1. Gasoline is a volatile and flammable hydrocarbon mixture liquid fractionated and cracked from petroleum, which can be used as fuel. The appearance is transparent liquid, flammable, and the distillation range is 30℃ to 220℃. The main components are C5 ~ C 12 aliphatic hydrocarbons and cycloalkanes, and a certain amount of aromatic hydrocarbons. Gasoline has a high octane number (anti-knock combustion performance), which is divided into 89, 90, 92, 93, 95, 97 and 98 according to the octane number.
2. Important characteristics of gasoline: evaporation, stability, antiknock, corrosiveness and cleanness.
3. Evaporation: In the engine cylinder, gasoline must evaporate quickly and form a uniform combustible mixture with air, which is mainly determined by the evaporation of gasoline itself. The main indexes reflecting evaporation are distillation range and saturated vapor pressure.
Safety: The oxidation stability of gasoline is called the oxidation stability of gasoline at room temperature and in liquid phase. The indexes for evaluating gasoline stability are divided into iodine value, actual colloid and induction period.
4. Antiknock: The property to measure whether the fuel is prone to knock is called antiknock, and the antiknock of gasoline is expressed by octane number (RON). The higher the octane number of gasoline, the better the antiknock performance. For similar hydrocarbons, it has small carbon number, good antiknock performance and high octane number. For hydrocarbons with the same carbon number, the order of octane number is aromatics >: isoalkanes and isoolefins >: normal olefins and cycloalkanes >: normal alkanes. The lighter the different straight-run fractions of the same crude oil, the higher the octane number; Fractions with the same boiling range of different crude oils have different chemical compositions and different octane numbers.
5. Corrosiveness: The corrosiveness of gasoline is related to sulfur and sulfur-containing compounds, organic acids, water-soluble acids or bases.
6. Cleanliness: Gasoline often contains mechanical impurities and moisture. Mechanical impurities will cause serious consequences such as oil circuit blockage and increased wear. Mixing water into gasoline will accelerate the oxidation of gasoline and form an acidic aqueous solution with organic acids with few water molecules in gasoline, which will corrode metals. It is easy to freeze at low temperature and form ice particles to block the oil circuit. Therefore, the mixing of mechanical impurities and moisture should be strictly controlled in motor gasoline.