Gasoline and diesel fuel are distillation products of crude oil. They are made up of many different hydrocarbons. The boiling point of gasoline ranges from 30 to 210 °C, and diesel fuel - from 180 to 370 °C. Diesel fuel ignites on average at a temperature of approximately 350 °C (lower limit - 220 °C), that is, at significantly lower temperatures compared to gasoline (average - 500 °C).
Content
Characteristics of automobile fuel
Fuel calorific value
Typically, the net heating value H n determines the energy content of the fuel; it corresponds to the usable amount of heat released during complete combustion. The gross heating value Hg, on the other hand, defines the total heat, including both mechanically generated heat and the heat generated by condensation of water vapor. However, this component is not taken into account for automobiles.
The net calorific value of diesel fuel, equal to 42.9-43.1 MJ/kg, is slightly higher than that of gasoline (40.1-41.9 MJ/kg).
Oxidizers, that is, fuels or fuel components containing oxygen such as alcohol fuels, fatty acid esters or methyl esters, have a lower heating value than pure hydrocarbons because the oxygen present in these compounds does not contribute to the combustion process. Therefore, an engine with comparable power to a motor powered by conventional fuel has increased fuel consumption.
Heat of combustion of the air-fuel mixture
The heat of combustion of the air-fuel mixture determines the power output of the engine. At a stoichiometric air/fuel ratio, the calorific value for liquefied gaseous and liquid automobile fuels is approximately 3.5-3.7 MJ/m3 .
Sulfur content in automobile fuel
In the interests of reducing emissions of sulfur dioxide SO 2 and protecting exhaust gas catalytic converters, the sulfur content of gasoline and diesel fuel has been limited since 2009 to 10 mg/kg throughout Europe. Fuel meeting this limit is known as "sulfur-free fuel". Thus, fuel desulfurization is achieved. Until 2009, the use of fuels containing sulfur was permitted for use in Europe, introduced at the beginning of 2005.<50 мг/кг. Германия занимает лидирующие позиции в обессеривании топлива — уже с 2003 года, под действием мер в области налогообложения, в этой стране используется топливо, свободное от серы.
In the United States, the sulfur content limit for commercially produced gasoline has been capped at 80 mg/kg since 2006, with an average of 30 mg/kg for total fuel sold and imported. Some states, such as California, have set lower limits.
In addition, since 2006, sulfur-free diesel fuel has been produced in the United States (sulfur content is a maximum of 15 mg/kg, ULSD - ultra-low sulfur diesel). By the end of 2009, however, only 20% of fuel had a sulfur content of no more than 500 mg/kg.
Gasoline
The following are sold in Germany : Normal, Super and Super Plus. Some suppliers have replaced Super Plus with 100 octane fuel (V-Power 100, Ultimate 100, Super 100), for which, in addition to the octane number, the additives have been changed.
In the US, gasoline is sold under the Regular and Premium brands; they are approximately comparable, respectively, to the Normal and Super produced in Germany. Super or Premium gasolines, due to their higher aromatic base content and the addition of oxygen containing components, exhibit high resistance to detonation and are preferable for use in engines with higher compression ratios.
Reformulated gasoline is a term used to describe gasoline that, due to an altered composition, has lower volatility and exhaust emissions than regular gasoline. The requirements for reformulated gasoline are set out in the Clean Air Act, passed in the United States in 1990. This law regulates, for example, lower values of saturated vapor pressure, aromatic and benzene content and boiling point. It also requires the use of additives to remove contaminants and deposits from the fuel system.
Fuel standards for gasoline
The European standard EN 228 (2008) defines the requirements for unleaded petrol for use in spark ignition engines. The individual values defined for each country are set out in the national annexes to this standard. Leaded gasoline is prohibited in Europe. US specifications for spark ignition engine fuels are contained in ASTM D4814 (ASTM - American Society for Testing and Materials).
Most spark ignition engine fuels sold today contain components that contain oxygen (oxidize). In this regard, ethanol has gained particular practical importance, since the EU Biofuels Directive provides for a minimum output volume for renewable fuels ( cm. ).
Many countries have defined minimum proportions for biogenic components in gasoline, which are achieved largely through the use of bioethanol. But ethers produced from methanol or ethanol are also used - MTBE (methyl butyl ethers) and ETBE (ethyl butyl ethers), they are added in Europe up to 15% by volume.
Adding alcohols can lead to some difficulties. Alcohols increase volatility and can damage materials used in the fuel system, such as elastomer swelling and corrosion. In addition, depending on the alcohol content and temperature, the appearance of even a small amount of water can lead to separation and the formation of an aqueous alcohol phase.
Esters in gasoline
Esters do not face the problem of separation. Esters, having a lower vapor pressure, higher calorific value and higher octane number than ethanol, are chemically stable components with good physical compatibility. They therefore demonstrate advantages in terms of both logistics and engine performance. For reasons of greater sustainability and greater CO 2 retention, ETBE is generally preferred when setting quotas for biogenic fuels. Existing MTBE plants are being converted to ETBE production.
