UTD-20 battle tank engine

When the piston moves from top dead center to bottom, the volume above the piston increases, and the pressure in the cylinder becomes below atmospheric. Outside air is forced into the cylinder through the open intake valves.

For better filling of the cylinder with a fresh charge of air, the intake valves open before the piston reaches the TDC. in the cycle of release (20 °), and closes after passing the NMT in the compression stroke (48 °).
The duration of the intake is 248 ° in the angle of rotation of the crankshaft (in the exhaust stroke - 20 °, the intake itself - 180 ° and compression - 48 °).

Despite the fact that the piston moves from bottom dead center to top dead center (during the period when the valves are open and before they are closed), fresh air enters the cylinder:

- in the compression stroke due to the inertia of the jet;
- in the exhaust stroke, he is carried away by the flow of exhaust gases.

Compression begins when the intake and exhaust valves close as the piston moves from bottom dead center to top dead center.

Fresh air entering the cylinder is compressed in a continuously decreasing volume of the above-piston space. The air at the end of the stroke is compressed to a pressure of 36–39 kgf / cm². The air temperature during compression rises to 550-600 ° C.

With the position of the piston at 24-27 ° before the TDC in the above-piston space diesel fuel is injected in a finely atomized form. The stroke ends when the piston reaches top dead center.

Due to the high temperature of the compressed air, the fuel injected into the combustion chamber ignites spontaneously. After the piston passes the top dead center, the gas pressure during fuel combustion increases sharply to 80-90 kgf / cm², and the temperature - up to 1800-1900 ° C.

The piston under gas pressure moves to the bottom dead center, acting through the connecting rod on the crankshaft crank and performing the only working stroke of four - the working stroke. As a result of expansion, the pressure of the gases decreases to 2.5-3 kgf / cm², and the temperature drops to 700-800 ° C. Thus, the thermal energy created by the combustion of gases. is converted into mechanical energy of piston movement.

The release of exhaust gases from the cylinder starts from the moment the exhaust valves are opened, i.e. when the piston position is 48 ° BC. in the stroke of the working stroke.

The cylinder is cleaned of combustion products:
- when the piston moves to N.m.t. in the stroke of the working stroke due to the pressure difference in the cylinder and the surrounding atmosphere (the pressure in the cylinder at the moment of opening the exhaust valves is 2.5-3 times higher than atmospheric);
- as a result of the expulsion of the exhaust gases by the piston moving towards the engine compartment. in the cycle of release;
- due to the inertia of the flow and its displacement by fresh air when the intake valves are opened in the intake stroke, when the piston moves from top dead center to bottom.

The duration of the release of the exhaust gases is 248 ° in the angle of rotation of the crankshaft (in the stroke - 48 °, forced exhaust - 180 °, in the intake stroke - 20 °).

From the beginning of the intake (20 ° before TDM) to the end of the exhaust (20 ° after TDM), i.e., within 40 ° along the angle of rotation of the crankshaft, the intake and exhaust valves are simultaneously open. In this range, which is called valve overlap, the cylinder is purged, which contributes to better cleaning of residual gases and better filling with fresh air charge.