1、TECHNICAL MEMORANDUMSNATIONAL ADVISORY COMMITTEE FOR AERONAUTICS7No. 952University of MarylandGlenn L. Martin L_o!t_-_it,_L_ol a ySTANDARDS FOR EISCHARGE M2ASUREMENT WITHSTANAR.DIZE_ NOZZLES AND ORIFICESGerman Industrial Standard 1952Fourth EditionVDI-Verlag. G.m.b.H., Berlin, 1937mWashingtonSeotemb
2、er 1940Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-zLProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IPREFACE TO THE _._IRD EDITI0_*The third edition of the Stand_rds has been _c,vi,odon the basis
3、 of new knowledge which h_%s been collectedthrough application of the first two editions to practice,The construction of the Standards is now clearly di-vided into definitions of standardized de_:ign?_ of throt-tlin devices and their standardized installations, andguiding information which is to be
4、considered v:hen devi_-tions from the standardized ma_ufacture or the standard-ized installation occur. Throu O.f upto m = ?.64. These investi,_atio!_s have shown ths, t thedi_char 0._5 are lower than ._iv?nin the first and second editions, and thst the basic tol-erance for m is to be increased for
5、high values of m.Figure 2, Data Sheet i. shows the desi;_n of the standardnozzle for m 0.45, and Data Sh_et 5 _ives the new ,AiT-charge coefficients 2 ,-74_.%,072A“0Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo repro
6、duction or networking permitted without license from IHS-,-,- VTA_ DA,DSC. SUPPLEMENTARY I:IFORMATION ON THE S _“ _ I. Effect of differences from the stand,telinstallationII. Throttling device_ at the inlet andoutlet of pipesIII. Throttling devices at r_tios of y,ros_uresabove the critics,IV. Thrott
7、lln_ devices with constant dizc:sr_ecoefficients at low t_lues of theReynolds numberV. Gener_,l inform;Ltion on the ccnuectiu_ linesand the differentia,1 pre_flure 3:_5 the profile of thai noz_:l_ i_ to beturned out, as shov, n in =_izure 2, Data Sh_t. 0.7, _, 150 r.n. the cc!_-_ei,_ distinctlyb_:ok
8、en, For such _on-sharp edges, the :lisch_.rge coeffi-cient must be increased (Data Sheet 5, figs. 24b), and i_-creases in the tolerance (Data Sheet 5, fi_;. 24f) _:.ust bemade if there is any doubt of the o_rfecti_n _f the cd_esharpness.The upstream face should be smooth. _t le:_st n_ar th_upstream
9、edge of the orifice.18. The orifice diameter is to be :c_:_urn(l_ihh _.,tol-erance of 0.001 d.The elate thickness sheud be equ:_l _o or Ic_ thanO.ID and the length of the cylindrical _str_am D_rt sho_.idbe equ:_tl to or le_,_ than O.02D. Thr aboutmm - if the condensate loots on the side ere u_,d. A_
10、._result of this requirement and that in fi_ure I, Data Shc_,t,.J1 - that the width of the pre_,sure top _-.O._ZD - only annu-lar chambers are applicable for sta_dardize_ ;te_m m(_,_,_.r_-merit in _ipes of small dlar:eter.With a anular chambers, the pressure tee slit ,_hould beas narrow as possible
11、in order to egu:,lize the, prc_,suresatisfactorily. (Tote, however, the effect of s_rf_,cetension if the slot is too nc,rro_v. )_.i. In making the throttlln_I devices, they :_a:.;besplit up into parts, as shown in figure_s _,to IS of Dat:tSheet i, in order to facilitate manufacture, inteichan_,-abil
