MBD Simulation on a Piston Assembly
AIM : MBD simulation of a piston assembly.
OBJECTIVE OF THE PROJECT:
Our main objective is to design a 3D model for various parts of the piston assembly, simulate it and plot the graph. Also to model different wrist pin offset which are:
1. 0mm offset at 2000 crank rpm.
2. 10mm positive offset if crank is rotating in clockwise direction.
3. 10mm negative offset if crank is rotating in clockwise direction.
ABOUT PISTON ASSEMBLY :
Piston assembly consist of piston, wrist pin , connecting rod, end cap of connecting rod and crank.
1. Piston - Piston has always linear motion. The power produce in the engine during power stroke forces the piston to move downwards imparting linear motion to it. The designed 3D model of piston is given below:
2. Wristpin - It is the component which connect piston and connecting rod. It is connected rigidly to the piston but can move freely inside the connecting rod.The 3D modelis given below:
3. Connecting rod and end cap - They are the component which converts linear motion of the piston into rotary motion of the crank. Its one end is connected to the piston amd other end is connected to the crank.End end is connected to the conncting rod with the help of bolts and between them crank is fitted. The 3D model is giveen below:
End Cap:
Crank - This component transmit the power produced in the engine to the wheel of the vehicle. It is connected to the one sidde of the connecting rod. The 3D model of the crank is :
Offset : It is the linear distance provided so that two component are at some distance apart.
Offset to the wrist pin :
1. 0mm offset-
2. 10mm negative offset and crank is rotating in clockwise direction:
3. 10mm positive offset and crank is rotated in clockwise direction:
OUTPUTS:
1. For 0mm offset.
2. 10mm negative offset:
3. 10mm positive offset:
Superimposing all the plot into one graph:
Link for the animation :
RESULTS:
1. When the piston pin is in the centre of the piston i.e 0 mm offset and piston reaches top or bottom dead centre then, in the rod is straight up and down placing huge load on the rod. The crank has to rotate past TDC or BDC in order to get the piston moving again. This takes a lot of both power and RPMs from the engine.
2.When a offset is provided positive or negative 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. Due to this stress is less in the connecting rod when it is at TDC or BDC
CONCLUSION :
- I have designed the components of the piston assembly successfully .
- I have obtained the plots for various conditon successfully.