The autoignition quality is quantified by cetane number cn, measured in a cfr engine or derived cetane number dcn, measured in a constantvolume combustion chamber. It pushed our capability to span long ignition delay times, bridging to gasoline range fuel studies. The curve for sunflower oil cetane number 35,8 is different fig. The autoignition quality of diesel fuels, quantified by their cetane number or. Octane number measures the performance of gasoline while cetane number measure the. First, based on the ignition delay data in shock tubes, the cetane number of various fuels. At the other end of the scale, heptamethylnonane, an isomer of cetane, has the assigned. Instead of 1methylnaphthalene, heptamethylnonane with a cetane number of 15 can also be used as the nonignitable reference fuel. Due to this it seems that the fuels behave similarly under combustion conditions. Cetane number ndecane c10h22 76 npentadecane c15h32 95 paraffins neicosane c20h42 110 3ethyldecane c12h26 48 4,5diethyloctane c12h26 20 heptamethylnonane c16h34 15 8propylpentadecane c18h38 48 7,8diethyltetradecane c18h38 67 isoparaffins 9,10dimethyloctadecane c20h42 59 decalin c10h18 48 3cyclohexylhexane c12h24 36 2methyl3. Isocetane replaced 1methylnaphthalene as the lower reference for cetane number 1methylnaphthalene has cetane number zero owing to the expense of 1methylnaphthalene, and difficulty in safe hand.
While gasolines octane number signifies its ability to resist autoignition also referred to as preignition, knocking, pinging, or detonation, diesels cetane number is a measure of the fuels delay of ignition time the amount of time between the injection of fuel into the combustion chamber and the actual start of combustion of the fuel. The kinetics of oxidation of isocetane 2,2,4,4,6,8,8heptamethylnonane, a cetane number reference fuel, was studied experimentally in a jetstirred reactor jsr at 10 atm and a constant residence time of 1 s, over the temperature range 770. Pdf understanding the relationship between cetane number. The haltermann solutions4 product designation for n cetane is hf3018 and determination. Cetane ignites easily under compression and was assigned a cetane number of 100, while alphamethyl naphthalene was assigned a cetane number of 0. Cetane is a chemical compoundalso known as hexadecan. Cetane index calculations can not account for cetane improver additives and therefore do not measure total cetane number for additized diesel fuels. Cetane numbers of branched and straightchain fatty esters determined in an ignition quality testerq gerhard knothea, andrew c. Sep 18, 2014 the disclosed reference standards can be used directly as substitutes for blends of nhexadecane and 2,2,4,4,6,8,8 heptamethylnonane in astm d610a for determining cetane number, or in astm d6890, astm 07170 or astm d7668 to determine a derived cetane number. Dependence of biodiesel fuel properties on the structure of. Cn is derived from the volume percent of cetane and heptamethylnonane.
Assessment of jp8 and df2 evaporation rate and cetane number differences on a military diesel engine peter schihl, laura hoogterp, and harold pangilinan u. Cetane number yang tinggi menunjukkan bahwa bahan bakar dapat menyala pada temperatur yang relatif rendah, dan sebaliknya cetane number rendah menunjukkan bahan bakar baru dapat. Hexadecane also called cetane ignites very easily under compression. In this diagram, the initial precompression temperature. This information is beneficial to perform computational simulations of. The estimated cetane numbers of the lpg with a 15 wt % cetane number improver were more than 50 suggesting the possibility of utilizing lpg as a diesel fuel. Nrel studied 2,2,4,4,6,8,8 heptamethylnonane iso cetane, or hmn, c 16 h 34 in detail. A number of different tests have evolved for the quantification of ignition quality, which can be grouped into three types of methods. Assessment of jp8 and df2 evaporation rate and cetane. On the cetane scale, the former is regarded asthe high quality standard with an assigned cn of 100, while the latteris of lowquality standard with poor ignition quality. Difference between octane number and cetane number. The present model, which can be easily applied to a conventional cfd code, is constructed simply from 59 chemical species and 96 reactions. Griffiths b a department of chemistry, y ork university, t oronto, ontario, canada m3j 1p3.
Effects of methyl substitution on the autoignition of c16 alkanes. Cetane number definition of cetane number by the free. Suggestions for reporting the fuel properties of biodiesel that correlate to cetane number are also provided. Sep 06, 2005 the cetane number is the percentage by volume of cetane in the mixture that has the same performance as the fuel being tested.
