ASTM D2885-21

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: D2885 − 21
Standard Test Method for
Determination of Octane Number of Spark-Ignition Engine
Fuels by On-Line Direct Comparison Technique
This standard is issued under the fixed designation D2885; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 1.6 The octane number difference between the stream
sample and the applicable comparison reference fuel is self-
1.1 This test method covers the quantitative online determi-
limiting by specifications imposed upon the standard and
nationbydirectcomparisonofthedifferenceinknockratingor
prototype fuels.
delta octane number of a stream sample of spark-ignition
engine fuel from that of a comparison reference fuel. 1.7 Specifications for selection, preparation, storage, and
dispensing of standard and prototype fuels are provided.
1.2 This test method covers the methodology for obtaining
Detailed procedures for determination of an appropriate as-
anoctanenumberusingthemeasureddeltaoctanenumberand
signedoctanenumberforbothstandardandprototypefuelsare
the octane number of the comparison reference fuel.
also incorporated.
1.3 The comparison reference fuel is required to be of
1.8 The values of operating conditions are stated in SI units
essentially the same composition as the stream sample to be
and are considered standard. The values in parentheses are
analyzed and can be a secondary fuel termed standard fuel or
historical inch-pound units. The standardized CFR engine
a tertiary fuel termed prototype fuel.
measurements continue to be expressed in inch-pound units
1.4 The test method utilizes a knock testing unit/automated
only because of the extensive and expensive tooling that has
analyzer system that incorporates computer control of a stan-
been created for this equipment.
dardized single-cylinder, four-stroke cycle, variable compres-
1.9 This standard does not purport to address all of the
sion ratio, carbureted, CFR engine with appropriate auxiliary
safety concerns, if any, associated with its use. It is the
equipment using either Test Method D2699 Research method
responsibility of the user of this standard to establish appro-
or Test Method D2700 Motor method operating conditions.
priate safety, health, and environmental practices and deter-
1.4.1 Knock measurements are based on operation of both
mine the applicability of regulatory limitations prior to use.
fuels at the fuel-air ratio that produces maximum knock
Formorespecificwarningstatements,seeSection8andAnnex
intensity for that fuel.
A1.
1.4.2 Measured differences in knock intensity are scaled to
1.10 This international standard was developed in accor-
provide a positive or negative delta octane number of the
dance with internationally recognized principles on standard-
stream sample from the comparison reference fuel when the
ization established in the Decision on Principles for the
fuels are compared at the same compression ratio.
Development of International Standards, Guides and Recom-
1.4.3 Measured differences in compression ratio are scaled
mendations issued by the World Trade Organization Technical
from the appropriate guide table to provide a positive or
Barriers to Trade (TBT) Committee.
negative delta octane number of the stream sample from the
comparison reference fuel when the fuels are compared at the
2. Referenced Documents
same knock intensity.
2.1 ASTM Standards:
1.5 This test method is limited to testing 78 to 102 octane
D1193Specification for Reagent Water
number spark-ignition engine fuels using either research or
D2699Test Method for Research Octane Number of Spark-
motor method conditions.
Ignition Engine Fuel
D2700Test Method for Motor Octane Number of Spark-
Ignition Engine Fuel
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.01 on Combustion Characteristics. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
CurrenteditionapprovedJuly1,2021.PublishedJuly2021.Originallyapproved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in 1970. Last previous edition approved in 2020 as D2885–20. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D2885-21. the ASTM website.
*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
D2885 − 21
D4057Practice for Manual Sampling of Petroleum and 3.1.4 determinability, n—quantitative measure of the vari-
Petroleum Products ability associated with the same operator in a given laboratory
D4175Terminology Relating to Petroleum Products, Liquid obtaining successive determined values using the same appa-
Fuels, and Lubricants ratus for a series of operations leading to a single result; it is
defined as that difference between two such single determined
D4177Practice for Automatic Sampling of Petroleum and
Petroleum Products values as would be exceeded in the long run in only one case
in 20 in the normal and correct operation of the test method.
D4814Specification for Automotive Spark-Ignition Engine
Fuel D6300
D5842Practice for Sampling and Handling of Fuels for
3.1.5 detonation meter, n—for knock testing, the signal
Volatility Measurement
conditioning instrument that accepts the electrical signal from
D6299Practice for Applying Statistical Quality Assurance
thedetonationpickupandprovidesanoutputsignalfordisplay.
