MBD Simulation on a Piston Assembly
AIM:
To create all the part and perform the motion analysis on Piston assembly by using SOLIDWORKS.
THEORY:
PISTON ASSEMBLY
Piston assembly consists of a piston, piston rings and piston pin known as gudgeon pin. Functions of piston assembly are given below:
- It transmits gas force generated during combustion to the connecting rod and crankshaft.
- As piston is connected to small end of the connecting rod with the help of gudgeon pin. It guides the connecting rod when gas force is transmitted.
- Air/fuel mixture is compressed by piston.
- Piston rings restrict the flow of hot gases into the crankcase. This is also referred as blow by control.
- Piston rings lubricate the cylinder wall.
- Piston rings restrict the amount of oil from crankcase into the gap between piston and cylinder head.
- Heat is transferred to the cylinder wall from piston by piston rings.
PISTON
Piston top is the part of combustion chamber. Top portion can be a flat or bowl is provided as per the combustion requirement. Grooves are provided in the ring belt area to accommodate piston rings. The heat flows from crown, out of the ring belt. Heat is transferred to the cylinder walls through piston rings and then small portion is transferred to the skirt. Some amount of heat is also taken by the lubricant.
PISTON RINGS
There are two types of piston rings: compression and oil control ring. Piston rings are generally made up of rectangular section. To prevent sticking of ring into the groove, their inner and outer edges are chamfered. Compression rings are subjected directly to gas pressure.
Gudgeon Pin or piston pin
Gudgeon pin is the main load carrying part in piston assembly. Small end of the connecting rod is connected to piston with the help of gudgeon pin. It consists of aluminum pads are placed at the ends; these will not damage the cylinder. In order to maintain a correct fit between piston and connection rod, external surfaces of gudgeon pins are finished to a high degree of accuracy.
CONNECTING ROD
The main function of a connecting rod is to form a link between a piston and crankshaft. A small end of the connecting rod is connected to the piston with gudgeon pin and big end is separated into two parts for ease of assembly with crankpin. The two parts of the big end are bearing cap and big end housing. Both are being bolted together. This is done for ease of assembly of connecting rod with crankpin. To supply oil to the big end, the oil hole is drilled from big end.
CRANKSHAFT
Crankshaft is the final link in the slider crank mechanism. The linear motion of a piston is converted into rotary motion of a crankshaft. The energy is generated into the combustion chamber by transforming the reciprocating motion of a piston into rotary motion of a crankshaft. Crankshaft consists of two main bearings at the other side of it, made up in to two half liners. Crankshaft, crankshaft oil seals, main bearings, pulley and vibration damper are parts of crankshaft assembly.
INPUTS:-
|
Sl.No |
Wrist Pin Offset ` |
Crank Speed (Rpm) |
|
1 |
"0" mm |
2000 |
|
2 |
10 mm Positive |
2000 |
OBJECTIVES:
- To create all part of piston assembly.
- To assemble all part.
- To perform motion analysis and obtain the plot for linear displacement of piston head.
PROCEDURE:
First create piston head by using sketch , revolve, fillet , extude and extruded cut tool. The piston head as shown in the figure below:
Now we have created connecting rod by using sketch(circle and line tool), extrude, extruded cut, fillet options. The connecting rod as shown below:
Now we have created end cap as shown on figure below:
Then we have created Gudgeon pin as shown below:
And at last we have created crank as shown below:
Now we have created all the parts then we go to the Assembly first import Crank and make it float and then import another part one by one and by using various concident and distance mate we have created the assembly of piston. The assembly of piston as showh in figure below:
Now we go to solidworks add inns and select solidworks motion and se up the motion analysis, set motor at 2000RPM and FPS as 7200, Enable precise concact then set up contact, and at last set gravity in Y-direction and run the calculation.
The drive link for each part and assembly file of Piston assemblyare shown below:
PLOTS:
CASE-1
|
Sl.No |
Wrist Pin Offset ` |
Crank Speed (Rpm) |
|
1 |
"0" mm |
2000 |
Piston head Linear displacement plot
CASE-2
|
Sl.No |
Wrist Pin Offset ` |
Crank Speed (Rpm) |
|
1 |
"10" mm Positive |
2000 |
Piston head Linear displacement plot
ANIMATION
Animation for case-1
Animation for case-2
CONCLUSION:
The motion study helpful in simulating the performance of the Piston assembly and also gives outline of the model for better output. we have also seen the variation of piston linear displacement in each of the two cases.
REFRENCES: