MBD Simulation on a Piston Assembly

AIM: To perform the MBD analysis of an IC Engine Piston Assembly

TASKS:
• Model each component required for the assembly
• Perform the assembly
• Perform the MBD analysis for
o 0 offset of wrist pin
o +10 mm offset of wrist pin
o -10 mm offset of wrist pin
• Obtain plots of linear displacement of the piston head

THEORY:

A piston crank assembly is an arrangement that is used to convert linear motion of the piston to a rotary motion of crankshaft.
Wristpin offset is the displacement provided to the axis of wrist pin from the axis of the crank, in a parallel direction. This has advantages, which have been discussed in the results and discussion section.

PART MODELS:
• Crank

• Piston

• Wrist pin

• Connecting rod

• End cap

• Final assembly

TOOLS USED:
• Line
• Circle
• Rectangle
• Smart dimension
• Constraints
• Fillet (2D and 3D)
• Extrude
• Revolve
• Extrude cut

MATES:

RESULTS AND DISCUSSION:

1. Case 1: 0 Offset

We observe that the crank has a linear displacement between 200-303mm for this case.
2. Case 2: +10mm offset

We observe that the crank has a linear displacement between 200-302mm for this case.

3. Case 3: -10mm offset

We observe that the crank has a linear displacement between 200-302mm for this case.
4. Combined graph

Series 1: -10mm offset
Series 2: +10mm offset
Series 3: 0mm offset
Providing such an offset would increase the clearance volume by `pi.r^2`(r-bore of cylinder) times and would decrease the load acting on the crankshaft when in the piston reaches TDC (known as piston slap). Hence it is better to provide an offset to the piston for free movement of the piston throughout its operating range. Such an offset would reduce the noise, vibration and harshness from the engine.