Diesel fuel: problems
Diesel fuel is the substance that makes the engines of cars work. Without him, the industry would simply stand up. It is this fuel that we put into the car tank every day that sometimes brings us big problems.ИСТОРИЯ И СОВРЕМЕННОСТЬ
Rudolf Diesel (1858-1913) was a talented inventor and engineer, but this did not bring him good luck in life. In 1893, he designed and manufactured an internal combustion engine with an efficiency of 26% . This was more than double the efficiency of steam engines of the time. In 1898, he demonstrated an engine that ran on peanut oil and was 75% efficient . In 1913, Rudolf Diesel suddenly dies under strange circumstances, perhaps it was suicide, but this is only one of the versions. Diesel was on his way to England to organize aproduction and operation of their engines, and fell overboard the ship. Soon after the death of the inventor, the First World War began, and German diesel-powered submarines began to sow death and destruction in the ranks of the Entente fleet.
Diesel's work was continued by other pioneers, notably Clessy L. Cummins . Until the 1920s diesel engines were mostly stationary and ran on biofuels. In the 1920s, engines powered by more liquid fuels, which were produced by the nascent oil refining industry, also began to be used. The time of oil tycoons and the rapid development of diesel technology began.
Modern diesels have higher power and efficiency, are equipped with a turbocharger and are more economical than their distant predecessors. These improvements were the result of the widespread use of electronics and in turn necessitated the use of higher quality fuels and oils.
Fuel use is a complex issue. Having understood all the intricacies, you can prevent malfunctions and save a lot of money during the operation of the machine. Diesel fuel is characterized by a number of qualities that together determine the efficiency of its operation. It is impossible to say which one is more important than the other. All of them contribute to the performance of fuel functions in the combustion process.
What are these functions? First of all, fuel is a source of energy, but its functions are not limited to this. Diesel fuel cools the combustion chamber and also lubricates the rubbing surfaces of parts and cleans the nozzle . Consider some characteristics of diesel fuel.ХАРАКТЕРИСТИКИ ДИЗЕЛЬНОГО ТОПЛИВА
cetane number .
This indicator characterizes the ability of diesel fuel to ignite after injection into the combustion chamber of the engine, that is, it determines the ignition delay period of the mixture from injection into the cylinder to the start of combustion. The higher the cetane number , the easier the fuel ignites , the shorter the delay, and the smoother and smoother the air-fuel mixture burns.
Most engine manufacturers recommend using diesel fuel with a cetane rating of at least 40 . Starting qualities during cold start , engine warm-up rate and uniformity of its operation depend on the value of cetane number . In Europe , diesel fuel is produced with a cetane number of about 51 , in Japan - about 50 . According to the Russian standard, the cetane number of summer and winter diesel fuel must be at least 45 , so the power of modern diesel engines isforeign production (which equip both foreign and domestic equipment), designed for "European" or Japanese diesel fuel, may slightly decrease when working on Russian diesel fuel. In addition, engines run harder on diesel fuel with a lower cetane number.
Surprising fact : the tax policy in our country is such that the higher the cetane number of diesel fuel (and the octane number of gasoline), the higher the excise tax, i.e. the situation is paradoxical - the state does not encourage industry to produce high-quality fuel! If the enterprise nevertheless produces high-cetane fuel, its price for consumers increases sharply in comparison with low-quality fuel. These are the "grimaces" of an unreasonable tax policy.
Fractional composition .
Sometimes, in order to improve low-temperature qualities , diesel fuel is diluted with kerosene , i.e., lighter oil fractions that have a lower boiling point. The use of fuel diluted with kerosene leads to *increased consumption and reduced power**, engines run harder, and their life is reduced. Turbodiesels with direct injection are especially sensitive to such fuel.
This is another important parameter, a measure of the " fat content " of diesel fuel. Particles of viscous fuel scatter less , i.e., the shape of the flame sprayed by the nozzle depends on this characteristic, and the course of the fuel combustion process depends on the shape of the flame. The combustion process should be as even as possible. This means that the temperature throughout the combustion chamber must be the same , without "cold" and "hot" zones. This, in turn, means a decrease in the level of toxicity of exhaust gases (EG) while maintainingother performance characteristics of the engine. The level of toxic nitrogen oxides N0x increases when combustion occurs at high temperatures , so lowering the temperature allows you to reduce their content in the exhaust gas and extend the life of the engine, since "hot spots" generate stress concentration zones. As a result of such overheating, pistons and liners can be destroyed. Unfortunately, the transition to a less viscous fuel , along with a positive effect, has negative consequences. To provide withlubrication of parts of fuel equipment, the viscosity of diesel fuel must be at least 1.3 cSt. Excessively liquid fuel does not have sufficient viscosity to lubricate the fuel pump parts, and this can cause problems: the fuel pump may fail, or wear products of the fuel pump parts - solid particles - will enter the fuel and damage the parts of the fuel system located after the pump. Both of these are undesirable.
