Octane number
Indication of octane numbers at an American gas station.
Octane number- an indicator characterizing the knock resistance of the fuel (the ability of the fuel to resist self-ignition during compression) for internal combustion engines. The number is equal to the content (in percent by volume) of isooctane (2,2,4-trimethylpentane) in its mixture with n-heptane , at which this mixture is equivalent in detonation resistance to the studied fuel in standard conditions tests.
Isooctane is difficult to oxidize even at high compression ratios, and its knock resistance is conventionally taken as 100 units. combustion in the engine n-heptane, even at low compression ratios, is accompanied by detonation, therefore, its knock resistance is taken as 0. For gasolines with an octane number above 100, a conditional scale has been created in which isooctane is used with the addition of various amounts of tetraethyl lead.
The characteristic metallic ringing during detonation is created by a detonation wave that is repeatedly reflected from the walls of the cylinder. Detonation reduces engine power and accelerates wear.
Fuel test
Knock resistance tests are carried out either on a full-size automobile engine or on special installations with a single-cylinder engine. On full-size engines, during bench tests, the so-called. actual octane number(FOC), and in road conditions- road octane number (DOCH). On special installations with a single-cylinder engine, it is customary to determine the octane number in two modes: harder (motor method) and less hard (research method). The octane number of a fuel determined by the research method is usually slightly higher than the octane number determined by the engine method. The accuracy of determining the octane number, more correctly referred to as reproducibility, is one. This means that gasoline with an octane rating of 93 can show a completely different value, for example, 92 It is essential that both values, 93 and 92, are both exact and correct, and yet refer to the same fuel sample.
Types of octane numbers: OCHI and OCMI
Research octane (EYES) is determined on a single-cylinder unit with a variable compression ratio, called UIT-65 or UIT-85, at a speed of crankshaft 600 rpm, intake air temperature 52°C and ignition timing 13 degrees. It shows how gasoline behaves in low and medium load modes.
Engine octane number (HMI) is also determined on a single-cylinder installation, at a crankshaft speed of 900 rpm, an intake mixture temperature of 149 ° C and a variable ignition timing. MON has lower values than RON. HMI characterizes the behavior of gasoline in the modes heavy loads. Affects high speed and knock at partial throttle and engine under load, hill driving, etc.
At least in the 1950s, it was also used temperature octane number.
Octane ratings for hydrocarbons and various fuels
| Substance | HMO | EYES |
|---|---|---|
| Methane | 110,0 | 107,5 |
| Propane | 100,0 | 105,7 |
| n-butane | 91,0 | 93,6 |
| Isobutane | 99,0 | 101,1 |
| n-pentane | 61,7 | 61,7 |
| Isopentane (2-methylbutane) | 90,3 | 92,3 |
| Isohexane (2,2-dimethylbutane) | 93,4 | 91,8 |
| 2,2,3-Trimethylbutane | 101,0 | 105,0 |
| n-Heptane | 0 | 0 |
| Isooctane (2,2,4-trimethylpentane) | 100 | 100 |
| 1-Penten | 77,1 | 90,9 |
| 2-Methyl-1-butene | 81,9 | 101,3 |
| 2-Methyl-2-butene | 84,7 | 97,3 |
| Methylcyclopentane | 80,0 | 91,3 |
| Cyclohexane | 77,2 | 83,0 |
| Benzene | 111,6 | 113,0 |
| Toluene | 102,1 | 115,7 |
| Straight run gasolines | 41-56 | 43-58 |
| Thermal cracking gasolines | 65-70 | 70-75 |
| Catalytic cracking gasolines | 75-81 | 80-85 |
| Catalytic reforming gasolines | 77-86 | 83-97 |
| Gasoline N-80 ((VOC + OPM) / 2)) | 76 | 84 |
| Gasoline AI-92 | 83,5 | 92 |
| Polymer gasoline | 85 | 100 |
| Alkylate | 90 | 92 |
| Alkylbenzene | 100 | 107 |
| ethanol | 100 | 105 |
| Methyl- tert-butyl ether | - | 117 |
The difference between RON and MON characterizes the sensitivity of the fuel to the engine operating mode.
