Diesel fuel ignition delay

The presence of low molecular weight, low flash point compounds in diesel fuel could lead to a shortening of the fuel ignition delay period. In a diesel engine, this could cause rough running due to early combustion of the low flash point compounds. 

The cetane number of a diesel fuel is the numerical result of an engine test designed to evaluate fuel ignition delay. To establish the cetane number... 

The nature of the fuel is also an important factor in reducing ignition delay. Physical characteristics such as viscosity, density, and medium boiling point are influencing parameters. Hydrocarbon composition is also important as it affects both the physical and combustion characteristics of the fuel. Ignition delay characteristics of diesel fuel are of primary importance since they directly influence the interval of uncontrolled combustion during the injection and, as such, the overall engine performance. 

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... 

Since diesel fuel combustion is an autoignition process, the quality and characteristics of the fuel can have a dramatic impact on the efficiency of engine operation. Ignition delay and cetane number go hand in hand to influence the quality of the fuel combustion process. They are the primary engine operability parameters directly related to fuel composition. 

TEMPERATURE. The ignition delay of most Diesel fuels decreases as the temperature increases (50, 67, 94, 139). In certain temperature ranges highly-branched and cyclic compounds are exceptions (50). If it is assumed that the chemical delay is long in relation to the physical delay at low temperatures, then it is possible to estimate an apparent over-all energy of activation of the preflame reactions, as indicated in Figure 3 (71). Results similar to those shown in Figure 3 can be represented by an empirical relationship (43, 44) of the form ... 

Diesel knock the result of a delayed period of ignition and accumulated diesel fuel in the engine. 

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. 

Anon. 2007b. D 6890 Standard Test Method for Determination of Ignition Delay and Derived Cetane Number (DCN) of Diesel Fuels Oils by Combustion in a Constant Volume Chamber. In Annual Book of ASTM Standards (05.05). West Conshohocken PA ASTM International. 

Hot-gas filtration can reduce the ash content of the oil to less than 0.01% and the alkali content to less than 10 ppm - much lower than reported for biomass oils produced in systems using only cyclones. Diesel engine tests performed on crude and on hot-filtered oil showed a substantial increase in burning rate and a lower ignition delay for the latter, due to the lower average molecular weight for the filtered oil (36). Hot gas filtration has not yet been demonstrated over a long-term process operation. Pyrolysis oils are not miscible with hydrocarbon fuels but with the aid of surfactants they can be emulsified with diesel oil. 

The cetane number is an important property of diesel fuel. In the majority of diesel engines, the ignition delay period is shorter than the duration of injection. Under such circumstances, the total combustion period can be considered to be divided into the following four stages (1) ignition delay, (2) rapid pressure rise, (3) constant pressure or controlled pressure rise, and (4) burning on the expansion stroke. 

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