MBD Simulation on a Piston Assembly

REPORT ON SIMULATION OF PISTON KINEMATICS USING SOLIDWORKS

Created by Shahbaaz khan deoda

On 6 June 2020

AIM: - To simulate the piston kinematics using solidworks.

PHYSICS: -A slider-crank linkage is a four-link mechanism. The rotation of the crank drives the linear movement of the slider or the expansion of gases against a sliding piston in a cylinder can drive the rotation of the crank.

There are two types of slider-cranks: in-line and offset.

1. In-line: It has its slider positioned so the line of travel of the hinged joint of the slider passes through the base joint of the crank.
2. Offset: In this the line of travel of the hinged joint of the slider doesn't pass through the base pivot of the crank.

In this project, motion analysis of a piston assembly is performed to determine the linear displacement of the piston and angular velocity of the crank.

PARTS OF ASSEMBLY: -

1.PISTON: -The piston is a component of the internal combustion engine. Together with the connecting rod and crankshaft, it forms the crank mechanism of the engine. The main function of the piston is to transform the pressure generated by the burning air-fuel mixture into force, acting on the crankshaft.

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. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder.

3D MODAL OF PISTON

GUDGEON PIN: -In internal combustion engines, the gudgeon pin (UK, wrist pin or piston pin US) connects the piston to the connecting rod, and provides a bearing for the connecting rod to pivot upon as the piston moves. In very early engine designs, including those driven by steam, and many very large stationary or marine engines, the gudgeon pin is located in a sliding crosshead that connects to the piston via a rod. A gudgeon is a pivot or journal. The origin of the word gudgeon is the Middle English word gojoun, which originated from the Middle French word goujon. Its first known use was in the 15th century.

3D MODAL GUDGEON PIN

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.

The predecessor to the connecting rod is a mechanic linkage used by water mills to convert rotating motion of the water wheel into reciprocating motion.

The most common usage of connecting rods is in internal combustion engines or on steam engines.

3D MODAL-

END CAP: - End cap is connected to the end of the connecting rod, which is assembled crank.

ENGINE 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 engines and consist of a series of cranks and crankpins to which the connecting rods are attached.

The crankshaft rotates within the engine block through use of main bearings, and the crankpins rotate within the connecting rods using rod bearings. Crankshafts are usually made from metal, with most modern crankshafts being constructed using forged steel.

3D MODAL

ASSEMBLY: - The piston, connecting rod, wrist pin, end cap and the crank are assembled as shown below using assembly mate option. First the crank is made coincident with the assembly planes so that it can rotate about its axis and then connecting rod and end cap assembly is made coincident with the crank axis. Then wrist pin is made coincident with the piston and with its front plane and it is then assembled to the connecting rod. This will result in the required assembly for the motion.

3D MODAL-

SOLIDWORKS MOTION ANALYSIS: -

In the Motion study the following steps are performed.

1. Select motion analysis in the dop down menu.
2. Motor is given to crank with the speed 2000 RPM.
3. Frames per second is given as 60 with precise contact.
4. Contact is given between end pin and crank, crank and connecting rod, connecting rod and wrist pin and wrist pin and piston. Material selected for each case is steel (Dry).
5. Gravity in the Y direction.

Calculation is performed for the motion analysis for about 5 sec. Linear displacement of the piston head w.r.t time is obtained.

There are 3 cases

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 centre 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. For the second and third case we need to offset the piston circle position to 10mm positive and negative respectively, and then in the assembly coincide the axis of that with the wrist pin.

o mm offset of wrist pin: -

plot between linear displacement of piston and and time for 0 mm offset

plot between angiular velocity of crank and time for 0 mm offset

1o mm possitive offset of wrist pin: -

plot between linear displacement of piston and and time for 10 mm possitive offset

plot between angiular velocity of crank and time for 10 mm possitive offset

1o mm negative offset of wrist pin: -

plot between linear displacement of piston and and time for 10 mm negative offset

plot between angiular velocity of crank and time for 10 mm negative offset

CONCLUSION: - We have successfully done the simulation of kinematics of piston of internal combustion engine and evaluated the plot the piston displacement and angular velocity of crank w.r.t time.