Diesel Exhaust Fluid is an aqueous
ureaUrea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....
solution used in
Selective Catalytic ReductionSelective catalytic reduction is a means of converting nitrogen oxides, also referred to as with the aid of a catalyst into diatomic nitrogen , , and water, . A gaseous reductant, typically anhydrous ammonia, aqueous ammonia or urea, is added to a stream of flue or exhaust gas and is absorbed...
(SCR) to lower
NOxNOx is a generic term for the mono-nitrogen oxides NO and NO2 . They are produced from the reaction of nitrogen and oxygen gases in the air during combustion, especially at high temperatures...
concentration in the exhaust emissions from
diesel engineA diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
s. The solution may also be referred to as
AUS32, shorthand for
Aqueous
Urea
Solution,
32.5%, or as
AdBlue, a trademark held by the German Association of the Automobile Industry (
VDAThe Verband der Automobilindustrie e. V., short VDA, is a German interest group of the German automobile industry, both automobile manufactures and automobile component suppliers. The group is located in Berlin, Germany...
), who ensure quality standards are maintained in accord with ISO 22241 specifications. Initially the specification was described in
DINDIN or Din or din can have several meanings:* A din is a loud noise.* Dīn, an Arabic term meaning "religion" or "way of life".* Din is one of the ten aspects of the Ein Sof in Kabbalah ....
70070. In 2006 the worldwide ISO 22241 standard was introduced, which also stipulates analytical test protocols to verify adherence to specifications, as well as requirements for storage, transport and handling of the fluid.
SCR systems are sensitive to potential chemical impurities in the urea solution, therefore the
solventA solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
is demineralized water. The solution is clear, non-toxic and safe to handle. However, it can
corrodeCorrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
some metals and so must be stored and transported in vessels made of materials not so affected. DEF is stored in a tank onboard the vehicle, and injected into the exhaust stream by a metering system at a rate of 3–5% of diesel consumption volume. This low dosing rate ensures long fluid refill intervals and minimises the tank's obtrusion into vehicle packaging space. An
Electronic control unitIn automotive electronics, electronic control unit is a generic term for any embedded system that controls one or more of the electrical systems or subsystems in a motor vehicle....
adjusts the addition of fluid in accord with such parameters as engine
operating temperatureAn operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...
and speed.
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