1、Designation: D 6424 04aAn American National StandardStandard Practice forOctane Rating Naturally Aspirated Spark Ignition AircraftEngines1This standard is issued under the fixed designation D 6424; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice covers ground based octane rating proce-dures for naturally aspirated spark
3、 ignition aircraft enginesusing primary reference fuels.1.2 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 applica-bilit
4、y of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 2700 Test Method for Motor Octane Number of Spark-Ignition Engine Fuel3. Terminology3.1 Definitions:3.1.1 amine number of reference fuels above 100, AN,ndetermined in terms of the weight percent of3-methylphenylami
5、ne in reference grade isooctane (2,2,4tri-methylpentane). For example, 5 % of 3methylphenylamine inreference grade isooctane has an amine number of 105 (AN105). No attempt has been made to correlate performancenumber of leaded reference fuels to the amine number ofunleaded reference fuels, and none
6、is implied.3.1.2 engine motor octane requirementone full motoroctane number greater than the maximum motor octane num-ber that results in knock (graphic knock level descriptions canbe seen in Annex A1). For example, a test engine knocks onprimary reference fuels with 96 and 97 motor octane numbers.T
7、he test engine does not knock on a primary reference fuelwith a 98 motor octane number. The maximum motor octanenumber that results in knock is 97, so the motor octanerequirement is 98.3.1.3 full richcondition in which the mixture control is atthe full stop position with the fuel flow within manufac
8、turersrecommended settings.3.1.4 house fuel, nfor octane rating, an unleaded, straighthydrocarbon fuel used for engine warm-up and all non-octanerating testing.3.1.5 knock, nin an aircraft spark ignition engine, abnor-mal combustion caused by autoignition of the air/fuel mixture.3.1.6 knock conditio
9、n, nfor octane rating, when theknock intensity in any cylinder is light knock or greater asdescribed in Annex A1.3.1.7 knock number, nfor octane rating, a numericalquantification of knock intensity.3.1.8 motor octane number of primary reference fuels above100determined in terms of the number of mill
10、ilitres oftetraethyl lead in isooctane.3.1.9 motor octane number of primary reference fuels from0to100the volume % of isooctane (equals 100.0) in a blendwith n-heptane (equals 0.0).3.1.10 naturally aspirated aircraft engine, naircraft pis-ton engine that breathes without forced means from eitherturb
11、ochargers or superchargers.3.1.11 no-knock condition, nfor octane rating, when thecombustion instability in all cylinders is less than light knock.Refer to Annex A1 for description of knock intensity.3.1.12 peak EGT, nfor octane rating, as the mixture ismanually leaned from a state rich of stoichiom
12、etric, the exhaustgas temperature will increase with the removal of excess fuel.As the mixture is continually leaned, a peak temperature willbe attained, after which continued leaning will result in lowerexhaust gas temperatures.3.1.13 primary reference fuels, nfor octane rating,blended fuels of ref
13、erence grade isooctane and n-heptane.3.1.14 stable engine conditions, nfor octane rating, cyl-inder head temperatures change less than 5C (9F) during a1-min period. Any changes or minor adjustments to throttle,mixture, or engine conditions mandate restarting the clock fordetermining stable condition
14、s.3.2 Acronyms:3.2.1 CHTcylinder head temperature.3.2.2 EGTexhaust gas temperature.3.2.3 inHginches of mercury.3.2.4 MAPmanifold absolute pressure.1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of Subcommittee D02.J
15、0 onAviation Fuels.Current edition approved Nov. 1, 2004. Published November 2004. Originallyapproved in 1999. Last previous edition approved in 2004 as D 642404.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book
16、of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.5 mmHgmillimet
17、res of mercury.3.2.6 MONmotor octane number.3.2.7 PRFprimary reference fuel.3.2.8 psigpounds per square inch gauge.3.2.9 rpmrevolutions per minute.3.2.10 TDCtop dead center.4. Summary of Practice4.1 A recently overhauled, remanufactured, or new, natu-rally aspirated aircraft engine is octane rated,
18、using PRFs, todetermine the minimum motor octane requirement. Minimummotor octane requirement is defined as one number above thehighest MON in which knock was detected. The engine istested at three or more of the worst power points subject todetonation behavior. These points usually involve high man
19、i-fold pressures. At the very least, takeoff power, a maximumcontinuous or climb power, and a cruise configuration shall betested. Takeoff power and climb power are tested under fullrich mixture conditions, and cruise power is tested under fullrich and lean mixture configurations in 5 % increment re