The European gasoline standard EN 228 limits ethanol content 5 % by volume (E5). In America, approximately one third of all gasoline contains ethanol - up to 10% by volume (E10), for which a vapor pressure exceeding approximately 7 kPa is allowed according to the American standard ASTM D4814.
Currently, not all vehicles on the European market are equipped with materials that allow them to function with E10. The European standard for E10 continues to apply. To allow E10 fuel to be introduced on the German market, the E standard DIN 51626-1:2010-04 was issued in April 2010. It establishes, in addition to E10 specifications, requirements protecting the existing standard with a maximum ethanol content of 5% by volume for vehicles that are not E10 compliant. In Brazil, gasoline always contains 22-26% ethanol by volume.
Gasoline characteristics
Density of gasolines
The European standard EN 228 limits the density of gasoline to the range of 720-775 kg/m 3 . Because premium fuels generally contain a higher proportion of aromatic compounds, they have a higher density than high-octane gasoline and also have a slightly higher calorific value.
Anti-knock properties (octane number)
The octane number determines the knock resistance of gasoline (knock resistance). The higher the octane number, the greater the resistance to detonation. Isooctane has the greatest detonation resistance, its resistance is taken to be 100 units, the least is p-heptane, whose resistance is taken to be zero.
The octane number of the fuel is determined on a standardized test engine. The numerical value corresponds to the proportion (% by volume) of isooctane in a mixture of isooctane and n-heptane that exhibits the same knock resistance as the fuel that will be tested.
Research and motor methods for determining octane number
The octane number determined by research method testing is abbreviated as RON (research octane number). RON characterizes the detonation resistance of gasoline when used in engines operating under unsteady conditions (city driving). The octane number determined by motor method testing is abbreviated as MON (motor octane number). MON determines the fuel's knock resistance at high speeds.
The engine method differs from the research method by using preheated mixtures, higher engine speeds and variable ignition distribution, thus creating more stringent thermal requirements for the fuel when tested. MON values for the same fuel are lower than RON.
Increased detonation resistance
Normal (unrefined) straight-run gasoline shows low anti-knock properties. Only by mixing such gasoline with various detonation resistant refinery components (converted components) can a high octane fuel suitable for modern engines be obtained. Knock resistance can be increased by adding oxygen containing components such as alcohols and ethers.
Gasoline volatility
To ensure successful engine operation, gasolines must meet fairly stringent volatility requirements. On the one hand, automobile fuel must contain a large amount of highly volatile compounds to ensure reliable starting of a cold engine, but, on the other hand, there are restrictions on the volatility of the fuel so as not to impair the operation and starting of a warm engine. In addition, fuel losses due to evaporation, in accordance with current environmental regulations, must be kept to a low level. The volatility of gasoline is determined in various ways.
The EN 228 standard classifies the volatility of fuels into classes that differ in saturated vapor pressure levels and the dependence of the evaporation temperature on the vapor lock index VLI. Depending on local climatic conditions, European countries have developed their own national standards for the volatility of automobile fuel. Different evaporation values are established in the standards for summer and winter.
Gasoline distillation temperature
In order to evaluate the effect of the fuel, it is necessary to consider different distillation temperatures. The EN 228 standard defines the limit values established for the evaporated volumes of fuel at 70, 100 and 150 °C. table. The volume of evaporated fuel at 70 °C should be sufficient to guarantee easy starting of a cold engine (this was important for carburetor engines). However, the volume of fuel distilled at this temperature should not be too large, otherwise steam bubbles will form in the fuel on a hot engine. The volume of fuel distilled at 100°C determines the warm engine characteristics, which affect the acceleration and response of the engine when warmed to normal operating temperature. The volume of fuel distilled at 150°C must be high enough to minimize engine oil dilution. This is especially important for a cold engine, when poorly evaporated non-volatile components of gasoline can pass from the combustion chamber along the cylinder walls into the engine oil.
Saturated steam pressure
Vapor pressure, measured at 37.8°C (100°F), according to EN 13016-1, is a safety indicator at which fuel can be pumped from and into a vehicle's fuel tank. The saturated vapor pressure has limits specified in the technical requirements. In Germany, for example, this is a maximum of 60 kPa in summer and a maximum of 90 kPa in winter.
When designing a fuel injection system, it is also important to know the vapor pressure at higher temperatures (80-100 °C), since the increase in vapor pressure due to alcohol, for example, becomes especially evident at higher temperatures. If the saturated vapor pressure exceeds the injection pressure, for example due to an increase in engine temperature during vehicle operation, this can lead to malfunctions caused by the formation of vapor bubbles.
Fractional composition of gasoline
Based on the fractional composition, expressed in the relative volume of evaporated fuel, the tendency of the fuel to distillation is assessed.
A drop in pressure in the fuel system (for example, while driving a car at high altitudes), accompanied by an increase in fuel temperature, contributes to fuel evaporation and changes in the fractional composition, leading to worsening operating conditions. ASTM D4814 specifies, for example, for each volatility class, the temperature at which the vapor to liquid ratio should not exceed 20.