Octane distribution
Since gasoline fractionation occurs during the operation of a full-size engine under variable conditions, it is necessary to separately evaluate the knock resistance of its various fractions. The octane number of gasoline, taking into account its fractionation in the engine, is called the "octane number distribution" (ORD). Due to the complexity of determining the octane number on engines, methods have been developed for indirect assessment of knock resistance by physical and chemical indicators and characteristics of a low-temperature gas-phase oxidation reaction that simulates pre-flame processes.
Hydrocarbons, which are contained in fuels, differ significantly in knock resistance: aromatic hydrocarbons and paraffinic hydrocarbons (alkanes) of a branched structure have the highest octane number, paraffinic hydrocarbons of a normal structure have the smallest octane number. Petroleum-derived fuels produced by catalytic reforming and cracking have higher octane numbers than those obtained by direct distillation.
High-octane components and anti-knock additives are used to increase the octane number of fuels. Many of them (MTBE, for example) evaporate more easily than gasoline, which has an interesting effect on cars with leaky gas tanks - as fuel is consumed and the additive evaporates, the octane number of gasoline remaining in the tank decreases by several units. This leads to a slight ringing at full engine power (unless equipped with a knock sensor). The vast majority of modern injection engines have knock sensors to allow the use of any gasoline with an octane rating of 91-98, for high compression engines it may be necessary to use gasoline with an octane rating of at least 95 or even 98.
What is an octane number and does it depend on it? Any motorist asked this question when filling up his car at a gas station with the thought of choosing a filling hose with some kind of conditional numbers above it.
Octane number is actually the knock level at which gasoline ignites and explodes in your car's combustion chamber. If the gasoline lights up earlier than necessary, at a time when they are not yet completely closed intake valves and the cylinder is not in top point then naturally the engine, not only can not work on full power, but work incorrectly, and even worse, in fact, we will get a detonation, but more on that later.
With such a low octane number, we get at long-term operation a bunch of problems with engine parts - wear on valves, valve seats, additional carbon deposits, etc. In addition, the mismatch of the octane number for the engine entails the same additional detonation, which is often confused with valve knock.
The octane number is obtained by shifting the constituents of gasoline. Isooctane is a substance that is almost non-explosive under increasing pressure, and its detonation resistance was taken as 100 units. At the same time, n-heptane is absolutely resistant to detonation with increasing pressure (it can be said to be self-detonating), so its detonation resistance is taken as 0. It is a mixture of these substances that allows you to adjust the octane number in gasoline. In addition, gasoline added trimethylpentane, on which the octane number depends little. There are gasolines with an octane rating of more than 100 units, they use isooctane with the addition of various additives.
Additives for increasing the octane number of gasoline
To increase the higher octane number, aromatic hydrocarbons and paraffinic hydrocarbons (alkanes) of a branched structure are added. It is with the use of these components that the octane number increases. But as you noticed, the substances used are called aromatic (aromatic hydrocarbons) i.e. speaking the language of the layman, high octane gasoline smells stronger than low octane. This has certain disadvantages, since high-octane gasoline, after the addition of aromatic components, is more volatile. That during long-term storage in an open container or a certain combination of container with external environment leads to a decrease in the octane number of gasoline. Therefore, it can be said that high octane gasoline should be "fresh".
Earlier in the USSR, to increase the octane number, tetraethyl lead- a toxic mixture in the composition with lead. Unfortunately, tetraethyl lead is not only poisonous in itself, but also quickly disables catalytic converters and lambda probes, which began to be used in the design modern cars, as a result of which this additive had to be abandoned. Manganese-based additives have also been used, but they are also now banned for environmental reasons. In addition, an additive is sometimes used to increase the octane number - ferrocene. This additive (ferrocene) has iron in its composition and creates a hard-to-remove conductive coating on candles (shades of red), which impairs performance and, accordingly, reduces the life of spark plugs. Gasolines also include other additives and impurities. Additives in gasoline perform different tasks. Reduce the amount of harmful impurities in gasoline - sulfur, water, clean engine parts or fuel system, increase the octane number of gasoline (this was mentioned above). A relatively harmless anti-knock additive for the engine is methyl tert-butyl ether. Now it is widely used in Ukraine, Russia and Europe.
