MBD Simulation on a Piston Assembly

Aim:- To model all the parts and assemble and do motion analysis of Piston assembly.

Theory:-

A slider-crank linkage is a four-link mechanism with three revolute joints and one prismatic, or sliding, joint. The rotation of the crank drives the linear movement the slider, or the expansion of gases against a sliding piston in a cylinder can drive the rotation of the crank.

There are two types of slider cranks

1. Inline:- The axis of crank and gudgeon pin are in same plane.
2. Offset:- The axis of crank and gudgeon pin are in different planes with some offset.

Part models:-

Features used:- Revolved boss, Extrude cut, Mirror, Linear pattern, Fillet.

Piston Connecting rod with end cap crank gudgeon pin

Assembled models:-

Mates used:- Concentric mate, Coincident mate, Parallel mate, Distance mate.

Zero offset Positive offset Negative offset

Motion Analysis:-

• First the rotary motor is set at the axis of crank and rpm of 2000 is set.
• Then the solid body contacts are given and material is selected.
• Then the motion analysis is calculated and required plots are obtained.

Case 1:- '0' mm Offset

• Linear Displacement of Piston Head.

Case 2:- 10 mm Positive Offset

• Linear Displacement of Piston Head.

Case 3:- 10 mm Negative Offset

• Linear Displacement of Piston Head.

Comparision of all three cases (Superimposed plot)

Conclusion:-

From the above plot we can conclude that

• The time taken by piston to travel from TDC to BDC and BDC to TDC are equal in case there is no wrist pin offset.
• But in case of wrist pin offset, the time taken by piston to travel from TDC to BDC and BDC to TDC is varying.
• In case of positive offset, the time taken to travel from TDC to BDC is lesser than from BDC to TDC.
• In case of negative offset, the time taken to travel from BDC to TDC is lesser than from TDC to BDC.

(TDC - Top dead centre, BDC - Bottom dead centre)

Project related links:-

Solidworks CAD files

Youtube link