MBD Simulation on a Piston Assembly
Aim: To study the motion analysis of piston assembly with different pin offset condition by modelling the piston assembly part.
Objective:
Plot the graph between linear displacement of piston head with time at different pin offset condition such as 10 mm negative, zero and 10 mm positive offset.
Theory:
Piston motion analysis is study of the reciprocating motion of the piston in the cylinder and motion of the piston assembly attached consist of connecting rod, end cap, crank and wrist pin.
Problem Statement:
Model all the parts and then assemble them in SolidWorks. The motion analysis is going to be carried out in three different conditions,
|
SR.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 - Run a simulation as seen in the video.
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.
Obtain the Linear displacement of the Piston Head in all the three cases. Then export the graphs into Excel. Then superimpose all the three graphs into a single graph.
- The part required for piston assembly are given bellow,
- Piston
- Connecting rod
- End cap
- Crank
- Wrist pin
- Piston: A piston is a compound of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinder, among other similar mechanism. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a connecting rod.
- Wrist pin: In internal combustion engines, the wrist pin connects the piston to the connecting rod and provides a bearing for the connecting rod to pivot upon as the piston moves.
- Connecting rod: A connecting rod is a rigid member which connects a piston to a crank or crankshaft in a reciprocating engine.
- End cap: End cap is connected to the end of the connecting rod, which is assembled crank.
- Crank: Is a mechanical part able to convert the reciprocating motion from the piston into rotational motion.
- Final Piston Assembly
The piston, connecting rod, wrist pin, end cap and the crank are assembled as shown in bellow figure using assembly mate option.
- Piston Assembly is shown in below link
https://drive.google.com/file/d/1bSPPz6LZvO1SVZ1_6wdP5HyuMLdytuym/view?usp=sharing
- Result
- Case 1:
Wrist offset = 0 mm
Crank speed = 2000 rpm
Output = linear displacement of piston head
- Case 2:
Wrist offset = 10 mm positive
Crank speed = 2000 rpm
Output = linear displacement of piston head
- Case 3:
Wrist offset = 10 mm negative
Crank speed = 2000 rpm
Output = linear displacement of piston head
- Superimpose of all the three graphs with three pin offset condition as shown below,
- Conclusion
- The Linear displacement graph is smooth for all the three cases of wrist pin offset for higher frames per second (FPS) with precise contact.
- When there isn’t any offset the piston displacement will be maximum than the offset condition as there is slight reduction in the piston displacement which is obvious since the piston has to travel a less distance because of offsetting because the connecting rod will not be straight at TDC and BDC because of 10 mm offset.
- Because of the wrist pin offset crank rotate with much less resistance giving the engine more power and speed.
- Superimpose of graph shows the increase in the piston displacement from negative to positive wrist pin offset.