Liquid Fuels Database Glossary

Click on the appropriate letter.

· A ·

API Gravity

An arbitrary scale representing the gravity or density of liquid petroleum products in terms of API degrees according to the following relationship: API Gravity (degrees) = 141.5/specific gravity - 131.5. Materials with higher API gravity are lighter materials.

Accelerated Stability (oxidation)

Oxidation of fuel during storage can cause deposit-forming and insoluble substances to form. An accelerated storage stability test is used to determine the susceptibility of distillate fuel oil to such oxidation.

Acid Number

The acid number is the quantity of base, expressed in milligrams of potassium hydroxide per gram of sample (mg KOH/g), that is required to neutralize the acid in the fuel to a specified end point.

Aromatics

Aromatics refers to a class of hydrocarbons based on a six-membered ring (also called an aromatic ring) having three double bonds. The simplest member is benzene, C₆H₆. Monoaromatics are hydrocarbon compounds containing exactly one aromatic ring. Polyaromatics (also called polynuclear aromatics or polycyclic aromatic hydrocarbons) are hydrocarbon compounds containing two or more aromatic rings. These rings may be fused together as in naphthalene or anthracene, or separate as in biphenyl. High levels of polycyclic aromatic hydrocarbons are related to the formation of smoke and particulate matter.

Ash

Ash is the non-volatile residue after combustion of a fuel has taken place. Ash is generally composed of non-volatile oxides. Too much ash leaves an abrasive residue that causes engine wear. Ash can also be the cause of injector clogging.

Autoignition Temperature

The autoignition temperature is the lowest temperature at which the spontaneous ignition (without an ignition source) of a mixture of air and fuel will occur.

· B ·

Boiling Point

The boiling point is the temperature at which the fuel boils under normal atmospheric pressure.

· C ·

Carbon

The amount of carbon in the fuel as measured by one of several techniques. The greater the carbon content of the fuel, the greater the amount of carbon dioxide formed when the fuel is burned.

Carbon Residue

Carbon residue is a measure of the carbonaceous residue formed during evaporation and pyrolysis of petroleum products. It provides a measure of the tendency of the heavy ends of the fuel to form coke. Coke can cause injector clogging and is related to smoke production.

Cetane Index

An approximation of cetane number based on an empirical relationship with density and volatility parameters such as mid-boiling point. This calculation is a useful tool for estimating the cetane number where a test engine is not available for this determination.

Cetane Index

An approximation of cetane number based on an empirical relationship with density and volatility parameters such as mid-boiling point. This calculation is a useful tool for estimating cetane number where a test engine is not available for this determination.

Cetane Number

The cetane number is a measure of the ignition quality of diesel fuel based on ignition delay in an engine. Fuels with a higher cetane number have shorter ignition delay, better ignition quality, and less tendency to knock when burned in a compression-ignition engine.

Chemical Formula

The chemical formula shows the ratios of the numbers of atoms in the fuel.

Cloud Point

The cloud point is the temperature at which a petroleum product just shows a cloud or haze of wax crystals when it is cooled under standard test conditions, as described in ASTM Standard D 2500. The cloud point measures the ability of the fuel to be used in cold weather without plugging filters.

Cold Filter Plugging Point

A test of the low temperature performance of a diesel fuel. Performed according to the IP-309 standard.

Copper Corrosion

The copper strip corrosion test is designed to assess the relative degree of corrosivity of petroleum products. The copper strip corrosion test is necessary because some of the sulfur compounds left in these fuels after refining can cause corrosion.

· D ·

Density

Density is defined as the mass of the fuel per unit volume. Fuel density is important because many other fuel properties can be related to it. In particular, fuels with lower hydrogen contents tend to be denser and form more soot and particulate matter during combustion.

Density

Density is defined as the mass of the fuel per unit volume. Fuel density is important because many other fuel porperties can be related to it. In particular, fuels with lower hydrogen content tend to be denser and form more soot and particulate matter during combustion.

