GPA TP-13-1985 Experimental Orifice Meter Studies《实验用孔板流量计研究》.pdf

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1、GPA TP-33 85 U 3824699 0033352 275 Technical Publication TP-13 Experimental Orifice Meter Studies R. G. Teyssandier 2. D. Husain M. F. Zendan Daniels Industries, Inc. Houston, Texas February 1985 1812 First Place Tulsa, Okla. 74103 Phone: 9181582.5112 GPA TP-13 85 m 3624699 0011353 101 m FOREWORD Ma

2、ss flow rate is one of the fundamen-al physical variables of fluid engineering. the development of process systems. At the American Society of Mechanical Engineers (ASME) 1984 Winter Annual Meeting various measurement subjects were discussed. Three papers presented by Daniel Industries, Inc. are rep

3、roduced herein as representing a portion of the ongoing research effort on orifice meters. The fundamental purpose of this research is to add to the industry knowledge about orifice meters. plimentary to the nearly completed three-year project sponsored by the American Petroleum Institute (API) and

4、the Gas Processors Association (GPA). mission to publish these papers as a GPA Technical Publication. Its measurement is an essential part of This research by Daniel is com- Thanks are extended to the ASME for per- J cari Sutton GPA Secretary EXPERIMENTAL INVESTIGATION OF AN ORIFICE METER PRESSURE G

5、RADIENT R. G. Teyitandier Director, Fluid Dynamics Research 2. D. Humain Senior Research Engineer Daniel Industries. Inc. Houston, Texas ABSTRACT Wall and plate pressure gradients wre investigated in a 3.5 inch (89mm) air flow orifice meter facility for 3 orifice plates covering a pipe Reynolds numb

6、er range of 21,000 to lO,000. The influence of the orifice plate on the upstream wall pressure gradient exteaded to 0.62D location. It was also found that the pressure gradient is a weak function of the orifice plate ratia The downstream minimum pressure point is located at about 3.3 dam heights. Th

7、e pressure gradient on the face of the orifice plate shows that the deflec- tion calculation based on any differential pressure taps is conservative. INTRODUCTION Improvement in the accuracy of flow measurement with orifice meters is dependent upon the accumulation of new data not only on general pa

8、rameters such as the discharge coefficient, but also on more specific parameters like the pressure field in the vicinity of the orifice. For the general parameters new data will soon be available. These data are currently being generated by three extensive studies, conducted under the auspices of th

9、e Gas Research Institute, the American Petroleum Institute and Gas Processors Association, and by the European Economic Community. While these data will presumably form the basis for a globally accepted coefficient equation, the development of that equation will require information regarding the pre

10、ssure gradients in the near field of the orifice This pressure gradient detail which was first recognized and used by Stolz 0.63. The results for the pipe- taps were generally similar but the deviation magnitude was slightly less at most values of 8. The authors did similar experiments on 100 mm (4

11、inch) and 200 mm (8 inch) lies. For the 1 O0 mm line, cd increased monotonically with 8 starting at 8 = 0.3. The deviation amounted to 0.5% at B = 0.5, and rose to a maximum of 2.4% at B = 0.75. For this case the depth ofthe recess was kept at 6 mm anditslengthwas38mm(1.5 inch)beforetheplateand34mm(

12、1.34inch) after the plate. The effect of using pipe taps instead of flange taps was similar to the 5 1 mm (2-inch) line case. For the 200 mm (8-inch) line, the trends were similar to those obtained in the 100 mm (4-inch) line. The deviation started at 8 = 0.5 and was less than0.596 at 8 = 0.6 increa

13、s- ing to 2.5% at 8 = 0.8. The authors varied the length ofthe recess in the tests in the 100 mm (4-inch) line. They found that a recess of length equal to 6.4 mm (U inch) or less had no effect on cd. Beyond 6.4 tnm (U inch) the deviation increased with the recess length up to a value of 2% at 34 mm

