MBD Simulation on a Piston Assembly
AIM:
The aim of this study is to find the linear displacement of piston assembly with zero,10mm negative and 10mm positive offset cases.
Parts required for piston assembly :
Piston:
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings.
Wrist pin :
In IC engines the Gudgeon pin (wrist pin) connects the piston to the connecting rod, and provides a bearing for the connecting rod to pivot upon as the piston moves.
Connecting rod and End cap:
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.End cap is a part of connecting rod.
END CAP
Crank :
A crank is an arm attached at a right angle to a rotating shaft by which reciprocating is imparted to or received from the shaft. It is used to convert circular motion into reciprocating motion, or vice versa. The arm may be a bent portion of the shaft, or a separate arm or disk attached to it. Attached to the end of the crank by a pivot is a rod, usually called a connecting rod.
FINAL ASSEMBLY
MBD STUDY:
For motion study the following steps are considered,
1.Motion analysis is selected.
2.Motor is given to the axis of the crank with 2000 rpm
3.Frames per second is given as 7200 with precise contact.
4.Contacts are given between end cap-crank,crank- connecting rod,connecting rod-wrist pin,wrist pin-piston.
5.Gravity is considered for this motion analysis.
6.Time for motion analysis is around 1 sec.Linear displacement of piston head is obtained with respaect to time.
Condition for Motion analysis:
| 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.
Case 1:- 0mm offset
Case 2:- positive 10mm offset
Case 3:- negative 10mm offset
Comparison of all the linear displacement plots on a single graph:
Conclusion:
thus we created the model ans done thwe motion analysis .The Motion Analysis of the Piston Assembly helps us to assess the working of a Slider-Crank Mechanism. Providing Offset offers much less resistance leading to more engine speed and power. It also helps to relieve the stress induced in case the Piston reaches the Top Dead Centre (TDC) and the Bottom Dead Centre (BDC).With offset, the stroke of piston is reduced. This can be used to slightly alter the piston kinematics in an engine.The horizontal lag has no significance since the time period is still the same.Offsetting might prevent the mechanism from locking in a toggle position since the force on connecting rod will never be in line with it. This can make the engine self-starting.