🔍 Key Concepts

• Cetane number as a measure of how easily diesel fuel starts to burn under compression • Difference between ignition quality and energy content (heating value) of a fuel • Why viscosity and acid content are important but separate fuel properties

💭 Think About

• When an engine designer looks at cetane number, what specific aspect of engine performance are they trying to control? • Does a higher cetane number mean the fuel has more energy per gallon, or that it starts burning more readily when injected? • Which property (from the choices) is most directly related to how quickly and smoothly a diesel fuel begins combustion after injection into a hot, compressed air charge?

✅ Before You Answer

• Be clear on the difference between how much heat a fuel can release vs. how quickly it starts burning. • Recall that viscosity deals with thickness/flow and is measured separately from cetane number. • Remember that acid content relates to corrosion issues, not how the fuel ignites in the cylinder.