1、AN AMERICAN NATIONAL STANDARDASME MFC-262011Measurement of Gas Flow by Bellmouth Inlet FlowmetersASME MFC-262011Measurement of Gas Flow by Bellmouth Inlet FlowmetersAN AMERICAN NATIONAL STANDARDThree Park Avenue New York, NY 10016 USADate of Issuance: August 10, 2011This Standard will be revised whe
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9、hout the prior written permission of the publisher.The American Society of Mechanical EngineersThree Park Avenue, New York, NY 10016-5990Copyright 2011 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll rights reservedPrinted in U.S.A.iiiCONTENTSForeword ivCommittee Roster vCorrespondence With the MF
10、C Committee vi1 General . 12 References . 13 Definitions and Symbols 24 Principle of Measurement and Method of Computation . 35 Flow Conditioning . 116 General Requirements 127 Discharge Coefficient Development 148 Uncertainties in the Measurement of Flow Rate 16Figures4.1-1 Bellmouth Inlet Flow Noz
11、zle General Description (Side View) 64.1-2 Bellmouth Inlet Flow Nozzle General Description (Front View) 64.3-1 Clean Inlet Method 84.3-2 Combo Probe: Ptand PsMethod . 94.3-3 Combo Probe: Ptand TtMethod . 105.2-1 Typical Boundary Layer Growth, Flat Plate Model 127.3-1 Inlet Instrumentation (Technique
12、 From Para. 4.3.1) . 15Table3.3-1 Symbols . 4Nonmandatory AppendicesA Sample Calculation Equation Set 19B Example of Empirically Derived Sensitivity . 20C Derivation of Sample Equation . 21D References for Additional Reading . 25ivFOREWORDThe bellmouth is a common device for flow conditioning and fl
13、ow measurement in the aerospace industry. Specifically, the bellmouth is attached to the front end of a turbofan gas turbine engine. Turboshaft engine applications also use the bellmouth but typically for flow conditioning and less frequently for flow measurement. The automotive industry also uses t
14、he bellmouth in some test applications. This Standard was prepared by Subcommittee 26, Bellmouth Inlet Flowmeters, of the ASME Standards Committee on Measurement of Fluids in Closed Conduits (MFC).This is the initial release of this Standard.This Standard provides information in both SI (metric) uni
15、ts and U.S. Customary units. Suggestions for improvement of this Standard are welcome. They should be sent to The American Society of Mechanical Engineers; Secretary, MFC Standards Committee; Three Park Avenue; New York, NY 10016-5990. This Standard was approved by the American National Standards In
16、stitute on March 30, 2011.vASME MFC COMMITTEEMEASUREMENT OF FLUID FLOW IN CLOSED CONDUITS(The following is the roster of the Committee at the time of approval of this Standard.)STANDARDS COMMITTEE OFFICERSR. J. DeBoom, ChairZ. D. Husain, Vice ChairD. C. Wyatt, Vice ChairC. J. Gomez, SecretarySTANDAR
17、DS COMMITTEE PERSONNELC. J. Blechinger, Honorary Member, ConsultantR. M. Bough, Rolls-Royce Corp.M. S. Carter, Flow Systems, Inc.G. P. Corpron, Honorary Member, ConsultantR. J. DeBoom, ConsultantD. Faber, Contributing Member, Badger Meter, Inc.C. J. Gomez, The American Society of Mechanical Engineer
18、sF. D. Goodson, Emerson Process Management, Daniel DivisionZ. D. Husain, Chevron Corp.C. G. Langford, Honorary Member, ConsultantT. O. Maginnis, ConsultantW. M. Mattar, Invensys/Foxboro Co.G. E. Mattingly, The Catholic University of AmericaR. W. Miller, Honorary Member, R. W. Miller however, they sh
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21、Attending Committee Meetings. The MFC Committee regularly holds meetings, which are open to the public. Persons wishing to attend any meeting should contact the Secretary of the MFC Standards Committee.ASME MFC-262011MEASUREMENT OF GAS FLOW BY BELLMOUTH INLET FLOWMETERS11 GENERAL1.1 ScopeThis Standa
22、rd applies only to the steady flow of single-phase gases and gas mixtures and applies only to bellmouth inlet flowmeters in which the flow remains subsonic throughout the measuring section and the flow is steady or varies only slowly with time. It also addresses procedures by which calibration of th
