1、Control Valve Aerodynamic Noise PredictionApproved 19 June 1991ANSI/ISAS75.171989AMERICAN NATIONAL STANDARDCopyright GA4 1989 by the Instrument Society of America. All rights reserved. Printed in the UnitedStates of America. No part of this publication may be reproduced, stored in a retrieval system
2、, ortransmitted in any form or by any means (electronic, mechanical, photocopying, recording, orotherwise), without the prior written permission of the publisher.ISA67 Alexander DriveP.O. Box 12277Research Triangle Park, North Carolina 27709ANSI/ISA-S75.17 Control Valve Aerodynamic Noise PredictionI
3、SBN 1-55617-207-9ANSI/ISA-S75.17-1989 3PrefaceThis preface is included for informational purposes and is not part of ISA-S75.17.This standard has been prepared as part of the service of ISA toward a goal of uniformity in the field of instrumentation. To be of real value, this document should not be
4、static, but should be subject to periodic review. Toward this end, the Society welcomes all comments and criticisms, and asks that they be addressed to the Secretary, Standards and Practices Board, ISA, 67 Alexander Drive, P.O. Box 12277, Research Triangle Park, NC 27709, Telephone (919) 549-8411, e
5、-mail: standardsisa.org.The ISA Standards and Practices Department is aware of the growing need for attention to the metric system of units in general, and the International System of Units (SI) in particular, in the preparation of instrumentation standards. The Department is further aware of the be
6、nefits to USA users of ISA standards of incorporating suitable references to the SI (and the metric system) in their business and professional dealings with other countries. Toward this end, this Department will endeavor to introduce SI-acceptable metric units in all new and revised standards to the
7、 greatest extent possible. The Metric Practice Guide, which has been published by the Institute of Electrical and Electronics Engineers as ANSI/IEEE Std. 268-1982, and future revisions, will be the reference guide for definitions, symbols, abbreviations, and conversion factors. Certain metric units
8、that are not a part of the SI system are in common accepted use. This standard uses bar as a pressure measurement that is convertible to kilopascals by multiplying by 100.It is the policy of ISA to encourage and welcome the participation of all concerned individuals and interests in the development
9、of ISA standards. Participation in the ISA standards-making process by an individual in no way constitutes endorsement by the employers of the individual, of the ISA, or of any of the standards that ISA develops.The information contained in the preface, footnotes, and appendices is included for info
10、rmation only and is not a part of the standard.The following people served as members of ISA Committee SP75.17, which prepared this standard.NAME COMPANYJ. Arant, Chairman E. I. du Pont de Nemours calculations prove that a simplified expression is justified.The equations in this standard make use of
11、 the valve sizing factors defined in ANSI/ISA-S75.01 and ANSI/ISA-S75.02.This method was developed from the fundamental principles of acoustics, fluid mechanics, and mechanics.2 LimitationsThe method presented in this standard considers only single-phase dry gases and vapors; it is based on the perf
12、ect gas laws. Predictions are limited at this time to a downstream maximum velocity of Mach 0.3. Ideal straight metal pipe is assumed downstream. Uncertainties become greater as the fluid behaves less perfectly for extreme temperatures and for downstream pressures far different from atmospheric or i
13、f near the critical point.The method can be used with all conventional control valve styles including: globe, butterfly, cage type (but not with low-noise trim), and modified ball types. Specifically excluded are multistage proprietary low-noise valves and full-bore ball valves.This standard address
14、es only aerodynamic noise and does not consider any noise generated by mechanical vibrations, unstable flow patterns, and other unpredictable behavior.In the typical control valve, little noise travels through the wall of the control valve. The noise of interest is that which travels downstream of t
15、he valve inside the pipe and then escapes through the wall of the pipe to be measured typically at 1 meter (3 feet) downstream of the valve body and 1 meter (3 feet) away from the outside surface of the pipe.The majority of the test data available to validate the method is from air at moderate downs
