MBD Simulation on a Piston Assembly

Aim: - To model all the parts of Piston assembly and then assemble them in solidworks and do the motion analysis for different offset conditions

S. No .	Offset distance (mm)	Crank speed (rpm)
1.	0	2000
2.	10 mm positive	2000
3.	10mm negative	2000

Theory

A piston is a component of reciprocating engines,reciprocating pumps , gas compressors and pneumatic cylinders , among other similar mechanisms.In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder.

An 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 swivelling gudgeon pin .

Parts

• Piston
  • File : - Aman_piston

• Gudgoen pin
  • File : - Aman_gudgeon_pin

• Connecting rod
  • File : - Aman_connecting_rod

• End cap
  • File : - Aman_end_cap

• Crank
  • File : - Aman_crank

Piston Assemble

Motion setup

• Add a motor with 2000rpm to the axis of crank
• Add solidbody contact between all the parts and select material as steel
• Add gravity in negative "y" direction
• Change motion property to 12000 frames per second with precise contact

NOTE : - For calculation of each crank angle with rotation of 2000rpm we should be used 12000 frames per second with precise contact in motion study properties , but it will increase our calculation time so we have calculation for only 0.2sec .

"0" mm offset

• Assembly
  • File : - Aman_piston_assembly

• Animation : -
  • Animation link : - https://youtu.be/Iv5mJUA0kGw

• Linear displacement of the Piston Head

10 mm positive offset

• Assembly
  • Assembly file : - Aman_piston_assembly_positive_offset

• Animation
  • Animation link https://youtu.be/-gfBCPq0o6M

• Linear displacement of the Piston Head

10mm negative offset

• Assembly
  • Assemble file : - Aman_piston_assembly_negative_offset

• Animation
  • Animation link https://youtu.be/xrVGaqy9f1o

• Linear displacement of the Piston Head

• Superimpose all the three graphs .

Observation and conclusion

The piston displacement is decreased if we give offset in any direction beacuse in offset condition the connecting rod is inclined at TDC(top dead centre) and BDC(bottom dead centre) position . This inclination of connecitng rod at TDC and BDC benifits the piston assembly because when piston is straight at TDC or BDC a lot of stress is developed in the connecting rod as there is only vertical a force acting on it and it has to change its direction from moving upwards to moving downwards or vice versa , but when the connecting rod is in inclined position at TDC and BDC there is a horizontal force also which helps it to move smoothly and reduce the stress developed in the pistion . The frequency of piston displacement also decrease due to offset but frequency in positive offset is decrease by a small amount as compared to frequency decrease in the negative offset