23、e device can be made to allow for application with consistent conclusions and within known limits of uncertainty. Bellmouth inlet flowmeters should be used only within the limits for which a given unit is tested, or if additional uncertainty can be tolerated, over a range within which extrapolation
24、is reliable.This Standard outlines the general geometry and method of use of bellmouth inlet flowmeters to deter-mine the mass or volumetric flow rate of the gas or gas mixture flowing through the device. It also gives nec-essary information for calculating the flow rate and its associated uncertain
25、ty.A bellmouth inlet flowmeter is a device that provides flow conditioning and flow measurement whose inlet is located or positioned in a large reservoir or supply source. The reservoir can be outside ambient, room, or plenum conditions depending on the application. The bellmouth inlet flowmeter is
26、also referred to as an airbell, nozzle with zero beta ratio, borda tube, etc. Typical geometry consists of a convergent inlet fol-lowed by a constant throat area. This flowmeter is a differential pressure type device that allows determi-nation of the flow rate from the differential pressure between
27、the total pressure and static pressure at a sin-gle specified axial location in the constant area throat of the bellmouth.1.2 PurposeThe purpose of this Standard is to provide guid-ance and recommendations for fluid flow measure-ment of gaseous applications using the bellmouth inlet flowmeter. This
28、Standard addresses the following:(a) principle of operation(b) design parameters and considerations(c) calibration methods and procedures(d) instrumentation and calculation methods(e) installation requirements and considerations(f) measurement uncertainty1.3 Field of ApplicationThe bellmouth inlet f
29、lowmeter is a common device that both conditions the flow and measures its rate and is widely used in the aerospace industry. Specifically, the discharge of the bellmouth flowmeter is often attached to the front end of a test article such as a turbofan gas turbine engine. Turboshaft engine applicati
30、ons also use the bellmouth but typically for flow conditioning and less frequently for flow measurement. The automotive indus-try also uses the bellmouth in some test applications.2 REFERENCESThe following documents form a part of this Standard to the extent specified herein. Unless otherwise speci-
31、fied, the latest edition shall apply.ASME Fluid Meters, 6th Edition, 1971ASME MFC-1M, Glossary of Terms Used in the Measu-rement of Fluid Flow in PipesASME MFC-3M, Measurement of Fluid Flow in Pipes Using Orifice, Nozzle, and Venturi ASME PTC 19.5, Flow MeasurementPublisher: The American Society of
32、Mechanical Engineers (ASME), Three Park Avenue, New York, NY 10016-5990; Order Department: 22 Law Drive, P.O. Box 2900, Fairfield, NJ 07007-2900 (www.asme.org)ISO 5167, Measurement of fluid flow by means of pres-sure differential devices inserted in circular cross-section conduits running full Publi
33、sher: International Organization for Standardization (ISO), Central Secretariat, 1, ch. de la Voie-Creuse, Case postale 56, CH-1211 Geneva 20, Switzerland (www.iso.org)ASME MFC-26201123 DEFINITIONS AND SYMBOLSThis Standard is written to serve the flow measure-ment community in general. Throughout th
34、is Standard flow measurement nomenclature will be given first, with aerospace-industryspecific nomenclature pro-vided as ancillary. Similar treatment will be made for equations.3.1 Definitions From ASME MFC-1Mbase flow rate: the flow rate calculated from flowing con-ditions to base conditions of pre
35、ssure and temperature.calibration: the experimental determination of the rela-tionship between the quantity being measured and the device that measures it, usually by comparison with a standard. Also, the act of adjusting the output of a device to bring it to a desired value, within a specified tole
36、rance, for a particular value of the input.differential pressure (of a Pitot tube): difference between the pressures measured at the total pressure tap and the static pressure tap.flow rate: the quantity of fluid flowing through a cross-section of a pipe per unit of time.ISA 1932 nozzle: a nozzle th