It is quite possible to get gasoline with an octane rating of more than 110 (which is aviation fuel). In addition, the well-known scheme with mixing gas condensate, because the octane number natural gas usually above 100.
Combustion of gasoline at various octane numbers.
The rate of combustion of gasoline, that is, in fact, an explosion, depends on the octane number. At high octane numbers, the combustion of gasoline occurs for a long time, smoothly .. At the same time, accordingly, the gases in the chamber do not put pressure on the pistons with the phenomenon of impact and excessive resonant detonation. The engine runs more evenly, smoothly and clearly. Therefore, in automotive industry and there is a tendency to produce engines of modern cars running on high-octane gasoline.
Determination of the octane number of gasoline
You can approximately determine the octane number using a specialized device - Octane meters, it gives an error in octane numbers by 5-10 units. Therefore, to put it simply, there is no way to check the quality of gasoline without laboratory tests.
In the laboratory, the octane number is determined in two ways:
- Motor (MON)
- Research (RON).
In the USA, the octane number is replaced by the so-called octane index, which is the arithmetic mean of the octane numbers obtained by the motor and research methods for this fuel. But in Japan, only a research method is used to designate brands of gasoline. Our gas stations also declare exactly the octane number obtained by the research method.
The use of gasoline with the wrong octane rating for the engine.
Use of low octane gasoline.
If it so happened that you refueled the car with low-octane fuel, then listen to the engine. If the engine runs stably but pulls poorly, there is nothing to worry about, just burn all the low-octane gasoline and then fill up with standard octane gasoline. At the same time, try to avoid dynamic driving, to avoid detonation in the engine.
But if ringing sounds are heard from the engine, which are often confused with the sound of valves, then this means that the mixture detonates before the valves close. In fact, this blast wave propagates through the engine block and into the exhaust system. IN this case this can cause the pistons to burn out and exhaust valves, the fact of the negative impact will be available. "Natural" detonation can sometimes be observed in cases of excessive engine load, when climbing a hill, when driving on overdrive. Long work engine, even with “natural” detonation, is unacceptable, as this can lead to engine overheating and, as a result, damage to the cylinder head gasket, burnout of pistons and valves.
Use of high octane gasoline
No need to try to use high octane gasoline for cars whose engines are not designed for it. The disadvantages of such an application are also obvious, if the design was originally designed for low-octane gasoline and you used high-octane gasoline, then this will entail a complete reconfiguration of the intake and exhaust gases, and possibly the replacement of some engine components. The burning time of gasoline in this case is longer and in fact it will need to be adjusted piston group and inflammation in such a way that the expansion of the volume of the cylinder - piston is equal to the burning time, while the valves would be closed. In fact, on a tuned engine, gasoline burns out late, and there will also be a loss of power.
In order to understand what an octane number is, it is necessary to have at least a small understanding of the principle of engine operation. internal combustion. In fact, this concept refers to the chemical resistance of fuel to ignition. The higher this indicator, the lower this probability.
Detonation
At one of the stages of its work, the piston of any car engine starts to compress air-fuel mixture. As a result of the action of high pressure, it is likely that it will spontaneously ignite before the spark from the spark plug appears. This phenomenon is called detonation and becomes a serious problem for many cars. Its main threat is damage to the connecting rods and melting of the piston bores. Repair of these breakdowns is quite expensive. Be that as it may, such cases are relatively rare in our time, since most manufacturers equip the power units of machines with computerized units capable of detecting frequencies that are characteristic of detonation.
Compression ratio
The high compression ratio allows the engine to deliver more power using less fuel. in motors modern models machines, it is 10:1. At the same time, if we are talking about direct injection units, it increases significantly. In this case, especially important role plays the octane number of the fuel. It should be noted that this indicator does not affect the consumption in any way. As a rule, most a high degree compression differ sports cars. In this regard, they most of all need high-octane fuel.
Methods for calculating the indicator
In order to calculate what is the octane number of a particular type of fuel, you must first select a mixture of reference hydrocarbons. These are isooctane and normal n-heptane. Their indicators are respectively 100 and 0. The value is then determined by the motor or research method, by applying special installation, providing a variable compression ratio. Using motor way a high engine load is simulated when the temperature fuel mixture reaches 150 degrees. In this case, the rotational speed is in the same value, which is 900 revolutions per minute. When using the second of these methods, the fuel mixture does not heat up, and the rotational speed is 600 revolutions per minute.
