Fuel for aircraft engines, recipes

Basic chemical composition of diesel fuel

Diesel fuel consists of a set of certain chemical elements:

• paraffin hydrocarbons (10-40% of the composition);
• naphthenic hydrocarbons (20-60% composition);
• aromatic hydrocarbons (15-30% of the composition).

The composition may contain additional elements: resinous, sulfur compounds, water, mechanical impurities.

Paraffin hydrocarbons (alkanes, petroleum paraffins) are a mixture of solid carbons containing a maximum number of hydrogen atoms and carbon atoms in the molecule in the amount of 18-35. Present in all natural liquid minerals - methane, oil, propane - and their derivatives. Susceptible to cracking.

Naphthenic hydrocarbons (cycloalkanes) are cyclic saturated hydrocarbons characterized by the cyclic structure of atoms in their molecules. In the petroleum products from which diesel fuel is produced, homologues of cyclohexane and cyclopentane are found predominantly. Present in all petroleum products, except gaseous substances.

Aromatic hydrocarbons (arenes) are organic cyclic compounds. They are characterized by an aromatic system: the arrangement of six carbon-hydrogen groups at the corners of a molecular hexagon. This phenomenon is called benzene ring. Prone to substitution reactions. Present in many end products obtained by processing petroleum fractions.

Fuel for two-stroke glow engines

The standard fuel composition contains: 20% oil and 80% methyl alcohol.

This fuel can be used on all brands of two-stroke engines. If the engine is well adjusted and the compression is correctly selected, then such fuel does not require additional additives. To improve engine starting and increase speed, you can add 2-3% nitromethane. However, this is not recommended in hot weather; such an additive can lead to overheating of the engine and failure of the operating mode. Many engines are specifically designed for fuel containing 2-5% nitromethane. Without such an additive, these engines will be difficult to start and achieving good and stable speeds from them will be problematic. Large volume two-stroke engines (15-35 cc) require a large amount of nitromethane, approximately 5-15%. As for the oil content, it must be at least 20%, otherwise you may damage the engine.

Instead of castor oil or in place of it, you can use synthetic oils for two-stroke engines, soluble in alcohol. Castrol M oil, produced for racing boats, has proven itself very well. When using such oils, the optimal fuel proportion will be as follows:

• 10% castor oil
• 10% synthetic oil
• 80% methyl alcohol

The nitromethane content of this composition depends on the type and brand of your engine.

If you decide to use oil from another brand, check its solubility in alcohol. Add one or two drops of oil to a small amount of alcohol; if the oil has taken the form of small balls and settled to the bottom, then such oil is not suitable and should not be used.

Synthetic oils have much better properties compared to castor oil. Such oils burn completely when the engine is running, leaving a thin, non-drying film on its surfaces. When the engine runs on synthetic oil, virtually no carbon deposits form on the piston, and the exhaust gases do not contain oil waste. The only drawback of synthetic oils is their high price and availability in stores.

Many companies selling aircraft model products sell individual fuel components, thereby giving you a choice of components.

What determines the chemical composition of diesel fuel?

The ratio of hydrocarbons of a certain group to the total mass of fuel, which means the overall composition of diesel fuel, depends on many factors:

• Oil production locations. A product from one region will have 20% alkanes, while in another region the figure will increase to 40%.
• Oil distillation temperatures. During heat treatment, many chemical substances enter into reactions of decomposition, substitution, addition, etc.; the composition of the product and its properties change.
• Active additives. Dispersion additives are added to the finished diesel fuel, which change its characteristics and also affect the final composition of the diesel fuel.

The main thing on which the ratio of fuel components depends is the initial composition of the oil from which it is produced.

Why is a prechamber needed in an engine?

The prechamber is a preliminary combustion chamber into which part of the total charge of the fuel-air mixture is supplied, where the fuel is ignited. The volume of the prechamber is about 30% of the total volume of the main combustion chamber. The purpose of this solution is to improve the filling of the cylinders, more efficient organization of gas flows in the main chamber, as well as improve the quality of mixture formation.

