1、Designation: D7739 11 (Reapproved 2016) An American National StandardStandard 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 a
2、doption or, in the case of revision, the year of 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 su
3、rface deposits produced during the thermal oxida-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 v
4、alues stated in SI units are to be regarded as thestandard. 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
5、 safety and health practices and determine the applica-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 e
6、xcite thequartz crystal and monitors its resonant 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 te
7、stconditions. Prior to testing, the fuel is bubbled 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 re
8、sonance frequencycan be quantitatively related, 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. Th
9、is practice provides a technique for thesimultaneous 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 inhibi
10、ting deposition or slowing oxidation, or both.Atest temperature of 140 C 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
11、 safety issues may need to be addressed by the user.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
12、 headwith several openings (for example, gas inlet via dip tube, gasrelease fitted with a dial gauge or pressure transducer,thermocouple, safety rupture disk, frequency signalconnection, sleeve for oxygen concentration probe). A0.952 cm (38 in.) hole is drilled in the center of the reactor headto ac
13、commodate the frequency signal connectors. This holeshall have a 0.952 cm (38 in.) clearance from any adjacentopening.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). Thec
14、able from the oscillator (see 4.6) connects to a subminiature1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-mittee D02.J0.03 on Combustion and Thermal Properties.Current edition approved Apr
15、il 1, 2016. Published May 2016. Originallyapproved in 2011. Last previous edition approved in 2011 as D7739 11. DOI:10.1520/D7739-11R16.2Klavetter, E. A., Martin, S. J., and Wessendorf, K. O., “Monitoring Jet FuelThermal Stability Using a Quartz Crystal Microbalance,” Energy overtightening can cause
16、 the quartzcrystal to fracture, while under-tightening will not create asuitable electrical connection.7.1.6 Lock the quartz crystal per the oscillator manufactur-ers instructions.21If locked properly, frequency will vary no15The sole source of supply of the apparatus (combination of a Cole-Parmer p
17、art#04660-40 stir plate and a Fisher Scientific part#14-513-98 stir bar) known to thecommittee 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
18、(Mettler Toledo InPro 6800 sensorand 4100e transmitter) known to the committee at this 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 isHon
19、eywell International, 101 Columbia Rd., Mailstop - M6/LM, Morristown, NJ07962.18The 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
20、 (Aldrich Catalog #26,406-7)known to the committee at this time is Sigma-Aldrich, 3050 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 Ser
21、ies Phase Lock Oscillator, Operation and ServiceManual, Inficon IPN 605800, Rev. G.FIG. 2 Quartz Crystal (Front) Showing Proper Location of IndiumWireD7739 11 (2016)3more than approximately 5 Hz and voltage will vary no morethan approximately 5 mV. If the readings are not steady, thecrystal may not
22、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 the 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
23、 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 surface of the test fuel. A disposablepipette has been found effective for this task. The proper settingfor the magnetic stir bar should be established duri
24、ng 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 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 Ori
25、ent the split ring assembly so the tightening boltswill not contact any part of the head assembly. Tighten thebolts on the split ring assembly to 33.9 N-m (25 lbf-ft) incre-mentally and in an alternating pattern to gradually and evenlysecure the head to the vessel.7.2.7 Tighten the outer locking rin
26、g.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 the oscillator manufacturersinstructions.7.2.10 An optional best practice is to record the voltage(also known as conductance) of the quartz crystal imm
27、ersed 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, flexible pressure relieftubing, gas inlet and release tubing, to the reactor head. Thethermocouple should be placed just off the bottom of thevessel. Compl
28、ete connections to the pressure transducer andoxygen concentration transmitter, if so equipped.7.2.13 Tighten the heating band securely to the outside 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
29、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 vessel 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 pr
30、essure 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 too quickly could disturb or possibly expel the testfuel.FIG. 3 Attachment of Quartz Crystal to AdapterD7739 11 (2016)47.2.16 Slowly introduce the tes
31、t gas to saturate the test fuel.Saturation may be conducted at either atmospheric or elevatedpressure. If saturation is to be conducted at atmosphericpressure, ensure the reactor exhaust valve is open and slowlyincrease test gas flow to 50 mL min 6 10 mL min. If satura-tion is to be conducted at ele
32、vated pressure, close the reactorexhaust valve, slowly introduce the test gas and allow pressureto build to the required pressure. Use the reactor exhaust valveto then regulate test gas flow to 50 mL min 6 10 mL min.7.2.17 While saturating the test fuel, frequency stabilizationshould be verified.7.2
33、.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 valves aresecurely closed, isolating the reactor.8. Procedure8.1 Energize the heater controller and activate data loggingon the c
34、ontrol software if so equipped. A data logging intervalbetween 15 s and 60 s has been found informative for this test.8.2 Initiate the test program via the control software.8.3 After the test run, turn the heater off and slowlydepressurize the reactor.8.4 Ensure the vessel has cooled to near ambient
35、 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 the TAM solution applied (see 5.2).Perform a subsequent rinse with acetone and allow the hard-ware to air dry.9. Calculatio
36、n or Interpretation of Results9.1 Calculate the surface mass per unit area, s, per Eq 1:s5 22.21 3105!*fo2 f!/fo2(1)where:s= surface mass per unit area, g/cm2,fo= initial quartz crystal resonant frequency after hightemperature stabilization, MHz, andf = quartz crystal resonant frequency at some reac
37、tion time,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 initial total gas pressure, kPa.10.4 Report the calculated surface mass, s, versus test time.10.5 If recorded, report oxygen c
38、oncentration 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 bias has not been established for this practice.12. Keywords12.1 gas turbine fuels; quartz crystal microbalance; thermaloxidative
39、stabilityFIG. 4 Fully Assembled ReactorD7739 11 (2016)5ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent
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