1、Designation: D7739 11Standard Practice forThermal Oxidative Stability Measurement via Quartz CrystalMicrobalance1This standard is issued under the fixed designation D7739; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This laboratory practice covers the quantitative determi-nation of surface deposits produced during the thermal oxida
3、-tion of gas turbine fuels by monitoring the oscillation fre-quency of a quartz crystal during thermal exposure. In thispractice, “thermal oxidative stability” refers to the tendency ofa fuel to resist surface deposit formation during heating.1.2 The values stated in SI units are to be regarded as t
4、hestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the a
5、pplica-bility of regulatory limitations prior to use.2. Summary of Practice2.1 A quartz crystal, fitted with gold electrodes, is fullyimmersed in test fuel contained within a reactor. An oscillatorcircuit, connected to the crystal, supplies energy to excite thequartz crystal and monitors its resonan
6、t frequency (nominally5 MHz) over time via a computer interface. The reactor isequipped with a magnetic stir bar, pressure gauge/transducer,oxygen sensor (not recommended for certain test conditions,see 4.11), and thermocouple to monitor and control testconditions. Prior to testing, the fuel is bubb
7、led with the test gasfor 30 min to equilibrate. After equilibration, the reactor vesselis isolated and raised to test temperature and pressure. Asdeposits accumulate on the crystal surface during the run, thecrystal frequency decreases. The shift in resonance frequencycan be quantitatively related,
8、in real time, to surface depositaccumulation via a variation of the Sauerbrey equation.23. Significance and Use3.1 The tendency of a jet fuel to resist the formation ofdeposits at elevated temperature is indicative of its oxidativethermal stability. This practice provides a technique for thesimultan
9、eous determination of deposit formation and oxygenconsumption during the thermal oxidation of jet fuels and otherhydrocarbon liquids. The practice can be used to evaluate thethermal stability of fuels and to determine the efficacy ofadditives in inhibiting deposition or slowing oxidation, or both.At
10、est temperature of 140C and run length up to 16 h has beenfound to be effective for the relative evaluation of fuels andfuel additives. This practice has also been employed for otherhydrocarbon liquids, such as gasoline and diesel fuels, butadditional safety issues may need to be addressed by the us
11、er.4. Apparatus4.1 All dimensions without tolerance limits are nominalvalues.4.2 ReactorA T316, 100 mL stainless steel reactor cylin-der with an internal diameter of 5.23 cm (2.06 in.) and a depthof 4.93 cm (1.94 in.).3,4A T316 stainless steel reactor headwith several openings (for example, gas inle
12、t via dip tube, gasrelease fitted with a dial gauge or pressure transducer, thermo-couple, safety rupture disk, frequency signal connection, sleevefor oxygen concentration probe). A 0.952 cm (3/8 in.) hole isdrilled in the center of the reactor head to accommodate thefrequency signal connectors. Thi
13、s hole shall have a 0.952 cm(3/8 in.) clearance from any adjacent opening.4.3 SMA Coaxial Connector AssemblyThis assembly pro-vides the electronic connection through the reactor head to thequartz crystal and consists of several key parts (see Fig. 1). Thecable from the oscillator (see 4.6) connects
14、to a subminiature1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of Subcommittee D02.J0.03on Combustion and Thermal Properties.Current edition approved June 1, 2011. Published August 2011. DOI: 10.1520/D773911.2Klave
15、tter, E. A., Martin, S. J., and Wessendorf, K. O., “Monitoring Jet FuelThermal Stability Using a Quartz Crystal Microbalance,” Energy overtightening can cause the quartzcrystal to fracture, while under-tightening will not create asuitable electrical connection.7.1.6 Lock the quartz crystal per the o
16、scillator manufactur-ers instructions.21If locked properly, frequency will vary nomore than approximately 5 Hz and voltage will vary no more15The sole source of supply of the apparatus (combination of a Cole-Parmer part#04660-40 stir plate and a Fisher Scientific part#14-513-98 stir bar) known to th
17、ecommittee at this time is Cole-Parmer Instrument Company, 625 East Bunker Court,Vernon Hills, IL 60061-1844. and Thermo Fisher Scientific, 81 Wyman St.,Waltham, MA 02454.16The sole source of supply of the apparatus (Mettler Toledo InPro 6800 sensorand 4100e transmitter) known to the committee at th
18、is time is Mettler-Toledo Inc.,1900 Polaris Parkway, Columbus, OH 43240.17The sole source of supply of the apparatus (Honeywell TJE pressuretransducer with a GM display unit) known to the committee at this time isHoneywell International, 101 Columbia Rd., Mailstop - M6/LM, Morristown, NJ07962.18The
19、sole source of supply of the apparatus (Inficon Model SC-501-1, Part#149211-1) known to the committee at this time is Inficon, Two Technology Place,East Syracuse, NY 13057.19The sole source of supply of the apparatus (Aldrich Catalog #26,406-7)known to the committee at this time is Sigma-Aldrich, 30
20、50 Spruce St., St. Louis,MO 63103.20The sole source of supply of the apparatus (Alfa Aesar #14728) known to thecommittee at this time is Alfa Aesar, 26 Parkridge Rd., Ward Hill, MA 01835.21See Section 4.1, PLO-10 Series Phase Lock Oscillator, Operation and ServiceManual, Inficon IPN 605800, Rev. G.F
21、IG. 2 Quartz Crystal (Front) Showing Proper Location of IndiumWireD7739 113than approximately 5 mV. If the readings are not steady, thecrystal may not be secure.7.1.7 An optional best practice is to record the voltage (alsoknown as conductance) of the quartz crystal in air, mV, prior toinstalling th
22、e reactor head (typically 3215 mV).7.2 Reactor:7.2.1 Insert the magnetic stir bar in the bottom of the reactorvessel.7.2.2 Charge the vessel with 60 mL of test fuel, ensuring thequartz crystal is full immersed.7.2.3 An optional best practice is to carefully remove any airbubbles from the upper surfa
23、ce of the test fuel. A disposablepipette has been found effective for this task. The proper settingfor the magnetic stir bar should be established during the initialtest setup with the reactor head off. The bar should create aslight vortex on the surface of the test fuel. Note this setting forfuture
24、 runs.7.2.4 Mate the reactor head to the reactor vessel and looselyattach the split ring assembly.7.2.5 Loosely attach the outer locking ring.7.2.6 Orient the split ring assembly so the tightening boltswill not contact any part of the head assembly. Tighten thebolts on the split ring assembly to 33.