and Control Charting Techniques to Evaluate Analytical
D2699/D2700
Measurement System Performance
3.1.6 detonation pickup, n—for knock testing,magnetostric-
D6300Practice for Determination of Precision and Bias
tivetypetransducerthatthreadsintotheenginecylinderandis
Data for Use in Test Methods for Petroleum Products,
exposed to combustion chamber pressure to provide an elec-
Liquid Fuels, and Lubricants
trical signal that is proportional to the rate-of-change of
D6624Practice for Determining a Flow-Proportioned Aver-
cylinder pressure. D2699/D2700
age Property Value (FPAPV) for a Collected Batch of
Process Stream Material Using Stream Analyzer Data
3.1.7 digital counter reading, n—for the CFR engine,a
D7453Practice for Sampling of Petroleum Products for
numerical indication of cylinder height, indexed to a basic
Analysis by Process Stream Analyzers and for Process
settingataprescribedcompressionpressurewhentheengineis
Stream Analyzer System Validation
motored. D2699/D2700
E29Practice for Using Significant Digits in Test Data to
3.1.8 fuel-air ratio for maximum knock intensity, n—for
Determine Conformance with Specifications
knock testing, that proportion of fuel to air which produces the
E177Practice for Use of the Terms Precision and Bias in
highest knock intensity for each fuel in the knock testing unit,
ASTM Test Methods
provided this occurs within the specified carburetor fuel level
E456Terminology Relating to Quality and Statistics
limits. D2699/D2700
3.1.8.1 Discussion—In the context of this test method, the
3. Terminology
fuel-air ratio for maximum knock intensity can be determined
3.1 Definitions:
manually or by the automated analyzer system.
3.1.1 accepted reference value, n—a value that serves as an
3.1.8.1 dynamic fuel-air ratio for maximum knock, n—for
agreed-upon reference for comparison, and which is derived
knock testing, the changing of the mixture of fuel and air for
as: (1) a theoretical or established value, based on scientific
engine combustion determined by continually varying fuel
principles, (2) an assigned value, based on experimental work
level in the carburetor delivery components, through the
ofsomenationalorinternationalorganization,or(3)aconsen-
maximum knock intensity so that the observed peak knock
sus value, based on collaborative experimental work under the
intensity value can be selected as maximum knock intensity
auspices of a scientific or engineering group. E456/E177
reading.
3.1.1.1 Discussion—In the context of this test method,
3.1.8.2 equilibrium fuel-air ratio for maximum knock,
acceptedreferencevalueisunderstoodtoapplytostandardfuel
n—forknocktesting,thechangingofthemixtureoffuelandair
or check fuel average research or motor octane numbers
for engine combustion determined by making incremental step
determined under reproducibility conditions by a recognized
changes in fuel-air ratio, observing the equilibrium knock
exchange testing organization having a minimum of 16 par-
intensity for each step and selecting the fuel-air ratio which
ticipants.
produces the highest knock meter reading.
3.1.2 analytical measurement system, n—acollectionofone
3.1.9 guide tables, n—for knock testing, the specific rela-
or more components or subsystems, such as a sampler, test
tionship between cylinder height (compression ratio) and
equipment, instrumentation, display devices, data handler, and
octane number at standard knock intensity for specific primary
printout or output transmitters that is used to determine a
reference fuel blends tested at standard or other specified
quantitative value of a specific property for an unknown
barometric pressure. [D02.01] D2699/D2700
sample. D6299
3.1.10 knock, n—in a spark-ignition engine, abnormal
3.1.2.1 Discussion—In the context of this test method, the
combustion, often producing audible sound, caused by auto-
analytical measurement system is comprised of the knock
ignition of the air/fuel mixture. D4175
testing unit, automated analyzer system, and any auxiliary
equipment required for the safe operation of the engine.
3.1.11 knock intensity, n—for knock testing, a measure of
the level of knock. D2699/D2700
3.1.3 cylinder height, n—for the CFR engine, the relative
vertical position of the engine cylinder with respect to the 3.1.11.1 Discussion—In the context of this test method, the
piston at top dead center (TDC) or the top machine surface of knock intensity signal may also be displayed using digital or
the crankcase. D2699/D2700 recording instrumentation.
D2885 − 21
3.1.12 knockmeter, n—analog, the 0 to 100 division analog 3.1.21 stream sample, n—thematerialtobeevaluatedbyan
indicating meter that displays the knock intensity signal from analytical measurement system, typically drawn from a flow-
the analog detonation meter. [D02.01] D2699/D2700 ing stream of either blended spark-ignition engine fuel or
process unit material.
3.1.13 knockmeter, n—digital, the 0 to 999 division digital
indicating meter that displays the knock intensity signal from
3.2 Definitions of Terms Specific to This Standard:
the digital detonation meter. [D02.01] D2699/D2700
3.2.1 comparison reference fuel, n—for direct comparison
knock testing, a spark-ignition engine fuel having an assigned
3.1.14 motor octane number, n—for spark-ignition engine
octanenumberthatisthereferenceforthedeterminationofthe
fuel, the numerical rating of knock resistance obtained by
delta octane number of stream samples.
comparison of the fuel’s knock intensity with that of primary
reference fuel blends when both are tested in a standardized
3.2.1.1 standard fuel, n—for direct comparison knock
CFR engine operating under the conditions specified in Test
testing, a spark-ignition engine fuel having an octane number
Method D2700.
