Читать книгу Internal Combustion Engines - Allan T. Kirkpatrick - Страница 25

Since internal combustion engines require both a fuel and an oxidizer for the combustion process, another engine parameter is the air–fuel ratio, AF, expressed on a mass or a mass flow‐rate basis.

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The reciprocal of the air–fuel ratio is the fuel–air ratio, FA:

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A dimensionless measure of the fuel–air ratio is the equivalence ratio, , which is the ratio of the actual fuel–air ratio to the stoichiometric fuel–air ratio. The word is from the Greek, meaning ”element measure.” A stoichiometric reaction of a hydrocarbon (HC) is defined such that the fuel burns completely and the only products are carbon dioxide () and water (O).

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The equivalence ratio is used to characterize the fuel–air mixture composition. If the mixture is stoichiometric, if the mixture is lean, and if the mixture is rich.