12、ity, etc. The materials of the throttling devices :_n,_tbe so chosen that they :viii not wear r,o_dl_._-“ P_rtic,_!ar-I_T with orifices, care _houid be t_en when zhioiu_ an,%installin_ th_t the sharp upstream edge is _ot d:%maged.Lil_ewi:_e, with nozzles the discharqe _d_e :_hould not be,dama_o,d. (
13、See, what is said about the orotec_iv,;, rir_, inpara_raph 14. )23. The mountin_ rings which hold the orifi_,m ol:_.,tcor the nozzle must have rounded ,_orners on the u!)_treamside (fi_s. 5 to IS, Date, Sheet .) and their inside di_,_me-ters should not be smaller than the pipe di:_m_tcr. It ispermi_
14、sible, however: to mc_ke the mountinz rin!r_ ?; _,crcc_.tlar_er than the pipe diameter :-ith sta:_dard oriCic 0.3 and within 2 perc_nt for m “beconsidered more nearly smooth as the _ia_:_ter _ncrenses.Quantitative roughness tony only be e_timated. As a _uid 0.5. no data can be _iv_n.30. The nece_z_r
15、y str_ight lengths of _oio_s u_tre.umaud downstream from the throt_lin_ devic_ ?re_ in :_ener_.l,shorter the smaller the ratio of :.teas. Con_cquently, inmany cases where a ,qufficiently !on;:_ str;oiqht length ofpipe is not ave.liable, the choice. _ of :_ _,_ler ratio ofareas will b_ _ help, in_:of
16、_r P_s the re_it_nt increase, indiffereutial prezs_re will allow.31. It is not _,ermissible to inzt_! r_ throttlin_ d_-vice close downstream from an cxp:tudin_ _,_red_., piecn. _ithorlfice_, a _trai _ _n_, section of pipe of cc_asta_:.t :_i_,_metermust be between _uch a oiece and t“.e orifice, of ,_
17、 lengthincreaszng with increms,ng ratio of _r_az of the o._ific _and with increasin_ expansion in the tnocrel l:_iece. A._ a_uide :viii serve the fact that with ori#ic_z “_,r,d a_., exo_n-sion to twice the _ipe diameter, _ str,-_i_ht u o_tream sec-tion of at i _ _t _0 D for m O.Z.ISDifferent from th
18、e third edition.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-16 ITACATechnical _,emor_,ncum id.accur_,tely, tho increased dischc_rqc coo“:icieuts ._ro vnl.dwith o tolerance concistinq of the basic tz!erance a;_d _.na._dition tl:ereto; this additio
19、:_ is -o be take: from fig_r_24f, Dat:z She.t 5.5_. In general, lac: of :_In this case both correction factors, %_ determined fromfigures 2a and 2_ib, are to be aoplied to the dischar._ecoefficient and the total toler,nce of th,_ ,_,i,seharqe coef-fi ci ent c, . _ e , .-%ncording to t,_ I_, fo _ com
20、.:inin;1 error _, i_equal to the sque. re root of the ,sum of th( _:._,u_res cf thetoleranc,_s for t_._ _ _ _.,_0_,_ _.i r th,“ pi-oerou,_hness; see examples, section V:i.15For ,mu_uring -._,.“ith_he stt;udard cz.:,.“_.,_ , “ith D =i00 am, m = 0.ZS, Re D = ,_,_,3,00, in ,o_.m,rci._ll,v,. rcu._;hpipe
21、 and _7ith the orifice ed_- z_ot abqo _:i_o-p.(Continued on p. 17)Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NAOA Technlcnl _emor_ndum No. 952 !7_5. If, in addition t.o the effects of pipe re_.ghne-:_and of lack of edge sharpness, there i_ also
22、an effectfrom the viscosity of the flowing mer_ium, the r_orrecticn_for the different effects are to be attached separately_The tolerance for the corrected discharge coefficient i_determined by means of the law for the combinln_ of orror_.(See para4raph 6.)b) For Gases and Vapors56. For the 19_0 Sta