Vapor lock index
The vapor lock index (VLI) is a mathematically calculated sum of ten times the vapor pressure (in kPa at 37.8°C) and seven times the volume of fuel that evaporates at 70°C. By means of this additional limit value it is possible to limit the volatility of the fuel so that ultimately the maximum values of vapor pressure and end boiling point cannot be reached during fuel production.
Gasoline additives
Additives are added to improve fuel quality to counteract the deterioration of engine performance and exhaust emissions during vehicle operation. Additive packages are mainly used in combination with individual components with different characteristics. Extreme care and precision are required when testing additives and determining their optimal compositions and concentrations. Unwanted side effects should be avoided. Additives are typically added to individually labeled fuels at refinery filling stations when tank trucks are full (end state dosing). Adding additives to a vehicle's fuel tank exposes the vehicle to the risk of technical failure if the additives are incompatible with the vehicle's design.
Fuel system pollution inhibitors (detergent additives)
Automotive engine fuel supply systems (fuel injectors, starting valves) must be protected from contamination and sediment. Maintaining these systems in an uncontaminated condition is a prerequisite for safe engine operation and minimizing the content of toxic components in exhaust gases. To achieve this, special detergent additives are added to the fuel.
Corrosion inhibitors for gasoline
Ingress of external water/humidity can cause corrosion of fuel system components. Corrosion can be effectively eliminated by adding corrosion inhibitors, which form a thin protective film on the metal surface.
Oxidation stabilizers for gasolines
Anti-aging additives (antioxidants) are added to fuel to improve its stability during storage. These additives prevent rapid oxidation of fuel by atmospheric oxygen.
Diesel fuel
Fuel standards for diesel fuel
Requirements for diesel fuels in Europe are established by the EN 590 (2009) standard. The most important characteristics of diesel fuels are listed in the table. Even special brands of diesel fuels sold at some gas stations (for example, Super, Ultimate, V-Power) meet this standard. All of these diesel fuels have differences in their basic characteristics and additive composition. V-Power contains 5% by volume synthetic diesel fuel.
In accordance with EN 590 standard, in It is allowed to add up to 7% by volume of biodiesel (FAME - fatty acid-based methyl esters), the quality of which is provided for by EN 14214 (2009). The addition of biodiesel improves the lubricity of the fuel, but also reduces oxidative stability. In order to test oxidation stability, the EN 590 standard was amended in 2009 to include an aging margin parameter, measured as an induction period at 110 °C of at least 20 hours under test conditions defined by EN standards 15751.
The US diesel fuel standard ASTM D975 specifies fewer characteristics and sets less stringent limits. It allows the addition of a maximum of 5% by volume of biodiesel, which must meet the requirements of ASTM D6751.
Characteristics of diesel fuel
Cetane number and diesel index
The cetane number (CN) characterizes the flammability of diesel fuel. The higher the cetane number, the greater the fuel's tendency to ignite. Since a diesel engine operates without an externally supplied ignition spark, the fuel must ignite spontaneously (autoignition) and with minimal ignition delay when injected into hot air compressed in the combustion chamber. A cetane number of 100 corresponds to the highly flammable n-hexadecane (cetane), and a cetane number of 0 corresponds to the slow-flammable alpha-methylnaphthalene. The cetane number of diesel fuel is determined on a standardized single-cylinder CFR test engine (CFR - Joint Committee on Motor Fuels Research). The compression ratio is measured with a constant ignition delay. Comparison fuels containing cetane and alpha-methylnaphthalene are tested at specified compression ratios. The cetane content of the mixture is varied until the same ignition delay is obtained. The percentage of cetane determines the cetane number.
A cetane number greater than 50 is preferred for optimal performance in modern engines, especially during cold start conditions. High-quality diesel fuels contain a large percentage of paraffins with high cetane numbers. On the contrary, aromatic hydrocarbons have low flammability.
Another parameter for fuel flammability is the diesel index, which is calculated based on the density of the fuel and various points on the boiling curve. This purely mathematical parameter does not take into account the effect of cetane improvers on flammability. In order to limit the regulation of cetane number by cetane improvers, cetane number and diesel index have been included in the list of requirements of the EN 590 standard. Fuel whose cetane number has been increased by cetane improvers behaves differently during combustion in an engine, than fuel with the same natural cetane number.
Temperature range of changes in fractional composition
The temperature range of changes in the fractional composition of the fuel, that is, the temperature range at which the fuel evaporates, depends on the composition of the fuel. A low boiling point makes the fuel more suitable for use in cold climates, but also means a lower cetane number and poor lubricity. This increases the risk of wear on the injection system components. However, if the boiling point is high, this can lead to higher soot emissions and carbon deposits in the injector nozzles. This in turn causes deposits to form as a result of the chemical decomposition of non-volatile fuel components in the atomizer ports and well and the addition of combustion residues. When the boiling point is higher, fuel can flow through the cylinder walls and mix with the engine oil. Therefore, the percentage of non-volatile fuel components should not be too high. Limiting biodiesel addition to a maximum of 7% by volume is also due to its high boiling point (320-360 °C).
