Gasoline is a practically colorless liquid withspecific odor, which is a complex combination of hydrocarbon chains that differ in their structure. From these chains, called fractions, depend on the fuel characteristics: boiling and freezing points, volatility and other properties.
Manufacture of gasoline
Gasoline is a product of oil refining.The octane number, as well as the purity, determines the brand of gasoline. The main ways of obtaining this type of fuel are reforming, cracking and direct distillation.
Gasoline can also be produced from natural andassociated gases, coal and oil shale. It is used not only as a fuel, but also as a solvent, extractor and wash, raw materials in the petrochemical industry.
Despite a rather wide range of applications,More than 90% of all gasoline produced in the world goes to fuel for internal combustion engines. There are two main types of gasoline: aviation and automobile.
Gasoline grades vary depending on the level of quality: the higher it is, the fewer problems with the operation and maintenance of the vehicle.
The main way to get gasoline is the processcracking, which is a secondary processing of petroleum products. During cracking, heavy hydrocarbons are split, increasing the volume of finished liquid by 60%. Thermal cracking is carried out at a temperature of more than 500 aboutC, thanks to which grades of gasoline with an octane number of not more than 70 are created.
Today, fuel for aviation and automotiveequipment is produced in oil refineries equipped with automated equipment. The incoming oil is mixed, sedimented and stored in special tanks. Then it is subjected to washing, dehydration and rectification. As a result, it produces straight-run gasolines, which are distinguished by a high level of chemical stability. Liquids are cleaned, sulfur is removed from their composition, octane values are increased.
The first use of straight-run gasolinesallowed to increase the power and efficiency of the engines, but the successes were short-lived: the fuel mixture exploded in the combustion chamber when it was heated from compression. The detonation caused the engines to break down. The solution to this problem was the use of special substances - antiknock detonators. The most effective of these is tetraethyl lead. As a result, the stability of gasoline to detonation was estimated by the octane number, which received the name of the brand. It is determined by several methods - research, motor and temperature.
Requirements for the quality of gasoline
Both aviation and automobilemeet certain requirements established by GOSTA to ensure high performance. Among these criteria are five main ones:
- Fractional composition.
- Stability of chemical composition.
- Evaporation.
- Resistance to detonation.
- Propensity to form carbon deposits.
Fractional composition
Fractional composition has a functionengine impact, characterized by several properties. The first of these is the ambient temperature. The percentage of light fractions depends on it. The lower it is, the more fractions should be contained in the fuel. At the same time, too many of them can lead to the formation of steam jams.
The second and third - the time spent on warming upengine and the degree of wear of the cylinders and pistons. The ambient temperature also has a considerable influence on these parameters, therefore, in the summer and winter grades of gasoline, the fractional composition differs. Poor volatility of gasoline can cause the combustion chamber and crankcase of its liquid fraction to enter the combustion chamber, which leads to the dilution of the engine oil and the failure of the engine.
Chemical stability
Varies depending on the rate of oxidationcomponents of fuel and can become the reason for the appearance on the candles, valves and other parts of the engine of the deposit. The chemical stability of gasoline is its ability to maintain its properties regardless of the environment.
Evaporability
Determines the ability of gasoline to transfer fromliquid state into gaseous and mix with air to form a combustible mixture. Evaporation affects the starting of the engine and depends on the fractional composition of gasoline.
Detonation properties
The ability of gasoline does not ignite when compressed.The phenomenon of detonation is not the most pleasant and harmless, since it can lead to engine overheating and its failure. This parameter depends not only on the composition of the fuel, but also on the design of the motor.
Cinder formation
The tar present in the gasoline composition becomesthe cause of carbon formation. Most often it is deposited on the carburetor, which leads to increased fuel consumption, reduced power and other malfunctions. Prevent the appearance of deposits can be by adding special additives.
Gasoline grades
Fuel is labeled according to itsoctane number: the higher it is, the greater the resistance of the fuel to detonation, respectively, it can be used in engines characterized by a high degree of compression of the fuel mixture. For example:
- Gasoline A-76 - octane number by motor method is not less than 76.
- Gasoline grade 80 - octane number is not less than 80.
- Gasoline grade 92 - octane number is not less than 92.
- Gasoline AI-95 is an octane number, correspondingly, not less than 95.
Automobile gasoline is marked with the letter "A"aviation - the letter "B", the numbers, respectively, are its numeric index, or octane number. If the letter "AND" stands before the index, then the octane number was measured by the research method. The absence of a letter indicates the use of the motor method.
The practical use of gasoline depends on itsThe main property is the resistance to detonation. The octane number expresses this parameter for automobile gasoline. For aviation fuel, its grade is a reflection of antiknock properties.
Motor gasoline grades are classifiedit is for this property. For aviation gasoline after the letter "B" - for example, B / -100 / 130 - indicates the octane number, in which the denominator is a grade of fuel. Increase the stability of gasoline to detonation can be added to its composition of special additives - tetraethyl lead.
Fuel marking
For today in the CIS countries several grades of gasoline of different grades are produced: summer, winter, leaded, unleaded and unleaded.
The branded petrol stains are painted in different shades, for example, A-72 pink, AI-93 red-orange, AI-98 blue.
In foreign countries, gasoline is produced by twothe main brands: "Premium" of the first grade with an octane number of 97-98 and "Regular" of the second grade with an octane number of 90-94. In the USA, England and some other countries of the world, Super fuel is produced, the octane number of which is 99-102.
On the question of which brand of gasoline is better,it is impossible to answer unequivocally: for each car a certain grade of gasoline is used. For imported cars, the manufacturer recommends the use of fuel, the octane number of which is not lower than 91-92, for cars produced in the 90's - with an octane rating of at least 94.
Characteristics of gasoline, a brand of gasoline and itsquality are determined by the content in the composition of alkalis, acids, sulfur and organic compounds and the degree of its contamination. Often, petrol stations of the CIS countries can face low-quality fuel, the use of which can lead to premature wear and damage to the engine of the car.
Modern ICEs require strict adherencerecommendations of the manufacturer regarding the fuel used: only the gasoline whose brand is indicated by the manufacturer of the power unit is filled. This is due to the degree of compression of the fuel mixture, the design of the engine and the working volume of the cylinders. For example, the larger the compression and the volume of the combustion chamber, the higher the octane rating of the fuel. One unit in the twenty-five hundredth of compression is, according to the designers, a unit of the octane number.
