The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is called a compression-ignition engine. This contrasts with engines using spark plug-ignition of the air-fuel mixture, such as a petrol engine or a gas engine.
Diesel fuel, also called diesel oil or historically heavy oil, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a result of compression of the inlet air and then injection of fuel. Therefore, diesel fuel needs good compression ignition characteristics.
An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without undergoing pre-ignition. The higher the octane number, the more compression the fuel can withstand before detonating. Octane rating does not relate directly to the power output or the energy content of the fuel per unit mass or volume, but simply indicates gasoline's resistance to detonating under pressure without a spark.
A four-strokeengine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed:
- Intake: Also known as induction or suction. This stroke of the piston begins at top dead center (T.D.C.) and ends at bottom dead center (B.D.C.). In this stroke the intake valve must be in the open position while the piston pulls an air-fuel mixture into the cylinder by producing a partial vacuum in the cylinder through its downward motion.
- Compression: This stroke begins at B.D.C, or just at the end of the suction stroke, and ends at T.D.C. In this stroke the piston compresses the air-fuel mixture in preparation for ignition during the power stroke (below). Both the intake and exhaust valves are closed during this stage.
- Combustion: Also known as power or ignition. This is the start of the second revolution of the four stroke cycle. At this point the crankshaft has completed a full 360 degree revolution. While the piston is at T.D.C. the compressed air-fuel mixture is ignited by a spark plug or by heat generated by high compression, forcefully returning the piston to B.D.C. This stroke produces mechanical work from the engine to turn the crankshaft.
- Exhaust: Also known as outlet. During the exhaust stroke, the piston, once again, returns from B.D.C. to T.D.C. while the exhaust valve is open. This action expels the spent air-fuel mixture through the exhaust port.
The flash point of a material is the "lowest liquid temperature at which, under certain standardized conditions, a liquid gives off vapours in a quantity such as to be capable of forming an ignitable vapour/air mixture".
Fuel oil is any of various fractions obtained from the distillation of petroleum. Such oils include distillates and residues. Fuel oils include heavy fuel oil, marine fuel oil (MFO), furnace oil (FO), gas oil (gasoil), heating oils, diesel fuel, and others.
Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable instead of the fluid. Most liquid fuels in widespread use are derived from fossil fuels; however, there are several types, such as hydrogen fuel, ethanol, and biodiesel, which are also categorized as a liquid fuel. Many liquid fuels play a primary role in transportation and the economy.
Cetane number is an indicator of the combustion speed of diesel fuel and compression needed for ignition. It plays a similar role for diesel as octane rating does for gasoline. The CN is an important factor in determining the quality of diesel fuel, but not the only one; other measurements of diesel fuel's quality include energy content, density, lubricity, cold-flow properties and sulphur content.
Hexadecane (also called cetane) is an alkane hydrocarbon with the chemical formula C16H34. Hexadecane consists of a chain of 16 carbon atoms, with three hydrogen atoms bonded to the two end carbon atoms, and two hydrogens bonded to each of the 14 other carbon atoms.
In organic chemistry, a radical anion is a free radical species that carries a negative charge. Radical anions are encountered in organic chemistry as reduced derivatives of polycyclic aromatic compounds, e.g. sodium naphthenide. An example of a non-carbon radical anion is the superoxide anion, formed by transfer of one electron to an oxygen molecule. Radical anions are typically indicated by .
Homogeneous Charge Compression Ignition (HCCI) is a form of internal combustion in which well-mixed fuel and oxidizer are compressed to the point of auto-ignition. As in other forms of combustion, this exothermic reaction produces heat that can be transformed into work in a heat engine.
JP-8, or JP8, is a jet fuel, specified and used widely by the US military. It is specified by MIL-DTL-83133 and British Defence Standard 91-87, and similar to commercial aviation's Jet A-1, but with the addition of corrosion inhibitor and anti-icing additives.
The calculated carbon aromaticity index (CCAI) is an index of the ignition quality of residual fuel oil.
The Calculated Ignition Index (CII) is an index of the ignition quality of residual fuel oil. It is used to determine the suitability of heavy fuel oil for (marine) engines.
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. It has a cetane number of 15. Isocetane replaced 1-methylnaphthalene in 1962 as the lower reference for cetane number owing to the oxidation instability and difficulty of use of 1-methylnaphthalene in the reference engine.
Cetane index is used as a substitute for the cetane number of diesel fuel. The cetane index is calculated based on the fuel's density and distillation range. There are two methods used, ASTM D976 and D4737. The older D976, or "two-variable equation" is outdated and should no longer be used for cetane number estimation. It is, however, still required by the United States Environmental Protection Agency (EPA) as an alternative method for satisfying its aromaticity requirement for diesel fuel. D4737 is the newest method and is sometimes referred to as "the four-variable equation". D4737 is the same method as ISO 4264. Cetane index in some crude oil assays is often referred to as Cetane calcule, while the cetane number is referred to as Cetane measure.
A two-stroke diesel engine is a diesel engine that uses compression ignition in a two-stroke combustion cycle. It was invented by Hugo Güldner in 1899.
LS-9 Inc was a venture-funded company focused on producing diesel fuel from transgenic organisms. It launched in 2005, took in $81 million in investment, and in 2013 was sold to Renewable Energy Group for $40 million in cash and stock, and an additional $21.5 million if technology and production milestones were met.
A cetane improver [′sē‚tān im′prüv·ər] is a chemical which has the effect of increasing a diesel fuel's cetane number. A few examples are nitrates, nitroalkanes, nitrocarbonates and peroxides.
Partially premixed combustion (PPC), also known as PPCI or GDCI is a modern combustion process intended to be used in internal combustion engines of automobiles and other motorized vehicles in the future. Its high specific power, high fuel efficiency and low exhaust pollution have made it a promising technology. As a compression-ignition engine, the fuel mixture ignites due to the increase in temperature that occurs with compression rather than a spark from a spark plug. A PPC engine injects and premixes a charge during the compression stroke. This premixed charge is too lean to ignite during the compression stroke – the charge will ignite after the last fuel injection ends near TDC. The fuel efficiency and working principle of a PPC engine resemble those of Diesel engine, but the PPC engine can be run with a variety of fuels. Also, the partially premixed charge burns clean. Challenges with using gasoline in a PPC engine arise due to the low lubricity of gasoline and the low cetane value of gasoline. Use of fuel additives or gasoline-diesel or gasoline-biodiesel blends can mitigate the various problems with gasoline.
