1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationFoil bearings Guidelines for testing of the performance of foil journal bearings Testing of load capacity, friction coefficient and lifetimeBS ISO 13939:2012National forewordThis
2、 British Standard is the UK implementation of ISO 13939:2012.The UK participation in its preparation was entrusted to Technical CommitteeMCE/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 inclu
3、de all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2013.Published by BSI Standards Limited 2013.ISBN 978 0 580 75458 6 ICS 21.100.10Compliance with a British Standard cannot confer immunity from legal obligations.This B
4、ritish Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2013.Amendments issued since publicationAmd. No. Date Text affectedBRITISH STANDARDBS ISO 13939:2012 ISO 2012Foil bearings Guidelines for testing of the performance of foil journal bearings
5、 Testing of load capacity, friction coefficient and lifetimePaliers-feuilles Lignes directrices pour les essais de performance des paliers radiaux feuilles non lubrifis Essais de la capacit de charge, du coefficient de friction et de la dure de vieINTERNATIONAL STANDARDISO13939First edition2012-08-0
6、1Reference numberISO 13939:2012(E)BS ISO 13939:2012ISO 13939:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, in
7、cluding photocopying and microfilm, without permission in writing from either ISO at the address below or 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 i
8、n SwitzerlandBS ISO 13939:2012ISO 13939:2012(E) ISO 2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope 12 Symbols . 12.1 Basic characters Roman alphabet . 22.2 Basic characters Greek alphabet . 22.3 Additional signs Subscripts 22.4 Additional signs Superscript (shown on X) 33
9、Purpose of test . 34 Test conditions . 34.1 General . 34.2 Design of test facility 34.3 Installation of sensors . 34.4 Calculation of bearing torque and loads . 54.5 Test specimens 55 Test methods 65.1 Principle . 65.2 Start-stop test cycle and evaluation of the take-off speed 65.3 Evaluation of sta
10、tic load capacity . 75.4 Calculation of non-dimensional static load capacity 85.5 Coefficient of bearing load capacity 86 Clearance and eccentricity ratio . 87 Friction coefficient 98 Durability test and lifetime 108.1 Test procedure .108.2 Determination of lifetime .109 Test report .10Annex A (norm
11、ative) The configuration of a typical foil journal bearing 12Annex B (informative) Test report 14Bibliography .16BS ISO 13939:2012ISO 13939:2012(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of
12、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 organizations, governmental and non-governmental,
13、 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.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main tas
14、k of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention
15、 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.ISO 13939 was prepared by Technical Committee ISO/TC 123, Plain bearings, Subcommittee SC 7, Special types of p
16、lain bearings.iv ISO 2012 All rights reservedBS ISO 13939:2012ISO 13939:2012(E)IntroductionFoil bearing is a special type of plain bearing; at the time of publication of this International Standard, no International Standards on foil bearings exist. This International Standard is an attempt to elabo
17、rate a test method for the basic performance of a foil bearing. ISO 2012 All rights reserved vBS ISO 13939:2012Foil bearings Guidelines for testing of the performance of foil journal bearings Testing of load capacity, friction coefficient and lifetime1 ScopeThis International Standard describes a me
18、thod of comparing the performance test results of foil journal bearings, which are lubricated by air (gas) and supported by hydrodynamic force generated by the rotation of the rotating shaft. The test procedure proposed in this International Standard aims to predict and evaluate the static load capa
