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octane rating
Definição1
The system used to rate the ability of a reciprocating-engine fuel to resist detonation. The higher the octane number, the more resistant the fuel is to detonation.The fuel being rated is run in a test engine whose compression ratio can be varied. This ratio is changed until the fuel detonates, or explodes inside the cylinder, rather than burning as it should. The engine is left with the compression ratio that caused the fuel to detonate, and a fuel composed of a mixture of iso-octane, a fuel that resists detonation, and heptane, a fuel prone to detonate, is fed to the engine. The ratio of the two fuels is varied until the engine detonates as it did with the fuel being rated. When the performance with the two fuels is matched, the ratio fo the octane to heptane is noted, and the fuel is rated with the percentage of octane used. If a mixture of 80% octane and 20% heptane causes the engine to perform as it did with the fuel being rated, the fuel is given an octane number of 80. At one time aviation gasoline was given a dual rating such as 80/87. The first number represented its antidetonation rating with a lean, cruise fuel-air mixture, and the highter number, its rating with a rich, takeoff mixture. Fuel with antidetonation characteristics better than that of iso-octane is rated in performance numbers.
Fonte1
CRANE, Dale (ed.). Dictionary of aeronautical terms. 2nd ed. Renton: ASA, 1991.
Fonte2
ARAÚJO, João Richard Barcelos. Inglês técnico: técnicos em manutenção de aeronaves. [S.l]: [s.n.], [200-]. 100 p.
Français
taux d'octane