acceptedreferencevalue(RON orMON )whichisused
ARV ARV
3.1.15 repeatability conditions, n—conditions where inde- asasecondarycomparisonreferencefuelfor(1)determination
of the octane number site assigned value (RON or
pendent test results are obtained with the same method on
SAV
identicaltestitemsinthesamelaboratorybythesameoperator MON )ofprototypefuels,(2)determinationofthe ∆O.N.of
SAV
a stream sample, or (3) pairing with another standard fuel for
using the same equipment within short intervals of time. E456
3.1.15.1 Discussion—In the context of this test method, analytical measurement system qualification checkout.
application of repeatability conditions is primarily applied to
3.2.1.2 prototype fuel, n—for direct comparison knock
the determination of variability of delta octane numbers
testing, a spark-ignition engine fuel or process unit material
generated by repeating the comparison measurements within a
having an octane number site assigned value (RON or
SAV
short time, by the same operator, using the same comparator,
MON ) referenced to an appropriate standard fuel, which is
SAV
on the same fuel pair.
used as a tertiary comparison reference fuel for determination
3.1.16 reproducibility conditions, n—conditions where test of the ∆O.N. of a stream sample.
results are obtained with the same method on identical test
3.2.2 delta octane number, n—for direct comparison knock
items in different laboratories with different operators using
testing, the algebraic difference in octane number between two
different equipment. E456
fuels under research or motor engine conditions, when deter-
3.1.17 research octane number, n—for spark-ignition en-
mined by the direct comparison technique.
gine fuel, the numerical rating of knock resistance obtained by
3.2.3 paired check fuels (A and B), n—for on-line knock
comparison of the fuel’s knock intensity with that of primary
testing system qualification checkout, two standard fuels used
reference fuel blends when both are tested in a standardized
for system qualification checkout of a analytical measurement
CFR engine operating under the conditions specified in Test
system.
Method D2699.
3.2.3.1 expected difference O.N., n—for on-line knock test-
3.1.18 site assigned value, n—a value that serves as an
ing system qualification checkout, the absolute octane number
agreed-upon reference for comparison, determined from mul-
difference between paired check fuels (A–B) based on the
tiple test results.
O.N. for both fuels.
ARV
3.1.18.1 Discussion—In the context of this test method, site
3.2.4 paired quality control fuels, n—for on-line system
assignedvalueisunderstoodtoapplytoprototypefuelaverage
quality control, a pair of fuels, one of which is a comparison
research or motor octane number determined using direct
reference fuel, to be used in the repetitive testing for ∆O.N. as
comparison delta octane number cycles comparing the proto-
a quality control check of the analytical measurement system.
type fuel to a standard fuel having an accepted reference value
octane number. 3.2.5 span, n—for direct comparison knock testing, a mea-
sure of the overall sensitivity of the analyzer measurement
3.1.19 site precision conditions, n—conditions under which
expressedastheratioofthechangeindeltaoctaneproducedby
test results are obtained by one or more operators in a single
a given change in either compression ratio or knock intensity.
location practicing the same test method on a single measure-
ment system using test specimens taken at random from the
3.3 Acronyms:
same sample of material over an extended period of time
3.3.1 AMS—analytical measurement system
spanning at least a 15 day interval. D6299
3.3.2 ARV—accepted reference value
3.1.19.1 Discussion—In the context of this test method,
3.3.3 RON —research octane number accepted reference
ARV
application of site precision conditions is primarily applied to
value
the determination of the variability of delta octane average
results, obtained by different operators, over different days, for 3.3.4 MON —motor octane number accepted reference
ARV
the same fuel pair, using the same comparator. Each delta
value
octane average result is obtained from repetitive comparisons
3.3.5 SAV—site assigned value
of the same fuel pair under repeatability conditions.
3.3.6 RON —research octane number site assigned value
SAV
3.1.20 spread, n—in knock measurement, the sensitivity of
3.3.7 MON —motor octane number site assigned value
SAV
the detonation meter expressed in knockmeter divisions per
octane number. D2699/D2700 3.3.8 C.R.—compression ratio
D2885 − 21
3.3.9 K.I.—knock intensity conditions or knock measuring instrumentation performance
and thus affect the ∆O.N. obtained for spark-ignition engine
3.3.10 O.N.—octane number
fuels.
3.3.11 ∆O.N.—delta octane number
6.2.1 Electrical noise can affect the ability of the knock
3.3.12 PRF—primary reference fuel
testing unit/automated analytical measurement system to accu-
3.3.13 CRF—comparison reference fuel rately determine the ∆O.N. of the sample stream fuel.
3.3.14 CFR—Cooperative Fuel Research
6.3 Precaution—Avoidexposureofsamplefuelstosunlight
orfluorescentlampUVemissionstominimizeinducedchemi-
3.4 Symbols:
cal reactions that can affect octane number ratings.
3.4.1 Q—accuracy qualification value
6.3.1 Exposure of these fuels to UV wavelengths shorter
3.4.2 K—accuracy qualification acceptance limit
than 550 nanometers for a short period of time may signifi-
cantly affect octane number ratings.
4. Summary of Test Method
4.1 The delta research (∆RON) or delta motor (∆MON)
7. Apparatus
octane number of a stream sample is determined using a
7.1 This test method utilizes a multi-component analytical
standard CFR engine operating under the appropriate test
measurement system (AMS). It incorporates a knock testing
conditions, using an automated repetitive cycle that compares
engine with instrumentation to measure and produce an output
its knock characteristics with those of a comparison reference
signalrepresentativeofthedifferenceinknockratingor ∆O.N.
fuel (CRF) having an assigned octane number. The difference
An associated automated control system includes a fuel deliv-
in knock characteristics may be measured as (1) the difference
ery system to introduce a stream sample or CRF to the engine
in knock intensity at constant compression ratio, or (2) the
critical carburetor components. The automated system shall
differenceincompressionratioatconstantknockintensity.The
also include equipment and controls for switching between the
system draws the stream sample from a flowing stream and
CRF and the stream sample, controls for operating the test
conditions it for delivery to the CFR engine carburetor.
engine and monitoring the critical operating conditions, and
Comparison reference fuel is stored in a suitable container and
instrumentation to convert the compression ratio (C.R.) or
is also appropriately conditioned for delivery to the CFR
knock intensity (K.I.) to a ∆O.N.
engine carburetor. System controls sequence the switching of
7.1.1 An appropriate CFR engine knock testing unit speci-
thetwofuelsaswellasmonitoringallcriticaltestingvariables.
fied for the determination of research octane number or motor
The fuel-air ratio of each fuel is adjusted to produce the
octane number and meeting the recommendations of the
maximum knock intensity for that fuel.
manufacturer of the AMS. Specific knock testing unit equip-
ment can include the following:
5. Significance and Use
7.1.1.1 For research octane number measurement, a Model
5.1 The delta octane number (∆O.N.) measure can quantify
CFR F-1, single cylinder engine knock testing unit assembly
the difference of in-line blended spark-ignition engine fuel or
comprised of the appropriate critical or equivalent equipment
process stream material octane number to a desired octane
components selected by the system manufacturer, and for
number to aid in optimizing control of blender facilities or
which specifications are provided in Test Method D2699,
refinery process units.
Annex A2.
5.2 The ∆O.N. measure, summed with a comparison refer- 7.1.1.2 For motor octane number measurement, a Model
ence fuels O.N. provides either research or motor octane CFR F-2, single cylinder engine knock testing unit assembly
number value of the current in-line blended spark-ignition comprised of the appropriate critical or equivalent equipment
engine fuel or process stream material. components selected by the system manufacturer, and for
which specifications are provided in Test Method D2700,
5.3 Through the use of cumulative flow-proportioned aver-
Annex A2.
aging of the repetitive ∆O.N. results, in accordance with
7.1.1.3 Instrumentation for the measurement of knock, tem-
Practice D6624, an average octane number can be assigned to
peratures or other knock testing unit variables as selected by
a tender or batch of in-line blended spark-ignition engine fuel.
the system manufacturer, and for which specifications are
provided in Annex A2, of either Test Method D2699 or Test
6. Interferences
Method D2700, whichever is appropriate.
6.1 Certain gases and fumes, which can be present in the
7.1.1.4 The AMS system installation requires a number of
area where the knock testing unit is located, may have a
components and devices to integrate the critical or equivalent
measurable effect on the ∆O.N. result.
equipment items into a complete working unit. Specific items
6.1.1 Halogenated refrigerant used in air conditioning and
to satisfy important criteria for proper operation of the respec-
refrigeration equipment can promote knock. Halogenated sol-
tive CFR engine unit are to comply with the appropriate
vents can have the same effect. If vapors from these materials
enter the combustion chamber of the CFR engine, the octane
number of spark-ignition engine fuel can be depreciated.
Supporting data have been filed atASTM International Headquarters and may
6.2 Electrical power subject to transient voltage or fre-
beobtainedbyrequestingResearchReportRR:D02-1502.ContactASTMCustomer
quency surges or distortion can alter CFR engine operating Service at service@astm.org.
D2885 − 21
non-critical equipment specifications in Annex A2, of either Annex A1.) A secondary comparison reference fuel that con-
Test Method D2699 or Test Method D2700, whichever is forms to the following:
appropriate.
8.3.1 Octane Number—Selected to have a RON or
ARV
7.1.1.5 Equipment for adjustment of engine compression MON with respect to the O.N. of the prototype fuel or the
ARV
ratio and a mechanism for relative measurement of this
stream samples to be analyzed.
variable when the ∆O.N. value is based on differences in 8.3.1.1 The difference between standard fuel and related
engine compression ratio.
prototype fuel shall not exceed 60.5 O.N.
7.1.2 Automated control equipment for adjustment and
8.3.1.2 The difference between standard fuel andthestream
monitoring of the critical operating variables of the knock
samples to be analyzed shall not exceed 61.0 O.N.
testing unit is required and selected in accordance with the
(1) Discussion—The difference between the standard fuel
recommendations and instructions of the system manufacturer.
and the stream sample refers to when the standard fuel is used
Specific variables and conditions to be handled by the auto-
in direct comparison to the stream sample.
mated control equipment can include the following:
8.3.1.3 Determine the appropriate O.N. of standard fuel
ARV
7.1.2.1 Amechanismtovaryfuel-airratioanddeterminethe
under reproducibility conditions using a minimum of 16
conditionthatproducesamaximumK.I.signal.Determination
different exchange participants (see Annex A3).
of the fuel-air ratio for maximum knock intensity can be
8.3.2 Volatility—For use with blended stream samples, the
performed using either the equilibrium or a dynamic search
standard fuel may be slightly less volatile than the stream
technique.
samples to be analyzed in the interest of minimizing weather-
7.1.2.2 An adjustable octane number scaling function to
ing.
convertthemeasuredsignalvariabletoanoutputsignal ∆O.N.