This scheme allows for a smoother and more uniform increase in pressure in the main combustion chamber, which reduces shock loads in the internal combustion engine cylinders.

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Engines with a pre-chamber operate more smoothly and fully burn the fuel-air mixture, reducing exhaust toxicity, increasing efficiency and reducing fuel consumption.

Recipes for fuel mixtures for compression engines.

The following mixture is considered the standard fuel composition for compression model aircraft engines.

• Mineral oil MK-8 33.3%
• Ethyl ether 33.3%
• Technical kerosene 33.4%

There are also many fuel recipes for compression microengines. I will give just a few recipes.

I have always used the standard fuel recipe, which is presented above, but I got even better results using a fuel composition where I used castor oil and MS-20 in equal parts. I used this composition on a 4 cm3 OS MAX 25FP engine.

This recipe is recommended by the site's editors if you find it difficult to choose a fuel mixture. It definitely won’t do any harm, and even with a stuck couple, the engine will run.

• Aircraft oil MS-20 16%
• Castor oil 17%
• Ethyl ether 33.3%
• Technical kerosene 33.3%

To obtain more power, amyl nitrite is added to the fuel mixture.

• Mineral oil MK-8 33.3%
• Ethyl ether 33.3%
• Technical kerosene 33.4%
• Amyl nitrite 2.5%

Or

• Castor oil 28.5%
• Ethyl ether 41%
• Technical kerosene 28.5%
• Amyl nitrite 2%

You can read more about fuel compositions in the book “Model Engines”

Demand for pre-chambers

The prechamber makes it possible to control air masses; it is installed directly in front of the cleaning system. For example, a prechamber in an electric locomotive is a small room through which air is filtered and later, through the ventilation system, enters the cars, where air conditioners use it. In other words, thanks to this, pre-filtered air enters the system.

The room provides the possibility of dividing air masses into channels. If you need the air to be warm, a thermostat is installed there, which allows you to regulate and control the temperature of the air flows. In winter, ventilation systems in trains and large rooms are used as a heating system. In this case, a radiator will not be needed: special grilles are installed in the air flow channels, and this is enough for complete control over the premises.

If necessary, the air in the prechamber can be subjected to technical treatment, for example, sanitary treatment. The device is used for closed and semi-closed ventilation systems, taking into account their large area. The laying of such a room occurs during the construction of the building, but if it does not exist, the pre-chamber can be completed or an empty room can be turned into it.

Basic auxiliary systems of a gasoline engine

Systems specific to gasoline engines

• Ignition system - ensures that the fuel is ignited at the right time. It can be contact, contactless or microprocessor-based. The contact system includes: switch-distributor, coil, ignition switch, spark plugs. A non-contact system includes the same equipment, but instead of a breaker there is a Hall sensor or an induction sensor. The microprocessor ignition system is controlled by a special computer unit; it includes a crankshaft position sensor, an ignition control unit, a switch, coils, spark plugs, and an engine temperature sensor. For an injection engine, a throttle position sensor and a mass air flow sensor are added to this system.
• The air-fuel mixture preparation system is a carburetor or an injection system.

Features of prechambers

Any modern climate system used in everyday life requires the presence of such a device. Thus, a prechamber is used in airplanes, swimming pools, trains, and is used on ships to supply fresh air to the cabins. You can read about the ventilation system on an airplane here.

To understand, it is worth considering the operation of the device using the example of a typical room; in fact, it works the same everywhere. The air conditioning system has several blocks - external and internal, both of which are quite complexly organized. In order to create optimal conditions in the room, various filters and other units are provided, the work of which is aimed at creating the desired microclimate. However, if the room is large, a conventional air conditioner will not be able to cope with its task.

• High-quality noise insulation. The prechamber and the rest of the system operate quite loudly;
• Correct calculation of fan operation, too high air flow speed creates drafts, and this is inappropriate for shopping centers;
• If the equipment is installed in a work shop, on the contrary, powerful engines will be required, since a powerful air flow is needed here that can remove all contaminants to the street through the valve;
• Temperature control. Powerful air currents, depending on thermal conditions, can change the microclimate of the room, so it is important to balance everything in the right proportions.

