1、Designation: D7668 17Standard Test Method forDetermination of Derived Cetane Number (DCN) of DieselFuel OilsIgnition Delay and Combustion Delay Using aConstant Volume Combustion Chamber Method1This standard is issued under the fixed designation D7668; the number immediately following the designation
2、 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. Scope*1.1 This test method covers the quantita
3、tive determinationof 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-sulfurdiesel fuel oils, European standard EN590, a
4、nd Canadianstandards CAN/CGSB-3.517 and CAN/CGSB3.6. The testmethod may be applied to the quantitative determination of thederived cetane number of biodiesel, blends of diesel fuel oilscontaining biodiesel material (for example, SpecificationsD975, D6751, and D7467), and diesel fuel oil blendingcomp
5、onents.1.2 This test method utilizes a constant volume combustionchamber with direct fuel injection into heated, compressedsynthetic air. A dynamic pressure wave is produced from thecombustion of the sample. An equation converts the ignitiondelay and the combustion delay determined from the dynamicp
6、ressure curve to a derived cetane number (DCN).1.3 This test method covers the ignition delay ranging from1.9 ms to 25 ms and combustion delay ranging from 2.5 ms to160 ms (30 DCN to 70 DCN). However, the precision statedonly covers the range of DCN from 39 to 67.1.4 The values stated in SI units ar
7、e to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 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, health, and environ
8、mental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards
9、, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D613 Test Method for Cetane Number of Diesel Fuel OilD975 Specification for Diesel Fuel OilsD1193 Specification for Reagent WaterD4057 Practice f
10、or Manual Sampling of Petroleum andPetroleum ProductsD4175 Terminology Relating to Petroleum Products, LiquidFuels, and LubricantsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD5854 Practice for Mixing and Handling of Liquid Samplesof Petroleum and Petroleum ProductsD6299 P
11、ractice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6300 Practice for Determination of Precision and BiasData for Use in Test Methods for Petroleum Products andLubricantsD6708 Practice for Statistical Assessment and I
12、mprovementof Expected Agreement Between Two Test Methods thatPurport to Measure the Same Property of a MaterialD6751 Specification for Biodiesel Fuel Blend Stock (B100)for Middle Distillate FuelsD7467 Specification for Diesel Fuel Oil, Biodiesel Blend(B6 to B20)E456 Terminology Relating to Quality a
13、nd Statistics2.2 EN Standards:3EN590 Automotive FuelsDieselRequirements and TestMethods1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.01 on Combustion Characteristics.Current edi
14、tion approved Oct. 1, 2017. Published October 2017. Originallyapproved in 2010. Last previous edition approved in 2014 as D7668 14a. DOI:10.1520/D7668-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMS
15、tandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from European Committee for Standardization. Central Secretariat:rue de Stassart, 36,B-1050 Brussels, Belgium.*A Summary of Changes section appears at the end of this standardCopyright ASTM Intern
16、ational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, G
17、uides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.12.3 Energy Institute Standards:4IP41 Ignition Quality of Diesel FuelsCetane Engine TestMethod2.4 Canadian Standards:5CAN/CGSB-3.517 Regular Sulphur Diesel FuelSpecificationCAN/CGSB 3.6 Autom
18、otive Low-Sulphur Diesel FuelSpecification2.5 DIN Standards:6DIN 73372 Einspritzdsen Grsse T und U3. Terminology3.1 Definitions:3.1.1 accepted reference value (ARV), na value that servesas an agreed-upon reference for comparison and that is derivedas (1) a theoretical or established value, based on
19、scientificprinciples, (2) an assigned value, based on experimental workof some national or international organization, such as the U.S.National Institute of Standards and Technology (NIST), or (3)a consensus value, based on collaborative experimental workunder the auspices of a scientific or enginee
20、ring group. E4563.1.1.1 DiscussionIn the context of this method, acceptedreference value is understood to apply to the ignition delay andthe combustion delay of specific reference materials deter-mined under reproducibility conditions by collaborative ex-perimental work.3.1.2 cetane number, na measu
21、re of the ignition perfor-mance of a diesel fuel oil obtained by comparing it to referencefuels in a standardized engine test. D41753.1.2.1 DiscussionIn the context of this test method,cetane number is that defined by Test Method D613/IP41.3.1.3 check standard, nin QC testing, a material having anac
22、cepted reference value used to determine the accuracy of ameasurement system.3.1.3.1 DiscussionIn the context of this test method,check standard refers to the calibration reference material.3.1.4 quality control (QC) sample, nfor use in qualityassurance programs to determine and monitor the precisio
23、n andstability of a measurement system, a stable and homogeneousmaterial having physical or chemical properties, or both,similar to those of typical samples tested by the analyticalmeasurement system. The material is properly stored to ensuresample integrity, and is available in sufficient quantity
24、forrepeated, long term testing. D62993.2 Definitions of Terms Specific to This Standard:3.2.1 calibration reference material, na pure chemical ora specified mixture of pure chemicals having an assignedignition delay accepted reference value and an assigned com-bustion delay accepted reference value.