Cetane has a short delay period during ignition and is assigned a cetane number of 100. The variation of cetane number of the fuels is shown in table. Isocetane 2,2,4,4,6,8,8 heptamethylnonane is a highly branched alkane used as a reference in determining the cetane number of diesel. The number corresponds to the percentage of cetane in a cetane heptamethylnonane mixture, or and originally in a cetane methylnaphthalene mixture, with the same ignition performance as the. The disclosed reference standards can be used directly as substitutes for blends of nhexadecane and 2,2,4,4,6,8,8 heptamethylnonane in astm d610a for determining cetane number, or in astm d6890, astm 07170 or astm d7668 to determine a derived cetane number. A highly branched compound, 2,2,4,4,6,8,8, heptamethylnonane hmn, also c 16h 34, a compound with poor ignition quality, is the lowquality standard and has an assigned cn of 15. The cetane number is the percentage by volume of cetane in the mixture that has the same performance as the fuel being tested. Instead of 1methylnaphthalene, heptamethylnonane with a cetane number of 15 can also be used. It was observed that the cetane number calculated using this mathematical model varied only by a small percentage when compared to available data. In this case the new reference fuel was 2,2,4,4,6,8,8 heptamethylnonane hmn, shown in. A cetane number is determined by a complex and expensive engine test astm d 6 and iso 5165 using two reference fuel blends with known cetane number. A high cetane number indicates the potential for easy starting and smooth operation of the engine. It is an inverse of the similar octane rating for gasoline.
This suggests that units withdifficultfeedscontaininghigh fractionsoflcoandothercracked stocks, or units without sufficient hydrogen,willexperiencedecreasingcetaneupliftduringthecycle. Any of a group of hydrocarbons, c16h34, having seven methyl groups on a ninecarbon chain. A study on a reduced kinetic model for ncetane and. Isocetane 2,2,4,4,6,8,8heptamethylnonane is a highly branched alkane used as a reference in determining the cetane number of diesel. The cn is an important factor in determining the quality of diesel fuel, but not the only one. Cetane number suatu bahan bakar didefinisikan sebagai persentase volume dari normal setana dengan campurannya tersebut. Cetane number cetane rating is an indicator of the combustion speed of diesel fuel and. Of the alternative methods, emphasis is given to those which appear or had appeared promising as good predictors of cetane number. Ryan iiib aus department of agriculture, agricultural research service, national center for agricultural utilization research, peoria, il 61604, usa bengine and vehicle research division, southwest research institute.
Assessment of jp8 and df2 evaporation rate and cetane number differences on a military diesel engine 2006011549 the u. Cetane number is a relative ranking of a fuels autoignition characteristics for use in compression ignition engines. In the range of 71 to 34 cetane numbers, the primary reference fuel blends alphamethyl naphthalene n cetane and heptamethylnonane n cetane and the secondary reference blends gave virtually the same compression ratios. The cetane scale 100 for hexadecane also known as cetane and 15 for 2,2,4,4,6,8,8 heptamethylnonane or hmn, both c 16 h 34 compounds is arbitrary. The cetane number of the test fuels was known by using mixtures of the cetane number secondary reference fuels srfs t26 and u19, which are fullblend certification fuels used in the place of 2,2,4,4,6,8,8 heptamethylnonane and nhexadecane for engine cetane number testing. Cetane number or cn is a measurement of the combustion quality of diesel fuel during compression ignition. The astm d 6 standard test method of diesel fuel oil now defines the cetane number scale.
Dependence of biodiesel fuel properties on the structure. Cetane number effect on engine performance and gas. So a fuel with a cetane number of 50 is exactly as ignitable as a mixture of 50% cetane and 50% 1methylnaphthalene. Chemical kinetic study of the oxidation of isocetane 2,2,4,4.
Biodiesel, cetane number, fatty acid ester composition, ignition quality. It is also a candidate branched alkane representative in surrogate mixtures for diesel and jet fuels. Nrel studied 2,2,4,4,6,8,8heptamethylnonane isocetane, or hmn, c 16 h 34 in detail. Investigation of cetane number and octane number correlation. Cetane number, exhaust gas emission, biodiesel property, fatty acid. In both cases, nhexadecane and 2,2,4,4,6,8,8 heptamethylnonane are used as reference hydrocarbons, and they are assigned cn100 and cn15, respectively. The din en 590 standard prescribes that a diesel fuel must have a cetane number of at least 51. Mixture cooling from heat of vaporization 102 101 1, fuel equilvalenceratio of mixture 0 25 50 75 100 125 temperature drop k adiabatic, constant pressure evaporation dodecane in air initial condition. What is the difference between derived cetane number and.
Diesel engine operation is primarily related to the actual cetane number and the cetane index is simply an estimation of the base unadditized cetane number. It is based on the amount of time between fuel injection and ignition, also known as ignition delay. Cetane number is the most important and universally accepted ignition quality test. Hmn defines the low end of the cetane scale dcn 15. Isocetane2,2,4,4,6,8,82,2,4,4,6,8,8 heptamethylnonane 150. The method was first published in 1941, and has changed little since, with the exception of substituting heptamethylnonane, with an assigned cetane number of 15, for. Advanced combustion and fuels us department of energy. The cetane number of a fuel is influenced by its physical and chemical. Title and subtitle assessment of jp8 and df2 evaporation rate and cetane number differences on a military diesel engine 5a.