8.3.3 Hydrocarbon Composition—Similar to that of a re-
value, recognizing any non-linear relationship that can exist.
lated prototype fuel or the stream samples to be analyzed.
7.1.2.3 Timingcontrolsforfuelswitchingandmeasurement
Users are cautioned to investigate the O.N. effect of any
functions to meet the specified operating principles of this test
significant differences in composition matrix between these
method.
related fuels.
7.1.2.4 Suitablesensorsformonitoringoperatingconditions
8.3.4 Antiknock Compound—The same organometallic lead
andsystemsafetyrelatedfunctionsthatareincorporatedinthe
or manganese additive compound, in a similar concentration,
system design.
shall be present in the standard fuel if it is present in the
7.1.3 A sample system to provide a continuously represen-
prototype fuel or stream sample to be analyzed.
tative stream and deal with the unconsumed stream sample.
8.3.5 Octane Enhancers—Compounds such as oxygenates
7.1.3.1 Equipment to treat the incoming stream sample fuel
shallbepresentinthestandardfuel,insimilarconcentration,to
to remove particulate matter and entrained water to meet the
that present in the prototype fuel or stream sample to be
requirements specified by the system manufacturer.
analyzed.
7.1.4 Storage vessels and associated equipment for storing
8.3.6 Antioxidant—Shall be added at the treat-rate recom-
and supplying one or more CRF materials.
mended by the additive supplier to ensure maximum storage
stability.
8. Reagents and Reference Materials
8.3.6.1 Addantioxidantpriortodistributionofstandardfuel
8.1 Cylinder Jacket Coolant—Use water in the cylinder
for the determination of the O.N. .
ARV
jacketforenginelocationswheretheresultantboilingtempera-
8.3.7 Metal Deactivator—If required, may be added in
ture will be 100°C 6 1.5°C (212°F 6 3°F). Use water with
accordance with supplier recommendations.
commercialglycolbasedantifreezeaddedinsufficientquantity
8.3.8 Storage and Handling—Controlled conditions to
to meet the boiling temperature requirements where altitude
minimize the possibility of octane number change or contami-
dictates.Acommercial multifunction water treatment material
nation. Systems and procedures shall conform to the require-
can be used in the coolant to minimize corrosion and mineral
ments set forth in Annex A2 of this test method.
scale that can alter heat transfer and rating results.
8.4 Prototype Fuel—(Warning—Prototype fuel is flam-
8.1.1 Water is understood to mean reagent water conform-
mable and its vapors are harmful. Vapors may cause flash fire.
ing to type IV, Specification D1193.(Warning—Ethylene
See Annex A1.) A tertiary comparison reference fuel that
glycol based antifreeze is poisonous and may be harmful or
conforms to the following:
fatal if inhaled or swallowed. See Annex A1.)
8.4.1 Octane Number—The difference between prototype
8.2 Engine Crankcase Lubricating Oil—SAE 30 viscosity
fuel and the stream samples to be analyzed shall not exceed
grade oil meeting the current API service classification for
61.0 O.N.
spark-ignition engines containing a detergent additive and
8.4.1.1 DeterminetheappropriateO.N. ofprototypefuel
SAV
2 2
having a kinematic viscosity of 9.3mm to 12.5mm per s
based on the average value of a minimum of 10 direct match
(cst) at 100°C (212°F) and a viscosity index of not less than
knock characteristic comparisons, obtained either manually or
85. Do not use oils containing viscosity index improvers or
automatically (see Annex A4).
multigradeoils.(Warning—Lubricatingoiliscombustibleand
8.4.2 Volatility—For use with blended stream samples, the
its vapor is harmful. See Annex A1.)
prototype fuel may be slightly less volatile than the stream
8.3 Standard Fuel—(Warning—Standardfuelisflammable samples to be analyzed in the interest of minimizing weather-
and its vapors are harmful. Vapors may cause flash fire. See ing.
D2885 − 21
8.4.3 Hydrocarbon Composition—Similar to that of the tions of the engine manufacturer. Assemble the supplemental
stream samples to be analyzed. Users are cautioned to inves- automated analyzer system and fuel delivery system compo-
tigate the O.N. effect of any significant differences in compo- nents in accordance with the instructions of the system
sition matrix between these related fuels. manufacturer.All installation aspects are to comply with local
8.4.4 Antiknock Compound—The same organometallic lead and national codes and installation requirements.
or manganese additive compound, in a similar concentration, 10.1.2 Proper operation of the CFR engine requires assem-
shall be present in the prototype fuel if it is present in the
bly of a number of engine components and adjustment of a
stream sample to be analyzed. series of engine variables to prescribed specifications. These
8.4.5 Octane Enhancers—Compounds such as oxygenates
settings and adjustments are specified in the CFR F-1 & F-2
shall be present in the prototype fuel, in similar concentration, Octane Rating Unit Operation & Maintenance Manual and in
to that present in the stream sample to be analyzed.
the Basic Engine and Instrument SettingsAnd Standard Oper-
8.4.6 Antioxidant—Shall be added at the treat-rate recom- ating Conditions sections of Test Method D2699 or Test
mended by the additive supplier to ensure maximum storage
Method D2700, or both, and are of the following types:
stability.