Determination of octane number
You can accurately calculate the value of the indicator as follows. This is done using a test bench, which is a motor with one cylinder and a carburetor. In this case, the level of detonation is fixed by special sensors. First, the engine is started with the test fuel, after which a reference mixture is selected. The mode of operation does not change. Expressed in percentage the amount of isooctane in the reference mixture that will result and will show the stability of the gasoline. In other words, if the mixture is 75 percent isooctane, this means that the octane number of the tested fuel is 75 units. When using the motor method, the detonation features of the machine are determined when driving with no high speed, frequent starts and regular stops power unit. As for the research method, it provides an opportunity to examine in detail the process of fuel combustion while driving along the highway in the same mode. As practice shows, in the second case, the value of the indicator will always be slightly larger.
Octane Boost
The more pronounced the smell of fuel, the higher its octane number. This is due to the fact that paraffinic and aromatic hydrocarbons, which have a branched structure, increase the value of the indicator. In this regard, it becomes clear why it is recommended to store gasoline in closed containers. By using special additives, the characteristics of the fuel are improved. It should be noted that each of their types is designed to perform a separate task. Some of them are designed to increase the octane number, while others are designed to reduce the emission of harmful elements into the atmosphere. Currently, in our country at gas stations you can see such brands of gasoline as AI-95, AI-92, AI-96, A-76 and A-80. It should be noted that the letter "I" in the name is evidence that the indicator was determined by the research method. At the same time, the number in the name is the octane number.
Gas
Gas has become a very convenient and relatively cheap type of fuel, which is becoming more and more popular among motorists from year to year. In this case, we are talking about a propane-butane mixture. It is produced from oil and associated concentrated petroleum gases. In order for it to always remain in a liquid state, it is stored and transported under a pressure of 16 atmospheres. It should be noted that in the mixture, butane acts as fuel, while propane provides pressure. This type of fuel, compared with others, has many significant differences, starting with chemical composition and ending with cost. There is an opinion among many car owners that gas harms the engine, and its performance is much worse than gasoline. In fact, this assertion is erroneous. Bright to that proof can be called the octane number of the gas, which for a propane-butane mixture is 110 units. As noted above, the maximum value of this indicator for gasoline is 98 units.
OCTANE NUMBER- a measure of the knock resistance of gasoline and motor oils.
A huge amount of gasoline is produced and consumed all over the world - as automotive fuel. In order for gasoline to burn in the cylinders of a car “correctly”, it must have a number of properties. One of the most important is the octane number. It is it that is written on all gas stations, and the quality and price of gasoline depends on it. When out exhaust pipe black smoke is coming out and the engine is making harsh sounds, this means that gasoline in the cylinders, instead of burning at the prescribed speed of 15–60 m/s, starts to explode - detonate at a speed of 2000–2500 m/s ( cm. EXPLOSIVES). The detonation wave is repeatedly reflected from the walls of the cylinder, creating unpleasant sound, sharply reducing engine power and accelerating its wear.
The cause of detonation is the release of energy with an increased formation of ROOH hydroperoxides in gasoline vapors during their oxidation with atmospheric oxygen ( cm. PEROXIDES). If the concentration of hydroperoxides exceeds a certain limit, their explosive decomposition will occur. The explosion of peroxides proceeds by the mechanism of branched chain reactions ( cm. CHAIN REACTIONS). There are two ways to increase knock resistance. The first is to increase the proportion of branched and aromatic compounds in the composition of gasoline. The second is to introduce small amounts of special additives into the fuel. Usually both ways are used.