19、city, friction coefficient and lifetime of the foil journal bearing, and compare the results with those occurring under different test conditions, i.e. dimensions of a foil bearing, rotational speed of a shaft, pressure and humidity of surroundings and so on. The magnitude of the static load capacit
20、y can change according to the test setting, as the test conditions can be changed.The test method described in this International Standard has the following application coverage:a) the criterion of the static load capacity is the steady-state, i.e. it is applied in a limited operating condition with
21、 a uniform magnitude, load direction and rotational speed;b) the evaluation procedure can be applied only if the foil journal bearing is under a uniform rotating inertia at an arbitrary rotational speed;c) the dynamic load with a time-variant magnitude and direction is not taken into consideration;d
22、) for the purposes of this International Standard (these guidelines), the configuration of a typical foil journal bearing is presented in Annex A.2 SymbolsFor the purposes of this document, the following symbols apply.INTERNATIONAL STANDARD ISO 13939:2012(E) ISO 2012 All rights reserved 1BS ISO 1393
23、9:2012ISO 13939:2012(E)2.1 Basic characters Roman alphabetTable 1 Symbol Basic characters Roman alphabetSymbol Description UnitC Clearance, coefficient Micrometres, Non-dimensionalD Diameter Millimetresd Diameter Millimetrese Eccentricity MicrometresF Force NewtonH Height Millimetresh Humidity Perce
24、ntageL Length, lifetime Number of revolutionsp Pressure Newton per square millimetreRa Surface roughness Micrometresr Distance MillimetresT Temperature, torque Degrees Celsius, Newton-metrest Thickness MillimetresFwMass, load Newton2.2 Basic characters Greek alphabetTable 2 Symbol Basic characters G
25、reek alphabetSymbol Description UnitEccentricity ratio Non-dimensionalFriction coefficient Non-dimensionalRotational speed Revolutions per minute2.3 Additional signs SubscriptsTable 3 Symbol Additional signs SubscriptsSubscript Descriptiona Air (surrounding), average, appliedah Air in bearing housin
26、gb Bump foil, bearingf Top foil, frictionfs Top foil surfaceh Housingmax Maximumn Netr Radial, radiusR Relativeto Take-offs Steady-state, static2 ISO 2012 All rights reservedBS ISO 13939:2012ISO 13939:2012(E)2.4 Additional signs Superscript (shown on X)Table 4 Symbol Additional signs SuperscriptSupe
27、rscript Description (shown on X)XNon-dimensional value3 Purpose of testThe primary purpose of the test is to measure and evaluate the static load capacity, friction coefficients and lifetime of the foil journal bearing. These are the primary performance metrics of the foil journal bearing as a mecha
28、nical element with a specific dimension. These are closely related to the performance of the mechanical systems to which the bearings are applied.4 Test conditions4.1 GeneralIn order to compare the static load capacity, the test should be performed after the ambient pressure, temperature and humidit
29、y of the environment in which the bearing operates have reached a state of equilibrium. The bearing performance is obtained by measuring the bearing torque and the rotational speed of the shaft. In this case, the take-off speed, at which the shaft floats on the top foil without contact, may be obser
30、ved. Bearing performance should be measured and compared at a rotational speed which is higher than the take-off speed.4.2 Design of test facilityThe bearing test facility should be designed to control the relative position of the bearing in relation to the shaft. The bearing housing may be connecte
31、d to a separate supporter, such as a spring or springs. Otherwise, a vibration-proof facility may be applied in order to prevent perturbation, which can have a severe effect on the test results. Also, excessive friction can have a severe effect on the test results due to misalignment of the bearing.