10.1.2.1 Conditions based on component specifications
8.4.7 Metal Deactivator—If required, may be added in
(Annex A2 and A3 of Test Method D2699 or Test Method
accordance with supplier recommendations.
D2700, or both).
8.4.8 Storage and Handling—Control conditions to mini-
10.1.2.2 CFR engine assembly settings and operating con-
mize the possibility of octane number change or contamina-
ditions.
tion. Systems and procedures shall conform to the recommen-
10.1.2.3 Proper operation of the automated analyzer system
dations set forth in Annex A2.
equipment and instrumentation.
8.5 Paired Check Fuels—The paired check fuels will have
10.2 CFR Engine Assembly Settings and Operating Condi-
an expected difference O.N. ranging from 0.2 to 1.0 and be
tions:
coded so the difference in the accepted reference values (Fuel
10.2.1 Compensation of Compression Ratio for Standard
A–Fuel B) is a positive value.
Knock Intensity—Knock testing engines operating at sites
8.5.1 The fuel characteristics, including those for antiknock
where the barometric pressure is lower or higher than
compound, octane enhancers, and antioxidant protection are to
29.92in.Hg, standard pressure, will knock softer or harder
be similar for the two check fuels of a pair.
respectivelythantheenginesoperatingatstandardpressure.To
compensate for this effect, the engine compression ratio is
8.6 Paired Quality Control Fuels—The two quality control
adjustedproportionaltothedifferencebetweenthesitemedian
fuels, one of which is a comparison reference fuel, shall have
and standard barometric pressure. The range of barometric
∆O.N. ranging from 0.2 to 1.0.
pressure experienced at any testing location is generally less
8.7 Primary Reference Fuels—Reference fuel grade
than 1.5in.Hg and the compression ratio compensation to
isooctane, heptane, the 80 O.N. blend of the two meeting the
causeessentiallystandardknockintensityatthelocationcanbe
specifications given in Test Method D2699 or Test Method
achieved using a fixed offset based on median barometric
D2700, or both. (Warning—Primary reference fuels are flam-
pressure for the site. This compensation can be made once by
mableandthevaporsareharmful.Vaporsmaycauseflashfire.
setting the offset between the two dials of the digital counter
See Annex A1.)
and using the compensated digital counter reading for the
∆O.N. measurement.
9. Sampling
10.2.1.1 Determine the range of barometric pressure that
9.1 Collect stream samples for on-line analysis in accor-
typicallyoccursatthesitefortheyearandcalculatethemedian
dance with Practice D4177 or D7453.
barometric pressure. If there are significant seasonal
9.1.1 Collect, treat, and deliver stream samples to the CFR
differences, it may be appropriate to calculate the median
engine carburetor in a way that minimizes exposure to light of
barometric pressure for each season.
any form.
10.2.1.2 Using the median barometric pressure and
9.2 Collect stream sample material for preparation, storage
TableA4.4 orA4.5 of Test Method D2699 for research octane
and laboratory testing as comparison reference fuels in accor-
number units and TableA4.9 orA4.10 of Test Method D2700
dance with Practices D4057, D4177, and D5842.
formotoroctanenumberunitsdeterminethecompensationfor
9.2.1 Collect and store sample fuels in an opaque container,
guide table cylinder height (digital counter reading).
such as a dark brown glass bottle, metal can, or a minimally
10.2.1.3 Setthedigitalcountersothatthelowerdialreading
reactive plastic container to minimize exposure to UV emis-
is compensated for the site median difference in barometric
sions from sources such as sunlight or fluorescent lamps.
pressure from the 29.92 in. Hg standard pressure.
10.2.2 Selecting and Setting Compression Ratio for On-line
10. Basic Engine and Instrument Settings and Operating
Operation—On-line ∆O.N. measurement for a given pair of
Conditions
fuels is initiated by setting the engine compression ratio to the
10.1 Standard Operating Conditions: guide table digital counter reading that corresponds to the
10.1.1 Installation of CFR Engine Equipment and appropriate CRF assigned octane number from the tables in
Instrumentation—Place the CFR engine on a suitable founda- Annex A4 in Test Method D2699 or Test Method D2700,
tion and hook up all utilities in accordance with the specifica- whichever is appropriate, for the AMS.
D2885 − 21
10.2.2.1 For systems that operate at a constant C.R., the reservoir in incremental steps. Selection of a horizontal jet
barometric pressure at the site may change slightly with time having the appropriate orifice size establishes the fuel level at
and this will result in minor shifts in engine K.I. level. If the which a typical sample fuel achieves maximum knock.
