1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
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4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/ARP868CAEROSPACERECOMMENDED PRACTICEARP868 REV. CIssued 1966-06 Revised 2001-11 Re
5、affirmed 2013-08 Superseding ARP868B Method-Pressure Drop Tests for Fuel System Components RATIONALE ARP868C has been reaffirmed to comply with the SAE five-year review policy. TABLE OF CONTENTS1. SCOPE .31.1 Purpose.32. REFERENCES .33. RECOMMENDED PRACTICES .33.1 General .33.1.1 Test Liquid 33.1.2
6、Units of Measurement .33.2 Instrumentation and Equipment 33.2.1 Pressure Measurement Devices .43.2.2 Flowmeters .43.2.3 Piezometer Tubes and Attaching Fittings .43.3 Test Setups and Methods .53.3.1 Using Single Piezometer Tubes63.3.2 Using Double Piezometer Tubes 63.3.3 Using Different Size Piezomet
7、er Tubes 63.3.4 Using Non-matching Piezometer Tubes .73.3.5 Using Only One Piezometer Tube 73.3.6 Setup Effects.73.4 Running the Test.83.5 Data Reduction .93.5.1 Reduction for Single Piezometer Tube Tests .93.5.2 Data Reduction for Double Piezometer Tube Tests .93.5.3 Analyzing and Normalizing the T
8、est Data Results 10TABLE OF CONTENTS (Continued)3.6 Data Correction .103.6.1 Data Correction for Velocity Differentials 113.6.2 Data Correction for Elevation Differentials 123.6.3 Data Correction for Different Liquid 123.6.4 Data Correction for Flow Rates .133.7 Error Analysis13SAE INTERNATIONAL ARP
9、868C Page 2 of 18_ 1. SCOPE:This document provides recommended methods and describes associated equipment and test setups to assist in understanding and conducting pressure drop tests on fuel system components. Background information and suggestions are provided as means of improving accuracy and re
10、peatability of test results. Although written specifically for fuel system components, the methods, equipment and suggestions presented herein apply equally to pressure drop tests of other liquid-handling devices.1.1 Purpose:The purpose of conducting a pressure drop test on a component is to establi
11、sh the energy (pressure) loss resulting from flowing liquid into one port and out of another under stated conditions such as flow rate, attitude, degree of valve opening, flow direction, fluid density, viscosity and temperature. Resulting pressure drop data may be used to predict or compare relative
12、 pressure drop of similar devices or to make various system analyses in conjunction with pressure drop data of associated piping and other components.2. REFERENCES:There are referenced publications specified herein.3. RECOMMENDED PRACTICES:3.1 General:3.1.1 Test Liquid: Any liquid having specific gr
13、avity and viscosity similar to that of the liquid intended for use in the test specimens may be used. If required by the procedure, the observed pressure drop value may be corrected for the liquid intended for use. Actual value of test liquid specific gravity should be measured and recorded at the t
14、ime of testing.3.1.2 Units of Measurement: The units of measurement such as flow, pressure, density, etc. will be stated or implied in the performance requirements for the component being tested. Ideally, these units will be used uniformly throughout all test readings, recordings and mathematics. Wh
15、en conversions are necessary, they must be performed using appropriate universal conversion factors and equations. Paragraph 3.6 addresses such conversions.3.2 Instrumentation and Equipment:Pressure gages, flowmeters and piezometer tubes are sensitive test instruments and the accuracy of pressure dr
16、op data depends on their integrity and proper use. Before each use, observe each unit for evidence of appropriate storage, handling, calibration, operation and any damage which might affect test readings.SAE INTERNATIONAL ARP868C Page 3 of 18_ 3.2.1 Pressure Measurement Devices: When selecting press
17、ure measurement devices, it is important to consider the range, the sensitivity, the hysteresis and the reading accuracy as related to the test needs. Before deciding, appropriate error analysis is advised to verify suitability for the intended purpose. For simplicity, unless otherwise appropriate,
18、the term “gage“ is used herein.Gages for fuel pressure drop testing are generally the mechanical dial type. In low pressure applications, the use of manometers may offer superior sensitivity and accuracy. Manometer liquid should be compatible with the test liquid. Electronic gages may be selected fo
19、r automated data acquisition. Either differential or single-reading types may be used (for manometers, these are the double-leg or single-leg types).For measuring each differential pressure, one differential gage or two single gages may be used. The differential pressure gage is strongly recommended
20、 because its use substantially reduces time, labor, gage mechanical errors and reading errors. In addition, its use automatically offsets elevation (head) effects and eliminates any need for gage elevation error corrections. If two single gages are used, they should be installed at the same elevatio
21、n to eliminate the potential need for elevation error corrections.When using manometers, as with gages, the double-leg (differential pressure) type is strongly recommended. If using two single-leg manometers, their wells should be at the same elevation. For precision, the levels of the manometer liq
22、uids within the two wells should be at the same elevation. But for practical purposes, keeping the wells at the same level should suffice.3.2.2 Flowmeters: When selecting flowmeters, it is important to consider range, sensitivity, hysteresis, readout units and reading accuracy as related to the test
23、 needs. Before deciding, appropriate error analysis is advised to verify suitability for the intended purpose.Flowmeters are available in variety of types including orifice, transparent vertical “bobbin,“ positive displacement, electronic (turbine, strain gage, etc.).3.2.3 Piezometer Tubes and Attac
24、hing Fittings: Piezometer tubes provide the recommended ten diameters length (minimum) of flow straightening upstream and downstream of the test specimen. They also provide ports of appropriate configuration and locations for convenient and repeatable means of sensing the differential pressures duri
25、ng testing. Sets of piezometer tubes should be identical and as described in Figure 2.Except in special cases requiring only one piezometer tube, or tubes of differential diameters, identical pairs of piezometer tubes should be used. They should be marked for flow direction and upstream and downstre
26、am position and used accordingly. When selecting piezometer tube sets, the inside diameters “d“ should be matched as closely as possible with the inlet and outlet port diameters of the test specimen.SAE INTERNATIONAL ARP868C Page 4 of 18_ 3.2.3 (Continued):Depending on the type of fittings on the pi