14、 (1.34 inch). Experiments with a recess on one side of the plate showed that the downstream recess did not have any effect on cd. GPA TP-13 85 3824679 00113bL 288 The second report found in the literature was by H. Bean 4. He reported the results of some tests done by manufacturers of orifice meter

15、equipment about 17 years earlier (in 1929). In most of these tests a refer- ence orifice was used to determine Cd. Three B ratios: 0.31.0.5 and0.69 were investigated in a 100 mm (4-inch) line using flange, radius and pipe taps. The recess depth was 2.4 mm (0.094 inch) and its length was 39.6 mm (1.5

16、6 inch). For B = 0.31, no effect on Cd was observed. For B = 0.5, the deviations were: 0.6% for flange taps and 0.25% for both radius and pipe taps. For 8 = 0.69, the deviations were: 1 .O% for flange taps, 0.5% for radius taps and 1.4% for pipe taps. McNulty and Spencer 5 investigated the effects o

17、f orifice plate carrier diameter (relative to the pipe diameter) in both rough and smooth pipes. A weigh tank system was used to determine the flow rate. The tests were done initially using a 100 mm (4-inch) line. Four orifice plates with 8 ratios of0.45,0.63,0.74 and 0.84 were used in the study. Th

18、e differential pressure was measured via comer taps of 4.8 mm (3/16 inch) diameter. The increase in carrier diameter relative to pipe diameter ranged from -2% to 14%. this corresponds to a protrusion or recess range of 1% and -7% of D (protrusions = 1 mm to -7.1 mm). Notice that a negative value ind

19、icates a recess. The results indicated that for 8 0.63, the pipe conditions and protrusions or recesses had no significant effect. For B = 0.74, Cd increased by 0.5% for recess of 5.5% of D (protrusion = -5.6 mm) and increased by 0.4% for recess of 2% of D (protrusion = -2 mm). For 8 = 0.84, the com

20、spondhghcrease in cd was about 1.5% for both recesses. For a protrusion of about 1.25% of D (protrusion = 1.3 mm), the increase in cd was negligible for 8 = 0.74 and went up to 1.8% for B = 0.84. The authors gave curve fits for the deviation in cd versus percentage change in camer diameter. Due toth

21、e limited number of points (about 4), these fits should be viewed with caution. In a previous study McNulty and Spencer 6 presented some limited data for 5 1 mm (2 inch) and 152 mm(6 inch) pipes. This data obtained in the 152 mm line indicated that for an upstream ledge (with an effective proirusion

22、 of 4.67% of D), Cd increased by 0.5% for 8 = 0.5, 1.15% for 6 = 0.6, 2% for B = 0.71 and 6% for B = 0.81, while cd did not change for the case with upstream recess of 2.5% D. The data obtained in the 5 1 mm (2-inch) line gave mixed results. The deviation of cd with a protrusion of 1.85% D (0.94 mm)

23、 from cd with the negligible recess of 0.375% D (0.2 mm) was-.16%forB = 0.44,-0.32%forB = 0.39.-1.125forB = 0.63 and +3.7% for 6 = 0.84. EXPERIMENTAL SET-UP AND TEST PROCEDURE Three orifice plates with 6 = 0.3,0.5 and0.7 were tested in a 5 1 mm (2-inch) line using water as the working fluid Figure 1

24、 gives a diagram- matic sketch of the experimental set-up. Fully developed turbulent flow was insured by having a straight pipe run of 105 diameters upstream of the test section. The actual flow rate was determined by using a dynamic weigh tank and a timer (0.001 second resolution) triggered by the

25、dynamic weight balance pointer. In the B = 0.5 and 0.7 tests reporied here, 3000 pounds of water were collected while in the B = 0.3 tests, 2000 pounds were used. The differential pressure across the orifice plate was measured via a pair of tange taps 9.5 mm (H inch) in diameter. Three DP cells were

