ASTM D7668-10
(Test Method)Standard Test Method for Determination of Derived Cetane Number (DCN) of Diesel Fuel OilsIgnition Delay and Combustion Delay Using a Constant Volume Combustion Chamber Method
Standard Test Method for Determination of Derived Cetane Number (DCN) of Diesel Fuel Oils<char: emdash>Ignition Delay and Combustion Delay Using a Constant Volume Combustion Chamber Method
SIGNIFICANCE AND USE
The ID and CD values and the DCN value determined by this test method provides a measure of the ignition characteristics of diesel fuel oil used in compression ignition engines.
This test can be used by engine manufacturers, petroleum refiners and marketers, and in commerce as a specification aid to relate or match fuels and engines.
The relationship of diesel fuel oil DCN determinations to the performance of full-scale, variable-speed, variable-load diesel engines is not completely understood.
This test can be applied to non-conventional diesel fuels.
This test determines ignition characteristics and requires a sample of approximately 370 mL and a test time of approximately 30 min using a fit-for-use instrument.
SCOPE
1.1 This test method covers the quantitative determination of the derived cetane number of conventional diesel fuel oils, diesel fuel oils containing cetane number improver additives, and is applicable to products typical of Specification D975, Grades No.1-D and 2-D regular, low and ultra-low-sulfur diesel fuel oils, European standard EN590, and Canadian standards CAN/CGSB-3.517 and CAN/CGSB3.6. The test method may be applied to the quantitative determination of the derived cetane number of blends of fuel oils containing biodiesel material (for example, Specification D975, biodiesel, and diesel fuel oil blending components.
1.2 This test method utilizes a constant volume combustion chamber with direct fuel injection into heated, compressed synthetic air. A dynamic pressure wave is produced from the combustion of the sample. An equation converts the ignition delay and the combustion delay determined from the dynamic pressure curve to a derived cetane number (DCN).
1.3 This test method covers the ignition delay ranging from 2.8 to 6.5 ms and combustion delay ranging from 5.5 to 120 ms (30.0 to 65.0 DCN). However, the precision stated only covers the range of DCN from 35 to 60.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D7668 − 10
StandardTest Method for
Determination of Derived Cetane Number (DCN) of Diesel
Fuel Oils—Ignition Delay and Combustion Delay Using a
Constant Volume Combustion Chamber Method
This standard is issued under the fixed designation D7668; 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.
1. Scope 2. Referenced Documents
1.1 This test method covers the quantitative determination 2.1 ASTM Standards:
of the derived cetane number of conventional diesel fuel oils, D613Test Method for Cetane Number of Diesel Fuel Oil
diesel fuel oils containing cetane number improver additives, D975Specification for Diesel Fuel Oils
and is applicable to products typical of Specification D975, D1193Specification for Reagent Water
Grades No.1-D and 2-D regular, low and ultra-low-sulfur D4057Practice for Manual Sampling of Petroleum and
diesel fuel oils, European standard EN590, and Canadian Petroleum Products
standards CAN/CGSB-3.517 and CAN/CGSB3.6. The test D4175 Terminology Relating to Petroleum, Petroleum
methodmaybeappliedtothequantitativedeterminationofthe Products, and Lubricants
derived cetane number of blends of fuel oils containing D4177Practice for Automatic Sampling of Petroleum and
biodiesel material (for example, Specification D975, biodiesel, Petroleum Products
and diesel fuel oil blending components. D5854Practice for Mixing and Handling of Liquid Samples
of Petroleum and Petroleum Products
1.2 This test method utilizes a constant volume combustion
D6299Practice for Applying Statistical Quality Assurance
chamber with direct fuel injection into heated, compressed
and Control Charting Techniques to Evaluate Analytical
synthetic air. A dynamic pressure wave is produced from the
Measurement System Performance
combustion of the sample. An equation converts the ignition
D6300Practice for Determination of Precision and Bias
delay and the combustion delay determined from the dynamic
Data for Use in Test Methods for Petroleum Products and
pressure curve to a derived cetane number (DCN).