25、3.2.2 chamber wall temperature, ntemperature, in C, ofthe combustion chamber wall.3.2.3 charge air, ncompressed synthetic air at a specifiedpressure introduced into the combustion chamber at the begin-ning of each test cycle.3.2.4 combustion analyzer, nan integrated compressionignition apparatus to
26、measure the ignition and combustioncharacteristics of diesel fuel oil.3.2.5 combustion delay (CD), nthat period of time, inmilliseconds (ms), between the start of fuel injection andmid-point of the combustion pressure curve.3.2.5.1 DiscussionIn the context of this test method, thestart of fuel injec
27、tion is interpreted as the rise in the electronicsignal that opens the injector and the combustion pressurecurve mid-point is interpreted as the part of the pressure curvemidway between the chamber static pressure and the maximumpressure generated during the combustion cycle, as measuredby a pressur
28、e sensor in the combustion chamber. The combus-tion delay CD measures the time between the injection of thesample and phase of combustion controlled by the diffusivemixing of the air and fuel.3.2.6 derived cetane number (DCN), na number calcu-lated using a conversion equation to determine a cetanenu
29、mber.3.2.6.1 DiscussionThe conversion equation relates a mea-sured ignition delay or ignition delay and combustion delayfrom a combustion analyzer, to a cetane number.3.2.7 ignition delay (ID), nthat period of time, in milli-seconds (ms), between the start of fuel injection and the start ofcombustio
30、n as determined using the specific combustion ana-lyzer applicable for this test method.3.2.7.1 DiscussionIn the context of this test method, startof fuel injection is interpreted as the rise in the electronic signalthat opens the injector; combustion is interpreted as the part ofthe pressure curve
31、generated during the combustion cycle whensignificant (+0.02 MPa above the chamber static pressure) andsustained increase in rate-of-change in pressure, as measuredby a pressure sensor in the combustion chamber.3.2.8 injection period, nthe period of time, in microsec-onds (s), that the fuel injector
32、 nozzle is open as determined bythe length of the electronic signal, in microseconds, that opensthe injector.3.2.9 operation period, nthe time, not to exceed 12 h,between successive calibration or QC testing, or both, of thecombustion analyzer by a single operator.3.3 Abbreviations:3.3.1 ARVaccepted
33、 reference value3.3.2 CDcombustion delay3.3.3 CNcetane number3.3.4 DCNderived cetane number3.3.5 IDignition delay3.3.6 QCquality control4. Summary of Test Method4.1 A small specimen of sample is injected into a heated,temperature-controlled, constant volume chamber, which has4Available from Energy I
34、nstitute, 61 New Cavendish St., London, WIG 7AR,U.K., http:/www.energyinst.org.uk.5Available from the Canadian General Standards Board, Sales Centre, Gatineau,Canada, K1A1G6. www.ongc-cgsb.ca.6Available from Beuth Verlag GmbH (DIN- DIN Deutsches Institut furNormung e.V.), Burggrafenstrasse 6, 10787,
35、 Berlin, Germany, http:/www.en.din.de.D7668 172previously been charged with compressed air of a specifiedquality. Each injection produces a compression ignition com-bustion cycle detected using a pressure sensor. The ignitiondelay and combustion delay are measured from the rise of theelectronic sign
36、al that activates the injector solenoid to twospecific points along the combustion pressure wave producedby the combustion cycle. A complete sequence comprises 5preliminary injection cycles and 15 subsequent injection cyclesused for the sample analysis. The ID and CD measurements forthe last 15 inje
37、ction cycles are statistically reviewed and theoutlying IDs and CDs are eliminated using Peirces Crite-rion.7The remaining IDs and CDs are averaged to producethe two independent results. An equation converts the averageID result and the average CD result into a DCN.5. Significance and Use5.1 The ID