27、ezometer tubes and the test specimen, attaching fittings may be required. Any additional pressure drop attributable to such fittings is charged to the test specimen automatically by the method of test. Therefore, the use of such fittings should be avoided if possible. If they are necessary, they sho
28、uld be short and straight, with smooth inside diameters the same as those of the piezometer tubes and concentrically aligned. The degree of error attributable to such fittings may be small enough to be ignored. When large or critical, they should be identified by analysis or test and subtracted. An
29、error analysis is advised to make this determination.3.3 Test Setups and Methods:The net pressure drop value derived from testing a component should be the pressure drop of the component alone and not include pressure drop effects associated with the test setup. Setup effects are generally attribute
30、d to the component attaching fittings and the piezometer tubes upstream and downstream of the component. The pressure drop of the piezometer tubes alone may be relatively large and requires data correction. That part of the measured pressure drop in a test setup which is attributable to the piezomet
31、er tubes is called the “tare pressure drop.“ The methods presented herein provide for deduction of the “tare pressure drop“ to yield the pressure drop of the component alone including that of any attaching fittings. Other potential errors in measured pressure drop values are also discussed herein.Th
32、e two basic methods for conducting pressure drop tests and making data corrections are addressed herein. They are the “single“ and the “double“ piezometer tube methods. The test setups and construction of the piezometer tubes are shown in Figures 1 and 2. Except as noted, the methods and suggestions
33、 herein apply equally to the use of single or double piezometer tubes. Variations of these two basic methods are also discussed.Note that the measured pressures are gage pressures yielding “static“ pressure drop values. Note also that most pressure drop test setups are horizontal and use identical u
34、pstream and downstream piezometer tubes. Given this, no corrections are needed for upstream to downstream differential elevation or velocity effects. Special cases where these effects must be considered are addressed herein.SAE INTERNATIONAL ARP868C Page 5 of 18_ 3.3.1 Using Single Piezometer Tubes:
35、 Probably the most common pressure drop test method is the “single piezometer tube“ method. Using this method, two successive tests are conducted. The first test yields “gross“ data and the test setup includes two single piezometer tubes, a differential pressure gage, attaching fittings and the test
36、 specimen. In the second “tare“ test, the test specimen is removed and the single piezometer tubes are jointed together. In both tests, pressure drop values are measured over a range of flow rates as required to measure the pressure drop characteristics of the test specimen and the setup. “Tare“ res
37、ults are then suitably deducted from “gross“ to yield component “net static“ pressure drop. Note that this deduction, as discussed in 3.5 requires the plotting of curves using regression analysis or curve averaging of both “gross“ and “tare“ data to compensate for data scatter then reading “gross“ a
38、nd “tare“ pressure drop values at identical flow rates from the curves before subtraction. This method will yield valid results with minimum test apparatus length, complexity and cost.3.3.2 Using Double Piezometer Tubes: The “double piezometer tube“ method offers some trade-offs in system and data c
39、omplexity as well as the potential for improved accuracy. The “double piezometer tube“ method differs from the “single piezometer tube“ method in that two double piezometer tubes are used with two differential pressure gages. Using this method, a system tare test is not required. Due to the system c
40、onfiguration and instrumentation the system tare pressure drop is automatically determined and subtracted from the system gross pressure drop simultaneously at any flow rate by algebraic manipulation of the test data as shown in 3.5.2. Regression analysis, curve averaging and plotting for the purpos
41、e of subtracting “tare“ are not required. The “double piezometer tube“ test setup requires a calibration test presented in 3.4.3 to assure accuracy. The double piezometer tubes are longer, more complex and more costly to manufacture.3.3.3 Using Different Size Piezometer Tubes: Sometimes the inlet an
42、d outlet ports of the test specimen are of different sizes. The methods are equally valid if different size, double or single piezometer tubes are used in the upstream and downstream ports. This can be verified by an analysis similar to that of Figure 3. Use of single piezometer tubes introduces an
43、error attributable to expansion or contraction loss, since in the tare test, the fitting joining the different size piezometer tubes must have different inside diameters (“d“) at the inlet and outlet. One way to correct for this error is to calculate this expansion or contraction loss for each tare
44、test flowrate and subtract it from the measured tare value. Due to varying configurations and magnitudes of expansions and contractions, the appropriate methods of calculation must be selected from readily available published material. Another way is to conduct two tare tests, one each on identical
45、pairs of the upstream and downstream piezometer tubes. The corrected tare values will be one half of the sum of the two measured values. It should be noted that with a larger diameter piezometer tube downstream, a negative static pressure drop may be indicated. This is due to velocity energy differe
46、ntial and still yields valid results when corrected using “tare“ data or data reduction per 3.5.2.SAE INTERNATIONAL ARP868C Page 6 of 18_ 3.3.4 Using Non-matching Piezometer Tubes: When the test specimen inlet and outlet ports are the same or different diameters, but not the same as the inside diame
47、ters of the piezometer tubes, an error is introduced due to the resulting expansion(s) or contraction(s). With very small diameter differences these errors may be negligible. The error can be reduced by using adapter fittings which transition the diameters with minimal pressure drop such as an entrance radius equal to half the difference of the two diameters for a contraction and a seven degree cone for an expansion.When using “double piezometer tubes“ these errors are automatically added to the pressure drop of the specimen. The same applies with “single piezo