K.I. on the comparison reference fuel trends 620 from the 10.2.4.2 Fixed Fuel Level—Variable Orifice System—Afuel
initial value theAMS may be taken off-line, for a short period
reservoir, in which the fuel can be maintained at a prescribed
of time, to reset the K.I. to the initial value by adjusting the constant level, supplies an adjustable orifice (special long-
detonation meter -METER READING- dial before continuing
tapered needle valve) used in place of the horizontal jet. Fuel
on-line analysis. mixture is changed by varying the needle valve position.
Typically, the constant fuel level selected is near the 1.0 level,
10.2.2.2 For systems that operate at a constant K.I. by
which satisfies the fuel level specification.
adjustment of compression ratio the barometric pressure at the
sitemaychangeslightlywithtimeandthiswillresultinminor 10.2.4.3 Dynamic or Falling Level System—A fuel
shifts in the digital counter reading. If the digital counter reservoir, filled to a higher level than that required for
reading for the reference fuel trends more than 20 units, the maximum K.I., delivers fuel through either a fixed bore or
AMS may be taken off-line, for a short period of time, to reset adjustable horizontal jet. With the engine firing, the fuel level
the K.I. to 50 at the CRF O.N. digital counter reading by falls as fuel is consumed. Fuel level changes at a specifically
selected rate that is established by the cross-sectional area of
adjusting the detonation meter -METER READING- dial
before continuing on-line. the fuel reservoir and associated sight glass assembly. Maxi-
mum K.I. is recorded as the fuel level passes through the
10.2.2.3 Typical minor shifts in either knock intensity or
critical level.
digital counter reading affect each of the fuels under test in
10.2.5 Intake Air and Mixture Temperature Setting Prac-
essentially the same manner and these shifts do not signifi-
tices:
cantly affect the ∆O.N. measurement.
10.2.5.1 Motor Method:
10.2.3 Span Determination and Adjustment—The span set-
(1) Intake Air Temperature—38°C 6 2.8°C (100°F 6
tingfortheanalyzeriscriticalfortheaccuratedeterminationof
5°F).
∆O.N. The engine spread for constant C.R. systems or adher-
(2) IntakeMixtureTemperature—149°C 61°C(300°F 6
ence to guide table readings for constant K.I. systems at the
2°F)maintainedwithin1°C(62°F)whenC.R.orK.I.results
octane range of the standard or prototype fuel must be
used for a delta octane measurement are recorded.
accurately determined and reflected in the analyzer span.
10.2.5.2 Research Method:
10.2.3.1 ForAMSoperatingataconstantcompressionratio,
(1) IntakeAir Temperature—52°C 61°C(125°F 62°F)
the span setting (K.I./octane) shall be determined by the
is specified for operation at standard barometric pressure of
running of two PRF fuels with a difference of 1.0 6 0.2 O.N.
101.0 kPa (29.92 in. Hg). IATs for other than standard
on the analyzer as per the manufacturer’s instructions. The
barometric pressure conditions need to be adjusted to compen-
difference between the two fuels’ K.I. readings divided by the
sate for the site median barometric pressure.
differenceinthetwofuels’O.N.willgivethespreadforengine
(2)Determine the site median barometric pressure (see
at that octane.The spread for the engine at the octane range of
detailspreviouslygivenunderSiteCompensationofCompres-
the PRFs will then need to be entered into the analyzer
sion Ratio for Standard Knock Intensity).
software as the span per the manufacturer’s instructions.
(3)UsethesitemedianbarometricpressureandTableA4.4
10.2.3.2 For AMS operating at a constant knock intensity
or A4.5 of Test Method D2699 to determine the applicable
the span setting (C.R./octane) is to be determined by the
intake air temperature.
running of two PRF fuels with a difference of 1.0 6 0.2 O.N.
(4)Adjustanalyzermeasurementsystemsettingstodeliver
on the analyzer as per the manufacturer’s instructions. The
the compensated intake air temperature and this temperature
difference in the C.R. between the two fuels divided by the
shall then be maintained within 61°C(62°F) when C.R. or
differenceO.N.willgivethespanfortheengineatthatoctane.
K.I. results used for a delta octane measurement are recorded.
The span for the engine at the octane range of the PRFs will
then need to be entered into the analyzer software as per the 10.3 Proper Operation of the Automated Analyzer System
manufacturer’s instructions. Equipment and Instrumentation:
10.2.4 Fuel-Air Ratio Characteristic—With the engine op- 10.3.1 Sample Stream Sampling Systems:
erating at a cylinder height that causes knock, variation of the 10.3.1.1 Cyclic and Continuous Fuel Sampling
fuel-air mixture has a characteristic effect, typical for all fuels. Techniques—AMS can determine the knock characteristic
This test method specifies that each stream sample and CRF
measurement using either a grab sample or continuously
shall be operated at the fuel-air ratio that produces the flowing sample.
maximumK.I.Tomaintaingoodfuelvaporization,arestrictive
10.3.1.2 Forthecontinuouslyflowingsampleapproach,fuel
orifice or horizontal jet is utilized so that the maximum knock
is continuously delivered to the CFR engine carburetor while
condition occurs for fuel levels between 0.7in. and 1.7in.
knockmeasurementisinprogress,andanyunconsumedfuelis
referenced to the centerline of the carburetor venturi. The
removed from the AMS.
mechanics for varying the fuel mixture can be accomplished
10.3.1.3 For the intermittent or grab sample approach, a
using various approaches.
carburetordeviceisolatesaportionofeitherthestreamsample
10.2.4.1 Fixed Horizontal Jet—Variable Fuel Level or CRF, then performs the knock measurement sequence on
System—Fuel level adjustments are made by varying the float that sample.
