Compression carburetor engine - a type of piston carburetor internal combustion engine in which the ignition of the fuel-air mixture occurs from high temperature when it is compressed.
Fuel is, as a rule, a mixture of diethyl (medical) ether , kerosene and castor oil in equal proportions. Fuel supply, as a rule, by gravity from the fuel tank .
In compression model engines, the carburetor is usually the simplest - just one nozzle with a screw needle is enough to control the fuel supply. Some models, for example, MK-17, had a replaceable diffuser ; with a small diameter - for beginner aircraft models, with a larger one - for more experienced ones. An engine with a small diffuser developed lower revs and power , an inexperienced “pilot” trained on a lower-speed “aircraft”. Purge - crank chamber with a rotating disk spool . Silencer and air filter are missing.
The compression ratio is regulated by a counter piston - a movable piston located in the cylinder head, which changes the volume of the combustion chamber . The counter piston is moved by a screw located in the cooling jacket of the cylinder and is fixed with a lock nut against spontaneous eversion.
Compression carburetor engines operate on the Otto cycle.
In the English-speaking technical tradition, compression carburetor engines are often called diesel engines, although compression and diesel engines have different operating principles, different designs, and no contribution of Rudolf Diesel to their design is known. [Note 1]
In compression carburetor engines, during the compression stroke, the fuel-air mixture is compressed in the cylinder, that is, a stoichiometric air mixture with fuel vapors prepared in the carburetor, and the ignition moment and fuel composition are selected so as to ensure smooth combustion of the air-fuel charge (all at once!) With maximum efficiency (that is, with a peak of combustion at 35-45 ° rotation of the crankshaft from TDC). Since the absolute volume of the combustion chamber is very small, and the operation of the compression engine occurs in a long steady state without changing the speed and torque, such adjustment is possible.
The compression ratio in compression engines is lower than in diesel engines.
Thus, compression engines are not diesel engines, since not the fuel-air mixture is compressed in the cylinders of the diesel engines, but clean air, and then at the end of the compression stroke, the diesel engine’s high pressure fuel pump injects diesel fuel through the nozzle into the cylinder, where it it ignites from heated to high temperature air and does not burn immediately, but as it is injected   .
The engine was started by sharp blows (sharp turning) by the fingers of the hand over the propeller (it is advisable to wear a solid leather glove). At the same time, the fuel supply and the compression ratio were regulated. After starting, the engine was adjusted to maximum speed [Note 2] . By moving the counter piston, they achieve stable engine operation at maximum speed.
Two -stroke engines “MK-16” and “MK-17” (displacement of 1.5 cc), “MK-12V”, “MARZ”, “Rhythm”, “KMD-2.5” ( working volume 2.5 cubic cm). They were installed on models of airplanes , cars , ships .
On car models, the engine is connected to the wheels through a reduction gear ; clutch , gearbox and final drive are generally absent. To perform forced air cooling, an axial fan is put on the motor shaft.
As of 2005, compression engines of the MDS series with various displacement were produced in Russia.
- In internal combustion engines with an electric ignition system, under certain conditions, it is possible to ignite the fuel-air mixture not from a spark , but from the red-hot elements of the combustion chamber - candle electrodes. carbon particles, etc. - self-ignition. In an engine designed for electric ignition at a certain moment, this process is undesirable: combustion occurs unevenly, power drops, the engine continues to work even after the ignition is turned off for some time (this is possible only in carburetor engines, and injection phenomena are unlikely during operation and completely impossible after switching off ignition). This phenomenon is often confused with detonation, sometimes it is incorrectly identified even in the technical literature.
- According to the passport, about 12-15 thousand revolutions per minute
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