Density

Density is defined as the mass of the fuel per unit volume. Fuel density is important because many other fuel properties can be related to it. In particular, fuels with lower hydrogen contents tend to be denser and form more soot and particulate matter during combustion.

Density

Density is defined as the mass of the fuel per unit volume. Fuel density is important because many other fuel properties can be related to it. In particular, fuels with lower hydrogen contents tend to be denser and form more soot and particulate matter during combustion.

Distillation (10% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (15% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (20% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (30% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which 90, 95 or 100 percent of the fuel distills.

Distillation (40% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (5% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (50% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (60% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (70% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (80% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (85% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (90% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (95% recovery)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (final boiling point)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

Distillation (initial boiling point)

The general process of vaporizing liquids in a cloud vessel, condensing vapors and collecting the condensed liquids. Since liquids vaporize generally in order of their boiling points, it provides a method of separating materials according to their volatility. Most fuel specifications set a limit on the temperature at which either 90, 95, or 100 percent of the fuel distills.

· F ·

Flammability Limit (lower)

Flammability limits are the range of mixtures over which fuel and air will burn. Below the lower flammability limit there is not enough fuel to support a flame, and the mixture is said to be too lean to burn. Above the upper flammability limit there is not enough air to support a flame, and the mixture is said to be too rich to burn. The flammability limits are usually stated as a percent of fuel by volume in air.

Flammability Limit (upper)

Flammability limits are the range of mixtures over which fuel and air will burn. Below the lower flammability limit there is not enough fuel to support a flame, and the mixture is said to be too lean to burn. Above the upper flammability limit there is not enough air to support a flame, and the mixture is said to be too rich to burn. The flammability limits are usually stated as a percent of fuel by volume in air.

Flash Point

The flash point of a flammable liquid is the lowest temperature at which the vapor pressure of the liquid is sufficient to produce a flammable mixture above the surface of the liquid. The flash point limitation is intended to address fire safety, especially fuel tank safety. The flash point of the fuel must be such that ignition could not occur in the vapor space in partially filled fuel tanks.

Fuel Injector Cleanliness

This test determines the effect of diesel fuel and/or diesel fuel additives on the generation, prevention, and clean up of deposits inside open-nozzle unit injectors. Superior neat fuels and fuels with additives will demonstrate 6% or less average flow loss and 10% or less average deposit rating.

· G ·

Gum Content (unwashed)

Gum is the evaporation residue of a fuel. Fuel with high gum can cause induction-system deposits and sticking of intake valves.

Gum Content (washed)

Gum is the evaporation residue of a fuel. Fuel with high gum can cause induction-system deposits and sticking of intake valves.

· H ·

Heat of Combustion, gross (HHV)

The heat of combustion of a fuel is the amount of heat that can be obtained when the fuel is burned completely. The higher heating value (HHV) or, gross heat of combustion, is the amount of heat that can be obtained when all the water in the products of combustion is condensed. Because such condensation is not considered possible when the engine exhaust is vented to the atmosphere, the lower heat of combustion (LHV) or, net heat of combustion, which does not count the heat of condensation of the water in the combustion products, is customarily reported in transportation applications. The lower and higher heating values of fuels may be stated on either an energy-per-unit mass or an energy-per-unit volume basis. In general, liquid hydrocarbon fuels with a higher fuel density have a higher heating value on a volume basis.

Heat of Combustion, net (LHV)

The heat of combustion of a fuel is the amount of heat that can be obtained when the fuel is burned completely. The higher heating value (HHV) or, gross heat of combustion, is the amount of heat that can be obtained when all the water in the products of combustion is condensed. Because such condensation is not considered possible when the engine exhaust is vented to the atmosphere, the lower heat of combustion (LHV)or, net heat of combustion, which does not count the heat of condensation of the water in the combustion products, is customarily reported in transportation applications. The lower and higher heating values of fuels may be stated on either an energy-per-unit mass or an energy-per-unit volume basis. In general, liquid hydrocarbon fuels with a higher fuel density have a higher heating value on a volume basis.

Hydrogen

The amount of hydrogen measured in the fuel.