D2885 − 21
10.3.1.4 Thecompressionratio(CR)systemstypicallyneed of the engine with the fuel level 0.4in. to 0.3in. above the
to operate on each fuel for a minimum of 4 min. The time level for maximum knock intensity.
periodsspentoneachfuelcanbesetbasedonengineoperation 11.2.3 Sequence the AMS between the paired check fuels
and site requirements. untilaminimumofsixcycleshascompleted.Acompletecycle
10.3.1.5 Theknockintensity(KI)systemstypicallystartthe comprisesoneperiodofoperationononefuel(A),followedby
fuel cycle at 0.4in. to 0.3in. above the expected fuel level for one period on the second fuel (B). Sequence the check fuels to
maximum knock intensity of the fuels. the analyzer measurement system so that the ∆O.N. values are
10.3.1.6 The system must be rating the sample stream for a determined by subtracting the fuel B result from the fuel A
minimum of 50% of the cycle time. result.
10.3.2 Sample Temperature—Deliver the CRF and sample
11.3 Determination of Average ∆O.N.:
fuel to the knock-testing unit critical carburetor components at
11.3.1 Discard the ∆O.N. result for the first complete cycle
the same nominal temperature. This temperature shall be
determination.
greater than 0°C (32°F) but not exceed 10°C (50°F).
11.3.2 Tabulate the remaining ∆O.N. values (Fuel B from
10.3.3 System Alarm Functions—AMS systems for unat-
Fuel A), including the proper algebraic sign.
tended operation utilize sensors, control logic, and other
11.3.3 Calculate the average ∆O.N., with respect to alge-
devices designed to protect the system and facilities from
braic sign.
abnormal conditions. Some typical sensors are: low crankcase
11.4 System Accuracy Qualification:
oil pressure, loss of jacket coolant, loss of sample stream
11.4.1 Assess the accuracy of the system by comparing the
pressure or flow, or both, excessive C.R. as evidenced by
measured average ∆O.N. for the paired check fuels to the
cylinder height limits, indication of system measurement
expected difference O.N.
instability as evidenced by out-of-limit repeatability measure-
11.4.1.1 Calculate Q,theaccuracyqualificationvalue,using
ments for comparison reference fuel, the presence of hydro-
the following formula:
carbon vapors at the unit, the presence of carbon monoxide in
Q 5measuredaverage ∆O.N.2expecteddifferenceO.N.
the room atmosphere, and so forth. Some alarm functions are
activeandresultinsystemshutdown.Otheralarmsarepassive
11.4.1.2 Use Table 1 to determine if the calculated Q value
and simply indicate an operating characteristic that is out of
iswithintheaccuracyqualificationacceptancelimit,K,forthe
performance limits.
applicable test method operating conditions (RON or MON).
11.4.1.3 The calculated Q value would, in the long run, in
11. System Qualification Checkout
the normal and correct operation of this test method, fall
11.1 Check the performance of the AMS at intervals in
outsidetheaccuracyqualificationacceptancelimits(K)inonly
accordance with the user quality system or after any mainte- 1 case in 20.
nance that could affect measurement system performance.
11.4.1.4 If Q is within the limits of K for the respective test
Operate the system using paired check fuels to determine
method, AMS is considered to be acceptably accurate.
whether it produces the correct ∆O.N. value and does so with
11.4.1.5 If QisoutsidethelimitsofKfortherespectivetest
appropriate system stability.
method, the system is considered to be inaccurate and evalu-
11.1.1 The ∆O.N.valueisdependentupon(1)knocktesting
ation is required to identify and correct the root cause(s) of the
unit sensitivity, (2) detonation meter sensitivity, and (3) auto-
inaccuracy before the system is used for ∆O.N. ratings of
mated analyzer span setting for the octane range to be used.
stream samples.
11.1.2 The knock testing unit must be able to repeatedly
11.5 System Stability Assessment:
measure the ∆O.N. for two fuels of different octane number.
11.5.1 Assess the stability of the system by comparing the
The latitude of engine condition is quite broad and when the
∆O.N.rangevalueforthepairedcheckfuelsdatatotheRange
knock testing unit is no longer satisfactory for automated
Limit (L) in Table 2 for the respective test method.
analyzer operation it will be evidenced as instability of knock
NOTE 1—Range limit (L) values listed in Table 2 are for use with data
intensity. This condition often can be rectified through carbon
sets of five independent ∆O.N. determinations and infer aType 1 error of
blasting and ultimately by cylinder overhaul.
approximately 1%.
11.1.3 Set the span according to the manufacturer’s instruc-
11.5.1.1 Calculate the range value, using the following
tionsforthedesiredoctanerangesothattheknockintensityor
formula:
compression
...