Ignition quality

Diesel fuel makeup can represent various combinations of volatility, ignition quality, viscosity, sulfur level, specific gravity, and other characteristics. Various additives are used to impart special properties... 

Cetane Number is a numerical indication of a fuel s (kerosene, dic.sel, heating oil) ignition quality. Cetane number is measured in a single-cylinder engine, whereas cetane index is a calculated value. 

In the case of diesel fuel, an important property that defines the fuel quality is the cetane number (CN). Fuels with low-CN have poor ignition quality (i.e. knocking, noise, PM emissions) and make starting the engine difficult on cold days.6,7 It is well known that CN is lowest for PAHs and highest for w-paraffins.8,9 In normal paraffins, CN increases with the number of carbon atoms in the molecule. For naphthenic compounds and iso-paraffins the CN falls between those of aromatics and w-paraffins. In iso-paraffins, the CN decreases as the degree of branching increases.10... 

IgG (immunoglobulin G), 12 145 Ignition, 7 431-442 acetylene, 1 181-185 acetylene mixtures, 1 186 energy required for, 23 117 sources of, 23 116-118 Ignition improvers, diesel, 12 427 Ignition quality, diesel fuel and,... 

Ignition Quality Tester (IQT), 12 422-423 Ignition resistant (IR) fiber blends, 13 385 Ignition-resistant applications, VDC copolymers in, 25 737 Ignition-resistant materials, 11 449-450 Ignition suppression, by silver, 22 640 Ignition temperatures, 10 871 21 840 of ethers, 10 579... 

Cetane number a number indicating the ignition quality of diesel fuel a high cetane number represents a short ignition delay time the ignition quality of diesel fuel can also be estimated from the... 

Ignition Quality of Diesel Fuels by the Cetane Method... 

The cetane number of a diesel fuel is determined by comparing its ignition quality with those for blends of reference fuels of known... 

Aromatics Content. Aromatic compounds have very poor ignition quality and, although they are not specifically limited in ASTM D975, there are practical limitations to using high aromatic levels in highway diesel fuel. In the United States, where gasoline demand represents about one-half of the... 

Ignition-Quality Improvers. Diesel fuels have found greatly increased use in recent years—so much so that refiners have had to look to cracked distillates from catalytic cracking operations for their extra Diesel fuels. While these cracked distillates have the advantages of relatively high heat content and low pour point, they are inferior in ignition quality (cetane number) to straight-run distillates from the same crudes. 

Many compounds have been tested as ignition quality improvers—additives which shorten the ignition delay to a desirable duration. An extensive review in 1944 (6, 43) listed 303 references, 92 dealing with alkyl nitrates and nitrites 61 with aldehydes, ketones, esters, and ethers 49 with peroxides 42 with aromatic nitro compounds 29, with metal derivatives 28 with oxidation and oxidation products 22 with polysulfides 16 with aromatic hydrocarbons nine with nitration and four with oximes and nitroso compounds. In 1950, tests at the U. S. Naval Engineering Experiment Station (48) showed that a concentration of 1.5% of certain peroxides, alkyl nitrates, nitroaikanes, and nitrocarbamates increased cetane number 20 or more units. 

Early in 1952, a blend of primary amyl nitrates was introduced commercially as a Diesel ignition improver. This additive is being used by refiners to upgrade distillates which are low in ignition quality (thereby increasing supplies of Diesel fuels), to increase the flexibility of refining operations, and to permit the marketing of diesel fuels of more uniform quality. Steps in its development and its properties have been reported in the literature (1, 18, 38). 

Am. Soc. Testing Materials, Philadelphia, Pa., Ignition Quality of Diesel Fuels by the... 

Cetane Number—The cetane number (C.N.) of a fuel is the percentage by volume of normal cetane in a mixture of cetane and alpha-methylnaphthalene which matches the unknown fuel in ignition quality when compared with a standard diesel engine under specified conditions. The C.N. scale ranges from 0 to 100 C.N. for fuels equivalent in ignition quality to alpha-methylnaphthalene and cetane, respectively. For routine-testing, secondary reference fuels having cetane values of about 25 and 74 are blended in any desired proportion. 

Cetane Number—The ignition quality of a diesel fuel measured using an engine test specified in ASTM Method D 613. Cetane number is determined using two pure hydrocarbon reference fuels cetane, which has a cetane rating of 100 and heptamethylnonane (also called isocetane), which has a cetane rating of IS [2.2]. 

In a fuel additive use for 2-ethylhexanol, the alcohol is reacted with nitric acid and the nitrate produced added in low concentrations to diesel fuel to improve ignition quality. Use of such a "cetane improver" allows the refiner greater flexibility in blending distillate into fuel such as aromatics, branched paraffins, and naphthenes. The "cetane improver" also helps meet sudden local increases in demand for diesel fuels by allowing refiners to upgrade stored heating oil to diesel fuel quality quickly and economically. 

The cetane number (CN) is an indicator of the ignition quality of a diesel fuel. It is conceptually similar to the octane number (ON) used for gasoline. Generally, a compound that has a high ON tends to have a low CN and vice versa. The CN of a diesel fuel is related to the ignition delay (ID) time, i.e., the time that passes between injection of the fuel into the cylinder and onset of ignition. A shorter ID corresponds to a higher CN and vice versa. 

Transesterification of fats or oils with medium-chain alcohols may increase CN, a parameter that can influence ignition quality and exhaust emissions (Klopfenstein, 1985). On the other hand, increased branching in saturated hydrocarbon chains also decreases CN. Two studies comparing isopropyl... 

Knothe, G., Matheaus, A. C., and Ryan, T. W. III. 2003. Cetane Numbers of Branched and Straight-Chain Fatty Esters Determined in an Ignition Quality Tester. Fuel, 82, 971-975. 

Ryan, T. W. Ill, and Stapper, B. 1987. Diesel Fuel Ignition Quality as Determined in a Constant Volume Combustion Bomb. In SAE Techn. Pap. Ser. Warrendale PA Society of Automotive Engineers (Paper No. 870586). 

Historically, explosives were invented in ancient China for use as a kind of "medicine with ignition quality", called fire medicine in Chinese. But these devices are dangerous and can cause accidents. Therefore, safety evaluation should be carried out in parallel with their development. 

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