25、9 N-m (25 lbf-ft)incrementally and in an alternating pattern to gradually andevenly secure the head to the vessel.7.2.7 Tighten the outer locking ring.7.2.8 Insert the reactor into the heater assembly.7.2.9 Ensure the green “LOCK” indicator on the oscillator islit. If not, adjust as necessary per th
26、e oscillator manufacturersinstructions.7.2.10 An optional best practice is to record the voltage(also known as conductance) of the quartz crystal immersed inthe test fuel, mV (typically 150 mV).7.2.11 Adjust the magnetic stirrer to the proper setting (see7.2.3).7.2.12 Attach the thermocouple, flexib
27、le pressure relieftubing, gas inlet and release tubing, to the reactor head. Thethermocouple should be placed just off the bottom of thevessel. Complete connections to the pressure transducer andoxygen concentration transmitter, if so equipped.7.2.13 Tighten the heating band securely to the outside
28、ofthe reactor vessel and attach the skin thermocouple if soequipped (see Fig. 4 and Fig. 5).7.2.14 Secure any safety shielding around the reactor if soequipped.7.2.15 A best practice is to ensure the reactor is sealedproperly via the following, optional steps.7.2.15.1 Slowly pressurize the reactor v
29、essel with nitrogento 689 kPa gauge (100 psig).7.2.15.2 Isolate the reactor and ensure there is no significantpressure drop for 30 min. Some minor pressure drop due tosaturation of the test fuel may be observed and is acceptable.7.2.15.3 After 30 min, slowly release the nitrogen pressure.Releasing t
30、oo quickly could disturb or possibly expel the testfuel.FIG. 3 Attachment of Quartz Crystal to AdapterD7739 1147.2.16 Slowly introduce the test gas to saturate the test fuel.Saturation may be conducted at either atmospheric or elevatedpressure. If saturation is to be conducted at atmosphericpressure
31、, ensure the reactor exhaust valve is open and slowlyincrease test gas flow to 50 6 10 mL/min. If saturation is to beconducted at elevated pressure, close the reactor exhaust valve,slowly introduce the test gas and allow pressure to build to therequired pressure. Use the reactor exhaust valve to the
32、nregulate test gas flow to 50 6 10 mL/min.7.2.17 While saturating the test fuel, frequency stabilizationshould be verified.7.2.18 After 30 min, achieve test pressure by adjusting thetest gas inlet and exhaust valves. Once test pressure has beenachieved, ensure both the test gas inlet and exhaust val
33、ves aresecurely closed, isolating the reactor.8. Procedure8.1 Energize the heater controller and activate data loggingon the control software if so equipped. A data logging intervalbetween 15 and 60 s has been found informative for this test.8.2 Initiate the test program via the control software.8.3
34、 After the test run, turn the heater off and slowlydepressurize the reactor.8.4 Ensure the vessel has cooled to near ambient conditionsprior to opening.8.5 Remove the reactor head and dispose of the test fuelproperly.8.6 Clean all hardware that came in contact with test fuelusing wipes or swabs with
35、 the TAM solution applied (see 5.2).Perform a subsequent rinse with acetone and allow the hard-ware to air dry.9. Calculation or Interpretation of Results9.1 Calculate the surface mass per unit area, rs, per Eq 1:rs5 22.21 3105! * fo f!/fo2(1)where:rs= surface mass per unit area, g/cm2,fo= initial q
36、uartz crystal resonant frequency after hightemperature stabilization, MHz, andf = quartz crystal resonant frequency at some reactiontime, t, after fo, MHz.10. Report10.1 Report test temperature, C.10.2 Report test gas utilized (for example, ultra-zero air, or60% oxygen and 40% nitrogen).10.3 Report
37、initial total gas pressure, kPa.10.4 Report the calculated surface mass, rs, versus test time.10.5 If recorded, report oxygen concentration versus testtime.10.6 If recorded, report total pressure versus test time.11. Precision and Bias11.1 Due to the limited number of installations, precisionand bia
38、s has not been established for this practice.12. Keywords12.1 gas turbine fuels; quartz crystal microbalance; thermaloxidative stabilityFIG. 4 Fully Assembled ReactorD7739 115ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentio
39、nedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee an
40、d must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting o
41、f theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box
42、 C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).FIG. 5 Close-Up of Reactor (Skin Thermocouple Shown Below Dial Pressure Gauge)D7739 116
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