To determine the anti-knock properties of the resulting mixture, a special scale was proposed in the 1930s, according to which the knock resistance of a given gasoline is compared with the resistance of standard mixtures. Two substances were chosen as standards: normal heptane and one of the octane isomers, 2,2,4-trimethylpentane (it is called "isooctane"). A mixture of heptane vapor with air under strong compression easily detonates, so the quality of heptane as a fuel is considered to be zero. Isooctane, being a branched hydrocarbon, is resistant to detonation, and its quality is taken equal to 100. The octane number is determined as follows. Prepare a mixture of normal heptane and isooctane, which is equivalent in characteristics to the test gasoline. The percentage of isooctane in this mixture is the octane number of gasoline. There are flammable liquids with better anti-knock performance than isooctane. Additives of such liquids make it possible to obtain gasoline with an octane number of more than 100. To evaluate an octane number above 100, a conditional scale has been created in which isooctane is used with the addition of various amounts of tetraethyl lead Pb(C 2 H 5) 4 . It is known that this substance already in very small concentrations significantly increases the octane number of gasoline. Knowing how much tetraethyl lead must be added to gasoline in order to increase its octane number by one unit, it is easy to prepare standard mixtures from isooctane with an octane number of 101, 102, etc.
Octane number is determined different ways. For motor gasoline, two methods are used - motor and research. In the first case, the operation of the engine is simulated under conditions of high loads (traffic along the highway at high speed), in the second case, in urban conditions (the speed is low and there are frequent stops). The letter "I" in the brand of gasoline AI-93 just means that the octane number of this gasoline was obtained by a research method. And if it is indicated that the octane number of gasoline is simply 76, then this means that it was obtained by the motor method.
The role of the hydrocarbon structure is clearly visible from the table, which shows the octane numbers of some pure chemical compounds obtained by the motor method:
It can be seen that chain branching, the introduction of a double bond, and the appearance of an aromatic ring contribute to an increase in the octane number. For example, if as a result of the isomerization of normal hexane (the process takes place in the presence of a catalyst) a mixture of branched isomers of this hydrocarbon is obtained:
n-C 6 H 14 ® (CH 3) 2 CHCH (CH 3) 2 + (CH 3) 2 CHCH 2 CH 2 CH 3 + CH 3 CH (C 2 H 5) 2, then the octane octane number of the mixture will increase immediately by 20 units.
Gasoline obtained from oil by simple distillation (such gasoline is called straight-run gasoline) has a low octane number - in the range of 41-56, so now such gasoline is not used. To increase the octane number, more modern methods of oil refining are used (thermal and catalytic cracking, reforming). Thermal cracking (from English cracking - splitting) is produced by heating oil to 450-550 ° C under a pressure of several atmospheres. At the same time, molecules of heavy hydrocarbons, which are abundant in crude oil, are split into shorter ones, among which there are many unsaturated ones. The world's first liquid oil cracking unit was patented by Russian engineers V.G. In thermally cracked gasoline, the octane number rises to 65–70. During catalytic cracking, the process is carried out in the presence of an aluminosilicate catalyst. In catalytic cracked gasoline, the octane number rises to 75–81. Reforming (from the English reform - to transform, improve) is carried out in the presence of catalysts that promote the aromatization of saturated hydrocarbons and increase the proportion of aromatic hydrocarbons from 10 to 60%. Previously, molybdenum and aluminum oxides were used as catalysts, now catalysts containing platinum are used (therefore, this process is called platforming). Catalytic reforming gasoline has an even higher octane rating of 77–86.
To increase the octane number, so-called high-octane components are also introduced into gasoline. These include aromatic hydrocarbons with a short branched side chain, for example, cumene C 6 H 5 CH(CH 3) 2 . Another additive is the so-called alkylate (alkylbenzene), a mixture of saturated hydrocarbons of isostructure, obtained by alkylation of isobutane with unsaturated hydrocarbons - alkenes, mainly butylenes. As a result, a mixture of isooctanes is formed:
CH 3 CH (CH 3) 2 + CH 3 CH \u003d CHCH 3 ® CH 3 C (CH 3) 2 CH (CH 3) CH 2 CH 3 (2,2,3-trimethylpentane); CH 3 CH (CH 3) 2 + (CH 3) 2 C \u003d CH 2 ® CH 3 C (CH 3) 2 CH 2 CH (CH 3) 2 (2,2,4-trimethylpentane). Alkylate has an octane rating of at least 90–91.5. It is very effective to add methyl- tert-butyl ether CH 3 -O-C (CH 3) 3 - non-toxic liquid with an octane rating of 117; up to 11% of this substance can be added to gasoline without reducing its performance. Thus, modern motor gasoline is a complex mixture of hydrocarbons obtained in various oil refining processes and special additives.
