Piston Assembly simulation using SolidWorks (Multi-body Dynamics)

Aim:

To model a piston crank assembly in solidworks using the given dimensions and to perform motion analysis on the assembly using SolidworksMotion Add-in. Plot the final linear displacment of piston with 3 different orientations as asked in a line graph.

Objective:

1. Model the parts required for assembly
2. Assemble the modeled components as per required
3. Perform motion analysis for 3 different congigurations of piston offset

Model Wrist pin offset Rpm

0 mm 2000

2 -10mm 2000

3 10mm 2000

Theory:

A piston crank assembly is uesd to convert a rotory motion into a reciprocating single line motion. As the crank rotates the piston moves linearly to perform the reciprocating motion. The connecting rod transfers motion from crank to piston via gudgeon pin.

This mechanism has four parts:

• The crank is attached to a motor that rotates it.
• The Connecting rod is attached to the crank and the piston at joints that are free to rotate.
• The guide is fixed in place; its purpose is to make the piston move in a line. The piston is free to move up and down in a line but cannot rotate.

This mechanism is widley used in Automobile engines , Reciprocating compressors and radial or gnone engines.

Model:

Piston:

Connecting rod:

Gudgeon pin:

Crank:

End-cap connecting rod:

Assembly:

Plots

piston with 0 mm Wrist-pin offset :

with negetive 10 mm Wrist-pin offset

with Positive 10mm Wrist-pin offset:

Superimposed plot:

Observations:

the above plot gives the comparison of linear displacments of the pistons woth the 3 given orientations from the data collected it is evident that the orientation with zero offset will have more linear displacment aswell as largest stroke length. But, when there is no offset the crank has to provide more effort to drive past the TDC and BDC of the engine this consumes lot of power. When an offset is given the piston it does not reach its TDC and BDC hence, crank drives piston with much less effort saving power and fuel.

Conclusion:

The motion analysis is performed for the piston assembly for the required orientations and observations are made for their respective linear displacments.