VI is calculated by the equation:

•          VI = (L – U)·100 /(L – H)

• L – worst oil (mostly asphaltenic oils) VI = 0

• U – viscosity of under tested oil

• H – best oil (paraffinic oils) VI = 100

Molecular mass

Molecular mass of HC is varied from 72 (pentane) to few thousand for resins and asphaltenes

Average molecular mass for most oils is varied from 250 to 300.

The more molecular mass – the high boiling point

Formula of Voinov B.P.

          М = a + bt + ct2

Where t – average boiling point of fraction

А,в,с - coefficients

Creg Formula

• М = 44,29 d¹⁵₁₅  / (1,03 - d¹⁵₁₅)

Temperature properties

• Flash point

• Fire point

• Autoignition point (autogeneous ignition)

• Pour point

• Freezing point

• Lower limit of explosibility

• Minimum concentration of combustible gas mixture with air which will be flared up if the fire is made

• Higher limit of explosibility

• Maximum concentration of combustible gas mixture above that do not flash because of shortage of air oxygen

Flash Point

The flash point of a flammable liquid is the lowest temperature at which it can form an ignitable mixture in air. (can vaporize and able to ignite).

At this temperature the vapor may cease to burn when the source of ignition is removed (it will continue to burn after ignition less then 5 seconds)

Flash point depends from fractional composition.

• The lower boiling range the lower flash point

• Flash Point:

• −30°С −4 5°С and lower for

• gasoline

• +28°С +60°С for

• kerosene;

• +13°С +325°С  for

• lubricating oils.

Fire Point

• The fire point is defined as the temperature at which the vapor continues to burn after being ignited.

• The fire point of a fuel is the temperature at which it will continue to burn after ignition for at least 5 seconds

• At the flash point, a lower temperature, a substance will ignite,

• but vapor might not be produced at a rate to sustain the fire.

• Fire point and autogenous ignition are additional considerations when selecting fire resistant greases.

• Industrially, fire point is the lowest temperature at which industrial greases produce sufficient vapors to form a mixture in air that continuously supports combustion after ignition.

•

• The fire point usually slightly higher then flash point

• This difference may be about 500C

AutoIgnition Point

• The autoignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark.

• It is usually applied to a combustible fuel mixture.

• The heaver residue spontaneous ignite under 210 °С, gasoline fraction – above 280 °С.

• n-alkanes have the lowest autoignition point

Pour Point

• The lowest temperature at which an oil is observed to flow under the conditions of the test.

• It is a rough indication of the lowest temperature at which oil is readily pumpable.

• Also, the pour point can be defined as the minimum temperature of a liquid, particularly a lubricant, after which, on decreasing the temperature, the liquid ceases to flow.

• Pour point data indicates the amount of long-chain paraffins (petroleum wax) found in a crude oil.

• Handling and transporting crude oils and heavy fuels is difficult at temperatures below their pour points.

• Pour point depressants are used to improve the flow properties of the fuel.

• Long-chain n-paraffins ranging from 16–60 carbon atoms in particular, are responsible for near-ambient temperature precipitation.

• In middle distillates, less than 1% wax can be sufficient to cause solidification of the fuel

• The bigger amount of solid paraffins the higher pour point

• The bigger amount of resins the lower pour point

• Pour Point

• for auto and diesel fuel -10 до -40⁰С

• For lubricating oils and aircraft engines

•     -55⁰С

Freezing Point

• The maximum temperature at which wax will begin crystallize and become visible

• Maximum temperature at which crystals of hydrocarbons are found out by visually

• Mostly – aromatic HC that crystallize at 5,5⁰С.

Octane Number

• The octane rating is a measure of the autoignition resistance of gasoline (or petrol) and other fuels used in spark-ignition internal combustion engines.

• It is a measure of anti-detonation of a gasoline or fuel.

• Incorrect work of motor engines.

• If only part of combustible mixture are burnt after spark ignition

• but small part (20%) of this mixture are autoignited very rapidly and such noises and knocking are formed inside the cylinder

•  tool deterioration -износ двигателя

• The octane number is determined by comparing, under standard conditions, the knock intensity of the fuel with that of blends of two reference fuels: isooctane, which resists knocking, and heptane which knocks readily.

• Octane rating is measured relative to a mixture of isooctane (2,2,4-trimethylpentane, an isomer of octane) and n-heptane

.

• An 87-octane gasoline, for example, has the same octane rating as a mixture of 87 vol-% isooctane and 13 vol-% n-heptane.

• This does not mean, however, that the gasoline actually should contain these chemicals in these proportions.

• It simply means that it has the same autoignition resistance as the described mixture.