Aim: To perform MBD Simulation on IC Engine Valve Train.

Description:

Valve Train: The valve train of an internal combustion engine includes components required to control the flow of gases into and out of the combustion chamber. This includes valves and related components required to allow the air-fuel mixture to enter the combustion chamber, seal the combustion chamber during compression and combustion, and evacuate exhaust gases when combustion is complete. The type of valve train used for a reciprocating engine depends on the engine design and whether the engine is a four-stroke cycle or two-stroke cycle unit.

Figure: IC engine valve train.

Components of the Engine valve train

• Cam: Cam, machine component that either rotates or moves back and forth (reciprocates) to create a prescribed motion in a contacting element known as a follower. The shape of the contacting surface of the cam is determined by the prescribed motion and the profile of the follower; the latter is usually flat or circular.
• Rocker arm: A rocker arm(in the context of an internal combustion engine of an automotive, marine, motorcycle, and reciprocating aviation types) is an oscillating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it.
• Push rod: A rod in an overhead-valve engine that is part of the linkage used to open and close the valves.
• Valve Mount: It limits the movement of the valve.
• Valve: Valves are mechanical components used in internal combustion engines to allow or restrict the flow of fluid or gas to and from the combustion chambers or cylinders during engine operation. Functionally, they perform similarly to many other types of valves in that they block or pass flow, however, they are a purely mechanical device that interfaces with other engine components such as rocker arms in order to open and close in the correct sequence and with the correct timing.

CAM Lift Formula

CAM Lift can be derived from the sketch

• The diameter of the lower circle (D1)- 35 mm
• The diameter of the upper circle (D2)- 20 mm
• The distance between two centers (L)- 30 mm

CAM Lift = (L-R1)+ R2

Objectives:

• To obtain the Valve Lift.

• To find out the contact forces between

• Cam and Push Rod
• Pushrod and Rocker Arm
• Rocker Arm and Valve

• To find out why the contact force between the Rocker arm and valve varies while measuring with respect to the X-direction and measuring with respect to magnitude.
• To run the simulation using the below parameters:

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

Figure: Flow of the project.

3D CAD models

Steps followed:

• CAD models are created on the basis of drawings provided in the video lectures.
• Individual parts are assembled to form an assembly.
• Contacts are established between the parts
• The motor is fixed on the cam to give the rotation to the cam of 1500 RPM.
• A linear spring is inserted between the valve and the valve mount of spring stiffness 10 N/mm and free length of 45 mm.
• Precise contact is established and 9000 frames per second were set.
• Carbon steel material is applied to the whole assembly.
• Motion analysis is done and desired plots are plotted.
• Both cases are done.
• The results were compared.

Results:

CASE 1

VALVE LIFT=52.8 mm( maximum)

CAM Lift (mm)	Speed (RPM)	Material
3.5	1500	Cast Carbon Steel

• The contact force between Cam and Push Rod

• At first, the magnitude is quite low, then the Contact force fluctuates in a repetitive manner after some time.
• Minimum value: 0 N
• Maximum value: 4547 N

• The contact force between Pushrod and Rocker Arm

• At first, the magnitude is quite low, then the Contact force fluctuates in a repetitive manner after some time.
• Minimum value: 0 N
• Maximum value: 4625 N

• The contact force between Rocker Arm and Valve

• At first, the magnitude is quite low, then the Contact force fluctuates in a repetitive manner after some time.
• Minimum value: 116 N
• Maximum value: 932 N

Video link: https://drive.google.com/file/d/1PW90Hd8HQ7mMiCnhfp8Ncw96lKKxowiW/view?usp=sharing

CASE 2

VALVE LIFT=56 mm(maximum)

CAM Lift (mm)	Speed (RPM)	Material
6	1500	Cast Carbon Steel

• The contact force between Cam and Push Rod

• At first, the magnitude is quite low, then the Contact force fluctuates in a repetitive manner after some time.
• Minimum value: 0 N
• Maximum value: 13657 N

• The contact force between Pushrod and Rocker Arm

• At first, the magnitude is quite low, then the Contact force fluctuates in a repetitive manner after some time.
• Minimum value: 0 N
• Maximum value: 13776 N

• The contact force between Rocker Arm and Valve

• At first, the magnitude is quite low, then the Contact force fluctuates in a repetitive manner after some time.
• Minimum value: 155 N
• Maximum value: 2620 N

Video link:

https://drive.google.com/file/d/1kQWONKnVKRKcCmqdHY-Y42sPS2wY5pzj/view?usp=sharing

Conclusions:

Why the contact force between the Rocker arm and valve varies while measuring with respect to the X-direction and measuring with respect to magnitude?

Ans: It’s because friction is acting in X-direction and at times magnitude of friction is negative also.

Figure showing the overall magnitude of friction.

Figure showing friction in the x-direction, it is negative also.

In the other two directions i.e. Y and Z, its value is near zero.

Friction in Z-direction

Friction in Y- direction