Lubricants
1.3 This test method covers the ignition delay ranging from
D6708Practice for StatisticalAssessment and Improvement
2.8to6.5msandcombustiondelayrangingfrom5.5to120ms
of Expected Agreement Between Two Test Methods that
(30.0 to 65.0 DCN). However, the precision stated only covers
Purport to Measure the Same Property of a Material
the range of DCN from 35 to 60.
E456Terminology Relating to Quality and Statistics
1.4 The values stated in SI units are to be regarded as 2.2 EN Standards:
EN590Automotive Fuels—Diesel—Requirements and Test
standard. No other units of measurement are included in this
standard. Methods
2.3 Energy Institute Standards:
1.5 This standard does not purport to address all of the
IP41Ignition Quality of Diesel Fuels—Cetane Engine Test
safety concerns, if any, associated with its use. It is the
Method
responsibility 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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
This test method is under the jurisdiction of ASTM Committee D02 on the ASTM website.
PetroleumProductsandLubricantsandisthedirectresponsibilityofSubcommittee Available from European Committee for Standardization. Central Secretariat:
D02.01 on Combustion Characteristics. rue de Stassart, 36,B-1050 Brussels, Belgium.
Current edition approved Oct. 1, 2010. Published November 2010. DOI: Available from Energy Institute, 61 New Cavendish St., London, WIG 7AR,
10.1520/D7668–10. U.K., http://www.energyinst.org.uk.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7668 − 10
2.4 Canadian Standards: 3.2.4 combustion analyzer, n—an integrated compression
CAN/CGSB-3.517 Regular Sulphur Diesel Fuel— ignition apparatus to measure the ignition and combustion
Specification characteristics of diesel fuel oil.
CAN/CGSB 3.6Automotive Low-Sulphur Diesel Fuel—
3.2.5 combustion delay (CD), n—that period of time, in
Specification
milliseconds (ms), between the start of fuel injection and
2.5 DIN Standards:
mid-point of the combustion pressure curve.
DIN 73372Einspritzdüsen Grösse T und U
3.2.5.1 Discussion—In the context of this test method, the
start of fuel injection is interpreted as the rise in the electronic
3. Terminology
signal that opens the injector and the combustion pressure
3.1 Definitions: curve mid-point is interpreted as the part of the pressure curve
midwaybetweenthechamberstaticpressureandthemaximum
3.1.1 accepted reference value (ARV), n—avaluethatserves
asanagreed-uponreferenceforcomparisonandthatisderived pressure generated during the combustion cycle, as measured
by a pressure sensor in the combustion chamber. The combus-
as (1) a theoretical or established value, based on scientific
principles, (2) an assigned value, based on experimental work tion delay CD measures the time between the injection of the
ofsomenationalorinternationalorganization,suchastheU.S. sample and phase of combustion controlled by the diffusive
mixing of the air and fuel.
National Institute of Standards and Technology (NIST), or (3)
a consensus value, based on collaborative experimental work
3.2.6 derived cetane number (DCN), n—a number calcu-
under the auspices of a scientific or engineering group. E456
lated using a conversion equation to determine a cetane
3.1.1.1 Discussion—In the context of this method, accepted
number.
referencevalueisunderstoodtoapplytotheignitiondelayand
3.2.6.1 Discussion—Theconversionequationrelatesamea-
the combustion delay of specific reference materials deter-
sured ignition delay or ignition delay and combustion delay
mined under reproducibility conditions by collaborative ex-
from a combustion analyzer, to a cetane number.
perimental work.
3.2.7 ignition delay (ID), n—that period of time, in milli-
3.1.2 cetane number, n—a measure of the ignition perfor-
seconds(ms),betweenthestartoffuelinjectionandthestartof
manceofadieselfueloilobtainedbycomparingittoreference
combustion as determined using the specific combustion ana-
fuels in a standardized engine test. D4175
lyzer applicable for this test method.
