MBD Simulation on a Piston Assembly
Aim: MODELLING AND SIMULATION OF PISTON KINEMATICS IN SOLIDWORKS AND DO MOTION STUDY TO FIND ANGULAR VELOCITY AT DIFFERENT CONDITION.
Introduction:
What is Piston Kinematics?
: Piston Kinematics will show the movement of the piston inside the cylinder with or without an offset of a wrist pin. This is very helpful to find the linear displacement of the piston and which then can be used for various purposes such as friction losses and life of the piston and its other component.
Application:
It is used in various applications starting from the IC engine to pumps. As it converts the circular motion into linear motion.
Design:
Below are the screenshot attached for the 3D model design. (ref: Skill-Lync)
GIVEN:
Solidworks Part Design Procedure:
For each part, open Solidworks and select new part and also select the unit system mm. Moreover, all extrude are midplane extrude except one. (This is very important to maintain consistency in part and it will be useful while doing the assembly)
Part 1
The open new part, select front plan and select line to draw, now draw a line from the center in a shape of half T, as shown below;
Once you drew this, exit the sketch and use revolve extrude open about the right plan. Now draw a small rectangle at the top corner (any corner) of the sketch or face as shown below;
After drawing this rectangle and defining it fully, use the cut revolve option and make the cut, then you will have the one cut around the piston surface as shown in the above screenshot. Now to make more patterns, use linear patterns, and select the right plan or draw a construction line from the center and select the pattern direction and show 3 patterns.
After this draw a circle vertical to the center and at a distance of 40mm (opposite- Y-axis) as shown below and use cut extrude as shown below;
Now select the right place and draw anther sketch, use three-point arc as shown below;
Now to lay a place for wrist pin, draw a circle on the same axis as for the extrude cut circle and now use the extrude option with an offset of 30mm with till next surface option and click ok. Now to replicate the same to the other side use the mirror option, select the surface and right plane and click OK. At last, fillet the sharp edges of arc cut as shown below with 10mm, and save the part.
Part 2- Connecting Rod
Draw 2 circles at the center and 2 more circles away from the center but on the same horizontal line and define these circles with given dimensions, now draw a mid-point line at the bigger circle and trim the lines as to get the below symmetry, now again draw from the outer circle to other outer arc and give the dimensions as shown below, and last give the fillet to the line endpoint as given dimension and exit the sketch.
Now extrude the given sketch fro 30mm.
Now select the flat surface of arc solid and draw a sketch, as shown below and extrude the same;
And also use extrude cut from the same center for 11.25mm, to get the bore.
At last, use the fillet for corer and some sketch geometry as shown below; and save the part.
Part 3- End Cap
Draw a sketch as shown below;
And extrude the sketch for 30mm, now
Draw a circle on the flat face of the part and use extrude option in the direction against the flat face as shown below;
And after extrude, draw a small circle of 11.25mm and use the extrude cut to get the bore.
At last use fillet of 2.7mm for the corner line and some symmetry as shown above. And save the part.
Part 4- Crank
Draw 2 arc at distance from each one bigger than other and both arcs are facing each other as shown below in the picture and then draw a line connecting each point of arc as shown and now give the dimensions to define the sketch;
And now draw 2 circles as shown and as given;
And extrude the 2 circles outwards from the surface (bigger circle for 16mm and a smaller circle for 20mm).
Now select the right plan and draw to arc the end surfaces of extruding as shown in the picture to get the desired shape, and use the extrude cut to get the shape as below;
Now use the mirror command for the right plan and save the part;
Part 5 –Wrist Pin
Draw 2 circles of 25.40mm and 5.50mm and extrude the sketch, after extruding use chamfer of 2.5mm at 45deg, as shown below; and save the part.
Assembly:
Go to new and select assembly and insert first part crank, and then use below mate;
Now insert connecting rod and end cap and use below mates;
Now insert piston head and wrist pin and use below mates;
And then save the assembly but before doing so just check all the parts are well constrained that is they are no moving in an unnecessary direction.
Motion Study:
| 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 - 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.
Now go to SOLIDWORKS ADD ONs and select SOLIDWORKS MOTION
Now select the MOTION ANALYSIS for the motion study.
Input Speed to crank axis (Clockwise) = 2000 rpm.
For all the motion study the contact will stay the same and the input speed will be given to the same axis i.e. crank.
Note: Time shown may vary for each study as I had to manually stop the simulation/motion study.
1 Task:
Wrist Pin "0" mm Offset
As the piston is constrained with a wrist pin and piston is also constrained with a crank and connecting rod, I will have to change one mate condition or parameter to get the output for three tasks, i.e. the above mate, for the 00mm offset, I have used coincident mate.
Plot:
The plot is plotted with Linear Displacement (mm) against time as shown below. The plot is showing the data for piston head face;
As we can see in the plot, the linear displacement in mm and it goes from 202 till 302 and it maintains the displacement over time. The motion is true with fluctuation but it is insignificant or we can neglect it.
- Task:
Wrist Pin "0" mm POSITIVE
As the piston is constrained with wrist pin and piston is also constrained with crank and connecting rod, this I will have to change one mate condition or parameter to get the output for three tasks, i.e. the above mate, for the 00mm offset, I have used distance mate of 10mm.
Plot:
The plot is plotted with Linear Displacement (mm) against time as shown below. The plot is showing the data for piston head face;
As we can see in the plot, the linear displacement in mm and it goes from 203 till 302 and it maintains the displacement over time. The motion is true with fluctuation but it is insignificant or we can neglect it.
- Task:
Wrist Pin "10" mm Offset NEGATIVE
As the piston is constrained with wrist pin and piston is also constrained with crank and connecting rod, this I will have to change one mate condition or parameter to get the output for three tasks, i.e. the above mate, for the 00mm offset, I have used distance mate of 10mm (Flip Direction).
Plot:
The plot is plotted with Linear Displacement (mm) against time as shown below. The plot is showing the data for piston head face;
As we can see in the plot, the linear displacement in mm and it goes from 203 till 302 and it maintains the displacement over time. The motion is true with fluctuation and it also has noticeable difference.
Result and Explanation:
I have examined and observed the differences between three motion studies as we can see in one plot; and I could understand 2 studies have shown almost identical results i.e. the 0mm and the 10mm positive; at least that is what I can see from the naked eye or from the plot. However, these changes will certainly have an effect on the motion of position and its wear and tear and at last the life of the part. The linear displacement doesn’t affect that much as it is constrained with the length. For the last study, i.e. 10mm negative, I can see the noticeable difference not is displacement but displacement with respect to time as it is different in time as compared to rest 2 studies.
Although, the linear displacement shows us the displacement of the piston along the plane is assigned to but the difference in the wrist pin (offset) will definitely have effect if we examine it on the micro-scale as it will define the life of the part in contact with piston head.
Errors or issues I faced:
Fortunately, none for the assignment.
Reference: