1、BRITISH STANDARD CONFIRMED OCTOBER1990 BS5791-2: 1979 ISO3857-II: 1977 Glossary of terms for Compressors, pneumatic tools and machines Part2: Compressors ISO title: Compressors pneumatic tools and machines Vocabulary Part II: Compressors UDC 621.51/.54:001.4BS5791-2:1979 This British Standard, havin
2、g been prepared under the directionof the Mechanical Engineering Standards Committee, was published underthe authority of the Executive Board and comes into effect on 31 October1979 BSI10-1999 The following BSI references relate to the work on this standard: Committee referenceMEE/39 Draft for comme
3、nt74/74136DC ISBN 0 580 10914 3 Cooperating organizations The Mechanical Engineering Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Associated Offices Te
4、chnical Committee Department of Trade (Marine Division) Association of Consulting Engineers Electricity Supply Industry in England and Association of Hydraulic Equipment Wales* Manufacturers Engineering Equipment Users Association* Association of Mining, Electrical and Federation of Manufacturers of
5、 Construction Mechanical Engineers Equipment and Cranes British Compressed Air Society* Health and Safety Executive* British Electrical and Allied Manufacturers Institution of Gas Engineers* Association (BEAMA)* Institution of Mechanical Engineers* British Gas Corporation* Institution of Plant Engin
6、eers British Gear Manufacturers Association Institution of Production Engineers British Internal Combustion Engine Lloyds Register of Shipping Manufacturers Association London Transport Executive British Pump Manufacturers Association Machine Tool Industry Research Association British Steel Corporat
7、ion Ministry of Defence* British Steel Industry National Coal Board* British Valve Manufacturers Association Oil Companies Materials Association Chartered Institution of Building Services* Process Plant Association Crown Agents for Oversea Governments and Railway Industry Association of Great Britai
8、n Administrations Society of Motor Manufacturers and Traders Department of Industry (Mechanical Limited Engineering) Telecommunication Engineering and Department of Industry (National Engineering Manufacturing Association (TEMA) Laboratory) Water-tube Boilermakers Association Department of the Envir
9、onment The organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: British Chemical Engineering Contractors Imperial College of Science and Technology Association Institu
10、te of Marine Engineers CBMPE Institution of Mining and Metallurgy Contractors Plant Association Institution of Mining Engineers Imperial Chemical Industries Limited South Wales Institute of Engineers Amendments issued since publication Amd. No. Date of issue CommentsBS5791-2:1979 BSI 10-1999 i Conte
11、nts Page Cooperating organizations Inside front cover National foreword ii Scope and field of application 1 1 General 1 2 Temperatures 1 3 Flow rates 1 4 Pressures 1 5 Powers 2 6 Specific energy requirement 2 7 Efficiencies 2 8 Related information 2BS5791-2:1979 ii BSI 10-1999 National foreword This
12、 British Standard has been prepared under the direction of the Mechanical Engineering Standards Committee and is identical with the English text of ISO3857-II “Compressors, pneumatic tools and machines Vocabulary PartII: Compressors, published by the International Organization for Standardization (I
13、SO). This glossary of terms has been prepared in three Parts, the other Parts being as follows. Part1: General; Part3: Pneumatic tools and machines 1) . Terminology and conventions. The text of the International Standard has been approved as suitable for publication, without deviation, as a BritishS
14、tandard. Some terminology and certain conventions are not identical with those used in British Standards; attention is especially drawn to the following. Where the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. A British Standard does no
15、t purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside f
16、ront cover, pagesi andii, pages1and2 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. 1) In course of preparation.BS5791-2:1979 BSI 10-1999 1 Scope and field of app
17、lication This International Standard constitutes the second part of a vocabulary relating to compressors, pneumatic tools and machines. It deals with compressors. Part I deals with basic concepts, symbols and units. PartIII 2)deals with pneumatic tools and machines. 1 General 1.1 swept volume for a
18、displacement compressor: The volume swept in one revolution by the compressing element(s) of the compressor first stage. 1.2 displacement for a displacement compressor: The volume swept by the compressing element(s) of the compressor first stage per unit of time. 1.3 clearance volume: The volume ins
19、ide a compression space, which contains gas trapped at the end of the compression cycle. 1.4 relative clearance volume: The ratio of clearance volume of the stage under consideration to the swept volume of the compressing element of this stage. 1.5 volume factor: A dimensionless number obtained by t
20、he division of the inlet volume rate of flow of one stage by the peripheral speed of the impeller and by the reference cross-section. In the case of axial flow compressors, the chosen reference cross-section is the annular cross-section formed by the outside diameter and the hub diameter of the impe
21、ller under consideration. 1.6 standard inlet point: The inlet point considered representative for each compressor. This point varies with compressor design and type of installation. (Refer to the acceptance test standard concerning each particular compressor type.) 1.7 standard discharge point. The
22、discharge point considered representative for each compressor. This point varies with compressor design and type of installation. (Refer to the acceptance test standard concerning each particular compressor type.) 1.8 standard inlet condition: The condition of the aspired gas at the standard inlet p