Diesel fuel filtration limit
Precipitation of wax crystals at low temperatures can cause the fuel filter to become clogged and ultimately cause a fuel shutdown. In the worst case, paraffin particles begin to precipitate at 0 °C or at even higher temperatures. The suitability of a fuel for use in cold weather is assessed by the "filtration limit" (CFPP). The European standard EN 590 regulates the CFPP value for various classes of diesel fuels, and, in addition, this limit value may be set by individual EU Member States, depending on the prevailing geographical and climatic conditions.
In the past, diesel vehicle owners sometimes added high-octane gasoline to the fuel tank to improve the diesel's cold performance. This practice is not required nowadays when the fuel is up to standard, and it could cause damage anyway, especially in high pressure fuel injection systems.
Diesel flash point
Flash point is the temperature at which the amount of fuel vapor accumulated in the atmosphere is sufficient to ignite the air-fuel mixture. Safety considerations (during the transportation and storage of fuels) dictate the need for diesel fuel to comply with the requirements of the Class A III “Hazardous Materials” standard, which specifies that the flash point must be above 55 ° C. Adding less than 3% gasoline to diesel fuel is sufficient to ensure that combustion of the combustible mixture can occur at room temperature.
Density of diesel fuel
The energy content of diesel fuel per unit volume increases with increasing density. Given the constant firing of the injectors (that is, the constant injection of a certain amount of fuel), the use of fuel with a density that varies widely causes a change in the mixture composition (a change in the excess air ratio λ) due to fluctuations in the calorific value of the fuel. When an engine runs on fuel that has a wide variation in density, this results in increased soot emissions; if the fuel density decreases, this parameter also decreases. Therefore, the requirements for low density variation of diesel fuel must be met.
Diesel fuel viscosity
Diesel fuel viscosity is a measure of the resistance to fuel flow due to internal friction. If the viscosity is too low, it results in increased fuel leakage losses, more heating of the injection system and an increased risk of wear and cavitation erosion. Excessive viscosity, such as occurs when using neat biodiesel (FAME), causes peak injection pressures at high temperatures in fuel systems such as electronically controlled unit injectors, compared to petroleum diesel. Conversely, the fuel injection system cannot develop acceptable peak pressure when using petroleum diesel fuel. High viscosity also changes the spray pattern due to the formation of large droplets.
Lubricity of diesel fuel
The lubricity of diesel fuels is important not so much for hydrodynamic friction as for mixed friction. The use of new hydrogenated and desulfurized diesel fuels with improved environmental characteristics leads to increased wear of high-pressure fuel pumps.
Desulfurization also removes fuel components that are important for lubricity. Special additives have to be added to the fuel to improve lubricity to avoid these problems. The EN 590 standard requires a minimum lubricity, determined by the diameter of the wear scar, which should be a maximum of 460 µm when tested on a high frequency reciprocating machine (HFRR machine).
Carbon deposit indicator
The carbon deposit index characterizes the ability of diesel fuel to form carbon deposits on the surfaces of the outlet of fuel injectors. The mechanism of soot formation is complex and cannot be easily described. Diesel fuel evaporation products have little effect on the formation of soot (coking).
General pollution
General contamination includes the total inclusions of insoluble foreign macroparticles in the fuel, such as sand, corrosion products, and insoluble organic components, including aging products of polymers contained in the fuel. The EN 590 standard allows a maximum total fuel contamination of 24 mg/kg. The hard silicates found in mineral dust are particularly destructive to high-pressure fuel injection systems with narrow spray holes. Even a fraction of particulate matter with an acceptable overall level of contamination can cause erosive and abrasive wear (for example, in solenoid valves). This type of wear causes valve leakage, which reduces injection pressure, impairs engine performance and increases particulate emissions. Typical European diesel fuels contain approximately 100,000 particulates per 100 ml. Particularly critical sizes of macroparticles are 4-7 microns. Therefore, high-performance fuel filters with good filtration efficiency are needed to prevent damage caused by particulate matter.
Water in diesel fuel
Diesel fuel can absorb approximately 100 mg/kg of water at room temperature. The solubility limit is determined by the composition of diesel fuel, its additives and ambient temperature. The EN 590 standard allows a maximum water content of 200 mg/kg in fuel. Although many countries have higher water content in diesel fuel, market research shows that water content rarely exceeds 200 mg/kg. Samples often do not detect water, or detection is incomplete because water settles on the walls in the form of undissolved “free” water, or it accumulates at the bottom of the fuel tank. While dissolved water is not harmful to the fuel injection system, it must be kept in mind that even a very small amount of free water over a short period of time can cause wear or corrosion damage to injection system components.
Diesel fuel additives
Additives to motor gasoline are also used for diesel fuel. Various substances are combined into additive packages to achieve multiple goals with one additive. Since the total concentration of the additive package in the fuel does not exceed 0.1%, the physical characteristics of the fuel - such as density, viscosity, and fractional composition - remain unchanged.
