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Piston mechanism of reciprocating combustion engine

**Library:**Simscape / Driveline / Engines & Motors

The Piston block represents the piston mechanism of a reciprocating combustion engine. The Piston block accounts for the instantaneous torque transmitted to the engine crankshaft, which enables you to simulate vibrations in the drivetrain due to piston revolution. To model a multi-piston engine, use the Piston Engine block.

Port **B** represents the translating piston and port
**F** represents the rotating crankshaft. The piston force follows
from the cylinder pressure and cross-sectional area. The block obtains the combustion
pressure from a lookup table parameterized in terms of the crank angle and, optionally,
the crank angular velocity and engine throttle level.

The crank torque follows from the piston force and crank angle, the crank and connecting rod lengths. In terms of these inputs, the ratio of the piston force and crank torque is

$$\frac{{T}_{\text{F}}}{{F}_{\text{B}}}=-\text{c}\left(sin(\theta )+\frac{sin(2\theta )}{2\sqrt{{\left(\frac{\text{r}}{\text{c}}\right)}^{2}-{\mathrm{sin}}^{2}(\theta )}}\right),$$

where:

*F*is the instantaneous piston force associated with the base port._{B}*T*is the instantaneous crank torque associated with the follower port._{F}*c*is the crank length.*θ*is the instantaneous crank angle.*r*is the connecting rod length.

**Piston Dimensions**

Port **T** lets you specify the engine throttle level as a fraction between
0 and 1. This fraction corresponds to the percentage of full power generated. The block
uses the data at point **T** whenever the pressure lookup table in the
block dialog box is parameterized only in terms of the crank angle.