To increase the octane number of gasoline, the second method is also widely used: special substances are added to it - antiknock agents. The very first of these was relatively inexpensive and very effective tetraethyl lead, a colorless toxic liquid. At high temperature in the molecules of this compound, Pb–C bonds are easily broken, with the formation of ethyl radicals ( cm. FREE RADICALS):
Pb(C 2 H 5) 4 = Pb + 4C 2 H 5 . Lead atoms are easily oxidized by oxygen to lead oxides (depending on the temperature, mixtures of PbO and PbO 2 are formed), and the dioxide effectively destroys hydroperoxides with the formation of inactive compounds - aldehydes, alcohols, etc., for example: 2RCH 2 COOH + 2PbO 2 ® 2RCHO + 2PbO +O2. So that the lead oxides formed during the combustion of tetraethyl lead do not deposit on the internal parts of the engine, a special “scavenger” of lead (0.3–0.4%) is simultaneously introduced into gasoline, usually ethyl bromide C 2 H 5 Br and dibromopropane C 3 H 6 Br 2 . Then the lead is taken out with exhaust gases in the form of PbBr 2 bromide. A mixture of tetraethyl lead and ethyl bromide is called ethyl fluid, and gasoline with such an additive is called leaded (to distinguish leaded gasoline from regular gasoline, it is colored). The addition of just 0.1% tetraethyl lead can increase the octane number of gasoline by 10 units. Up to 0.3% tetraethyl lead is added to aviation gasolines. However, this compound is highly toxic: the maximum permissible concentration of its vapor in the air is only 0.005 mg / m 3 - much less than that of chlorine. In addition, toxic lead compounds heavily pollute near-highway areas of the earth. All this has led in many countries to a complete ban on leaded gasoline as a fuel. automotive fuel or to a significant limitation of its use.
Other, less toxic antiknock agents have been developed, for example, tricarbonyl (232-cyclopentadienyl) manganese Mn (CO) 3 (C 5 H 5), carbonyl (232-cyclopentadienyl) nickel 2 dimer, ferrocene Fe (C 5 H 5) 2. Unfortunately, these antiknock agents are too expensive, and in addition, they form hard deposits on the cylinder walls in much greater quantities than tetraethyl lead, so work in this area continues.
The role of increasing the octane number can be illustrated by the example of aviation gasoline during the Second World War. This war is often called the "war of engines". Motors are tanks, self-propelled guns, planes. Engines need fuel, and lack of fuel played a part in the defeat of Germany and its allies. Lesser known but no less important factor- the presence of the best quality gasoline in the countries of the anti-Hitler coalition. The Germans and Japanese had an octane number of aviation gasolines that did not exceed 87-90, while their opponents had at least 100. Although the difference may seem small, the pilots fully appreciated it: it allowed a 30% increase in power aircraft engine during takeoff and climb; reduce fuel consumption by 20% and increase the flight range by the same amount, increase by 25% payload(and these are bombs, shells, additional weapons), increase by 10% top speed and 12% - flight altitude. As British Minister David Lloyd George noted, his country would not have been able to win the 1940 air "battle for Britain" if the British pilots had not had aviation gasoline of the 100 brand.
Mass production of "100" gasoline began in the United States in the late 1930s, when the industry switched to a catalytic oil refining process developed by French engineer Eugène Goudry. He immigrated to the United States in 1930, and already in June 1936, Goodry's semi-industrial plant began operating with a capacity of 2,000 barrels per day (an American barrel for crude oil and petroleum products is 139 liters). Successful work installation made it possible to put into operation a full-scale plant with a capacity of 15 thousand barrels per day in 10 months. Other oil companies also began to introduce Goodry installations at their enterprises, and in 1939, on the eve of World War II, their total productivity reached 220 thousand barrels per day. In 1940, Goodry managed to significantly improve the operation of reactors by replacing natural clays with a more efficient synthetic aluminosilicate catalyst. As a result, Goodry's gasoline had an octane number of 82, while previously it was not possible to obtain more than 72. Therefore, it was gasoline produced at Goodry's plants that became the basis for obtaining new high-quality gasoline (with an octane number unheard of at that time, reaching 100 or more) on a large scale.
