Designation:D 6424–99
An American National Standard
Standard Practice for
Octane Rating Naturally Aspirated Spark Ignition Aircraft Engines 1
This standard is issued under the fixed designation D 6424;the number immediately following the designation indicates the year of original adoption or,in the ca of revision,the year of last revision.A number in parenthes indicates the year of last reapproval.A superscript epsilon (e )indicates an editorial change since the last revision or reapproval.
祝新根
1.Scope
1.1This practice covers ground bad octane rating proce-dures for naturally aspirated spark ignition aircraft engines using primary reference fuels.
1.2This standard does not purport to address all of the safety concerns,if any,associated with its u.It is the responsibility of the ur of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to u.
2.Referenced Documents 2.1ASTM Standards:
D 2700Test Method for Motor Octane Number of Spark-Ignition Engine Fuel 23.Terminology 3.1Definitions:派出所实习总结
3.1.1engine motor octane requirement —one full motor octane number greater than the maximum motor octane num-ber that results in knock (graphic knock level descriptions can be en in Annex A1).For example,a test engine knocks on primary reference fuels with 96and 97motor octane numbers.The test engine does not knock on a primary reference fuel with a 98motor octane number.The maximum motor octane number that results in knock is 97,so the motor octane requirement is 98.
3.1.2full rich —condition in which the mixture control is at the full stop position with the fuel flow within manufacturer’s recommended ttings.
3.1.3hou fuel ,n —for octane rating ,an unleaded,straight hydrocarbon fuel ud for engine warm-up and all non-octane rating testing.
3.1.4knock ,n —in an aircraft spark ignition engine ,abnor-mal combustion caud by autoignition of the air/fuel mixture.
3.1.5knock condition ,n —for octane rating ,when the knock intensity in any cylinder is light knock or greater as described in Annex A1
3.1.6knock number ,n —for octane rating ,a numerical quantification of knock intensity.
3.1.7motor octane number of primary reference fuels from 0to 100—the volume %of iso octane (equals 100.0)in a blend with n -heptane (equals 0.0).
3.1.8motor octane number of primary reference fuels above 100—determined in terms of the number of millilitres of tetraethyl lead in iso octane.
3.1.9naturally aspirated aircraft engine ,n —aircraft piston engine that breathes without forced means from either turbo-chargers or superchargers.
3.1.10no-knock condition ,n —for octane rating ,when the combustion instability in all cylinders is less than light knock.Refer to Annex A1for description of knock intensity.
3.1.11peak EGT ,n —for octane rating ,as the mixture is manually leaned from a state rich of stoichiometric,the exhaust gas temperature will increa with the removal of excess fuel.As the mixture is continually leaned,a peak temperature will be attained,after which continued leaning will result in lower exhaust gas temperatures.
3.1.12primary reference fuels ,n —for octane rating ,blended fuels of reference grade iso octane and n -heptane.3.1.13stable engine conditions ,n —for octane rating ,cyl-inder head temperatures change less than 5°C (9°F)during a 1min period.Any changes or minor adjustments to throttle,mixture,or engine conditions mandate restarting the clock for determining stable conditions.3.2Symbols:
职场情商
3.2.1CHT —cylinder head temperature.3.2.2EGT —exhaust gas temperature.3.2.3inHg —inches of mercury.
3.2.4MAP —manifold absolute pressure.3.2.5mmHg —millimeters of mercury.3.2.6MON —motor octane number.3.2.7PRF —primary reference fuel.
3.2.8psig —pounds per square inch gauge.3.2.9rpm —revolutions per minute.3.2.10TDC —top dead center.
1
This test method is under the jurisdiction of ASTM Committee D-2on Petroleum Products and Lubricants and is the direct responsibility of Subcommittee D02.J on Aviation Fuels.
Current edition approved June 10,1999.Published August 1999.2
Annual Book of ASTM Standards ,V ol 05.01.
1
Copyright ©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.
NOTICE:This standard has either been superded and replaced by a new version or withdrawn.
