MBD Simulation on a Piston Assembly
Aim:- Multi Body Dynamics Simulation on a IC Engine Piston Assembly.
Introduction:-
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors 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. 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. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder.
Theory:-
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 swiveling gudgeon pin. This pin is mounted within the piston unlike the steam engine, there is no piston rod or crosshead.
This type of piston is widely used in car diesel engines. According to purpose, supercharging level and working conditions of engines the shape and proportions can be changed.
Motion study setup:-
- First we will understand the basic concept of the IC Engine.
- Then According to the dimensions we will model all the parts and then assemble them in SolidWorks. The motion analysis is going to be carried out in three different conditions (or) cases mentioned below:-
|
Sl.No |
Wrist Pin Offset ` |
Crank Speed (Rpm) |
|
1 |
"0" mm |
2000 |
|
2 |
10 mm Positive |
2000 |
|
3 |
10 mm Negative |
2000 |
Wrist Pin Offset - The position of the wrist pin is going to be varied as followed. But the center of the axis of the piston head and the crank are coincident to each other i.e., They are on the same plane in all the three cases.
"0" mm Offset – we will run a simulation.
10 mm Positive Offset - If the crank rotation is in the Clockwise direction.
10 mm Negative Offset - If the crank rotation is in the Clockwise direction.
- Then we will obtain the Linear displacement of the Piston Head and observe the variation in graph in all the three cases.
Designed parts:-
fig.1.piston with zero offset
fig.2.piston with positive offset
fig.3.piston with negative offset
fig.4.End cap
fig.5.Connecting Rod
fig.6.Wrist Pin
fig.7.IC Engine Piston Assembly with zero offset
fig.8.IC Engine Piston Assembly with positive offset
fig.9.IC Engine Piston Assembly with negative offset
simulation setup:-
- First we will design all the components and assemble it
- And then we will provide required degress of freedom i.e., we will constraint the components.
- Then we will conduct a motion analysis for all the given cases.
- And we will add motor and we will set rpm as 2000 and select the precise contact option.
- And we will add contacts between the components and we will add gravity in 'Y' direction and
- We will set the frames per second as 8000 i.e., in order to get a nice plot for each degree of revolution.
- And then we will plot the Linear Displacement of the Piston Head in all the three cases.
Video of IC Engine Piston Assembly with zero offset:-
Video of IC Engine Piston Assembly with positive offset:-
Video of IC Engine Piston Assembly with negative offset:-
Linear Displacement plot for zero offset:-
Linear Displacement plot for postive offset:-
Linear Displacement plot for negative offset:-
Explanation:-
In this above plots we can see the Linear diplacement of the piston head and for each degree of rotation the graph varies with each and every frame and due to the offset we can also see a slight variation of the graphs.
Google Drive link for CAD files:-
https://drive.google.com/drive/folders/15ez73wKTuhpi59jeSoSzrJnvQJg-qcnJ?usp=sharing
Conclusion:-
Hence we have successfully completed the Multi Body Dynamics of IC Engine Piston Assembly and determined the Plots for Linear Displacement.