23、oint of the compressor. 1.9 standard discharge condition: The condition of the compressed gas at the standard discharge point of the compressor. 1.10 tip Mach number: The ratio of the circumferential or peripheral velocity of a compressor impeller to the velocity of sound in the fluid at the tempera
24、ture and inlet pressure under consideration. 2 Temperatures 2.1 inlet temperature: The total temperature at the standard inlet point of the compressor. 2.2 discharge temperature: The total temperature at the standard discharge point of the compressor. 3 Flow rates 3.1 actual volume rate of flow of a
25、 compressor (actual capacity) 3) . The actual volume rate of flow of gas compressed and delivered at the standard discharge point, referred to conditions of total temperature, total pressure and composition (for example, humidity) prevailing at the standard inlet point. 3.2 standard volume rate of f
26、low (standard capacity) 3) : The actual volume rate of flow of compressed gas as delivered at the standard discharge point, but referred to standard conditions (for temperature and pressure). 4 Pressures 4.1 inlet pressure: The total mean absolute pressure at the standard inlet point. NOTEThe total
27、absolute pressure may be replaced by the static absolute pressure provided that gas velocity and density are sufficiently low. 4.2 discharge pressure: The total mean absolute pressure at the standard discharge point. NOTEThe total absolute pressure may be replaced by the static absolute pressure pro
28、vided that gas velocity and density are sufficiently low. 4.3 total pressure ratio: The ratio between the discharge pressure and the inlet pressure. 4.4 stage pressure ratio: The pressure ratio for any particular stage in a multi-stage compressor, the discharge pressure being taken before the interc
29、ooler. 4.5 overall stage pressure ratio: The pressure ratio for any particular stage in a multi-stage compressor, the discharge pressure being taken after the intercooler (including separator). 2) In preparation. 3) The expressions “actual capacity” and “standard capacity” must be avoided as they ma
30、y be confusing.BS5791-2:1979 2 BSI 10-1999 4.6 pressure coefficient for one dynamic compressor stage. The dimensionless characteristic number obtained by division of the theoretical mass specific energy of one stage by the square of the peripheral velocity of the impeller of the stage under consider
31、ation. 4.7 overall pressure coefficient for a dynamic compressor: The dimensionless characteristic number obtained by division of the theoretical overall specific energy by the average of the squares of the peripheral velocities of the dynamic compressor impellers. 4.8 ideal multi-stage compression:
32、 The compression when a perfect gas is isentropically compressed and the gas inlet temperature as well as the amount of work spent is the same for each stage. 5 Powers According to the chosen reference process, the thermodynamic cycle may be: isothermal, i.e.assuming a compression at a constant temp
33、erature in a compressor without losses; isentropic (reversible adiabatic), i.e.assuming a compression with constant entropy; polytropic, i.e.assuming a reversible compression following a curve as close as possible to the true curve. 5.1 theoretical required power: In a compressor without losses, pow
34、er which is theoretically required to compress a gas according to the chosen reference process, from a given inlet pressure to a given discharge pressure. 5.2 indicated power: Power corresponding to the pressure-volume diagram recorded by means of an indicator. 5.3 internal power: The indicated powe
35、r to which are added the losses due to heat transmission and leaks. 5.4 shaft power: Power required on the compressor driving shaft. It is obtained by adding the mechanical losses to the internal power. The losses in external transmissions such as gear drives or belt drives are not included. 6 Speci
36、fic energy requirement 6.1 theoretical specific energy requirement: The work necessary to compress a unit mass of gas (mass specific energy) or unit volume of gas 4)(volume specific energy) according to the chosen reference process (isothermal, isentropic, polytropic) 5) . 6.2 actual specific energy
37、 requirement: The shaft input energy per unit of compressor actual rate of flow. 7 Efficiencies 7.1 theoretical efficiency: The ratio of the theoretical required power to the indicated power. According to the chosen reversible reference process, the theoretical efficiency may be polytropic, isentrop
38、ic or isothermal. 7.2 internal efficiency: The ratio of the theoretical required power to the internal power. 7.3 mechanical efficiency: The ratio of the internal power to the shaft power. 7.4 overall efficiency: The ratio of the theoretical required power to the shaft power. 7.5 volumetric efficien
39、cy: The ratio of the actual volume rate of flow to the displacement of a displacement compressor. Condensates may possibly be taken into account. 8 Related information 8.1 heat balance of a dynamic compressor: The power required by a dynamic compressor can be calculated from the heat balance if it i
40、s impossible to ascertain the electrical or mechanical power. For obtaining the heat balance, the flow and temperature rises of the compressed gas and of the coolant are measured, including those of the oil used for cooling and lubricating bearings. 8.2 specified performance: The performance fixed c
41、ontractually. NOTENot to be confused with “nominal characteristics”, wording commonly used by manufacturers, for guidance, for the definition of their machines. 4) See3.2. 5) See clause5.blankBS5791-2: 1979 ISO3857-II: 1977 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI
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