· K ·

Kinematic Viscosity

Viscosity is the ease with which a fluid flows. The ratio of viscosity to density is often useful in doing fluid flow calculations and is known as "kinematic viscosity." The SI units for kinematic viscosity are m²/s and mm²/s. If the diesel fuel viscosity is too high, it is atomized poorly by the fuel injectors and combustion is poor. On the other hand, if the viscosity is too low, the fuel is likely to be too thin to pump well into the injectors. Insufficient viscosity can even cause the fuel injection pump to seize.

· L ·

Low Temperature Flow Test

This is a test performed to evaluate the low temperature flow of a test fuel. The results are indicative of the flow performance of the test fuel in some diesel vehicles.

Lubricity (HFRR)

The lubricity of a fuel is the ability of the fuel to allow moving contact without wear. Lubricity is necessary to prevent excessive fuel system wear.

Lubricity (HPHFRR)

The lubricity of a fuel is the ability of the fuel to allow moving contact without wear. Lubricity is necessary to prevent excessive fuel system wear.

Lubricity (SLBOCLE)

The lubricity of a fuel is the ability of the fuel to allow moving contact without wear. Lubricity is necessary to prevent excessive fuel system wear. SLBOCLE is the test method conducted by the Scuffing Load Ball-on-CylinderLubricity Evaluator. HFRR is the lubricity test conducted using a High Frequency Reciprocating Rig.

· M ·

Material Safety Data Sheet

Monoaromatics

Aromatics refers to a class of hydrocarbons based on a six-membered ring (also called an aromatic ring) having three double bonds. The simplest member is benzene, C₆H₆. Monoaromatics are hydrocarbon compounds containing exactly one aromatic ring.

· N ·

Nitrogen

The amount of nitrogen measured in the fuel. The nitrogen content of a fuel is important because nitrogen that is chemically combined with the fuel is burned with the fuel to form nitrogen oxides. Such fuel-derived NO_x is in addition to NO_x formed by the thermal reaction of the oxygen and nitrogen in the combustion air at the high temperatures present in flames.

Nitrogen

The amount of nitrogen measured in the fuel. The nitrogen content of a fuel is important because nitrogen that is chemically combined with the fuel is burned with the fuel to form nitrogen oxides. Such fuel-derived NO_X is in addition to NO_X formed by the thermal reaction of the oxygen and nitrogen in the combustion air at the high temperatures present in flames.

· O ·

Odor Threshold

The odor threshold is the lowest concentration (usually stated in ppm) at which the human nose can detect that an odor is present (compared to purified, odor-free air), but not necessarily identify the odor. The odor thresehold can vary with the type of test used and the experience of the test subjects. Often the practical odor threshold in an industrial setting is considerably higher than that recorded during laboratory testing. Sometimes an "odor recognition threshold" is distinguished whereby not only is the presence of an odor recognized, but the identity of the substance causing the odor can also be recognized.

Olefins

Olefins, or alkenes, are straight or branch chain compounds with one or more double bonds. The double bond is a very reactive group, so olefins can react readily with many compounds, and are easily oxidized. In ASTM analyses, olefins include alkenes, cycloalkenes, plus some dienes.

Oxygen

The amount of oxygen measured in the fuel.

· P ·

Polyaromatics

Aromatics refers to a class of hydrocarbons based on a six-membered ring (also called an aromatic ring) having three double bonds. The simplest member is benzene. Polyaromatics (also called polynuclear aromatics or polycyclic aromatic hydrocarbons) are hydrocarbon compounds containing two or more aromatic rings. These rings may be fused together as in napthalene or anthracene, or separate as in biphenyl. High levels of polycyclic aromatic hydrocarbons are related to the formation of smoke and particulate matter.

Pool Burn Rate

The pool burn rate is the rate at which a pool of liquid fuel burns, given as the mass of fuel burned per unit area. The pool burn rate is a measure of the intensity of the fire which may result from a given size fuel spill.

