MBD Simulation on a Piston Assembly

AIM:

MBD Simulation of a Piston Assembly.

OBJECTIVES:

1. Performing Motion Analysis of the Piston Assembly in No Offset, Positive Offset, and Negative Offset condition of the Piston
2. Obtaining Plots for Linear Displacement of the Piston Head in the three cases mentioned.
3. Superimposing the three graphs in excel to compare the diagnostics of the cases.

SIMULATION CASES:

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

THEORY:

Internal combustion engines

The internal combustion engine piston sectioned to show the gudgeon pin. The internal combustion engine is acted upon by the pressure of the expanding combustion gases in the combustion chamber space at the top of the cylinder. This force then acts downwards through the connecting rod and onto the crankshaft. The connecting rod is attached to the piston by a swiveling gudgeon pin (US: wrist pin). This pin is mounted within the piston: unlike the steam engine, there is no piston rod or crosshead (except big two-stroke engines).

Parts and Assembly:

Piston-

Connecting Rod-

End Cap of Connecting Rod-

Gudgeon Pin-

Crank:

Assembly:

Results and Plots:

CASE-1:

0 mm Offset pin

CASE-2:

10 mm Positive offset pin

CASE-3:

10 mm negative offset pin

Comparison of all three plots:

Conclusion:

The Motion Analysis of the Piston Assembly helps us to assess the working of a Slider-Crank Mechanism. Providing Offset offers much less resistance leading to more engine speed and power. It also helps to relieve the stress-induced in case the Piston reaches the Top Dead Centre (TDC) and the Bottom Dead Centre (BDC).

1. Omm, offset piston pin has piston displacement range from 230mm to 330mm.
2. Positive 10mm piston pin offset has piston displacement range from 202mm to 302mm.
3. Negative 10mm piston pin offset has piston displacement range from 202mm to 302mm.

The upper limit of piston displacement is reduced (from 330 to 302) and lower limit displacement increase (from 230 to 202) with 10mm offset of piston pin because of same length of connecting rod, a vertical displacement between the upper surface of piston head centre and rotating crank pin.

Animation:

https://youtu.be/2qqCWj3119o

Reference:

https://en.wikipedia.org/wiki/Piston#Piston_engines