MBD Simulation on a Piston Assembly
Aim
In this project, we're going to create a 3d model of a piston assembly and perform mbd simulation. MBD analysis was done for three different cases at 2000 rpm, 12000 frames with precise contact, and generated plots of linear displacement for the same.
The criterion we'll be using here is the giving offset to the wrist pin and observe the displacement of the piston.
Introduction
Piston assembly motion is a type of reciprocating motion that has been seen in many places and is most common in automobile vehicles. This is the list of components used in a piston assembly and we are going to analyze based on the different offset positions of a wrist pin.
Components Used
Piston head: It is the upper part of the assembly which is used in conjugation with the cylinder and helps to transfer the forces for the expansion of gas using the rotary motion of cam. Moreover, piston grooves are used for piston rings which help to get easier compression, leakproof expansion, and compression.
wrist pin: It is a hollow shaft that is used to connect the piston with the connecting rod.
Connecting rod: It is the component used in an IC assembly and acts as a link between piston and crank. It is used to transmit linear motion into rotary motion. It is designed on the basis of tension, compression, buckling, and bending.
Endcap: It is used to connect the connecting rod with a crank.
Crankshaft: It is the component with which we transmit the reciprocating motion into the rotary motion.
We've designed each of the components and assembly in Solidworks.
Components model:
1. Piston Head
- Wrist pin
3. Connecting rod
4. Endcap
5. Crank
6. Final Assembly
After providing the given constraints based on different motion and dimensions, this assembly was made.
The mbd analysis has been done on this system for the given condition.
|
S.No |
Wrist pin offset |
Crank Speed (rpm) |
|
1. |
0mm |
2000 |
|
2. |
10mm positive |
2000 |
|
3. |
10mm negative |
2000 |
Wrist pin offset- In this case the position of the wrist pin is going to be varied according to the given condition. However, the center of the axis of piston and crank will remain coincident with each other, that is They are on the same plane in all three cases.
For the motion analysis, we'll go for the following steps
- Selected the motion analysis.
- ROTATION OF 2000RPM is given to the axis of the crank.
- Contacts are being defined for the various parts.
- Taking gravity into account for the motion analysis.
- Obtaining linear displacement results.
- Import the graphs in excel to superimpose at the end for comparison.
RESULTS:
Case 1: 0mm offset with motor input in the clockwise direction.
Linear displacement Plot:
The linear displacement for the piston varies between 200-300mm w.r.t time and graph is more accurate because fps was set to higher values.
Case 2 10 mm positive offset
Linear displacement Plot:
Case 3 10 mm negative offset
Linear Displacement Plot:
Superimposed Plot: This plot was made using Ms-excel.
where green represents no offset condition
blue represents positive offset condition.
Orange represents a negative offset condition.
Observation & conclusion: 1. The graphs are smooth and uniform in nature.
2. 0mm offset is the condition in which piston has to travel the least distance but it makes the stress to be higher compared to offset conditions.
3. There is some offset in the graph, that is because of the reason that as the offset is provided which makes the piston to travel more and due to which it doesn't exactly same as for 0mm case in linear displacement.
4. Providing offset helps to reduce the stress on the pin due to which stresses in the connecting rod also decrease and the system can generate more output/ power for the same conditions.
5. Even offsetting a wrist pin helps to improve the noise characteristics of the piston assembly.
Animation Link: https://drive.google.com/file/d/1W9Liv3IHjKivN-jkVB_TFVKCgTjThBkg/view?usp=sharing