of a similar numerical accuracy. 3.5 ISO 7902-3 includes permissible operational parameters towards which the result of the calculation shall be oriented in order to ensure correct functioning of the plain bearings. In special cases, operational param
37、eters deviating from ISO 7902-3 may be agreed upon for specific applications. 4 Calculation procedure 4.1 Calculation is understood to mean determination of correct operation by computation using actual operating parameters (see Figure 1), which can be compared with operational parameters. The opera
38、ting parameters determined under varying operating conditions shall therefore lie within the range of permissibility as compared with the operational parameters. To this end, all operating conditions during continuous operation shall be investigated. 4.2 Freedom from wear is guaranteed only if compl
39、ete separation of the mating bearing parts is achieved by the lubricant. Continuous operation in the mixed friction range results in failure. Short-time operation in the mixed friction range, for example starting up and running down machines with plain bearings, is unavoidable and does not generally
40、 result in bearing damage. When a bearing is subjected to heavy load, an auxiliary hydrostatic arrangement may be necessary for starting up and running down at a slow speed. Running-in and adaptive wear to compensate for deviations of the surface geometry from the ideal are permissible as long as th
41、ey are limited in area and time and occur without overloading effects. In certain cases, a specific running-in procedure may be beneficial, depending on the choice of materials. 4.3 The limits of mechanical loading are a function of the strength of the bearing material. Slight permanent deformations
42、 are permissible as long as they do not impair correct functioning of the plain bearing. 4.4 The limits of thermal loading result not only from the thermal stability of the bearing material but also from the viscosity-temperature relationship and by degradation of the lubricant. 4.5 A correct calcul
43、ation for plain bearings presupposes that the operating conditions are known for all cases of continuous operation. In practice, however, additional influences frequently occur, which are unknown at the design stage and cannot always be predicted. The application of an appropriate safety margin betw
44、een the actual operating parameters and permissible operational parameters is recommended. Influences include, for example: spurious forces (out-of-balance, vibrations, etc.); ISO 2013 All rights reserved 3BS ISO 7902-1:2013ISO 7902-1:2013(E)yes Figure 1 Outline of calculation deviations from the id
45、eal geometry (machining tolerances, deviations during assembly, etc.); lubricants contaminated by dirt, water, air, etc.; corrosion, electrical erosion, etc. Data on other influencing factors are given in 6.7. 4.6 The Reynolds number shall be used to verify that ISO 7902-2, for which laminar flow in
46、 the lubrication clearance gap is a necessary condition, can be applied:4 ISO 2013 All rights reservedBS ISO 7902-1:2013ISO 7902-1:2013(E) (4) In the case of plain bearings with (for example as a result of high peripheral speed), higher loss coefficients and bearing temperatures shall be expected. C
47、alculations for 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 a
48、nd lubricant film 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 applied; modification of the calculation sequence is possible. 5 Symbols and units See Figure 2 and Table 1. Minimum lubricant film thickness, h min :