26、 used to insure redundancy. Each of the D-P cells was caliirate against a deadweight tester and also a Werential mercury manometer. Calibrations were conducted once every two weeks or whenever a di5 crepancy appeared between readings of the three DP cells. In a typical test, the DP cell output is fe

27、d into the computer, digized and averaged. A total of 3000 samples were averaged for the B = 0.5 and 8 = 0.7 tests and 7000 samples for the 8 = 0.3 tests. These averages together with appropriate calibration curve constants, were used to obtain the mean pressure measured by each D-P cell. Agreement

28、was generally within 0.05% or less for the DP cells at the low end of the flow range. Whenever discrepancies were higher than that, the- D-P cells were checked for air bubbles and/or recabrated. The repeatability of the results for a number of representative configurations was checked and the data f

29、ound to lie within a band of width equal to O. 15% Of cd. The test program lasted for about three months. FIGURE 1 Schematic of Experimental Set-up. The test fixture is shown in Figure 2. Provisions were made for pro- trusionshecesses by using a number of rings. The width of each Mg is 12.7 mm (0.5

30、inch). This width presents an extreme from the practical point of view. All the rings have the same outside diameter (to fit in pro- vided locations in the fixture) while the inside diameter varied between different Mgs to provide different protnisions/recesses. The protrusions used in the study wer

31、e 6.35,5.3,4.3,3.2,1.6,0.15, -3.2 and -6.35 mm (0.25,0.21,0.17.0.125,0.0625,0.006,0, -0.006, -0.125 and -0.25 inches) respectively. A protrusion or recess of height equal to 0.15 mm represents the limit set by the IS0 standard based on pipe diameter toler- ance. Notice a negative value indicates a r

32、ecess. The test fixture was de signed with a provision to change protrusions (rings) at the four locations. These locations are: Adjacent to the upstream and downstream faces of the plate and two diameters upstream of the plate. The fourth location. two diameters downstream of the plate. was obtaine

33、d by inverting the whole fixture. In this investigation, the heightldepth of the protrusiodrecess was changed at one axial location while keeping the remaining locations in the flush configuration (zero protrusion). For each test the discharge coefficient was determined at 9 - 10 flow rates (Reynold

34、s numbers) for B = 0.5 and 0.7 and at about 5 - 7 flow rates for B = 0.3. H W *- - .(CI I FIGURE 2 Test Fixture. I I Fi- :. a;- ri- n I i- E 2 RESULTS AND DISCUSSIONS The results ofthis experimental program are displayed for each test in the form of a devistion of the measured discharge coefficient

35、Cd from the corresponding base line coefficient Cdo. This base line coeficient for each B ratio was obtained with no protmsions or recesses. These deviations are plotted versus OVRD, where RD is the pipe Reynolds number. Immediate Upstream Location This protrusion is located next to the plate on the

36、 upstream side (Figure 2). Figure 3a shows the deviations plotted for 6 = 0.3. The graph indicates that deviations are within a band of width = 0.10% cdo for protrusions = 1.6 mm (0.0625 inch) and less. For protrusions = 3.2, 4.3 and 6.35 mm (0.125,0.17 and 0.25 inch) the deviations are approxi- mat

37、ely 0.21, 0.63 and 1.63% of cdo. For recesses there is virtually no effect. For B = 0.5, the effect of protrusions are more pronounced while the recesses still have a negligible effect as shown in Figure 3b. For a pro- trusion = 6.35 mm (0.25 in) deviations as high as 11 5% of cdo were measured. The

38、 deviation drops to 8% for a protrusion = 5.3 mm (0.21 inches), 5% for protrusion = 4.3 mm (0.1 7 inch) and continuesthis trend down to 0.66% for protrusion = 1.6 mm (0.0625 inch). The deviation for a protrusion = O. 15 mm (0.006 inch) which is equal to the allowed pipe tolerance is negligible. Figu