Contact ASTM International ()for the latest information
法国简介
4.Summary of Practice
4.1A recently overhauled,remanufactured,or new,natu-rally aspirated aircraft engine is octane rated,using PRFs,to determine the minimum motor octane requirement.Minimum motor octane requirement is defined as one number above the highest MON in which knock was detected.The engine is tested at three or more of the worst power points subject to detonation behavior.The points usually involve high mani-fold pressures.At the very least takeoff power,a maximum continuous or climb power,and a crui configuration shall be tested.Takeoff power and climb power are tested under full rich mixture conditions,and crui power is tested under full rich and lean mixture configurations in5%increment reduc-tions from full rich fuelflow.Engine operating temperatures and oil temperatures are kept at maximum allowable limits, while induction and cooling air temperatures are maintained at extreme hot day conditions for vere ca testing.
4.2Octane ratings are determined under stable engine conditions using PRFs of known MON.
4.3Knock nsor installation and knock quantification are described in Annex A1.
5.Significance and U
5.1This practice is ud as a basis for determining the minimum motor octane requirement of naturally aspirated aircraft engines by u of PRFs.
5.2Results 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 afleet requirement.
6.Apparatus
6.1Instrumentation:
6.1.1The engine shall be equipped with the following instrumentation,which shall be accurate within62%of full scale unless noted otherwi.
6.1.1.1Absolute Manifold Pressure Transducer—Location of MAP nsor shall conform to engine manufacturer’s speci-fied location.Manifold pressures shall be measured with an accuracy of less than2.5mmHg and recorded to ensure proper engine behavior and repeatability.
6.1.1.2Cooling Air Pressure Transducer,located so as to determine the pressure within the cowling.
6.1.1.3Cooling Air Temperature Sensor,located either within the cowling or at the entrance to the cowling.If a thermocouple is utilized,it should extend at least a third of the way across the measured area.
6.1.1.4Crankshaft Angle Encoder,if required for knock detection.The encoder shall have a sample resolution of at least0.4°of crank shaft rotation.The encoder TDC pul shall be aligned with the TDC of cylinder number one prior to octane rating.关羽过五关斩六将
6.1.1.5Cylinder Head Temperature Sensors,installed in each cylinder.The nsing locations and types of thermo-couples shall conform to the engine manufacturer’s recommen-dations.The CHT measurements shall be accurate to within 1%of full scale.
6.1.1.6Exhaust Gas Temperature Sensors,on all cylinders. Installation shall conform with manufacturer’s recommended location and proper material lection.EGT probes are usually installed within5cm(2in.)of the exhaust stackflange.The EGT probes shall be accurate to within1%of full scale. 6.1.1.7Engine Speed Sensor—The dynamometer or propel-ler stand shall measure the engine shaft speed to determine power development.The engine speed nsor shall be accurate to within65rpm.
6.1.1.8Fuel Flow Meter—If the device is calibrated for a particular fuel,then the device shall be recalibrated for each different and subquent fuel.Data should be reported in mass flow units.
6.1.1.9Fuel Pressure Transducers—Locations of fuel pres-sure transducers shall conform with tho recommended by the engine manufacturer.One transducer is required for the me-tered fuel pressure,if necessary,and another is required for the pump pressure.The fuel inlet pressure shall not fall below the minimum specified by the engine manufacturer during the rating process.
6.1.1.10Induction Air Pressure Transducer,located so as to measure the pressure of the induction stream prior to the throttle plate.
6.1.1.11Induction Air Temperature Sensor,located so as to measure the temperature of the induction stream prior to the throttle plate.
6.1.1.12Knock Sensors—The referee method for knock detection is described in Annex A1.This method requiresflush mounting piezoelectric transducers.At the very least,the four cylinders with the highest CHTs shall be monitored.The transducers are connected to charge amplifiers and shall be capable of measuring combustion pressures under a high temperature environment.
6.1.1.13Oil Pressure Transducer—Location of pressure measurement shall conform to engine manufacturer’s specified location.
6.1.1.14Oil Temperature Sensor—Location of temperature measurement shall conform with manufacturer’s specified location.
6.1.1.15Torque Meter—The dynamometer or propeller stand shall measure the torque to determine power develop-ment.The torque measurement shall be accurate to within1% of full scale.
6.1.2The engine should be equipped with the following instrumentation,which shall be accurate within62%of full scale unless noted otherwi.
