MBD Simulation on a Piston Assembly

MBD Simulation on a Piston Assembly

Aim:

Model all the parts and then assemble them in SolidWorks. The motion analysis is going to be carried out in three different conditions,

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

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.

1. To Obtain the Linear displacement of the Piston Head in all the three cases.
2. Then export the graphs into Excel.
3. Then Superimpose all the three graphs into a single graph.

Solution:

3D Modelling of the parts:

1) Crank: It is the first primary part of the engine system to which the energy is given in rotary motion.

2) Connecting rod with end cap: It forms the connection between the crank and the piston head. Undergoes two different motion (radial and axial partially) to convert rotary into linear motion.

3) Wrist/Gudgeon pin: This acts as a connection between the connecting rod and the piston head. It is responsible to take up the force from the connecting rod and impacts it to piston head.

4) Piston: This is the major part responsible for combustion. It imparts high pressure energy on the particles through its linear motion.

Assembly of Piston:

Setting up of Motion Study:

1. Motor is placed to the axis of crank at an RPM of 2000

2. Solid Contacts has been established between the parts which have contact between them.

3. Gravity is imparted in the Y downward direction.

Results:

Case 1 : 0mm offset- Linear Displacement of Piston

Case 2 : 10 mm positive offset- Linear Displacement of Piston

Case 3 : 10 mm negative offset- Linear Displacement of Piston

Inference:

From the above plots it is very clear that there is not much of difference in linear displacement of piston when the pin is offset. However, if the graph is noticed at the top peak, it shows that the travel and starting position varies.

The objective to provide offset is to prevent direct impact loads when 0 offset is given. It greatly reduces the stress induced to the components.