Pour Point

The pour point is the lowest temperature at which a fuel will just flow when tested under the standard conditions described in ASTM Standard D 97.

· R ·

Ramsbottom Carbon Residue

Carbon residue, also called Ramsbottom carbon residue, is a measure of the carbonaceous residue formed during evaporation and pyrolysis of petroleum products. It provides a measure of the tendency of the heavy ends of the fuel to form coke. Coke can cause injector clogging and is related to smoke production.

Reid Vapor Pressure

The Reid vapor pressure is the pressure exerted by the vapor over the liquid at a specified ambient temperature. The Reid vapor pressure is a measure of the tendency of the fuel to evaporate.

· S ·

Saturates

Saturates are hydrocarbons with only single bonds. Saturates are more stable and react less readily than unsaturated hydrocarbons (those with double and triple bonds). Saturates include alkanes and cycloalkanes (paraffins and cycloparaffins).

Sediment

Water and sediment content of fuel oil is significant because it can cause corrosion of parts and problems in use.

Storage Pressure

The storage pressure is the pressure under which the fuel is usually stored on board vehicles.

Sulfated Ash

Sulfated ash is the residue remaining after the sample has been carbonized, and subsequently treated with sulfuric acid and heated to a constant weight. It can be used to indicate the concentration of known metal-containing additives in new oils.

Sulfur

The amount of sulfur measured in the fuel. Sulfur in the fuel is burned to form sulfur oxides, principally SO₂. This SO₂ in turn forms solid sulfate compounds that contribute to the amount of particulate matter in the exhaust. Sulfur in the fuel can also contribute to the formation of acidic compounds in the engine oil which are corrosive and cause the deterioration of engine components. Lower sulfur is associated with lower mass emissions of particulate matter. Many sulfur compounds adhere to metal parts and help protect them from wear.

Sulfur

The amount of sulfur measured in the fuel. Sulfur in the fuel is burned to form sulfur oxides, principally SO₂. This SO₂ in turn forms solid sulfate compounds that contribute to the amount of particulate matter in the exhaust. Sulfur in the fuel can also contribute to the formation of acidic compounds in the engine oil which are corrosive and cause the deterioration of engine components. Lower sulfur is associated with lower mass emissions of particulate matter. Many sulfur compounds adhere to metal parts and help protect them from wear.

· T ·

Test Date

Date (approximately) on which this fuel was tested.

Thermal Stability (aging time)

Thermal stability is the resistance of fuel to formation of degradation products, which might cause operating problems when thermally stressed.

Thermal Stability (visual filter pad rating)

Thermal stability is the resistance of fuel to formation of degradation products, which might cause operating problems when thermally stressed.

Threshold Limit Value (TLV)

Threshold limit values are established by the American Council of Governmental Industrial Hygienists. TLVs are the airborne concentration of a substance to which it is believed that nearly all workers may be exposed day after day without adverse effects.

Total Aromatics

Aromatics refers to a class of hydrocarbons based on a six-membered ring (also called an aromatic ring) having three double bonds. The simplest member is benzene, C₆H₆. Monoaromatics are hydrocarbon compounds containing exactly one aromatic ring. Polyaromatics (also called polynuclear aromatics or polycyclic aromatic hydrocarbons) are hydrocarbon compounds containing two or more aromatic rings. These rings may be fused together as in naphthalene or anthracene, or separate as in biphenyl. High levels of polycyclic aromatic hydrocarbons are related to the formation of smoke and particulate matter.

· V ·

Vapor Pressure

The vapor pressure is the pressure exerted by the vapor over the liquid at a specified ambient temperature. The vapor pressure is a measure of the tendency of the fuel to evaporate.

· W ·

Water

Water and sediment content of fuel oil is significant because it can cause corrosion of parts and problems in use.

Water Solubility

Water solubility refers to the degree to which the fuel will dissolve in water. A substance that will mix with water in any proportion is said to be totally miscible with water.

Water and Sediment

Water and sediment content of fuel oil is significant because it can cause corrosion of parts and problems in use.

Fuels Property Database Search Page