Cetane number cetane rating is an indicator of the combustion speed of diesel fuel and compression needed for ignition. Evaluation of ignition quality of lpg with cetane number improver. Also, because of the cost of high purity primary reference fuels, less costly secondary reference fuels have 4 geocenters, inc. Cetane number cetane number 0 20 40 60 80 100 120 elevated pressure autoignition t 400 450 500 550 600 650 hexadecane heptamethylnonane isooctaneheptane df2gasoline fischer tropschehn lcn has some relationship to epait lcn does not universally relate to epait lon relationship is worse than the cn relationship. A reduced kinetic model for nheptane, ioctane, n cetane and heptamethylnonane is developed based on that for the primary reference fuel nheptane and ioctane. In this case the new reference fuel was 2,2,4,4,6,8,8heptamethylnonane hmn, shown in. By definition, isocetane heptamethylnonane, hmn has a cetane number of 15 and cetane nhexadecane, c 16 h 34 has a value of 100. Sixteen biodiesel cetane number cn predictive models.
Hence, use of methyl esters of vegetable oils may be an alternative for the diesel fuel in future. The cetane number scale is defined by blends of two pure hydrocarbon reference fuels. What is the cetane number of heavy fuel oil used in marine. Standard test method for cetane number of diesel fuel oil. A number of other measurements determine overall diesel fuel quality these other measures of diesel fuel quality include density, lubricity, coldflow properties, and sulfur content. It is a significant expression of the quality of a diesel fuel. Iso cetane 2,2,4,4,6,8,8 heptamethylnonane, c 16 h 34 is a highly branched alkane reference compound for determining cetane ratings.
The cetane number test uses a standard single cylinder variable compression ratio diesel engine. Industry standards edit the industry standards for measuring cetane number are astm d6 iso 5165 for the cfr engine, d6890 for the iqt, and d7170 for the fit. Cetane number effect on engine performance and gas emission. Diesel with high cetane number gives better fuel economy. Pdf evaluation of ignition quality of lpg with cetane. This is because the calorific value of this type of fuel is higher. Better antiknock quality allows us to compress the airfuel mixture to a larger extent befo. Octane number and cetane number are the standards to measure the tendency of fuel to ignite spontaneously. A comparative assessment of biodiesel cetane number. The kinetics of oxidation of isocetane 2,2,4,4,6,8,8 heptamethylnonane, a cetane number reference fuel, was studied experimentally in a jetstirred reactor jsr at 10 atm and a constant residence time of 1 s, over the temperature range 770. Higher cetane number is always desired in diesel engines. The cetane number is calculated by determining which mixture of cetane hexadecane and isocetane 2,2,4,4,6,8,8 heptamethylnonane will result in the same ignition delay.
Download full text article pdf international journal of energy. Heptamethylnonane was determined to have a cetane number accepted reference value cnarv of 15 based on engine testing by the astm diesel national exchange group, using blends of n cetane and amn as primary reference fuels. The cetane number describes the percentage of cetane found in the mixture that corresponds to the ignition quality of the test fuel. The scale is based upon the ignition characteristics of two hydrocarbons, nhexadecane cetane and 2,3,4,5,6,7,8 heptamethylnonane. In the original procedures omethylnaphtalene c 11 h 10 with a cetane number of zero represented the bottom of the scale. Just as the octane number is meaningful for automobile fuels, the cetane number is a means of determining the ignition quality of diesel fuels and is equivalent to the percentage by volume of cetane in the blend with heptamethylnonane, which matches the ignition quality of. Difference between octane number and cetane number december 15, 2017 february 23, 2018 admin 0 comments automobile.
It plays a similar role for diesel as octane rating does for gasoline. The objective of this paper is to discuss the possible reasons for the wide range in reported values of the cetane number of biodiesel. In 1962, difficulties in handling alphamethylnapthalene and its expense led the astm to replace it with a secondary reference fuel. The astm d 6 standard test method of diesel fuel oil now defines the cetane. Heptamethylnonane definition of heptamethylnonane by the. Few experimental data exist, all at higher temperatures, outside of critical.
The cetane number is the analog of the automobile engine octane number, with cetane nhexadecane, c 16 h 34 having the arbitrarily assigned number of 100. Asmentionedpreviously,thecata lystsystemwillalsohaveanimpact on the degree of cetane uplift. Cetane number is a relative ranking of a fuels autoignition characteristics for use in compression. Chemical kinetic study of the oxidation of isocetane 2,2. Army utilizes both world wide available diesel fuel and jet fuel jp8 for ground mobility applications and must maintain such fuel flexibility in order to meet mission requirements. Cetane numbers of branched and straightchain fatty esters. The cetane number is typically measured either in a singlecylinder engine or a constantvolume combustion chamber.
388 996 182 1493 1256 927 354 1565 200 300 1607 788 1444 1245 1315 510 1456 94 946 724 588 1238 777 327 908 167 1098 820 658 1174 120 1086 1028 755 340 225 262