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Reciprocating combustion engine with variable number of pistons

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

The Piston Engine block represents a reciprocating combustion engine with multiple cylinders. The piston model accounts for the instantaneous torque transmitted to the engine drive shaft. The instantaneous torque enables you to model vibrations in the drivetrain due to piston revolution. To model just the piston mechanism of a combustion engine, use the Piston block.

Port **B** represents the translating piston and port
**F** 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 as well as 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**

Physical signal 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 physical signal input whenever the pressure lookup table in the block dialog box is parameterized only in terms of the crank angle.