6.1.2.1Induction Air Flow Meter—Data should be pre-nted in massflow units.
6.1.2.2Induction Air Humidity Sensor,located in either the induction air plenum or induction air duct.Data should be prented in absolute,rather than relative,quantities.
6.1.2.3Outside Air Temperature Sensor,capable of measur-ing both the ambient wet bulb and the dry bulb temperatures prior to any engine testing.
6.2Data Acquisition:
6.2.1The instrumentation listed in6.1shall be scanned and the data recorded at least once every15s by an automatic data acquisition system.The data shall be stored in a universal format(for example,comma parated values(CSV)for IBM compatible machines)that can be retrieved at a later
date.
6.2.2If in-cylinder pressures are recorded to determine knock intensity,the pressure data shall be sampled at a rate of at least1800samples per pressure cycle per cylinder.
6.3Power Absorption—The testing is to be performed in a ground bad test cell using either a dynamometer or propeller test stand that shall be capable of maintaining a constant speed to within610rpm.
6.4Fuel System:
6.4.1The fuel supply shall have a disposable or cleanable filter.Thefilter shall allow the proper minimum fuelflow. 6.4.2The fuel lection valve shall be capable of lecting at least two different fuel sources without the possibility of cross contamination of either source.
6.4.3The fuel supply system must comply with federal, state,and local regulations related tofire,hazards,and health issues.
7.Reagents and Materials
7.1The MON of PRFs is confirmed by using Test Method D2700.All fuels ud for the initial engine octane ratings are PRFs that consist of blends of reference grade iso octane and n-heptane.The PRFs will be prepared in increments of one MON.
N OTE1—Warning:PFR isflammable,and its vapor is harmful.Vapors may cauflashfire.
7.1.1Iso octane(2,2,4-trimethylpentane)shall be no less than99.75%by volume pure,contain no more than0.10%by volume n-heptane,and contain no more than0.5mg/L(0.002 g/U.S.gal)of lead.
N OTE2—Warning:Iso octane isflammable,and its vapor is harmful. Vapors may cauflashfire.
7.1.2n-Heptane shall be no less than99.75%by volume pure,contain no more than0.10%by volume iso octane,and contain no more than0.5mg/L(0.002g/U.S.gal)of lead.
N OTE3—Warning:n-Heptane isflammable,and its vapor is harmful. Vapors may cauflashfire.
7.1.3A sample shall be taken of each primary reference fuel and subjected to Test Method D2700for motor octane verification.
7.2Fuels ud for operations other than octane rating(for example,warm-up)shall consist of unleaded hydrocarbons and should be capable of satisfying the test engine’s octane requirement under the conditions for the fuel to be ud.
N OTE4—Warning:The fuels areflammable,and their vapor is harmful.Vapors may cauflashfire.
7.3Engine break-in oil shall be one approved by the engine manufacturer.
7.4All engine operations,other than during the break-in period,shall be performed with an oil approved by the engine manufacturer.
N OTE5—Warning:Lubricating oil is combustible,and its vapor is harmful.
8.Preparation of Apparatus
8.1The history and condition of each test engine should be known and documented by means of engine log books,test run sheets,and any other documentation issued by the original equipment manufacturers or repair overhaul shops before any octane rating tests are performed.
8.2Only the engine accessories required to operate the engine shall be installed on the test engine when conducting the octane ratings.
8.3The exhaust system employed shall not induce a back pressure greater than the back pressure called for in the engine manufacturer’s specifications.
8.4If the test engine’s fuel system is designed to recirculate fuel to the tank,provisions shall be made to ensure that no fuel is recirculated to the containers with the PRFs.
8.5The idle mixture tting and full rich fuelflow rate shall be t in accordance with the engine manufacturer’s recom-mendations.
8.6The idle stop and full throttle throw positions shall be t in accordance with the engine manufacturer’s recommen-dations.
8.7Before any octane rating,and after all break-in and power baline runs have been performed,a cylinder compres-sion test shall be performed on all cylinders and the results recorded.