Lubricity additives
The lubricity of diesel fuels with poor lubrication properties, caused, for example, by hydration processes during desulfurization, can be improved by adding fatty acids or glycerides to the fuel. Biodiesel also contains glycerides as a by-product. In this case, if it already contains some kind of biodiesel additive, additives that improve lubricity do not need to be added to diesel fuel.
Additives that increase cetane number
Additives that increase the cetane number are alcohol derivatives of nitric acid esters, the addition of which leads to a reduction in ignition delay. These additives help, especially during cold starts, to prevent increased combustion noise (engine noise) and excessive smoking.
Flow additives
Flow improvers consist of polymeric materials that lower the filtration limit. They are mainly added in winter to ensure trouble-free operation of the engine at low temperatures. Although these additives cannot prevent the formation of wax crystals in diesel fuel, they can severely limit their growth. The size of the crystals formed becomes so small that they can pass through the pores of the fuel filter.
Detergent additives
Detergent additives clean the fuel supply system to form an effective working mixture; slow down the formation of deposits on the surfaces of the outlet of the fuel pump injectors.
Corrosion inhibitors
Corrosion inhibitors coating the surfaces of metal parts increase the corrosion resistance of metal elements of the engine fuel system.
Antifoam additives
Adding an anti-foam additive helps prevent excessive foaming of the fuel when the vehicle is quickly refueled.
In the next article I will talk about
.
Drivers have long been waging a kind of “information war” regarding the choice between diesel and gasoline on blogs and forums. Dilemma of choice, Which is better: diesel or gasoline is an eternal problem when buying a car.
What is diesel fuel?
Diesel fuel(or as it is popularly called “diesel oil”) is a liquid product that is used as fuel in a diesel engine. Diesel fuel is obtained by distilling oil from kerosene-gas oil fractions. It is a rather viscous and difficult to evaporate flammable liquid. It consists mainly of carbon, and also contains small percentages of hydrogen, oxygen, sulfur and nitrogen.
The scope of diesel fuel is quite wide. Its main consumers are trucks, water and rail transport, and agricultural machinery. In addition, residual diesel fuel (or diesel oil) is often used as boiler fuel, in cooling lubricants for mechanical and quenching fluids in the heat treatment of metals, and also for impregnating leather.
Types of diesel fuel and their characteristics
Diesel fuel is characterized by the following main indicators: depending on the nature of the application, a distinction is made between distillate low-viscosity diesel fuel for high-speed engines and residual, high-viscosity diesel fuel for low-speed engines.
If low-viscosity consists of straight-distilled kerosene-gas-oil fractions and up to 1/5 of cat-cracking gas oils, then viscous is a mixture of kerosene-gas-oil fractions with fuel oil. When distilling oil, three grades of diesel fuel are obtained:
A- Arctic.
Z– winter.
L– summer.
Characteristics of seasonal diesel fuel:
A – Arctic diesel fuel. It is used at ambient temperatures up to – 50 degrees Celsius. Its cetane number is 40, density at 20 degrees Celsius is no more than 830 kg/cubic meter, viscosity at 20 degrees Celsius is from 1.4 to 4 sq.mm/s, and the pour point is 55 degrees Celsius.
Z – winter diesel fuel. Winter fuel is used at ambient temperatures down to – 30 degrees Celsius. Cetane number of winter fuel is 45, density at 20 degrees Celsius is no more than 840 kg/cubic meter, viscosity at 20 degrees Celsius is from 1.8 to 5 sq.mm/s, pour point is 35 degrees Celsius .
L – summer diesel fuel. It is used at ambient temperatures up to 0 degrees Celsius and above. Its cetane number is not lower than 45, density at 20 degrees Celsius is no more than 860 kg/cubic meter, viscosity at 20 degrees Celsius is from 3 to 6 sq.mm/s, the pour point is 10 degrees Celsius.
What is gasoline?
- This is the lightest of the watery fractions of oil. This fraction is obtained, among others, in the process of petroleum sublimation in order to obtain various petroleum products. The usual hydrocarbon composition of gasoline is molecules in length from C 5 to C 10. However, gasolines differ from each other, both in composition and in properties, since they are obtained not only as a product of the primary sublimation of oil. Gasoline is produced from associated gas (gas gasoline) and from heavy fractions of oil (cracking gasoline).
Gasoline is a product of processing of associated petroleum gas, containing saturated hydrocarbons with more than 3 carbon atoms. Distinguish measured(BGS) and unstable(BGN) variants of gas gasoline. BGS comes in two grades - light (BL) and heavy (BT).
It is used as a raw material in petrochemicals, in organic synthesis plants, and also for compounding auto gasoline (producing gasoline with these qualities by mixing it with other gasolines).
Cracking gasoline is a product of additional oil refining. Ordinary distillation of oil produces only 10-20% gasoline. To increase its quantity, heavier or high-boiling fractions are heated to break up huge molecules to the size of the molecules that make up gasoline. This is called cracking. Fuel oil cracking is carried out at a temperature of 450-550°C. Thanks to cracking, it is possible to obtain up to 70% gasoline from oil.
