MBD Simulation on IC Engine Valve Train

MBD Simulation on IC Engine Valve Train

Aim: To model and assemble Valve train of IC Engine and to simulate to obtain Linear displacement and contact forces between the components.

IC Engine Valve train: The valve is a component in the engine which controls the flow, quantity and time of the fuel entering into the engine for combustion. It is also used in diesel engine to control the air intact inside the engine.

More over it also controls the out let of the burned exit gas from the engine.

The basis work of a valve in an engine is to block the Unblock in the way of the fuel by getting fitted into the seat.

The basic components that helps the simple valve train to work is as follows

• CAM
• Push rod
• Rocker arm
• Valve

CAM: Cam is a rotating component that which is used to transfer Rotatory motion into linear motion. the face of the cam can be smooth or can be of simple toothed cam which can be used to transfer series of power train. The structure of the cam varies in relation with the operation it needs to perform.

Push rod: Push rod helps to transfer the rotation of the cam to linear motion. The rod is placed on the side face of the cam and he motion of the rod occurs in the vertical direction occurs when the bulge part of the cam makes contact with the push rod. the end face of the push can be sharp, flat or even with a roller depending upon the application.

Rocker arm: Rocker arm is a common type of arm with closely looks like the arm used in the Ratchet mechanism which is pivoted at a point and transfer the upward hit on the push rod from on end to downwards motion in on the other end that helps in pushing the valve downwards.

Valve: The vale has a long rod and a flat face at the end which lock the path of the fuel inlet and outlet by getting placed in the valve seat when the rocker arm is not pushed and moves downwards to allow the gas to let in when the rocker arm pusher the valve. The valve is held at the place with the help of the spring.

Objective

• To model the parts of the Valve train and to simulate them to obtain the displacement of the valve and the contact force between each part.
• To vary the cam structure by changing the cam lift for 3.5 mm and for 6 mm.
• To obtain the plot for al the contact forces and the linear displacement and the contact force for each degree rotation of the cam.
• To compare the graph of the contact force between the rocker arm and the valve in both magnitude as well as in x-axis.

Body of content:

Condition:

Formula for Cam lift = (L-R1)+R2

Where,

L is the distance between the centers of the two-cam circle

R1 is the radius of the base circle

R2 is the radius of the cam circle

The frames are set to 9000 fps as the speed is 2000 Rpm in both the cases

From the condition

For 3.5 mm cam lift L = 11 mm

For 6 mm cam lift L = 13 mm

Plots

Linear displacement of CAM

Contact force between CAM and Push rod

Contact force between Push rod and rocker arm

Contact force between rocker arm and valve in terms of Magnitude

Contact force between rocker arm and valve in terms of X-axis

By comparing both the contact force between the rocker arm and the vale we can see the highest of the force in magnitude is above 2000 N and the highest at the X-axis is more than -5000. The reason why the force in the X-axis is negative is because of the spring tension acts in the opposite direction to pull the valve back to the position.

Conclusion: The analysis of contact force between the components and linear displacement of the valve is analyzed.

Model parts and spread sheet link : https://drive.google.com/drive/folders/1NDcEydbC_s94pRxdc1llxV3Zea9kZo83?usp=sharing