3.1.2.1 Discussion—In the context of this test method,
3.2.7.1 Discussion—In the context of this test method, start
cetane number is that defined by Test Method D613/IP41.
offuelinjectionisinterpretedastheriseintheelectronicsignal
3.1.3 check standard, n—inQCtesting,amaterialhavingan that opens the injector; combustion is interpreted as the part of
thepressurecurvegeneratedduringthecombustioncyclewhen
accepted reference value used to determine the accuracy of a
measurement system. significant (+0.02 MPa above the chamber static pressure) and
sustained increase in rate-of-change in pressure, as measured
3.1.3.1 Discussion—In the context of this test method,
check standard refers to the calibration reference material. by a pressure sensor in the combustion chamber.
3.1.4 quality control (QC) sample, n—for use in quality 3.2.8 injection period, n—the period of time, in microsec-
onds(µs),thatthefuelinjectornozzleisopenasdeterminedby
assuranceprogramstodetermineandmonitortheprecisionand
stability of a measurement system, a stable and homogeneous the length of the electronic signal, in microseconds, that opens
the injector.
material having physical or chemical properties, or both,
similar to those of typical samples tested by the analytical
3.2.9 operation period, n—the time, not to exceed 12 h,
measurement system.The material is properly stored to ensure
between successive calibration or QC testing, or both, of the
sample integrity, and is available in sufficient quantity for
combustion analyzer by a single operator.
repeated, long term testing. D6299
3.3 Abbreviations:
3.2 Definitions of Terms Specific to This Standard:
3.3.1 ARV—accepted reference value
3.2.1 calibration reference material, n—a pure chemical or
3.3.2 CD—combustion delay
a specified mixture of pure chemicals having an assigned
3.3.3 CN—cetane number
ignition delay accepted reference value and an assigned com-
bustion delay accepted reference value. 3.3.4 DCN—derived cetane number
3.2.2 chamber wall temperature, n—temperature, in °C, of 3.3.5 ID—ignition delay
the combustion chamber wall.
3.3.6 QC—quality control
3.2.3 charge air, n—compressed synthetic air at a specified
4. Summary of Test Method
pressure introduced into the combustion chamber at the begin-
4.1 A small specimen of sample is injected into a heated,
ning of each test cycle.
temperature-controlled, constant volume chamber, which has
previously been charged with compressed air of a specified
AvailablefromtheCanadianGeneralStandardsBoard,SalesCentre,Gatineau,
quality. Each injection produces a compression ignition com-
Canada, K1A1G6. www.ongc-cgsb.ca.
bustion cycle detected using a pressure sensor. The ignition
Available from Beuth Verlag GmbH (DIN-- DIN Deutsches Institut fur
delay and combustion delay are measured from the rise of the
Normunge.V.),Burggrafenstrasse6,10787,Berlin,Germany,http://www.en.din.de.
electronic signal that activates the injector solenoid to two
D7668 − 10
specific points along the combustion pressure wave produced Thereisanopeningatoneendofthechambertoaccommodate
by the combustion cycle. A complete sequence comprises 5 insertion of the fuel injection nozzle assembly and there are
preliminaryinjectioncyclesand15subsequentinjectioncycles openings at the other end of the chamber to insert air, remove
usedforthesampleanalysis.TheIDandCDmeasurementsfor exhaust, and attach a pressure sensor.
the last 15 injection cycles are statistically reviewed and the
7.1.2 Fuel Injection System—A high pressure sample, gen-
outlying ID’s and CD’s are eliminated using Peirce’s Crite- erated using a hydraulic pump and pressure multiplier, is
rion. The remaining ID’s and CD’s are averaged to produce
delivered to a commercial electronic diesel fuel injector. A
the two independent results.An equation converts the average sample reservoir supplies the pressure multiplier with sample
ID result and the average CD result into a DCN.
to ensure proper and repeatable injection of calibration, QC
material,andtestspecimensintothecombustionchamber.The
5. Significance and Use
system includes:
5.1 The ID and CD values and the DCN value determined 7.1.2.1 Fuel Sample Reservoir—Ametal reservoir having a
by this test method provides a measure of the ignition nominal volume of 200 mL.
characteristics of diesel fuel oil used in compression ignition 7.1.2.2 Hydraulic Pump—Capable of producing fuel pres-
engines.
sures up to 19 MPa.
