Internal Combustion Engines
By higher octane number of spark ignition fuel, it is meant that the fuel has

Higher heating value
Higher flash point
Longer ignition delay
Lower volatility

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Internal Combustion Engines
In a typical medium speed, 4-stroke cycle diesel engine

Fuel injection starts at just before top dead center and ends just after top dead center
Fuel injection starts at 10° before top dead center and ends at 20° after top dead center
May start and end anywhere
Fuel injection starts at top dead center and ends at 20° after top dead center

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