8.8Prior to testing,the integrity of the fuel lection system shall be confirmed and the systemflushed.The engine fuel lector apparatus shall be checked to ensure no leakage. 8.9All engine ttings shall be checked after the break-in period and before any octane rating.As a minimum,this shall include fuel pressures,oil pressure,fuelflow,and magneto timing.坐车礼仪
8.10A systems check shall be performed,as per specific aircraft engine manufacturer’s recommendations,prior to start-ing the test engine.As a minimum,this shall include the following:idle throttle stop,wide open throttle throw,mixture cut-off position,and mixture full rich position.
8.11A systems check shall be performed after starting the test engine.This shall include as a minimum the following items:oil pressure,magneto ground check as per the engine manufacturer’s recommendations,and instrumentation indica-tions within normal ranges.
9.Calibration and Standardization
9.1The engine shall be t up in accordance with the manufacturer’s specifications.The ignition timin
g shall be t within61°of the recommended tting.The fuelflows shall be t within62%of the recommended fuelflow(or65% of the recommended pressure when appropriate).
9.2Instrumentation shall be calibrated and checked to ensure accuracy to within62%of full scale,unless noted otherwi.
10.Procedure
10.1Engine Break-in:
10.1.1If the test engine is new,remanufactured,or recently overhauled,it shall be broken in prior to conducting initial octane ratings.The break-in shall be conducted in accordance with the engine manufacturer’s recommendations.Break-in shall be conducted with a non-metallic
fuel.
10.1.2The engine is started and the engine manufacturer’s warm-up procedures are followed.A magneto check is per-formed as per the engine manufacturer’s recommendation. 10.1.3The engine is operated at the manufacturer’s recom-mended power ttings,and the oil consumption is recorded until either oil consumption is stabilized or10h of engine operation is attained.Oil consumption stabilization should conform to the engine manufacturer’s recommendation. 10.1.4During the engine break-in runs,the engine operating temperatures and oil temperature should be maintained in accordance with the manufacturer’s recommendations.
10.2Power Balines:
10.2.1After oil consumption is stabilized,three parate power baline tests of the engine shall be performed.Each test requires measuring the power developed at combinations of every100rpm and50mmHg(2inHg)MAP increments from takeoff power to low crui power(that is,55%normal rated power).This ensures that proper power is being developed.
10.2.2Record engine parameter data at a rate of at least one (1)full channel scan for every15s of engine operation,and attach the results to the octane rating data.
10.2.3The installation of the knock nsing equipment is performed after the power balines have b
een performed. 10.2.4If this knock nsor installation alters the cylinder/ ignition system in any way,such as drilling of cylinders,u of longer reach spark plugs,or u of modified spark plugs,then three power balines shall be performed again,after the knock nsor installation.The same MAP and rpm ttings tested in 10.2.1shall be retested and the results recorded.Engine parameter data shall again be recorded at a rate of at least one (1)full channel scan for every15s of engine operation. 10.3Cylinder Compression Check:
10.3.1After power mapping the engine,cylinder compres-sion checks shall be performed and the results recorded. 10.3.2The engine shall be warm when the cylinder com-pression checks are performed.
10.4Octane Rating:
10.4.1After the cylinder compression checks have been performed,the octane rating shall be performed.
10.4.2For this test,record the engine parameter data at a minimum rate of one(1)full channel scan for every15s of engine operation.The knock data sample rate shall be equal to or greater than at least one(1)pressure sample per cylinder for every0.4°of crank shaft rotation.Knock data shall enco
著作等身的意思mpass at least100concutive engine cycles per power tting for each cylinder monitored.
最最10.4.3Start the engine on hou fuel.Allow engine to warm up.Ensure all instrumentation indications are within proper range.Conduct ignition systems check.
10.4.4The cooling and induction air temperatures shall be adjusted to39°C62°C(103°F64°F).The ttings shall be maintained throughout the octane rating.
10.4.5The cooling air pressure shall be adjusted to maintain the maximum CHT within66°C(10°F)of manufacturer’s recommended maximum limit.All CHTs shall be maintained within28°C(50°F)of the maximum CHT.The ttings shall be maintained throughout the octane rating.
10.4.6The oil temperature shall be maintained within66°C (10°F)of the engine manufacturer’s recommended maximum limit throughout the octane rating.
10.4.7Set takeoff engine rpm,full throttle,and full rich mixture conditions on the hou fuel.