39、re 3c shows similar results for 8 = 0.7. The protrusion effects are very high. Deviations vary from 47.7% of cdo for a protrusion = 6.35 mm to 0.1% for protrusion = 0.15 mm. Re- cesses have some effect for this B; 0.9% for protrusion = -3.2 mm (-0.125 inch) and 0.77% for protrusion = -6.35 mm (-0.25

40、 inch). It should be noted that neither the protrusion nor the recess effected the slope of the calibration curves. These results at the immediate upstream location are summarized in Figure 4 in the form of deviation versus normalized protrusion plotted at a given Reynolds number for each 6. These R

41、eynolds numbers are: 0.625 fr lo5 for B = 0.3, 1.67 X lo5 for 8 = 0.5 and 4 X lo5 for B = 0.7. The protrusion is normalized by the dam height H which is equal to (D-d)/2, where D and d are the pipe and orifice diameters, respectively. The figure supports the observations discussed earlier in general

42、. It shows that the shape of this relation is quite similar for different Bs; however, the magnitude of the deviation is sensitive to the valve of 8. As for the effect of recesses, they appear to have negligible effects for = 0.3 and 0.5. For = 0.7, recesses of depth 3.2 mm (0.125 inch) or greater c

43、aused an increase of cd roughly equal to 0.8%. I +-*-*-+- I . x 1L “ n.x = = * x *-* 11.1 12.1 14.0 16.0 111.0 21.W 9.1 24.1 1000,000/RD FIGURE 3a Effect of Upstream ProtrusiorRecesses for 6 = 0.3; for Symbols, See Caption of Figure 3b. *.* * c. * * * I it FIGURE 3b Effect of Upstream Protrusions/Re

44、cesses for: 13 = 0.5;$, protrusion = 6.35 mm;4, protrusion = 5.3 mm;, protrusion = 4.3 mm;%, protrusion = 3.2 mm;a, protrusion = 1.6 mm; 4, protrusion = 0.15 mm;A, protrusion = -0.15 mm; +, protrusion = -3.2 mm; .X , protrusion = -6.35 nun. “I , * . . c*-+-c-+-*-r-, q 1.1 1.5 2.1 2.5 S.1 S.5 4.1 1.6

45、 1800, BBB/RO 1 FIGURE 3c Effect of Upstream Protrusions/Recesses for: 8 = 0.7; for symbols, See Caption of Figure 3b. n *I n ! a. . . s e+ . *- , , .I I -s .IcPh - FIGURE 4 Deviation of cd for Various Upstream Protrusions/Re cesses for: 6 = 0.3 (+) at RD = 0.625 X lo5, 8 = 0.5 (+) at RD = 1.67 X lo

46、5 and 8 = 0.7 (0) at RD = 4 x 105. GPA TP-13 85 II 3824699 OOLL363 050 9 - The large increase in cd at large upstream protrusions for large 8s may be attributed to a nozzle type flow. For the extreme case of 8 = 0.7 and protrusion = 6.36 mm (0.25 inch), the flow stream in the pipe con- verges before

47、 arriving at the plate because of the relatively large annular protrusion. Obviously, the length of the protrusion is expected to be an important parameter since it determines ifthe flow has a chance to reattach and if it does, it effects the velocity profile in the vicinity of the plate. Also, one

48、may look at this configuration as a plate with a 8 = 0.933 which is determined based on the diameter of the upstream ring (which may be considered as a very, very short upstream pipe). This definitely reduces the contraction of the jet and therefore increases cd. The reason for the increase of Cd du

49、e to large upstream recesses for the 8 = 0.7 case is not clear; however, this behavior agrees with what was reported by Beitier and Overbeck 3 and by Bean 4 and with some of the results of McNulty and Spencer 161. Two Diameter Upstream Location This protrusion is located 2 pipe diameters upstream of the orifice plate. Figures 5a, 5b and 5c give the detailed results for the cd deviation from the base line case for 8 = 0.3,0.5 and0.7, respectively. The results show general trends similar to the previous case of protrusions directly upstre