ASTM D6424-04a(2019)
(Practice)Standard Practice for Octane Rating Naturally Aspirated Spark Ignition Aircraft Engines
Standard Practice for Octane Rating Naturally Aspirated Spark Ignition Aircraft Engines
SIGNIFICANCE AND USE
5.1 This practice is used as a basis for determining the minimum motor octane requirement of naturally aspirated aircraft engines by use of PRFs.
5.2 Results from standardized octane ratings will play an important role in defining the actual octane requirement of a given aircraft engine, which can be applied in an effort to determine a fleet requirement.
SCOPE
1.1 This practice covers ground based octane rating procedures for naturally aspirated spark ignition aircraft engines using primary reference fuels.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6424 − 04a (Reapproved 2019)
Standard Practice for
Octane Rating Naturally Aspirated Spark Ignition Aircraft
1
Engines
This standard is issued under the fixed designation D6424; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope ber that results in knock (graphic knock level descriptions can
be seen in Annex A1). For example, a test engine knocks on
1.1 This practice covers ground based octane rating proce-
primary reference fuels with 96 and 97 motor octane numbers.
dures for naturally aspirated spark ignition aircraft engines
The test engine does not knock on a primary reference fuel
using primary reference fuels.
with a 98 motor octane number. The maximum motor octane
1.2 This standard does not purport to address all of the
number that results in knock is 97, so the motor octane
safety concerns, if any, associated with its use. It is the
requirement is 98.
responsibility of the user of this standard to establish appro-
3.1.3 full rich—condition in which the mixture control is at
priate safety, health, and environmental practices and deter-
the full stop position with the fuel flow within manufacturer’s
mine the applicability of regulatory limitations prior to use.
recommended settings.
1.3 This international standard was developed in accor-
3.1.4 house fuel, n—for octane rating, an unleaded, straight
dance with internationally recognized principles on standard-
hydrocarbon fuel used for engine warm-up and all non-octane
ization established in the Decision on Principles for the
rating testing.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.1.5 knock, n—in an aircraft spark ignition engine, abnor-
Barriers to Trade (TBT) Committee.
mal combustion caused by autoignition of the air/fuel mixture.
3.1.6 knock condition, n—for octane rating,whentheknock
2. Referenced Documents
intensity in any cylinder is light knock or greater as described
2
2.1 ASTM Standards:
in Annex A1.
D2700 Test Method for Motor Octane Number of Spark-
3.1.7 knock number, n—for octane rating, a numerical
Ignition Engine Fuel
quantification of knock intensity.
3. Terminology
3.1.8 motor octane number of primary reference fuels above
3.1 Definitions:
100—determined in terms of the number of millilitres of
3.1.1 amine number of reference fuels above 100, AN,
tetraethyl lead in isooctane.
n—determined in terms of the weight percent of
3.1.9 motor octane number of primary reference fuels from
3-methylphenylamine in reference grade isooctane (2,2,
0 to 100—the volume % of isooctane (equals 100.0) in a blend
4–trimethylpentane). For example, 5 % of 3–methylphenylam-
with n-heptane (equals 0.0).
ine in reference grade isooctane has an amine number of 105
3.1.10 naturally aspirated aircraft engine, n—aircraftpiston
(AN 105). No attempt has been made to correlate performance
engine that breathes without forced means from either turbo-
number of leaded reference fuels to the amine number of
chargers or superchargers.
unleaded reference fuels, and none is implied.
3.1.11 no-knock condition, n—for octane rating, when the
3.1.2 engine motor octane requirement—one full motor
combustion instability in all cylinders is less than light knock.
octane number greater than the maximum motor octane num-
Refer to Annex A1 for description of knock intensity.
1 3.1.12 peak EGT, n—for octane rating, as the mixture is
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom- manuallyleanedfromastaterichofstoichiometric,theexhaust
mittee D02.J0.02 on Aviation Piston Engine Fuels.
gas temperature will increase with the removal of excess fuel.
Current edition approved May 1, 2019. Published June 2019. Originally
As the mixture is continually leaned, a peak temperature will
approved in 1999. Last previous edition approved in 2014 as D6424 – 04a (2014).
be attained, after which continued leaning will result in lower
DOI: 10.1520/D6424-04AR19.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
exhaust gas temperatures.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3.1.13 primary reference fuels, n—for octane rating,
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. blended fuels of reference grade isooctane and n-heptane.
Co
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