MBD Simulation on a Piston Assembly
Aim:
To model and perform motion analysis with different piston positions
Introduction:
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod.
Components of a piston:
a. Piston Head
b. Connecting Rod
c. Gudgeon Pin
d. End Cap
e. Crank
Modelling and Assembly
1. Start by modelling the parts according to the given assembly file using functions such as Revolve, Mirror etc.
2. Import parts in an Assembly file and start assembling the model with appropriate mates.
3. The piston head should be mated in such a way that it moves only along the y axis. Crank should only rotate about its axis.
4. Assemble rest of parts accordingly.
Motion Analysis
For motion analysis we consider three cases
1. No offset
2. Negative offset of Piston
3. Positive offset of Piston
CASE 1: No offset
The piston and the crank axis are on the same axis with no offset
OUTPUT:
CASE 2: Negative Offset
The piston and crank axes are at an offset of -10mm.
OUTPUT:
CASE 3: Positive Offset
The piston and crank axes are at an offset of +10mm.
OUTPUT:
Comparing all outputs together by superimposing the graphs
Conclusions:
1. When the piston pin is in neutral position and the piston reaches top or bottom dead centre then the rod is straight up & down placing huge load on the rod. The crank has to rotate past TDC(top dead center) or BDC(Bottom Dead Centre) in order to get the piston moving again. This robs a lot of both power and RPMs from the engine.
2. Now with an offset pin, the piston wrist pin is a little offset to one side of the piston therefore the rod is not straight up and down when the piston is at TDC or BDC. This in turn allows the crank to rotate with much less resistance giving the engine more power and speed.
Google Drive Link:
https://drive.google.com/drive/folders/1Jdiz1c-1Kig84NBxRX24J4OmewY_zQH4?usp=sharing
Contains all parts and assembly.