MBD Simulation on IC Engine Valve Train

AIM:

To perform multibody dynamic simulation on IC engine valve train.

OBJECTIVE:

1)To model the parts of IC engine valve train.

2)To assemble and perform multibody dynamic simulation.

3)To plot various graphs and to study from it.

THEORY:

An IC engine valve train is a mechanical system that controls operation of the intake and exhaust valves in an internal combustion engine. The intake valves control the flow of air/fuel mixture (or air alone for direct-injected engines) into the combustion chamber, while the exhaust valves control the flow of spent exhaust gasses out of the combusion chamber once combustion is completed.

The valvetrain consists of all the components responsible for transferring the rotational movement of the camshaft into the opening and closing of the intake and exhaust valves. Typical components are listed below:

CAM:

A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion. It is often a part of a rotating wheel (e.g. an eccentric wheel) or shaft (e.g. a cylinder with an irregular shape) that strikes a lever at one or more points on its circular path.

PUSHROD:

Pushrods are long, slender metal rods that are used in overhead valve engines to transfer motion from the camshaft (located in the engine block) to the valves (located in the cylinder head). The bottom end of a pushrod is fitted with a lifter, upon which the camshaft makes contact. The camshaft lobe moves the lifter upwards, which moves the pushrod. The top end of the lifter pushes on the rocker arm, which opens the valve.

ROCKER ARM:

Rocker arm is actuated by a pushrod and pivot on a shaft or individual ball studs in order to actuate the valves.

VALVE:

Most modern engines use poppet valves type, although sleeve valves, slide valves and rotary valves have also been used at times. Poppet valves are typically opened by the camshaft lobe or rocker arm, and closed by a coiled spring called a valve spring.

VALVE MOUNT:

It is used as a support device for the valve.

IC ENGINE VALVE TRAIN:

PROCEDURE:

1)Firstly, model all the parts of the IC engine valve train namely the cam, push rod, rocker arm, valve and the valve mount.

2)All the parts are assembled and simulation is done for a time period of 0-4 seconds.

3)A graph is plotted for the contact force between:

a)Cam and push rod

b)Push rod and rocker arm

c)Rocker arm and valve

d)Rocker arm and valve in X direction

for two cases.They are:

4)Compare all the graphs and study from it.

MODELS:

1)CAM

2)PUSHROD:

3)ROCKER ARM:

4)VALVE:

5)VALVE MOUNT:

ASSEMBLY:

CASE 1:Simulation for cam lift of 3.5mm

Using cam lift formula:

Given: R1 = 12.5; R2 = 5; Cam lift = 3.5mm

Cam lift = (L-R1)+R2

L = (12.5+3.5) - 5

L = 11mm

Therefore using the above data cam is modelled.

The following graphs are obtained for case 1:

1)Contact force between cam and push rod:

2)Contact force between push rod and rocker arm:

3)Contact force between rocker arm and valve:

4)Contact force between rocker arm and valve in X direction:

We can see from the graph that contact force between rocker arm and valve in magnitude and in X direction varies. This is because the contact force in magnitude represents the net contact force between the parts whereas the contact force along X direction is the frictional force between the bodies that arise due to the rocker arm sliding over the surface of the valve head.

CASE 2:Simulation for cam lift of 6mm

Given: R1 = 12.5; R2 = 5; Cam lift = 3.5mm

Cam lift = (L-R1)+R2

L = (12.5+6) - 5

L = 13.5mm

Therefore using the above data cam is modelled.

The following graphs are obtained for case 2:

1)Contact force between cam and push rod:

2)Contact force between push rod and rocker arm:

3)Contact force between rocker arm and valve:

4)Contact force between rocker arm and valve in X direction:

SIMULATION:

I have attached the link of simulation of IC engine valve train:

https://www.youtube.com/watch?v=gpbTosIukmw&feature=youtu.be

RESULT:

Thus the parts of the IC engine valve train is modelled, assembled and simulated. Various graphs are plotted, compared and studied.