20、duc-tions from full rich fuel flow. Engine operating temperaturesand oil temperatures are kept at maximum allowable limits,while induction and cooling air temperatures are maintained atextreme hot day conditions for severe case testing.4.2 Octane ratings are determined under stable engineconditions
21、using PRFs of known MON.4.3 Knock sensor installation and knock quantification aredescribed in Annex A1.5. Significance and Use5.1 This practice is used as a basis for determining theminimum motor octane requirement of naturally aspiratedaircraft engines by use of PRFs.5.2 Results from standardized
22、octane ratings will play animportant role in defining the actual octane requirement of agiven aircraft engine, which can be applied in an effort todetermine a fleet requirement.6. Apparatus6.1 Instrumentation:6.1.1 The engine shall be equipped with the followinginstrumentation, which shall be accura
23、te within 62 % of fullscale unless noted otherwise.6.1.1.1 Absolute Manifold Pressure TransducerLocationof MAP sensor shall conform to engine manufacturers speci-fied location. Manifold pressures shall be measured with anaccuracy of less than 2.5 mmHg and recorded to ensure properengine behavior and
24、 repeatability.6.1.1.2 Cooling Air Pressure Transducer, located so as todetermine the pressure within the cowling.6.1.1.3 Cooling Air Temperature Sensor, located eitherwithin the cowling or at the entrance to the cowling. If athermocouple is utilized, it should extend at least a third of theway acro
25、ss the measured area.6.1.1.4 Crankshaft Angle Encoder, if required for knockdetection. The encoder shall have a sample resolution of atleast 0.4 of crank shaft rotation. The encoder TDC pulse shallbe aligned with the TDC of cylinder number one prior tooctane rating.6.1.1.5 Cylinder Head Temperature
26、Sensors, installed ineach cylinder. The sensing locations and types of thermo-couples shall conform to the engine manufacturers recommen-dations. The CHT measurements shall be accurate to within1 % of full scale.6.1.1.6 Exhaust Gas Temperature Sensors, on all cylinders.Installation shall conform wit
27、h manufacturers recommendedlocation and proper material selection. EGT probes are usuallyinstalled within 5 cm (2 in.) of the exhaust stack flange. TheEGT probes shall be accurate to within 1 % of full scale.6.1.1.7 Engine Speed SensorThe dynamometer or propel-ler stand shall measure the engine shaf
28、t speed to determinepower development. The engine speed sensor shall be accurateto within 65 rpm.6.1.1.8 Fuel Flow MeterIf the device is calibrated for aparticular fuel, then the device shall be recalibrated for eachdifferent and subsequent fuel. Data should be reported in massflow units.6.1.1.9 Fue
29、l Pressure TransducersLocations of fuel pres-sure transducers shall conform with those recommended by theengine manufacturer. One transducer is required for the me-tered fuel pressure, if necessary, and another is required for thepump pressure. The fuel inlet pressure shall not fall below theminimum
30、 specified by the engine manufacturer during therating process.6.1.1.10 Induction Air Pressure Transducer, located so as tomeasure the pressure of the induction stream prior to thethrottle plate.6.1.1.11 Induction Air Temperature Sensor, located so as tomeasure the temperature of the induction strea
31、m prior to thethrottle plate.6.1.1.12 Knock SensorsThe referee method for knockdetection is described in Annex A1. This method requires flushmounting piezoelectric transducers. At the very least, the fourcylinders with the highest CHTs shall be monitored. Thesetransducers are connected to charge amp
32、lifiers and shall becapable of measuring combustion pressures under a hightemperature environment.6.1.1.13 Oil Pressure TransducerLocation of pressuremeasurement shall conform to engine manufacturers specifiedlocation.6.1.1.14 Oil Temperature SensorLocation of temperaturemeasurement shall conform wi
33、th manufacturers specifiedlocation.6.1.1.15 Torque MeterThe dynamometer or propellerstand shall measure the torque to determine power develop-ment. The torque measurement shall be accurate to within 1 %of full scale.6.1.2 The engine should be equipped with the followinginstrumentation, which shall b
34、e accurate within 62 % of fullscale unless noted otherwise.6.1.2.1 Induction Air Flow MeterData should be pre-sented in mass flow units.6.1.2.2 Induction Air Humidity Sensor, located in either theinduction air plenum or induction air duct. Data should bepresented in absolute, rather than relative, q