10.4.8Select the PRF to be tested.The test quence should begin with a PRF of100MON or below that is likely to result in no knock.
10.4.9Each time a different PRF is lected or the engine power tting is changed,conditions shall be allowed to become stable.Allow time for fuel to enter engine and for conditions to stabilize.The waiting period shall be a minimum of2min,the time required to consume three(3)times the volume of fuel contained in the fuel system upstream of the lector valve,or the time it takes for the conditions to stabilize,whichever is longer.
10.4.10Record knock data,and determine the combustion condition(normal combustion,light knock,moderate knock,or heavy knock).See Annex A1for more detail.Do not allow the test engine to operate under heavy knock for extended periods of time.
10.4.11If knock occurs,lect the hou fuel,reduce the engine power,and return to step10.4.7with a higher MON PFR.
10.4.12If no knock occurs,lect the hou fuel and t the power on the test engine to the recommended climb power tting or maximum continuous power tting,if appropriate. Leave the mixture at the full rich tting.
10.4.13Select the PRF with the same MON as the fuel lected in10.4.8.
10.4.14Record knock data,and determine the combustion condition.
10.4.15If knock occurs,lect hou fuel and return to step 10.4.7with a higher MON PFR.
10.4.16If no knock occurs,lect hou fuel and t the test engine to the maximum recommended crui tting at which the mixture can be leaned.Leave the mixture at the full rich position.
10.4.17Select the PRF with the same MON as the fuel lected in10.4.8.
10.4.18Record knock data,and determine the combustion condition.
10.4.19If knock occurs,lect the hou fuel and return to step10.4.7with a higher MON PFR.
10.4.20If no knock occurs,calculate a5%reduction in fuel flow from the reading obtained from the maximum recom-mended crui full rich mixture tting.
10.4.21Hold the throttle and engine speedfixed at the maximum recommended crui ttings.Starting with full rich mixture ttings,lean until the fuelflow decreas by the5% increment just determined.The engine should still be operating on the PRF.
10.4.22Allow conditions to stabilize after adjusting the mixture.
10.4.23Record knock data,and determine the combustion condition.
10.4.24If knock occurs,lect hou fuel and return to step 10.4.7with a higher MON
PFR.
10.4.25If no knock occurs,continue leaning by the5% increment determined in step10.4.20at the maximum recom-mended crui position until either knock occurs or peak EGT, in any cylinder,is attained.The engine shall be stabilized and knock data recorded after each5%increment change in fuel flow.
N OTE6—Warning:Excessive leaning may cau engine damage.All cylinder EGTs should be monitored so that the mixture is not leaned past peak EGT for any cylinder.Rapid lean mixture adjustments may propa-gate vere detonation and may lead to engine damage.
10.4.26If peak EGT in any cylinder has been reached without experiencing a knock condition,the mixture shall be enriched and a lower MON PFR shall be lected.If that lower MON PFR has alread
y been found to produce a knock condition,then the motor octane requirement is the last knock-free PRF tested.
10.4.27It is suggested when choosing a lower MON PFR to choo a rating fuel of only one MON lower so as to minimize any potential engine damage.Continue testing with a lower MON PFR until a knock condition is encountered.The motor octane requirement is defined as one MON higher than the highest MON PFR that produced a knock condition.
10.4.28At the conclusion of the test,lect the hou fuel, gradually reduce the power tting to idle,and allow the engine to cool.
10.4.29After shutdown,make sure the lector valve does not leak.If the valve leaks,repair the valve and repeat the test to ensure the PFRs were not contaminated.
10.4.30Fig.1illustrates,inflow chart form,the octane rating test procedures.
11.Report
11.1A description of the history of the aircraft engine shall be attached to the results.
11.1.1As a minimum,this shall include information regard-ing whether or not the engine was recently remanufactured, overhauled,or new.The history shall also include the number of hours since last overhauled.
11.2The results from the cylinder compression checks shall be reported.The data shall be reported in terms of measured cylinder pressure when the applied pressure is equal to551.6 kPa(80psi).
11.3Annex A1details the referee method for knock detec-tion and the quantification of the combustion condition.If that method is utilized,the results shall include a description of
the FIG.1Flow Chart Illustrating the Octane Rating
Procedures
