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Glossary: Diesel Terms

After treatment devices - Devices such as filters which remove constituents of diesel exhaust as they leave the equipment.

Aftercooling - Cooling intake air prior to induction into the combustion chamber to increase power and reduce the emission of oxides of nitrogen.

Approval plate quantity - The quantity of ventilating air given in cubic feet per minute (cfm) that will dilute the concentrations of gaseous exhaust contaminants from a single diesel engine to specified limits for CO2, CO, NO and NO2.  This is sometimes called the nameplate quantity.

Aromatic content - Hydrocarbons in diesel fuel are numerous but generally fall into three families: paraffins, naphthenes and aromatics.  Reducing fuel aromatic content will reduce hydrocarbons in the exhaust and the organic portion of DPM.

Autoregeneration - Self-cleaning of a filter by an engine which has high enough exhaust temperatures to oxidize the diesel particulate matter captured on the filter.  See "regeneration" below.

Exhaust Back pressure - The buildup of pressure against the engine created by the resistance of the exhaust flow passing through the exhaust system components.

Cetane number - The cetane number describes the ignitability of diesel fuel.  Fuels with high cetane numbers have low self-ignition temperatures.  Fuels with low cetane numbers cause engine roughness.

Cloud point - The cloud point is the highest temperature at which the first trace of paraffin visibly separates from the fuel.

Diesel particulate matter - Generally refers to the small particles of matter produced by diesel exhaust, which can be collected on filters.  The term is abbreviated as DPM.  The term "diesel particulate", or "DP", means the same thing.

Elemental carbon - Elemental carbon is sometimes used as a surrogate measure for DPM.  It is composed of graphitic carbon, as opposed to organic carbon, and usually accounts for 40 to 60 percent of the DPM by mass.

Fuel-to-air ratio - The ratio of the amount of fuel to the amount of air introduced into the diesel combustion chamber.

Gm/hp-hr - Gram per horsepower-hour:  The hourly mass of a contaminant in diesel engine exhaust emissions divided by the engine horsepower.

Impactor - Device used to separate particles by size using their inertial characteristics.

Nameplate quantity - Another term for approval plate quantity.

Permissible - As applied to diesel powered mining machinery, refers to a piece of equipment on which safety components and temperature controls have been added to prevent the ignition of methane or coal dust so that it can be safely used in areas of an underground mine where methane is likely to accumulate (i.e., face areas).

Regeneration - The process of oxidizing DPM collected on a diesel exhaust particulate filter.  This process cleans the filter and reduces backpressure to acceptable limits.

Respirable combustible dust (RCD) - A method of measuring DPM using a combustion process.

Threshold limit value (TLV) - The time-weighted average concentration (established by the American Conference for Governmental Industrial Hygienists) for a conventional 8-hour workday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.

Turbocharge - The process of increasing the mass of intake air by pressurization to the engine which allows more fuel to be burned and results in increasing the engine's power output.

Volatility - Volatility is a measure of the distillation rate of a fuel.

Wax separation - The separation of the paraffinic portion of diesel fuel at low temperature which can cause fuel flow problems.