7.1.2.3 Pressure Multiplier—10:1 ratio.
5.2 This test can be used by engine manufacturers, petro-
7.1.2.4 Fuel Injector—Asolenoid-basedcommonraildiesel
leum refiners and marketers, and in commerce as a specifica-
fuel injector from Bosch with the part number 0445110181
tion aid to relate or match fuels and engines.
(Annex A6).
5.3 The relationship of diesel fuel oil DCN determinations
7.1.2.5 Safety Burst Disk—Relieves the high pressure if the
to the performance of full-scale, variable-speed, variable-load
samplepressureexceeds180MPa.Theburstdiskisattachedto
diesel engines is not completely understood.
the high pressure sample system manifold block opposite the
5.4 This test can be applied to non-conventional diesel
injector.
fuels.
7.1.2.6 Flush Valve—High pressure air actuated valve used
to exchange samples.
5.5 Thistestdeterminesignitioncharacteristicsandrequires
7.1.3 Coolant System—A closed loop circulating coolant
a sample of approximately 370 mL and a test time of
system to control the temperature of the combustion injector
approximately 30 min using a fit-for-use instrument.
nozzle and dynamic pressure sensor. The system includes an
6. Interferences
auxiliary heat exchanger with built-in circulating pump and
flow control valves.
6.1 Warning—Minimizeexposureofsamplefuels,calibra-
7.1.4 Instrument Sensors—Sensors used to measure and
tion reference materials, QC samples, and check standards to
either indicate the value of a variable or transmit the condition
sunlight or fluorescent lamp UV emissions to minimize in-
for control or data acquisition purposes such as:
duced chemical reactions that can affect the delay measure-
7.1.4.1 Combustion Chamber Static Pressure Sensor—A
ments.
calibrated sensor installed to correct the temperature offset of
6.1.1 Exposure of these fuels and materials to UV wave-
dynamic pressure sensor.
lengths shorter than 550 nm for a short period of time can
significantly affect ignition delay measurements. 7.1.4.2 Combustion Chamber Dynamic Pressure Sensor—A
calibrated sensor installed to measure the pressure within the
NOTE 1—The formation of peroxide and radicals can affect ignition
combustion chamber.
delay measurement. These formations are minimized when the sample or
7.1.4.3 Sample Pressure Sensor—A calibrated sensor in-
material is stored in the dark in a cold room at a temperature of less than
10°C and covered by a blanket of nitrogen.
stalled to measure the pressure of the sample injected into the
combustion chamber.
7. Apparatus
7.1.4.4 Nitrogen Pressure Sensor—A sensor installed to
7.1 General—Thistestmethodusesanintegratedautomated
measure the inlet pressure from the nitrogen regulator.
analytical measurement system comprised of:
7.1.4.5 Combustion Chamber Inner Wall Temperature
7.1.1 Combustion Chamber—Acylindrical chamber having
Sensor—Type K thermocouple with a stainless steel sheath.
a volume of 0.473 6 005 L, with external heating elements,
7.1.4.6 Injector Nozzle Cooling Jacket Temperature
heatshield,andelectricallyactuatedintakeandexhaustvalves.
Sensor—Type K thermocouple with stainless steel sheath,
inserted in the injector nozzle coolant passage.
7 7.1.5 Computerized Control, Data Acquisition, Data Analy-
Ross, Stephen, “Peirce’s Criterion for the Elimination of Suspect Experimental
Data,” Journal of Engineering Technology, Fall 2003.
sisandReportingSystem—Amicroprocessorcontrolledsystem
Supporting data, “Sunlight and Air Exposure Effects on Octane Number or
with a keyboard for manual entry of operating instructions, an
Cetane Number of Petroleum Product Samples,” have been filed at ASTM
LCD monitor for visual observation of all tes
...
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