MBD Simulation on IC Engine Valve Train

Aim: To Perform Motion Analysis of IC Engine Valve Train

Objectives:

1. To create cad model of all components of IC engine valve train and assemble them.
2. To perform motion study and extract useful information from motion study.
3. To do analysis of different plots of contact force.

Theoretical background:

Introduction:

A valvetrain or 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 combustion 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 in order from the crankshaft to the valves.

1. Cam:

The timing and lift profile of the valve opening events are controlled by the camshaft, through use of a carefully shaped lobe on a rotating shaft. The camshaft is driven by the crankshaft and— in the case of a four-stroke engine— rotates at half the speed of the crankshaft. Motion is transferred from the crankshaft to the camshaft most commonly by a rubber timing belt, a metallic timing chain or a set of gears.

https://drive.google.com/file/d/1a7Im1dVKWywShYfza-somGjsZIoj59bb/view?usp=sharing

2. 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.

https://drive.google.com/file/d/1s6k2MU8CrnATabQHiWuTjuaWKsj3FHIl/view?usp=sharing

3. Rocker arm:

Depending on the design used, the valves are actuated by a Rocker arm, finger or bucket tappet. Overhead camshaft engines use fingers or bucket tappets, upon which the cam lobes contact. Overhead valve engines use rocker arms, which are actuated by a pushrod and pivot on a shaft or individual ball studs in order to actuate the valves.

https://drive.google.com/file/d/1nmlpx93eh9QATSNjrUMNQIvPZcwwZgQ9/view?usp=sharing

4. 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 float occurs when the valve spring is unable to control the inertia of the valvetrain at high engine speeds (RPM).

https://drive.google.com/file/d/1vnuRaMfEadDdUG5jOr7Lw25leZpVGGu2/view?usp=sharing

5. valve mount:

https://drive.google.com/file/d/1vnuRaMfEadDdUG5jOr7Lw25leZpVGGu2/view?usp=sharing

Assembly:

https://drive.google.com/file/d/1-o9Ci9kU09t9QYpJZxSvlRC_Hbn16zfc/view?usp=sharing

Problem Statement:

To perform motion analysis of for two different cam lift.

Sl.No	CAM Lift (mm)	Speed (RPM)	Material
1	3.5	1500	Cast Carbon Steel
2	6	1500	Cast Carbon Steel

Case-I Motion analysis of Cam-lift of 3.5mm

To calculate distance between two centers(L)

Given R₁=12.5mm, R₂=5mm, cam lift =3.5mm

Cam lift = (L- R₁) + R₂

L= (12.5+3.5)-5

L=11mm

Case-II Motion analysis of Cam-lift of 6 mm

To calculate distance between two centers (L)

Given R₁=12.5mm, R₂=5mm, cam lift =6 mm

Cam lift = (L- R₁) + R₂

L= (12.5+6)-5

L=13.5mm

Procedure followed:

1] create cad model of all component of IC engine valve train and assemble them with proper constraint.

2] perform motion analysis with crank speed is 1500 Rpm and frames per second is 7200 with precise contact to get each degree variation of cam.

3] add spring between valve and valve mount of 10KN/M stiffness and free length equal to 45 mm.

4] change material of assembly by selecting it completely and by right click you will find edit material in drop down, choose cast carbon steel as assembly material.

5] edit the calculation time so that it will cause less time to complete the calculation.

6] after calculation extract the data from simulation.

Problem encountered:

1] If there is interference of material is there in assembly then you can not check for physical dynamics. To resolve this problem there should be clearance between mating part.

Plots:

Case-I Motion analysis of Cam-lift of 3.5mm

Case-II Motion analysis of Cam-lift of 6 mm

Conclusion:

1] Contact force between the Rocker arm and valve varies while measuring with respect to the X direction and measuring with respect to magnitude because point of contact and line of action of contact force is varrying between rocker arm and valve. Due to this reaction force perpendicular to valve motion develop and which causes losses in system.

Result:

Motion Analysis of IC Engine Valve Train has done successfully.