Pyrolysis- this is cracking at temperatures of 700-800°C. Cracking and pyrolysis make it possible to increase the total gasoline yield to 85%. It is worth noting that the discoverer of cracking and the creator of the industrial plant project in 1891 was the Russian engineer V.G. Shukhov.
There are several types of gasoline:AI-72, AI-76, AI-80, AI-92, AI-95, AI-98. The first three types from the list have recently not been sold in Ukraine, due to the introduction of the Euro-3 gasoline standard in the country. The main debate revolves around the question “Which gasoline is better to refuel with, 92 or 95?”
By and large there is no difference. On the AI-95, the ride will be more confident and smooth. The difference in fuel consumption between these brands is quite insignificant - hundredths of a liter. Simply put, on the 95 you will drive a little more perky and more fun, on the 92 you will save money. Let’s not forget that AI-92 was sentenced in absentia to an untimely death due to the introduction of the Euro-4 standard in 2014. Now let's talk about AI-98.
The standard 98 engine is absolutely not needed. Moreover, by pouring gasoline of this brand into a regular engine, you can lose power and increase consumption. AI-98 is necessary for highly accelerated inflatable engines with high fuel detonation resistance.
What are the similarities and what are the differences?
Differences in the production of gasoline and diesel fuel. What is the difference between these two types of fuel, which are the main ones today and on which 90% of automotive vehicles worldwide operate? Both in their technical properties and in the production method, these two types of fuel have a number of differences. Diesel fuel has three stages of production.
First stage obtaining diesel fractions by heating petroleum feedstock and obtaining fractions at different temperatures.
On second stage The process of producing diesel fuel occurs directly by splitting (cracking) fractions. This is followed by the diesel hydrotreating process. At this stage, sulfur is removed from the resulting diesel fuel.
On third stage Additives are added to the resulting diesel fuel, thereby bringing the fuel to modern quality requirements, and also to obtain winter diesel, a dewaxing process is performed. The process of producing diesel fuel is quite complex, and only oil refineries equipped with modern equipment can produce fuel that meets all modern standards and is suitable for use in modern car engines. See also, maybe this will be useful to you.
The process of producing gasoline is similar to the production of diesel fuel. Also at the first stage, fractions are separated at different temperatures, after which gasoline fractions or so-called straight-run gasoline, which is unsuitable for use in modern engines, since this gasoline has an octane number of no more than 91 and has a high content of sulfur and aromatic hydrocarbons. Therefore, at the second stage, gasoline fractions undergo a reforming or cracking process to increase the octane number and produce commercial gasoline. Today, many gas stations offer for sale so-called branded fuel, gasoline or diesel with the addition of additives that improve the technical characteristics of the fuel and protect the vehicle’s fuel system from the effects of combustion products.
Advantages and disadvantages of each fuel
The debate between diesel drivers and drivers who prefer gasoline engines has been going on for a long time. The use of each of these types of fuel has its pros and cons, advantages and disadvantages.
Benefits of gasoline
Cars equipped with a gasoline engine are more maneuverable and dynamic. When driving in the urban cycle, on asphalt roads, such cars cope better with heavy traffic and emergency situations. A car running on gasoline, unlike diesel fuel, can start abruptly and brake sharply. In winter, in order to start the car, you only need gasoline and a spark. In addition, it is possible to warm up the gasoline engine while idling.
This is a highly flammable and fire hazardous substance, so when handling it you need to be extremely careful. In addition, gasoline vapors are very highly toxic and can cause poisoning. In rainy weather, the ignition circuit contacts may become damp due to increased humidity, making it impossible to start the car. Gasoline cars typically consume more fuel per 100 km than diesel cars. This problem can be solved to some extent by special fuel additives, which eliminate excessive consumption of gasoline and improve the environmental performance of exhaust gases.
Advantages of diesel
Diesel engines have a simpler design and are more stable. Due to fewer parts, troubleshooting is easier. In wet and rainy weather, a diesel engine starts much easier than a gasoline engine. It is advantageous to use diesel vehicles for off-road driving; in addition, the traction properties of a diesel engine are better. Fuel consumption per 100 km averages 6-8 liters, depending on whether you are driving on the highway or in the city. Diesel fuel is a more environmentally friendly substance and produces significantly less harmful emissions into the atmosphere than gasoline.
Disadvantages of diesel
If the air temperature drops below -5 degrees Celsius, summer diesel fuel crystallizes, which leads to clogging of fuel filters. To avoid this, it is necessary to use winter fuel and special additives for diesel fuel that prevent diesel fuel from thickening. In addition, repair and maintenance of diesel engines will cost you more than gasoline engines. Diesel fuel used to have an undeniable advantage over gasoline - lower cost. But in recent years, prices for these types of fuel have become equal. Therefore, the choice - a gasoline or diesel engine - must be based on future operating conditions and your own preferences.
conclusions
So, let's summarize. Each type of engine has its own disadvantages and advantages. Diesel engines have gained little demand and popularity in Ukraine and neighboring countries due to the low quality of diesel fuel. Perhaps the situation will soon change for the better, and cars with diesel power units will be as in demand as cars with gasoline engines.