35、uantities.D 6424 04a26.1.2.3 Outside Air Temperature Sensor, capable of measur-ing both the ambient wet bulb and the dry bulb temperaturesprior to any engine testing.6.2 Data Acquisition:6.2.1 The instrumentation listed in 6.1 shall be scanned andthe data recorded at least once every 15 s by an auto
36、matic dataacquisition system. The data shall be stored in a universalformat (for example, comma separated values (CSV) for IBMcompatible machines) that can be retrieved at a later date.6.2.2 If in-cylinder pressures are recorded to determineknock intensity, the pressure data shall be sampled at a ra
37、te ofat least 1800 samples per pressure cycle per cylinder.6.3 Power AbsorptionThe testing is to be performed in aground based test cell using either a dynamometer or propellertest stand that shall be capable of maintaining a constant speedto within 610 rpm.6.4 Fuel System:6.4.1 The fuel supply shal
38、l have a disposable or cleanablefilter. The filter shall allow the proper minimum fuel flow.6.4.2 The fuel selection valve shall be capable of selectingat least two different fuel sources without the possibility ofcross contamination of either source.6.4.3 The fuel supply system must comply with fed
39、eral,state, and local regulations related to fire, hazards, and healthissues.7. Reagents and Materials7.1 The MON of PRFs is confirmed by using Test MethodD 2700. All fuels used for the initial engine octane ratings arePRFs that consist of blends of reference grade isooctane andn-heptane. The PRFs w
40、ill be prepared in increments of oneMON. (WarningPRF is flammable, and its vapor is harmful.Vapors may cause flash fire.)7.1.1 Isooctane (2,2,4-trimethylpentane) shall be no lessthan 99.75 % by volume pure, contain no more than 0.10 % byvolume n-heptane, and contain no more than 0.5 mg/L (0.002g/U.S
41、. gal) of lead. (WarningIsooctane is flammable, and itsvapor is harmful. Vapors may cause flash fire.)7.1.2 n-Heptane shall be no less than 99.75 % by volumepure, contain no more than 0.10 % by volume isooctane, andcontain no more than 0.5 mg/L (0.002 g/U.S. gal) of lead.(Warningn-Heptane is flammab
42、le, and its vapor is harmful.Vapors may cause flash fire.)7.1.3 Asample shall be taken of each primary reference fueland subjected to Test Method D 2700 for motor octaneverification.7.2 Fuels used for operations other than octane rating (forexample, warm-up) shall consist of unleaded hydrocarbons an
43、dshould be capable of satisfying the test engines octanerequirement under the conditions for the fuel to be used.(WarningThese fuels are flammable, and their vapor isharmful. Vapors may cause flash fire.)7.3 Engine break-in oil shall be one approved by the enginemanufacturer.7.4 All engine operation
44、s, other than during the break-inperiod, shall be performed with an oil approved by the enginemanufacturer. (WarningLubricating oil is combustible, andits vapor is harmful.)8. Preparation of Apparatus8.1 The history and condition of each test engine should beknown and documented by means of engine l
45、og books, test runsheets, and any other documentation issued by the originalequipment manufacturers or repair overhaul shops before anyoctane rating tests are performed.8.2 Only the engine accessories required to operate theengine shall be installed on the test engine when conducting theoctane ratin
46、gs.8.3 The exhaust system employed shall not induce a backpressure greater than the back pressure called for in the enginemanufacturers specifications.8.4 If the test engines fuel system is designed to recirculatefuel to the tank, provisions shall be made to ensure that no fuelis recirculated to the
47、 containers with the PRFs.8.5 The idle mixture setting and full rich fuel flow rate shallbe set in accordance with the engine manufacturers recom-mendations.8.6 The idle stop and full throttle throw positions shall beset in accordance with the engine manufacturers recommen-dations.8.7 Before any oct
48、ane rating, and after all break-in andpower baseline runs have been performed, a cylinder compres-sion test shall be performed on all cylinders and the resultsrecorded.8.8 Prior to testing, the integrity of the fuel selection systemshall be confirmed and the system flushed. The engine fuelselector a
49、pparatus shall be checked to ensure no leakage.8.9 All engine settings shall be checked after the break-inperiod and before any octane rating. As a minimum, this shallinclude fuel pressures, oil pressure, fuel flow, and magnetotiming.8.10 A systems check shall be performed, as per specificaircraft engine manufacturers recommendations, prior to start-ing the test engine. As a minimum, this shall include thefollowing: idle throttle stop, wide open throttle throw, mixturecut-off position, and mixture full rich position.8.11 A system
