The Physics
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Ignition Temperature of Diesel Fuel

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Bibliographic Entry Result
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Maynard, Philip. 65742 Fire and Explosion Investigation [pdf]. UTS: Centre for Forensic Science. "2. What is the autoignition temperature of
a) Petrol 246°C
b) Diesel 210°C"
483 K
Material Safety Data Sheet [pdf]. Syntroleum, 19 Oct 2004. "Flammable properties:
Flash point (PMCC): 100-125 F(37.8-51.5 C)
OSHA Flammability Class: Combustible Class II Liquid LEL (vol%): ~0.6 UEL (vol%): ~4.7
Autoignition temperature: ~257°C (~494°F)"
530 K
Fire and Arson Accelerants. Excerpts from The Pocket Guide to Accelerant Evidence Collection Appendix II: Twenty Common Ignitable Liquids used as Fire Accelerants. 1999. "7. Fuel oil no.2 (home heating fuel, diesel fuel), Chemical formula is a carbon range of C9-C23; flash point 126°F–204°F (52–96°C); ignition temperature 494 F (257°C)" 530 K
Diesel fuel and exhaust emissions. World Health Organization, 1996. [see table below]
No. 1:  450 K–602 K
No. 2:  527 K–558 K
No. 3:  536 K
Table 5. Physiochemical properties of diesel fuel
Property Diesel Fuel (general) Diesel Fuel No. 1 Diesel Fuel No. 2 Diesel Fuel No. 4
Autoignition Temperature (°C)   177–329 254–285 263

Diesel fuel is derived from crude oil. It is a mixture of hydrogen and carbon molecules. It is developed for engines that provide energy for power, flow readily in cold temperature, provide low emission, provide good fuel economy, and allow easy start-up. Power generators are run by diesel fuel. The fuel also runs diesel-powered vehicles, such as ships, buses, or trucks. Diesel engines of these types of vehicles are internal combustion engines.

Diesel is used in a high-compression engine. Air is compressed until it is heated above the autoignition temperature of diesel. Then the fuel is injected as a high pressure spray. There is no ignition source. As a result, diesel is required to have a high flash point and a low autoignition temperature. The flashpoint of a fuel is the lowest temperature at which it can form an ignitable mix with air. The high flash point in diesel fuel means that it does not burn as easily as gasoline, which is a safety factor. Too low of a flash point is a fire hazard because ignition may continue and lead to explosion.

Autoignition temperature is the temperature at which a substance can be brought to flames without any sort of external force, such as a flame or spark. There are three different types of diesel fuel. These are Diesel No. 1, Diesel No. 2, and Diesel No. 4. The ignition temperature of Diesel fuel No.1 ranges from 450 to 602 Kelvin, Diesel fuel No. 2 ranges from 527 to 558 Kelvin, and Diesel fuel No .4 is 536 Kelvin.

Eileen Tang -- 2005