37、at consists of an upstream face that is perpendicular to the throat axis, a convergent section defined by two arcs, a cylindrical throat, and a recess. ISA 1932 nozzles always have corner tappings.long radius nozzle: a nozzle that consists of an upstream face that is perpendicular to the throat axis
38、, a convergent section whose shape is a quarter ellipse, a cylindrical throat, and a recess or a bevel.Mach number: the ratio of the fluid velocity to the veloc-ity of sound in the fluid at the same temperature and pressure.mass flow rate: the rate of flow of fluid mass through a cross-section of a
39、pipe.nozzle: convergent device having a curved profile with no discontinuities leading to a throat.Pitot tube: tubular device consisting of a cylindrical head attached perpendicularly to a stem. It is provided with one or more pressure tap holes, and it is inserted into a flowing fluid, thus giving
40、the stagnation or static pressure.Pitot-static tube: a Pitot tube provided with static pres-sure tap holes drilled at specific positions on the cir-cumference of the cylinder that is oriented parallel to the flow direction. These holes can be drilled at one or more cross-sections. The total pressure
41、 tap faces the flow direction at the tip of the axisymmetric nose or head of the cylinder.NOTE: When there is no possibility of confusion, the expression Pitot tube without further explanation may be used to designate a Pitot-static tube.pressure taps (piezometric taps): a hole or annular slot in a
42、flange, fitting or the wall of a pipe, or throat of a primary device that is flush with the inside surface.steady flow: flow in which the flow rate in a measuring section is constant with the measurement uncertainty and over the time period of interest, aside from varia-tions related to natural turb
43、ulence generated.NOTE: The steady flows observed are, in practice, flows in which quantities such as velocity, pressure, mass, density, and tempera-ture vary in time about mean values that are independent of time; these are actually statistically steady flows.Taylor series: a power series to calcula
44、te the value of a function at a point in the neighborhood of some refer-ence point. The series expresses the difference or differ-ential between the new point and the reference point in terms of the successive derivatives of the function. NOTE: The function is not listed as it is not referenced in t
45、his Standard.total pressure Pitot tube: a Pitot tube with only a total pressure tap hole.NOTE: A total pressure Pitot tube is generally associated with a separate static pressure tap located on the pipe wall.traceability: property of a result of measurement whereby it can be related to appropriate s
46、tandards, generally inter-national or national standards, through an unbroken chain of comparisons. In the United States, the unbroken chain of comparison is with the standards at the NIST or at the state agency of weights and measures.NOTE: Measurements have traceability if and only if scientifical
47、ly rigorous evidence is produced on a continuing basis to show that the measurement process is producing measurement results (i.e., data) for which the total measurement uncertainty is quantified.uncertainty (of measurement): range within which the true value of the measured quantity can be expected
48、 to lie with a specified probability and confidence level.volume flow rate: the rate of flow of fluid volume through a cross-section of a pipe.wall taps: annular or circular hole drilled in the wall of the pipe in such a way that its edge is flush with the internal surface of the pipe, the tap being
49、 such that the pressure within the hole is the static pressure at that point in the pipe.3.2 Definitions Specific for This Standardbase conditions: specified conditions, base pressure, and base temperature to which the measured mass of a fluid is converted to the volume of the fluid. base pressure: a specified reference pressure to which a fluid volume at flowing conditions is reduced.base temperature: a specified reference temperature to which a fluid volume at flowing conditions is reduced.ASME MFC-2620113bellmouth inlet flowmeter: a device that provides flow condition