16、tream pressures and temperatures; however, it is believed that the method is generally applicable for other gases and vapors and at higher pressures. The equations include terms that account for fluid density and ratios of specific heat.10 ANSI/ISA-S75.17-19893 NomenclatureSymbol DescriptionCustomar
17、y US Units SI Unitsc2Speed of sound, downstream ft/s m/sCvValve flow coefficientgpm/ 1cvcSpeed of sound at the vena contracta at subsonic flow conditionsft/s m/scvccSpeed of sound at the vena contracta at sonic flow conditions ft/s m/sDjDiameter of jet ft mDiDiameter, internal, pipe 2 ft mFdModifier
18、, valve style dimensionless dimensionlessFLLiquid pressure recovery factor dimensionless dimensionlessFLPProduct of the liquid pressure recovery factor of a valve with attached fittings and the piping geometry factordimensionless dimensionlessfpFrequency, peak, generated inside pipe Hz HzFPPiping ge
19、ometry factor dimensionless dimensionlessfoFrequency, coincidence Hz HzgcGravitational constant 32.17 lbm-ft/lbf-s23k Ratio of specific heats dimensionless dimensionlessLgCorrection for pipe Mach number dB dBLpiSound pressure level, internal dB dBLa“A“-weighted sound level dB (A) dB (A)MjMach number
20、, freely expanded, in the jet dimensionless dimensionlessMnMach number dimensionless dimensionlessMwMolecular weight lbm/lbm-mole kg/kg-moleNoNumber of apparent, independent, flow passages in the valve trimdimensionless dimensionlessN Numerical constants 4 4PaPressure, outside pipe, absolute lbf/ft2
21、PaP1Pressure, upstream, absolute lbf/ft2PaP2Pressure, downstream, absolute lbf/ft2PaP2BPressure, outlet at break point, absolute lbf/ft2PaP2CPressure, outlet at critical flow conditions, absolute lbf/ft2PaP2CEPressure, outlet where region of constant acoustic efficiency begins, absolutelbf/ft2PaPvcP
22、ressure, vena contracta, at subsonic flow conditions, absolute lbf/ft2PapsidANSI/ISA-S75.17-1989 11PvccPressure, vena contracta, at critical flow conditions, absolute lbf/ft2PaPoPressure, standard, reference 2116 lbf/ft25 101325 Par Radial distance centerline of pipe to observer 6 ft mR Universal Ga
23、s Constant 1545 ft-lbf/ lbm-mol-R8314 J/kgmole-KT1Temperature, upstream, absolute R KT2Temperature, downstream, absolute R KTvcTemperature, vena contracta, at subsonic flow conditions, absoluteR KTvccTemperature, vena contracta, at critical flow conditions, absolute R KtpPipe wall thickness ft mTLTr
24、ansmission loss dB dBTLfoTransmission loss at coincidence frequency dB dBTLfpCorrection for ratio of peak frequency and coincidence frequencydB dBUvcVelocity, vena contracta, at subsonic flow conditions ft/s m/sUvccVelocity, vena contracta, at critical flow conditions ft/s m/sw Mass flow rate lbm/s
25、kg/sWmStream power of mass flow ft-lbf/s WWmsStream power of mass flow at sonic velocity ft-lbf/s WwsMass flow rate at sonic velocity lbm/s kg/sWaSound power ft-lbf/s WG44 Recovery correction factor dimensionless dimensionlessG4B Acoustical efficiency factor dimensionless dimensionlessG551Mass densi
26、ty, upstream lbm/ft3kg/m3G552Mass density, downstream lbm/ft3kg/m3NOTES:1) Units for valve flow coefficient Kvare m3/h. Substitute 1.157 Kvfor Cv. The SI unit is Av = 2.40 x 10-5Cv. Kvis not SI; its use is discouraged.2) Usually, nominal diameter can be used with little loss in accuracy.3) gcis not
27、required in the SI system; use a value = 1.00 in the equations.4) Values of numerical constants are given in Ta ble 1 .5) 2116 lbf/ft2= 14.696 lbf/in26) The distance r is typically taken as 1 m (3 ft) plus the outer pipe radius.Symbol DescriptionCustomary US Units SI Units12 ANSI/ISA-S75.17-1989Tabl
28、e 1 Numerical constants, N4 Pressures and pressure ratiosThe pressure in the vena contracta is developed from the definition of FL(see ANSI/ISA-S75.01):(4.1)NOTE: When the valve has attached fittings, replace FLwith FLP/FP.The pressure in the vena contracta at critical flow conditions is:(4.2)The do
29、wnstream pressure where sonic flow begins is:(4.3)NOTE: When the valve has attached fittings, replace FLwith FLP/FP.Constant Units Used in EquationsNDi, Djr, tpWa2c2P1,P2Pa, PoNJ1.5 X 10-24.6 X 10-3ftmNL5.7 X 10108.0 X 108ftmft-lbf/sWlbm/ft3kg/m3ft/sm/sNT1.1 X 10-71.1 X 10-7ftmlbf/ft2PaNF1.6 X 1045.
