[L1] 1 Octane Number [L2] 1) Definition of Octane Number [L4] - A fuel performance value for quantitatively judging the knock resistance (anti-knock quality) of a gasoline engine. [L4] - Determined by standardizing fuel, operating with a sample fuel, and considering the anti-knock quality to be the same if the same degree of knock occurs. This quantitative expression of the sample fuel is the octane number. [L4] - Octane number is a criterion for judging the degree of knocking occurrence, not a scale for evaluating the good/bad of the fuel itself. [L4] - Knock resistance (anti-knock quality) appears differently depending on engine operating conditions. [L5] * Fuel anti-knock quality varies depending on air-fuel ratio, supply air temperature, etc. [L2] 2) Meaning of Octane Number [L4] - Octane number represents the volume percentage of iso-octane in a mixture of iso-octane and normal heptane. [L5] * Meaning of Octane Number 85: Meaning it is a fuel with the same anti-knock quality as a mixture of 85% iso-octane and 15% normal heptane. [L4] - Iso-octane (C8H18) is harder to cause knock than ordinary gasoline, and normal heptane (C7H16) is easy to cause knock, so mixing them appropriately creates a standard fuel with intermediate anti-knock quality. [L5] * Both iso-octane and normal heptane are paraffinic hydrocarbons. [L4] - Regular gasoline and premium gasoline originate from the difference in octane number. [L5] * Based on Octane Number standard RON, 91~under 94 is treated as regular gasoline, and over 94 as premium gasoline. [L2] 3) Test Method of Octane Number [L4] - A CFR engine capable of changing the compression ratio is used to test anti-knock quality. [L1] 2 Cetane Number [L2] 1) Definition of Cetane Number [L4] - One of the performance evaluation items for diesel oil, a value numerically representing the ignitability of the fuel. [L4] - Represents the degree of ignition delay time of diesel. (Cetane Number ∝ Ignition Promotion) [L2] 2) Meaning of Cetane Number [L4] - Related to the anti-knock quality of fuel, created by mixing cetane (good ignitability) and alpha-methylnaphthalene (poor ignitability) in an appropriate ratio to make a standard fuel with arbitrary ignitability, and comparing ignitability with test fuel using a specific engine. [L4] - The volume percentage of cetane contained in the standard fuel when ignitability is the same is called the Cetane Number. [L4] - If the Cetane Number is excessive, ignition time is too fast causing incomplete combustion and engine power loss; if low, knocking occurs easily. [L2] 3) Tendency of Cetane Number [L3] ① When Cetane Number is High [L4] - Ignition delay time shortens. [L4] - Engine output and efficiency improve during combustion, and noise decreases. [L4] - If excessively high, ignition time is too fast, causing incomplete combustion and engine output reduction. [L3] ② When Cetane Number is Low [L4] - Knocking occurs easily. [L2] 4) Test Method of Cetane Number [L4] - Ignitability of the fuel itself is represented by Cetane (C16H34), etc., comparing the value of Cetane with excellent ignitability (Value 100) and alpha-methylnaphthalene with poor ignitability (Value 0) with the standard fuel for testing. [L4] - Low-speed engine Cetane Number: 25~35 [L4] - High-speed engine Cetane Number: 45~65