32、4.3 Installation of sensorsThe equipment to measure the bearing torque and static load capacity of the foil journal bearings may be installed as shown in Figure 1. Using the measurement system clarified in Figure 1, the bearing torque and applied load may be measured and calculated as explained in 4
33、.4.As shown in Figure 2, the displacement sensors are installed at right angles to each other at both ends of the bearing housing. The displacement of the shaft centre may be observed by measuring and comparing the values arrived at. The rotational speed of the shaft may be obtained by applying a fa
34、st Fourier transform (FFT) algorithm to the measured displacement data or by the use of a rotational speed meter. A thermocouple is installed inside the bearing housing to measure the temperatures of surrounding air (gas). To measure the surface temperature of a top foil, the thermocouple should be
35、welded to the top foil surface. ISO 2012 All rights reserved 3BS ISO 13939:2012ISO 13939:2012(E)Key1 applied load2 cable3 deadweight housing4 shaft5 torque rod6 pulley7 load cell8 counterweight preloadFigure 1 Measurement system for the bearing torque and applied load4 ISO 2012 All rights reservedBS
36、 ISO 13939:2012ISO 13939:2012(E)Key1 displacement sensor2 deadweight housing3 thermocouple for measuring air temperature4 thermocouple for measuring top foil surface temperature5 shaft6 top foilFigure 2 Installation of sensors4.4 Calculation of bearing torque and loadsThe friction force, F, may be m
37、easured using a load cell linked to the torque rod installed on the outside of the housing. Then, the bearing torque, T, generated by the rotation of the shaft is obtained as the product of the friction force, F, and the distance, r, between the two centres of the housing and load cell, as given by
38、Formula (1):TF r= (1)whereT is the bearing torque;F is the friction force;r is the distance between the housing centre and the sensor-linked location of the torque rod.The net load, Fw,n, exerted on the foil journal bearing, as shown in Figure 1, is obtained by subtracting the applied load, Fw,a, me
39、asured from the load cell installed between the housing and the loading apparatus to the mass of the housing, Fw,h. Where the load is applied in the lower direction, the net load, Fw,n, is obtained by adding the mass of the housing, Fw,h, to the applied load, Fw,a.4.5 Test specimensThe housing, bump
40、 foil, top foil and shaft comprising the foil journal bearing may be designed and fabricated according to the purpose of use. ISO 2012 All rights reserved 5BS ISO 13939:2012ISO 13939:2012(E)5 Test methods5.1 PrincipleTo operate and test the foil journal bearing, the take-off speed is measured and th
41、e load-carrying capacity is evaluated after sufficient preheating has taken place. The variables necessary for test and estimation are presented in the test report (see Annex B).5.2 Start-stop test cycle and evaluation of the take-off speedUsing an electric motor or a turbine operated by a high-pres
42、sure air supply system, rotate the shaft and then the foil journal bearing starts to operate. Once the shaft begins its rotation, the bearing torque should be measured as the speed of rotation is gradually increased.Figure 3 shows a typical example of variation in bearing torque, which is measured w
43、ith the rotational speed of the shaft from the start-stop test. As the rotational speed increases, the bearing torque increases suddenly at a certain rotational speed and then decreases to maintain the steady-state condition with a relatively constant torque value. As the bearing torque decreases to
44、 meet its steady value, the rotational speed is determined as the take-off speed of the foil journal bearing and should be recorded in the test report (see Annex B). As the rotational speed decreases to zero, the bearing torque suddenly rises again and then decreases.Figure 3 Rotational speed versus
45、 bearing torque6 ISO 2012 All rights reservedBS ISO 13939:2012ISO 13939:2012(E)The following processes comprise a single start-stop test cycle.a) Firstly, the load for the start-stop test should be determined and applied. Where selecting a load to evaluate the load capacity and lifetime of the beari
46、ng, the loading value exerted on the actual rotating system should be applied. Otherwise, the initial applied load, Fw, for a start-stop test may be calculated as follows, as a rule of thumb, then applied load, Fw,a, may be evaluated by the test process in 5.3.FCLddw= ( )( ) (2)whereC is the coeffic
47、ient of foil bearing load capacity, i.e. equal to 2 000;L is the axial length of top foil, in millimetres (mm);d is the shaft diameter, in millimetres (mm); is the shaft rotational speed, in thousands of revolutions per minute (r/min).b) After the shaft reaches the take-off speed, the state should c
48、ontinue for 15 s, and then the power to the motor should be shut off to maintain a stopped state for 5 s.c) This process is defined as a start-stop test. In the start-stop test, the rotational speed, the accumulated number of shaft rotations, the bearing torque, the temperature inside the housing an
49、d the top foil surface are observed.5.3 Evaluation of static load capacityThe static load capacity, Fw,s, is the maximum steady load which may be delivered by a foil bearing in a steady-state condition.The following is the process to determine the static load capacity.a) The rotational speed of the shaft is controlled to a given test speed, for example the speed of the actual foil bearing; measurement shall not take place before thermal equilibrium is reache
