ASTM_D_6424_-_04a_2014.pdf

Designation:D642404a(Reapproved 2014)An American National StandardStandard Practice forOctane Rating Naturally Aspirated Spark Ignition AircraftEngines1This standard is issued under the fixed designation D6424;the number immediately following the designation indicates the year oforiginal adoption 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 practice covers ground based octane rating proce-dures for naturally aspirated spark 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-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D2700 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,ndeterminedintermsoftheweightpercentof3-methylphenylamine in reference grade isooctane(2,2,4trimethylpentane).For example,5%of 3methylphenylam-ine in reference grade isooctane has an amine number of 105(AN 105).No attempt has been made to correlate performancenumber of leaded reference fuels to the amine number ofunleaded reference fuels,and none 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.The 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 manufacturersrecommended 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 condition,nfor octane rating,when the knockintensity in any cylinder is light knock or greater as describedin Annex A1.3.1.7 knock number,n for octane rating,a numericalquantification of knock intensity.3.1.8 motor octane number of primary reference fuels above100determined in terms of the number of millilitres oftetraethyl lead in isooctane.3.1.9 motor octane number of primary reference fuels from0 to 100the volume%of isooctane(equals 100.0)in a blendwith n-heptane(equals 0.0).3.1.10 naturally aspirated aircraft engine,naircraft pistonengine that breathes without forced means from either turbo-chargers 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 stoichiometric,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 reference 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,1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts,Liquid Fuels,and Lubricants and is the direct responsibility of Subcom-mittee D02.J0.02 on Spark and Compression Ignition Aviation Engine Fuels.Current edition approved Dec.15,2014.Published February 2015.Originallyapproved in 1999.Last previous edition approved in 2010 as D6424 04a(2010).DOI:10.1520/D6424-04AR14.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 mixture,or engine conditions mandate restarting the clock fordetermining stable conditions.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.3.2.5 mmHgmillimetres 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 ne