Lubricity
Encyclopedia
Lubricity is the measure of the reduction in friction
of a lubricant
. The study of lubrication and mechanism wear is called tribology
.
is caused to a surface by a given friction-inducing object in a given amount of time. Other factors such as surface size, temperature, and pressure are also specified. The greater the wear scar the worse the lubricity. For this reason lubricity is also termed a substance's anti-wear property.
Examples of test setups include "Ball-on-cylinder" and "Ball-on-three-discs" tests.
, the fuel is part of the engine lubrication process. Diesel fuel naturally contains sulfur
compounds that provide good lubricity, but because of regulations in many countries (such as the US and the EU
) sulphur must be removed. Reformulated diesel fuel that does not have biodiesel added has a lower lubricity and requires lubricity improving additives to prevent excessive engine wear.
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
of a lubricant
Lubricant
A lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...
. The study of lubrication and mechanism wear is called tribology
Tribology
Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear...
.
Measurement of lubricity
Lubricity of a material cannot be directly measured, so tests are performed to quantify a lubricant's performance. This is done by determining how much wearWear
In materials science, wear is erosion or sideways displacement of material from its "derivative" and original position on a solid surface performed by the action of another surface....
is caused to a surface by a given friction-inducing object in a given amount of time. Other factors such as surface size, temperature, and pressure are also specified. The greater the wear scar the worse the lubricity. For this reason lubricity is also termed a substance's anti-wear property.
Examples of test setups include "Ball-on-cylinder" and "Ball-on-three-discs" tests.
Lubricity in diesel engines
In a modern diesel engineDiesel engine
A 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...
, the fuel is part of the engine lubrication process. Diesel fuel naturally contains sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
compounds that provide good lubricity, but because of regulations in many countries (such as the US and the EU
European emission standards
European emission standards define the acceptable limits for exhaust emissions of new vehicles sold in EU member states. The emission standards are defined in a series of European Union directives staging the progressive introduction of increasingly stringent standards.Currently, emissions of...
) sulphur must be removed. Reformulated diesel fuel that does not have biodiesel added has a lower lubricity and requires lubricity improving additives to prevent excessive engine wear.