30、0 X 103ftmNP1.5 X 10-41.3 X 10-5ftmlbf/ft2PaNS7.0 X 10-36.5 X 10-4ftmPvcP1P1P2()FL2-=PvccP12k 1+-kk 1-=P2CP1FL2P1Pvcc()=ANSI/ISA-S75.17-1989 13The factor , the ratio between the external pressure ratio and the internal pressure ratio at critical pressure drop, is defined:(4.4)The downstream pressure
31、 at the break point between Regimes III and IV (see Section 5 for definitions of regimes) is:(4.5)The downstream pressure at the start of the region of “constant acoustic efficiency,“ where any further decrease in P2will result in no increase in noise, is:(4.6)5 Regime definitionA control valve cont
32、rols flow by converting pressure energy into kinetic energy; some of this energy is transferred to the pipe wall as vibration, and a portion of this is radiated as noise. Most of the energy is converted to heat through viscous friction.At the vena contracta there is a pressure that may be even lower
33、 than the downstream pressure.The different regimes of noise generation are the result of differing sonic phenomena or reactions between the molecules in the gas and the sonic shock cells.In Regime I, flow is subsonic and the gas pressure is partially recovered or recompressed, thus the use of the f
34、actor FL.In Regime II, sonic flow exists, with interaction between shock cells and with turbulent choked flow mixing. Pressure recovery is less as the limit of Regime II is approached.In Regime III no isentropic pressure recovery takes place.In Regime IV the shock cell structure diminishes as a “Mac
35、h disk“ is formed.In Regime V there is a constant acoustic efficiency.IF: P1 P2 P2CTHEN REGIME = I (5.1)IF: P2C P2 PvccTHEN REGIME = II (5.2)IF: Pvcc P2 P2BTHEN REGIME = III (5.3)IF: P2B P2 P2CETHEN REGIME = IV (5.4)IF: P2CE P2 0 THEN REGIME = V (5.5)P1P2C-P1Pvcc-PvccP2C-=P2BP1-1k-kk 1-=P2CEP122-=14
36、 ANSI/ISA-S75.17-19896 Preliminary calculationsNo is the number of apparent independent flow passages. Note that for cage-type trims this is usually the number of openings in the cage. Where a number of flow passages are in close proximity, as in some cage trims, the values require tests. The valve
37、style modifier Fd(see Table 2) is:(6.1)For flow-to-open valves with contoured plugs at small openings, a special case occurs:(6.2)Fd(maximum) = 0.7 for this equation.NOTE: Use the required value of Cv, not the rated value of Cv.The jet diameter is:(6.3)NOTE: Use the required value of Cv, not the rat
38、ed value of Cv.The Mach number in a freely expanded jet is:(6.4)FdNo12()=Fd0.7NSCvFL4 Di2-12()=DjNJFdCvFL()12()=Mj2k 1-P1 P2-kk 1-112()=ANSI/ISA-S75.17-1989 157 Regime I (subsonic flow)The temperature in the vena contracta is:(7.1)The speed of sound (Mn = 1) is:(7.2)Table 2 Typical Noand Fdfactors T