Types of diesel fuel.
GOST R 52368-2005 “Euro diesel fuel. Technical Specifications” provides for the production of modern diesel fuel for temperate, cold and arctic climates of 6 grades, 5 classes and 3 types. This GOST is unified with the European standard EN590 and meets the requirements for Euro-3, Euro-4 and Euro-5 engines.
1. Temperate climate.
Fuel grades 6 types (A, B, C, D, E and F) of environmental fuel classes K4 and K5 (designation according to the technical regulations of the Customs Union) are provided for temperate climates, are characterized by the maximum filterability temperature (Table 1). The table shows data for 4 and 5 environmental fuel classes.
Table 1.
| Fuel grade | Ecological class according to TR CU | Limit filterability temperature, °C, not higher | Sulfur content, mg/kg, no more | Cetane number, not less | |
| K4 (type II) | |||||
| K5 (type III) | |||||
| K4 (type II) | |||||
| K5 (type III) | |||||
| K4 (type II) | |||||
| K5 (type III) | |||||
| K4 (type II) | |||||
| K5 (type III) | |||||
| K4 (type II) | |||||
| K5 (type III) | |||||
| K4 (type II) | |||||
| K5 (type III) |
Varieties A, B, C are summer varieties D, E, F – to transitional.
Filterability temperature refers to the temperature below which diesel fuel does not pass through a standard filter at the required flow rate.
2. Cold and arctic climate.
2.1. Diesel fuel for these climatic zones in accordance with GOST R 52368-2005 is produced according to classes 5 values (0, 1, 2, 3, 4), characterized by the maximum filterability temperature, cloud point and other indicators (Table 2).
Table 2.
| Indicators | Winter fuel classes | ||||
| Limit temperature of filterability, °C | |||||
| Cloud point, °C, not higher | |||||
| Cetane number, not less | |||||
| Kinematic viscosity at 40°C, mm 2 /s | |||||
| Density at 15°C, kg/m 3 | 800-840 | ||||
| Flash point in a closed crucible, °C, not lower | 30 | ||||
2.2. According to Table 1 of GOST R 52368-2005 and Appendix 1 to the technical regulations of the Customs Union, winter diesel fuel is classified as follows (Table 3).
Table 3.
2.3. An example of recording products when ordering and in technical documentation according to GOST R 52368-2005:
“EURO diesel fuel according to GOST R 52368-2005 (EN 590:2009)
— Grade A (B, C, D, E, F), type I (type II, type III);
— class 0 (1, 2, 3, 4), type I (type II, type III).”
Autotrans-consultant.ru.
Diesel fuel. Properties.
Due to a higher compression ratio, diesel engines consume 20-25% less fuel per unit of work performed than gasoline engines.
This advantage was the main reason for the widespread use of cars with diesel engines.
The main operational properties of diesel fuel are its volatility, flammability, pumpability, viscosity, cloud point, pour point, tendency to form deposits and soot, and its corrosive effect.
1. Diesel fuel volatility determined by fractional composition.
With a high content of light fractions, the rate of fuel combustion increases, but the engine operates more harshly due to a decrease in fuel viscosity. The boiling point (distillation) of 50% of the fuel characterizes its starting properties (using diesel fuel with a lower boiling point makes engine starting easier).
The boiling point of 95% of the fuel indicates the content of heavy fractions in it, which impair mixture formation and lead to incomplete combustion of the fuel.
2. Flammability– the ability of the fuel to ignite in the combustion chamber of the cylinder without the influence of an external ignition source.
Self-ignition of fuel injected into the combustion chamber does not occur immediately, but after a certain period, which is called auto-ignition delay period. During the auto-ignition delay period, the fuel pump continues to supply fuel to the combustion chamber. The longer this period, the more fuel accumulates in the cylinder at the time of self-ignition. This causes a sharp increase in pressure in the cylinder during self-ignition of the fuel, which is accompanied by dull knocks and often leads to premature wear of the bearings and crankshaft journals (the engine runs harshly).
To ensure normal engine operation, it is necessary to use fuels with an optimal ignition delay period, which is assessed by the cetane number. The cetane number is determined on a single-cylinder engine in the same way as the octane number, comparing the spontaneous ignition of the test and reference fuels. Two hydrocarbons were taken as reference fuels: cetane and alpha-methylnaphthalene. Cetane is flammable, its cetane number is taken to be 100; alpha-methylnaphthalene has poor self-ignition (cetane number is taken as 0 units).
3. Cetane number diesel fuel is numerically equal to the percentage (by volume) of cetane content in a mixture with alpha-methylnaphthalene, which is equivalent in self-ignition to this fuel.
The lower the cetane number, the longer the auto-ignition delay period. Therefore, the use of diesel fuels with a cetane number of less than 45 leads to harsh engine operation.
As the cetane number increases, the combustion process proceeds more smoothly, the engine runs more economically and less harshly. But with a cetane number of more than 50 units, the fuel in the cylinder ignites before it has time to spread throughout the combustion chamber and mix with air: as a result, incomplete combustion occurs, power decreases and fuel consumption increases.