Diesel engine

1. rocker shaft;
2. outer bearing support;
3. water pump with thermostat housing;
4. camshaft;
5. intermediate plate of the timing cover;
6. timing chain;
7. timing cover;
8. mounting flange of the high pressure fuel pump (HPF) gear;
9. outer bearing support bolt;
10. nozzle with spray;
11. mounting an oil filter with an oil cooler;
12. crankshaft needle and roller bearing;
13. oil pump with oil intake.

Other types of engines running on motor gasoline

The key property of motor gasoline is its versatility. This is an energy source that can drive devices of various types and purposes. Most often it is used in such units:

• Small vehicles: motor boats, speedboats. While for large vessels diesel fuel is more appropriate.
• Wheeled vehicles other than automobiles. This group includes snowmobiles, all-terrain vehicles, ATVs, motorcycles and other types of equipment powered by an internal combustion engine.
• Construction and agricultural equipment. Motors running on gasoline are used in many devices: asphalt vibrators, chainsaws, brush cutters, etc.
• Generating installations. Despite the fact that in most cases the requirements for the efficiency of electric generators are better met by diesel fuel, gasoline units are also quite popular, especially when it comes to backup power installations.

The scope of application of motor gasoline directly depends on the brand of the product, quality, as well as other technical characteristics. For example, in the cold season it is possible to use only fuel with special additives that ensure stable ignition at low temperatures.

Engine manufacturers specify which type of fuel is properly suited for the engine. When operating power units, it is important to strictly follow these recommendations.

Content

• 1 Classification of gasoline engines
• 2 Duty cycle of a gasoline engine 2.1 Duty cycle of a four-stroke engine
• 2.2 Duty cycle of a two-stroke engine

Engine flushing and preservation

After completing the flights, the engine and model must be cleaned of residual fuel and traces of exhaust! The fuel contains caustic substances, which can lead to engine corrosion and damage the model's casing. For long-term preservation of the engine, it is necessary to disassemble and thoroughly wash all engine parts in methyl alcohol. After this, lubricating all parts with synthetic oil, assemble the engine. This procedure will help protect your engine from prolonged exposure to metal from fuel residues, and you will also be able to check its technical condition.

Prechamber-torch ignition system

The main elements that make up a diesel engine with a prechamber are:

Note: we will go through the path along with the fuel in order to fully understand the principle of operation of the prechamber engine.

1. The channel leads diesel fuel into the antechamber.
2. Then there is a section intended for the over-enriched mixture.
3. The valve of the prechamber itself.

4. The spark plug performs its main role (igniting the fuel when the injectors inject it).
5. At the same time that the fuel ignites from a spark, the timing distribution admits fuel into the main chamber by opening the valve.
6. Now the fuel is at the finish line - in the central chamber of the internal combustion engine.

Now, we hope, it has become clear to you how a pre-chamber diesel engine works and what the pre-chamber structure consists of.

Fuel for four-stroke glow engines

As for fuel for four-stroke engines, it differs from standard fuel only in the nitromethane content. Almost all four-stroke engines are designed to use fuel with a nitromethane content of at least 15%. This is due to the fact that the gas distribution system of these engines is designed for a certain octane number of the fuel used. Accordingly, nitromethane in fuel is a mandatory condition. The use of castor oil in these engines is undesirable. As a rule, such engines are equipped with a direct injection system and a fuel pump, which have many very thin bypass channels. All these channels become clogged very quickly with hardening castor oil, which leads to problems when starting the engine.

In most cases, the fuel of a four-stroke engine consists of:

• 20% synthetic oil
• 55% methyl alcohol
• 25% nitromethane

It is not advisable to run a four-stroke engine with fuel without nitromethane! Severe detonation can lead to failure of the timing mechanism and other mechanical engine parts.