38、and CD values and the DCN value determinedby this test method provides a measure of the ignitioncharacteristics of diesel fuel oil used in compression ignitionengines.5.2 This test can be used by engine manufacturers, petro-leum refiners and marketers, and in commerce as a specifica-tion aid to rela
39、te or match fuels and engines.5.3 The relationship of diesel fuel oil DCN determinationsto the performance of full-scale, variable-speed, variable-loaddiesel engines is not completely understood.5.4 This test can be applied to non-conventional dieselfuels.5.5 This test determines ignition characteri
40、stics and requiresa sample of approximately 370 mL and a test time of approxi-mately 30 min using a fit-for-use instrument.6. Interferences6.1 WarningMinimize exposure of sample fuels, calibra-tion reference materials, QC samples, and check standards tosunlight or fluorescent lamp UV emissions to mi
41、nimize in-duced chemical reactions that can affect the delay measure-ments.86.1.1 Exposure of these fuels and materials to UV wave-lengths shorter than 550 nm for a short period of time cansignificantly affect ignition delay measurements.NOTE 1The formation of peroxide and radicals can affect igniti
42、ondelay measurement. These formations are minimized when the sample ormaterial is stored in the dark in a cold room at a temperature of less than10 C and covered by a blanket of nitrogen.7. Apparatus7.1 GeneralThis test method uses an integrated automatedanalytical measurement system9comprised of:7.
43、1.1 Combustion ChamberA cylindrical chamber havinga volume of 0.473 L 6 005 L, with external heating elements,heat shield, and electrically actuated intake and exhaust valves.There is an opening at one end of the chamber to accommodateinsertion of the fuel injection nozzle assembly and there areopen
44、ings at the other end of the chamber to insert air, removeexhaust, and attach a pressure sensor.7.1.2 Fuel Injection SystemA high pressure sample, gen-erated using a hydraulic pump and pressure multiplier, isdelivered to a commercial electronic diesel fuel injector. Asample reservoir supplies the pr
45、essure multiplier with sampleto ensure proper and repeatable injection of calibration, QCmaterial, and test specimens into the combustion chamber. Thesystem includes:7.1.2.1 Fuel Sample ReservoirA metal reservoir having anominal volume of 200 mL.7.1.2.2 Hydraulic PumpCapable of producing fuel pres-s
46、ures up to 19 MPa.7.1.2.3 Pressure Multiplier10:1 ratio.7.1.2.4 Fuel InjectorAsolenoid-based common rail dieselfuel injector from Bosch with the part number 0445110181(Annex A6).7.1.2.5 Safety Burst DiskRelieves the high pressure if thesample pressure exceeds 180 MPa.The burst disk is attached tothe
47、 high pressure sample system manifold block opposite theinjector.7.1.2.6 Flush ValveHigh pressure air actuated valve usedto exchange samples.7.1.3 Coolant SystemA closed loop circulating coolantsystem to control the temperature of the combustion injectornozzle and dynamic pressure sensor. The system
48、 includes anauxiliary heat exchanger with built-in circulating pump andflow control valves.7.1.4 Instrument SensorsSensors used to measure andeither indicate the value of a variable or transmit the conditionfor control or data acquisition purposes such as:7.1.4.1 Combustion Chamber Static Pressure S
49、ensorAcalibrated sensor installed to correct the temperature offset ofdynamic pressure sensor.7.1.4.2 Combustion Chamber Dynamic Pressure SensorAcalibrated sensor installed to measure the pressure within thecombustion chamber.7.1.4.3 Sample Pressure SensorA calibrated sensor in-stalled to measure the pressure of the sample injected into thecombustion chamber.7Ross, Stephen, “Peirces Criterion for the Elimination of Suspect ExperimentalData,” Journal of Engineering Technology, Fall 2003.8Supporting data, “Sunlight