4. Pumpability The flow of diesel fuel through the fuel system, mainly through coarse and fine filters, is assessed by viscosity, cloud point and pour point, content of mechanical impurities and water. Coarse filters retain mechanical particles larger than 50-60 microns, fine ones - larger than 2-5 microns.
5. The viscosity of diesel fuel largely determines the quality of fuel atomization and mixture formation.
Viscosity is regulated by current GOSTs for diesel fuel at a temperature of 20°C and is in the range of 1.2-6.0 mm 2 /s (s St).
Fuels with low viscosity atomize well, but if the viscosity is too low, they leak through the spray holes of the injectors, causing them to coke. Due to the insufficient range of the jet, the fuel concentrates and burns at the nozzle nozzle, without being distributed evenly throughout the combustion chamber. The result is heterogeneity of the mixture, deterioration of the combustion process and a drop in power. Low-viscosity fuel worsens the lubrication conditions for fuel equipment parts.
With increasing fuel viscosity, the quality of mixture formation deteriorates, because When spraying, droplets are formed that do not have time to evaporate. The fuel does not burn completely, its consumption increases, and smoky exhaust gases are observed.
For summer operation, the viscosity of diesel fuel should be in the range of 3.0-6.0, for winter operation 1.8-5.0 and for Arctic operation - within 1.2-4.0 centistokes (mm 2 /s).
6. Cloud point is the temperature at which diesel fuel becomes cloudy due to the release of crystals of solid hydrocarbons (paraffins) from the fuel. For normal operation of a diesel engine, the cloud point of diesel fuel must be 3-5°C below the ambient temperature.
7. Pour point is the temperature at which the fuel loses its fluidity. This temperature should be 10°C lower than the ambient temperature.
8. The tendency of fuel to form deposits and soot. When diesel fuel contains a significant amount of resinous deposits, heavy fractions and mechanical impurities, varnish-like compounds and carbon deposits form on valves, injectors and piston rings. They cause engine overheating, burning (coking) of piston rings, and clogging of the injector nozzle holes.
The tendency of diesel fuel to form carbon deposits is assessed by indicators of coking and ash content. Coking is the property of fuel to form carbon residues as a result of its calcination without air access. The lower the coking index, the higher the quality of the fuel. The ash content of the fuel should be no more than 0.01%, since ash is non-combustible and promotes increased carbon formation and causes increased wear of engine parts.
Autotrans consultant ru.
Diesel fuel is a liquid fuel and is intended for diesel and gas turbine engines. It operates: trucks, railway and certain types of urban transport, agricultural machinery, sea and river vessels. Recently, such engines are increasingly used in passenger cars. Such transport is of interest to buyers, since it requires cheaper fuel, the consumption of which is one third lower due to the high degree of compression of the mixture. In addition, this type of fuel is considered more environmentally friendly. The product is also used for space heating; mobile electric generators run on it.
Main operational characteristics of diesel fuel
The main characteristics of the fuel include cetane number, fractional composition, viscosity, degree of purity, and low-temperature properties. The cetane number in this list is the main indicator that demonstrates the degree of flammability of a combustible substance and reflects the period of time after which the fire occurred. The higher the number, the easier it is to start the engine, and the smoother it will run. A low indicator makes it difficult to start the engine and contributes to high smoke formation. A cetane number above 55 can cause uncontrolled engine acceleration.
The fuel must have optimal viscosity and density. If the consistency of the fuel is too thin, it will not provide the necessary lubrication of the fuel system parts, which leads to jamming and rapid engine wear. With high viscosity, it is more difficult to regulate the fuel supply. High-density fuel produces more energy. It is economical and efficient.
Types of diesel fuel
Summer fuel can be used at temperatures not lower than 0. It solidifies at -10 degrees. Typically, in our latitudes, this type of fuel is used from April to October. Its use in winter leads to cloudiness and the formation of paraffin crystals. When frozen, the fuel settles on the surface of the fuel system, resulting in the formation of carbon deposits. Self-ignition does not occur. At -5 degrees the substance becomes heterogeneous, paraffin flakes and small crystals appear. Fluidity is still observed, but the presence of dense components clogs the filters. At lower temperatures, the fuel has a gel-like state, it cannot be pumped, and an attempt to start the engine risks breaking the entire fuel supply system. Externally, it is impossible to distinguish between fuel types.
Winter fuel has a lower viscosity, since during production the paraffin fraction is removed from its composition. This technology is quite complex, which is reflected in the price of the product. Using special depressant additives, it is possible to reduce the size of paraffin crystals. This method is cheaper and allows you to reduce the temperature of summer fuel to -15 degrees. Winter products come in two types: for use at temperatures not lower than -20 degrees and for more severe winters - up to -35 degrees. For the conditions of the Far North, arctic fuel is produced, which can be used down to -50 degrees. Winter types are not intended for refueling the engine in summer, as this can cause a decrease in engine power and increased emissions of exhaust gases.
