4.7.3.a Gasoline engine piston
In gasoline engines, the piston top has a flat surface and thick walls with internal ribs that increase its strength and provide good heat dissipation. However, in modern gasoline engines, the piston top has a more complex shape: starting from grooves for valves and ending with a very complex shape, which is necessary for better mixture formation while using direct fuel injection into the cylinder.
Grooves for installing O-rings are located on the side surface of the piston. Two piston rings and one oil scraper ring (it consists of three elements, see figure 4.27) are installed in modern engines.
Note
There are specific names for separate piston surfaces. Thus, the upper surface, which directly perceives all the loads from expanding gases during combustion of the fuel-air mixture, is called the piston top, and the side vertical surface is called piston skirt.
Figure 4.27 Piston with piston rings
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