Lubricity and sulfur content .
Fuel reduces the friction force of parts in fuel pumps and injectors, as well as the piston on the cylinder mirror. Contaminants also reduce the lubricity of the fuel. Water has a particularly strong influence in this regard. Solid particles can cause accelerated wear of parts and failure of power system units. Methods for determining the lubricity of fuels are not as well developed as they should be. There are two standard methods for testing this property: HFRR methods (Highreciprocating motion) and SBLOCLE (ball-in-cylinder friction), however, none of the methods gives unambiguously accurate results.
Studies have shown that a side effect of the hydrotreating processes used to remove sulfur compounds from the fuel is to reduce the content of compounds on which the fuel's lubricity depends . In Europe and the USA, the problem of lubricity has become especially acute in recent years due to the tightening of sulfur content standards in fuel : the number of malfunctions of high-pressure fuel pumps immediately increased .
Sulfur content is the main " environmental " indicator of diesel fuel. The combustion products of sulfur, when interacting with water, form acids. Sulfur causes damage not only to nature, but also to the engine - the products of its combustion provoke metal corrosion, and when they come into contact with engine oil, solid deposits form (the engine cokes).
According to Russian GOST , the sulfur content in diesel fuel should not exceed 0.2% . European and Moscow city requirements are tougher - no more than 0.05% . Some domestic refineries have already begun to produce diesel fuel with a sulfur content of no more than 0.035%, however, Russian diesel fuel with a low sulfur content is considered to have poor lubricity, and to compensate for this shortcoming, manufacturers introduce anti-wear additives into it.
Filterability coefficient .
An extremely important parameter that characterizes the presence of mechanical impurities in diesel fuel, water, resinous substances and paraffins that affect the efficiency and reliability of the fuel equipment. It is determined by the degree of clogging of a calibrated paper filter after passing 20 ml of fuel through it at atmospheric pressure. According to Russian GOST, the filterability coefficient of diesel fuel must be at least 3.0 . For diesel fuel of the highest grade , the filterability coefficient ne is greater than 2.0 . As you understand, foreign-made diesel engines are especially sensitive to fuel purity. The service life of paper fuel filters is highly dependent on the degree of fuel contamination. According to some reports, when the filterability coefficient is changed from 3.0 to 2.0, the service life of filters more than doubles.
foreign matter in fuel .
Some foreign substances are present in the fuel initially (for example, sulfur), others appear after oil refining. Microalgae and bacteria can grow in diesel fuel! If microorganisms multiply strongly, they can clog the fuel system and damage injectors and pumps. This happens if the tanks of the tankers are not regularly treated. The list of works performed during the maintenance of fuel tanks must necessarily include measures to prevent the reproduction of microorganism.zmov. However, before using microbial killers, you should make sure that they do not adversely affect the beneficial properties of diesel fuel.
Another substance that has a negative effect on the quality of diesel fuel is paraffin . It impairs combustion and clogs the fuel system . To dissolve paraffin, alcohol is sometimes added to diesel fuel, but this is strongly not recommended! A mixture of alcohol and diesel fuel is explosive ! In addition, the addition of a small amount of alcohol will impair lubricity. It should also be noted that the addition of alcohol increases the cetane number of the fuel.
The most common type of foreign matter is particulate matter such as dust. Dust can get into the fuel if you do not follow the rules for operating the tanker, for example, use a dirty stick as a fuel dipstick.Двигатели на электричестве.
By the way, electricity for electric motors is devoid of these problems - the " quality " and " quantity " of electricity that enters the sailboat's battery is easy to check with a wattmeter connected to the battery. You can always see how much Wh of energy has gone in and how much is spent on movement. Lithium batteries, unlike lead ones, have practically no self-discharge (up to 25% charge per year) and a lithium battery charging efficiency of 99%.
- Magazine "Fixed Assets", No. 9/2007
- Article "What is diesel fuel and how to deal with it"