39、he gas velocity in the vena contracta is:(7.3)NoFdFlow to: Flow to:Valve Type Open Close Open CloseSingle-Seat Globe 2.0 1.0 0.721.0Butterfly, Standard 2.0 2.0 0.7 0.7Angle 2.0 1.0 0.7 1.0Eccentric, Rotary Plug 2.0 1.0 0.7 1.0Ball 1.0 1.0 1.0 1.0Cage 1 1 Double Seat, Parabolic 4.0 4.0 0.5 0.5NOTES:1
40、) Use the number of apparent independent openings in the cage at the actual valve stem position (refer to the manufacturers catalog for the valve under consideration).2) See Equation 6.2.TvcT1PvcP1-k 1k-=cvckRgcTvcMw-12()=Uvc2gckk 1-1PvcP1-k 1k-P11-12()=16 ANSI/ISA-S75.17-1989The stream power of the
41、 fluid in the vena contracta is:(7.4)By definition, the Mach number is:(7.5)The acoustic efficiency for Regime I is:(7.6)The sound power generated is:(7.7)NOTE: When the valve has attached fittings, replace FL with FLP/FP.The peak frequency of the generated noise from the geometry is:(7.8)8 Common e
42、quations for sonic and aboveThe temperature in the vena contracta at sonic conditions is:(8.1)The orificial velocity of sound is:(8.2)WmwUvc()22gc-=MnUvccvc-=G4BI1104()Mn3.6()=WaG4BIWmFL2=fp0.2UvcDj-=Tvcc2T1k 1+-=cvcckRgcTvccMw-12()=ANSI/ISA-S75.17-1989 17The gas velocity in the vena contracta, at c
43、ritical conditions, is:(8.3)Stream power, at sonic (choked) velocity is:(8.4)9 Regime IIThe acoustic efficiency for Regime II is:(9.1)NOTE: When the valve has attached fittings, replace FL with FLP/FP.The sound power generated is:(9.2)The peak frequency of the generated noise from the geometry is:(9
44、.3)10 Regime IIIThe acoustic efficiency for Regime III is:(10.1)NOTE: When the valve has attached fittings, replace FL with FLP/FP.The sound power generated is:(10.2)The peak frequency of the generated noise from the geometry is:Uvcc2gckk 1-1PvccP1-k 1k-P11-12()=WmswUvcc22gc-=G4BII1104()Mj()6.6FL2()
45、=WaG4BIIWmsP1P2P1Pvcc-=fp0.2MjcvccDj-=G4BIII1104()Mj()6.6FL2()=WahIIIWms=18 ANSI/ISA-S75.17-1989(10.3)11 Regime IVThe acoustic efficiency for Regime IV is:(11.1)NOTE: When the valve has attached fittings, replace FL with FLP/FP .The sound power generated is:(11.2)The peak frequency of the generated
46、noise from the geometry is:(11.3)12 Regime V(12.1)fp0.2MjcvccDj-=G4BIV1104()Mj22-2()6.6FL2()=WaG4BIVWms=fp0.35cvcc1.25DjMj21()12()-=Mj2k 1-22()k 1k-112()=ANSI/ISA-S75.17-1989 19The acoustic efficiency for Regime V is:(12.2)NOTE: When the valve has attached fittings, replace FL with FLP/FP .The sound
47、 power generated is:(12.3)The peak frequency of the generated noise from the geometry is:(12.4) 13 Noise calculationsThe downstream temperature T2 may be determined using thermodynamic isenthalpic relationships, provided that the necessary fluid properties are known. However, if the fluid properties are not known, T2may be taken as approximately equal to T1.Downstream density is:(13.1)The speed of sound under downstream conditions is:(13.2)This is calculat
