MBD SIMULATION ON A PISTON ASSEMBLY

Objective:

1. To model and assemble internal combustion piston assembly
2. To carry out motion analysis using Solidworks.
3. To study the effect of wristpin offset on the linear displacement of the piston.

Introduction:

Piston motion analysis:

Piston motion analysis is the study of the reciprocating motion of the piston in the cylinder and the motion of the assembly attached i.e. connecting rod, end cap, crankshaft & wrist pin. First of all for the assembly of a connecting rod, crankshaft, end cap, wrist pin, and the piston itself, we will prepare the geometric model of all the necessary components.

Procedure :

1. 3d modelling as per dimensions.
2. assembly by proper mates
3. providing motor at the crank with 2000 rpm
4. carry out motion analysis and modify piston for wristpin offset and repeat analysis
5. plot linear displacement vs time for a piston for all cases.

We have to design all the different parts of the cylinder-piston arrangement separately. The parts are as follows :

Piston Head

Gudgeon Pin (Wrist pin)

Connecting rod

End Cap

Crank

Modelled all the parts and then assembled them in SolidWorks. The motion analysis carried out in three different conditions,

Sl.No	Wrist Pin Offset `	Crank Speed (Rpm)
1	"0" mm	2000
2	10 mm Positive	2000
3	10 mm Negative	2000

Case 1: Motion Analysis for "0" mm Offset:

Case 2: Motion Analysis for 10 mm positive Offset

Case 3: Motion Analysis for 10 mm Negative Offset

Superimposed graph:

Here linear displacement graph from each case is exported to excel and then superimposed there.

Observation and conclusion:

1. From the plots obtained, we can see that Linear Displacement increases as we move from negative wrist pin offset to positive wrist pin offset i.e. the magnitude of the Linear displacement increases.
2. Also from the graph obtained after superimposing it, we can see that for a given time-frequency of rotation of piston with wrist pin offset negative is higher compared to one with zero offsets and pin with zero offsets has a higher frequency than one with a positive offset.