MBD SIMULATION ON IC ENGINE VALVE TRAIN
AIM: Design and motion analysis of an IC ENGINE VALVE TRAIN ASSEMBLY
INTRODUCTION:
Valvetrain-
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.
OBJECTIVE:
- Performing motion analysis of IC engine valve train mechanism
- Obtaining plots
- Valve lift vs time
- Contact force (cam and pushrod) vs time
- Contact force (pushrod & rocker arm) vs time
- Contact force (rocker arm & valve) vs time
SIMULATION CASES: -
|
S. No |
CAM Lift (mm) |
Speed (RPM) |
Material |
|
Case 1 |
3.5 |
1500 |
Cast Carbon Steel |
|
Case 2 |
6 |
1500 |
Carbon Steel |
CAM Lift Formula:
CAM Lift can be derived from the sketch
- The diameter of lower circle (D1)- 35 mm
- The diameter of upper circle (D2)- 20 mm
- The distance between two centres (L)- 30 mm
CAM Lift = (L-R1) + R2
PROCEDURE:
Initially, a Cam is designed according to the mentioned Cam Lift.
The 3D model of pushrod is designed keeping in mind the Cam and the Rocker arm.
The Rocker arm is modelled with appropriate dimensions in order to have harmony between parts with contact.
The valve stem is designed with shaft hole size equal to the valve width.
The final is the valve which is loaded with the spring. This component is the most calibrated due to its precise performance.
All parts are assembled in an assembly file with proper no. of mates and constraints.
RESULTS:
Case 1-
Valve lift vs Time
The valve lift depends on the rocker arm ratio thereby giving successive moments of opening and closing of valve.
Contact force (cam & pushrod) vs Time
The contact force projected shows the time of engagement between the Cam and Pushrod with the extent of force transmitted from the Cam to the pushrod.
Contact force (pushrod & rocker arm) vs Time
The graph shows tremendous similarity to the previous graph, thereby resembling the uniform transfer of motion.
Contact force (rocker arm & valve) vs Time – magnitude
The graph intends to represent the downward force that the Rocker arm exerts on the valve.
Contact force (rocker arm & valve) vs Time – X direction
The plot work as a comparison between contact force measured in the X direction.
Case 2-
Valve lift vs Time
Contact force (cam & pushrod) vs Time
Contact force (pushrod & rocker arm) vs Time
Contact force (rocker arm & valve) vs Time – magnitude
Contact force (rocker arm & valve) vs Time – X direction
CONCLUSION:
The motion analysis gives a satisfactory idea about the functioning of the IC Engine Valve Train where in further scope of improvement exists to make it smoother and more efficient.