MBD Simulation on a Piston Assembly

AIM:

Design and motion analysis of 'IC ENGINE PISTON ASSEMBLY' using solidworks.

THEORY:

PISTON: A piston is a moving disk enclosed in a cylinder which is made gas-tight by piston rings. The disk moves inside the cylinder as a liquid or gas inside the cylinder expands and contracts. A piston aids in the transformation of heat energy into mechanical work and vice versa.

CONNECTING ROD: A connecting rod, also called a con rod, is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the crankshaft. The connecting rod is required to transmit the compressive and tensile forces from the piston, and rotate at both ends.

CRANK: A crankshaft is a rotating shaft which (in conjunction with the connecting rods) converts reciprocating motion of the pistons into rotational motion. Crankshafts are commonly used in internal combustion engine and consist of a series of cranks and crankpins to which the connecting rods are attached

WRIST PIN: In internal combustion engine, the wrist pin or gudgeon pin connects the piston to the connecting rod, and provides a bearing for the connecting rod to pivot upon as the piston moves

OBJECTIVE:

The main objective of the project are:

1. Making CAD MODEL of all the compenents and performing motion analysis of the piston assembly for three cases like no offset,positive offset ad negative offset of wrist pin.
2. Obtaining plots for linear displacement of the piston head in the three cases mentioned.
3. Superimposing the three graphs in excel and comparing them.

PROCEDURE:

1)Initially we make 2-D drawings of all the components with mentioned dimensions and then convert them into 3-D models by using extrude command.The screenshot of isometric view of all the CAD MODELS are shown below.

Isometric view of 3-D CAD MODEL of piston:

Isometric view of 3-D CAD MODEL of connecting rod:

Isometric view of 3-D CAD MODEL of end cap:

Isometric view of 3-D CAD MODEL of wrist pin:

Isometric view of 3-D CAD MODEL of crank:

2)After finishing with all the cad model of the compnents we open assembly and insert all the compnents in assembly file one by one and then give them the desired mates and complete the piston assembly.The isometric view of 3-D cad model of piston assembly is shown below.

3)After finishing with assembly we do the motion study analysis for the piston assembly.

MOTION STUDY ANALYSIS:

1. First select solidworks motion from solidworks add-ins.Then click on motion analysis from the drop down list at the left bottom corner.
2. After that apply motor of 2000 rpm to the crank axis.
3. Then apply 4 contact pairs between (Crank-End Cap) , (Crank-Connecting Rod) , (Piston-Wrist Pin) and (Connecting Rod-Wrist Pin).
4. After that apply gravity in Y direction.
5. After that select motion study properties and from that type frames per secod as 12000 and click on precise contact.
6. After doing all this click on calculate and wait for the calculation to get over.
7. Then click on results and plots and then plot the graph of linear velocity v/s time of the piston head for all the three cases ad export that to excel spreadsheet.
8. At last we make the animation of all the three cases.
9. The output plot for all the three cases are shown below.

CASE 1: NO OFFSET OF WRIST PIN.

OUTPUT PLOT:

The plot of linear displacement v/s time of piston head shows us sinusoidal behaviour having it's maxima and minima at specific points.

The animation link of case 1 is provided below.

https://youtu.be/2P2pEGYsKBw

CASE 2: POSITIVE OFFSET OF 10 MM OF WRIST PIN.

OUTPUT PLOT:

The above plot is also similar to the previous one but there is slight difference in the extreme values due to the offset provided betwee wrist pin and crank.

The animation link of case 2 is provided below.

https://youtu.be/fEcCWz_PBhE

CASE 3: NEGATIVE OFFSET OF 10 MM OF WRIST PIN.

OUTPUT PLOT:

The negative offset plot also shows the sinusoidal wave but difference exists in the crank angle at which the piston reaches its maximum or minimum.

The animation link of case 3 is provided below.

https://youtu.be/IzX-Az7uvbs

After getting plots for all the three cases we superimpose all the three plots in a single plot.The superimpose plot is shown below:

CONCLUSION:

1. Thus we have made 3-D cad models of all the components and their assembly was also done.Also the motion analysis of the piston assembly was done and thier plots were also obtained.
2. The motion study shows that when the wrist pin is not provided with any offset, the piston reaches TDC and BDC making the connecting rod straight which place a huge load on the rod so less power is generated from the engine.
3. When offset of 10mm in positive and negative side is provided the rod is not straight while reaching TDC and BDC so less load is placed on the rod which helps us to generate more power.

REFERENCES:

https://x-engineer.org/automotive-engineering/internal-combustion-engines/ice-components-systems/internal-combustion-engine-piston/

https://en.wikipedia.org/wiki/Piston

APPLICATION AND USES:

In reciprocating engines,steam engine etc.

THE LINK FOR SOLIDWORKS PARTS,ASSEMBLY FILE AND EXCEL PLOT IS GIVEN BELOW:

https://drive.google.com/drive/folders/1eSmw4FndEhhHPN2axxoImrTIbxOE-R7e?usp=sharing