MBD SIMULATION ON IC ENGINE VALVE TRAIN
AIM
To run MBD simulation on IC Engine valve train.
OBJECTIVES
To run the simulation for the following parameters
|
S. No |
CAM Lift(mm) |
Speed (RPM) |
Material |
|
1 |
3.5 |
1500 |
Cast Carbon Steel |
|
2 |
6 |
1500 |
Cast Carbon Steel |
To obtain the contact force between
- Cam and Push rod
- Push rod and Rocker arm
- Rocker arm and Valve.
THEORY
A valve train is a mechanical system that controls the operation of intake and exhaust valves in an Internal Combustion engine. The in-take valve controls the flow of air-fuel mixture into the combustion chamber and exhaust valve controls the flow of exhaust gases out of the combustion chamber once the combustion process is complete.
COMPONENTS
The following are the major components of an valve train
- Camshaft
- Push rod
- Rocker Arm
- Valves
CAMSHAFT
The timing and lift profile of valve opening events are controlled by camshaft. The camshaft is driven by a crank shaft. In four stroke engine the camshaft rotates half the speed of crank shaft. Motion is usually transferred from camshaft to crankshaft by a rubber timing belt.
PUSH ROD
Pushrods are long slender metal that are used in valve engine to transfer motion from camshaft to the valves. The bottom end of the pushrod is fitted with a lifter, which makes contact with the camshaft. When the camshaft rotates, it moves the pushrod. The top end of the pushrod makes contact with the rocker arm which opens the valve.
ROCKER ARM
Rocker arm is used to actuate the valves. The opening and closing of valves are done by rocker arm.
VALVES
Valve is a device to close and open a passage. Inlet valve and exhaust valve are present in each cylinder in an internal combustion engine.
VALVE STEM
A valve stem is a self-contained valve which opens to allow the passage of gas into the chamber and it is automatically closed and kept sealed by the pressure in the chamber or spring to prevent the gas from leakage.
The assembled 3D model of IC engine valve train is shown below
CAM LIFT FORMULA
CASE 1
CAM LIFT 3.5mm
R1 = 12.5
R2 = 10
CAM LIFT = (L-R1) +R2
3.5 = L – 12.5 + 10
L – 2.5 = 3.5
L = 6mm
CASE 2
CAM LIFT 6mm
R1 = 12.5
R2 = 10
CAM LIFT = (L-R1) +R2
6 = L – 12.5 + 10
L – 2.5 = 6
L = 8.5mm
PROCEDURE
- Create the 3D models for the components of valve train with the given dimension and assemble them using proper constraints.
- The material for all components is given as Cast Carbon Steel.
- Click on Solidworks Add-Ins and enable Soildworks Motion.
- Click on motor and select the axis of cam shaft and specify the direction of rotation. 1500 is given as rpm.
- Click on contacts and enable body contacts between camshaft and pushrod, pushrod and rocker arm and rocker arm and valves. Specify the material as Steel (dry).
- Click on Spring and enable the contact between the valve and valve stem. Specify the value for spring stiffness.
- Click on Settings and change the frames per second to 7200.
- Enable precise contact.
- Click on Calculate to run the simulation.
- Click on Results and plots and specify the necessary parameters to get the required plots.
The following are the plots obtained after the simulation under different conditions.
CASE 1
CAM LIFT 3.5 mm
LINEAR DISPLACEMENT
CONTACT FORCE BETWEEN CAM AND PUSHROD
CONTACT FORCE BETWEEN PUSHROD AND ROCKER ARM
CONTACT FORCE BETWEEN ROCKER ARM AND VALVE
CONTACT FORCE BETWEEN ROCKER ARM AND VALVE (X-DIRECTION)
CASE-2
CAM LIFT 6mm
LINEAR DISPLACEMENT
CONTACT FORCE BETWEEN CAM AND PUSHROD
CONTACT FORCE BETWEEN PUSHROD AND ROCKER ARM
CONTACT FORCE BETWEEN ROCKER ARM AND VALVE
CONTACT FORCE BETWEEN ROCKER ARM AND VALVE (X-DIRECTION)
ANIMATION LINK
PART DRAWING
https://drive.google.com/drive/folders/17W6nxUPOxANrUmERVoALCwwAp4kIiHkc?usp=sharing
Why the contact force varies with respect to the X-direction and measuring with respect to magnitude?
The magnitude represents the net contact force between the parts. The contact force along X-direction is the frictional force between the bodies that arises due to the contact between rocker arm and valve. The contact force along the X-direction is positive when the valve moves downwards and negative when the valve moves upwards.
RESULTS
The MBD on IC Engine valve train is carried out successfully.
From the plots it is clear that when the cam lift increases contact force between the bodies also increases.
REFERENCES