23、ndard i_ozzle, the oxpr_nsion f_c-tot is to be taken from figures 25 and 26 of D_t_ Sh: t6 for low differential pressures and from figures 7 :_nd 28for high differential pressures, for _ = 1.31 and _ =1.4,14 respectively. Fiwure V Ires the expansion factorfor any value of _ as _ function of (Pa/?l)
24、I/_ up tothe critical pressure.57. The calculated expsnsion factor for the sta_:dardnozzle for m _ 0.4 zhows absolute arcemont with experi-(Continued from p. 16)1. The vrlue of the dischs_r4e coef-_icicnt (_a. 3asic value (fi_. 22) . 0.646b. Correction factor for rou_:hnes_ (fi_. 24:_) i._07c. Corre
25、ction factor for lack of edge sharg-hess (fi_. 2_b) 1,007d. Correction for the effect of vi_cosity(fi_. 2,c) I. r_08The corrected value of _ is a b o d = 0.6602 The valu_ of the expansion factor for “ P_ - P2pl0.15 (assumed) (fi_. 26, Data Sheet 6) 0.95_. Tolerance for _e. Basic tol_:,rance for _ fr
26、om _,9 bolo_ %he _t_ erance limit . _I.0_f. Additional tolerance because of rou_hnc_s(fi_ 24e) ,-_._g. Additional tolerance for lack ef ed_esharpness (fi_. 2,_f) . , . . 0,6% olGrancefor , (ta ZL .V/ .ca + fm + _a + ha = . m!.6 %l_Different from the third edition, to a;rioe with u,_U:lpractice: the
27、value of ( is practic_lly not affected.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-18 I_AOATechnical l_lemor_.ndumVo. 952mental v._lues. (See reference .) The tr_,ts were con-ducted with suoerhGated steam uD to the, c_itic_l pressureratio, in a r
28、ange of the Reynolds number obeys the toler-ance limit, and consequently without a zimultr_neous effectof viscosity. The same was found Is for air (Tith tke 1012standard nozzle) at a pre,_sure ratio of P_/PI = 0.9.Therefore it may be expected that the cxo_r_sion factorm_y be calculated with the theo
29、retical equetions for ethere_ases and _,_nrheated steam with the sen _ o_ differentHowever, a tolerance for , ;iven in tr-ble if, is feces:-mended for the gases sad vapors that have not been ts_ted.For superheated stezm and air the _x_o-_-_s-_n_ factor _ _Iapplied without talorr_nce, as long as m _
30、?.4 and.PI - Pa 0.2 and “_s lon_, n,s the ReynoiSn :umber _ s aboTcPI =the toler:_nc_ limit. Table II ires a ,su!_,rsr?_of t.,letol-err_,_ce s.TABLE iI Tnler,_nces o,_“ the _.:_, n o ctor forSt:tndard Nozzles :_n4 8t_:-dr/! 0rifice,_Pressure 0rific_z !_r _1 sratio ._r,r For $ u e,:,r!“ ee.t e i c t
31、,e:m Cth_rPI - _ “a m _ 0.4_m _ _.-_i- “:- r; 6 ._:“,d_or- “,)or- - iPz - i i, “:_ “o rcent cent percenti),rccnt_:p, _cent percentq. -t- . . + . _0 to 0.01| 0 “ _ 0 A !, !1 !“o Ol , _, c_2! =o4 =:_. II it , _ _ I!o 0 i _ “o.o2 , O.l =o,_ =:L. _, ;“ I, “ i; “ ti _zo.l , 0.2 ! =0 !; liover 0.2 I =2_ 2
32、 ml ! _2 , _2 2.J I I l -58. The ex)qnsion factors far the 19F:_ _:ta:%dr_,rd ori-fice ms detcrmin:d b,v tests are -iso shown iu fiuze,s 25 to28. .The,v are v:_lid ._ith the tolor:_nces sho.:n in table ii,an long as the Reynold_ number is above thn tclerr_nco iir_it.59, The tolerancns for orifices a
33、re introduces princi-pally because of the stil. unexplained jumps found fn thetests with steam. (See reference 2Z.)60. The tolerances for are to be combi:ind uith tl_etolerances for the discharge coefficient b_- me,%ns of th_law for combining errors.q_UnDublished tests of H. :ueller and H. Peters (Gottin_en,with air.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