As early as 1934, US Army officials became interested in gasoline with an octane rating of 100. Tests showed that it provides significant advantages and is a strategic product. But this gasoline was at that time very scarce. It was obtained by adding tetraethyl lead, isooctane, isopentane and other components to the best grades of aviation gasoline. The Goodry process halved the amount of expensive additives required to produce "gasoline-100". The merits of Goodry were appreciated by the American government: soon after the US entered the war, he became a citizen of this country. In 1941–1942, installations operating on the basis of the Goodry process produced 90% of all aviation gasoline of the countries of the anti-Hitler coalition. By 1944, the productivity of the installations was brought to a maximum - 373 thousand barrels per day.
Goodry received many patents for catalytic oil refining. Until now, petrochemical specialists use the terms “goodryflow”, “udriforming”, etc.; V English-Russian Dictionary of Chemistry and Oil Refining seven such terms are given.
Ilya Leenson
The quality of the fuel used and its main characteristics directly affect how long the car will last. Octane and cetane numbers are basic characteristics liquid fuel quality.
Gasoline is a mixture of hydrocarbons, the amount of each component in this mixture determines the brand of gasoline and its performance characteristics. Photo: tuning-lada-2109.ru
In outline
Octane number shows us the resistance of the fuel to detonation (the ability of the fuel to self-ignite) for engines.
The number in the brand of gasoline indicates the content of isooctane in its mixture with heptane. The larger the value of the number, the lower the chance that the fuel can detonate.
Lowering the octane rating can interfere with the smooth operation of the engine. At a high pressure value, it is capable of self-ignition. There is a sharp unpleasant sound, power is reduced. Detonation can damage internal parts of the engine and require repair.
To increase resistance to detonation, different kinds additives. This method quite often used at gas stations in Russia. When refueling at the station with gasoline improved in this way, you need to pay attention to the candles. If soot has appeared, then this is a sign of non-compliance of gasoline with technical specifications.
Value scale and types of octane number
When determining the OC value, a scale is used that allows you to compare the test sample of gasoline and the standard mixture. Photo: evo-rus.com
The standard standard contains two substances: heptane, whose vapors are capable of rapidly detonating, and isooctane, which is resistant to detonation. For the analysis of gasoline, a mixture of these substances is taken, which has the characteristics of the gasoline under study, and the amount of isooctane in the mixture is calculated. If you add unique combustible liquids to gasoline, then the octane number (octane number) can increase to more than 100. In this case, the conditional scale, which is based on a mixture of tetraethyl lead and isooctane, serves as a guide.
Types of octane numbers
ROI is an exploratory ROI. To determine it, a single-cylinder installation is used, which has variable degree compression. OCHI shows how gasoline behaves at low loads.
OCHM - motor octane number. It is determined similarly to OCHI, but with an increased crankshaft speed. The RON is less than the RON and indicates the behavior of the fuel at high loads.
Cetane number of diesel fuel
cetane number - main characteristic likelihood of ignition and combustion diesel fuel. high value cetane number ensures complete burnout of the fuel mixture. Photo: do.nn.ru
In numerical terms, this characteristic is comparable to the volume of cetane in a special mixture, which has a delay period similar to the fuel taken for the test.
The cetane value of 40-55 is the standard for diesel fuel. More quality fuel has an indicator from 51 to 55 units.
This premium class fuel contains fractions that allow you to quickly start the engine even in winter.
Methods for increasing the octane number
In accordance with GOST 2084-77, grades A-72 and A-76 according to motor method have an octane rating of 72 and 76, respectively, and AI-93 and AI-95, according to the research method, have a detonation resistance of 93 and 95. Be careful when refueling your car. Gasoline brand AI-76 it can not be. It does not use the research method.
Increasing the octane number is possible in several ways:
Unfortunately, as Rosstandart found out, gasoline often evaporates from gasoline at gas stations and the octane number in half of the cases is lower than stated. This leads to problems with the engine of the car. By appearance such fuel is difficult to distinguish from high-quality. It is better to find a gas station for yourself, the quality of gasoline at which you are well aware.
You will learn about the results of fuel tests from this video:
