MBD Simulation on IC Engine Valve Train
AIm :
The aimof the experiment is to perform the multi-body dynamic simulation on the IC Engine Valve Train Assembly for two scenarios where in the cam lift is varied as 3.5 mm and 6 mm respectively and plot the obtained result.
Introduction:
The valve train refers to the assembly of components designed to open and close the intake and exhaust valves
The Different components present are :
1.Cam
2.Push Rod
3.Rocker Arm
4.Valve
5.Valve Mount
Cam:
A cam is a mechanical device used to transmit motion to a follower by direct contact. The driver is called the cam and the driven member is called the follower. In a cam follower pair, the cam normally rotates while the follower may translate or oscillate.
Push Rod:
The valve-in-head engine has pushrods that extend upward from the cam followers to rocker arms mounted on the cylinder head that contact the valve stems and transmit the motion produced by the cam profile to the valves.
Rocker Arm:
Rocker Arm is an oscillating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it. One end is raised and lowered by a rotating lobe of the camshaft (either directly or via a tappet (lifter) and pushrod) while the other end acts on the valve stem. When the camshaft lobe raises the outside of the arm, the inside presses down on the valve stem, opening the valve. When the outside of the arm is permitted to return due to the camshafts rotation, the inside rises, allowing the valve spring to close the valve.
Valve:
Valves form an integral component of an internal combustion engine and every cylinder in an engine atleast has two of them, i.e. an intake (intake of fuel-air mixture) and an exhaust valve (exhaust gases).The opening and closing of valves is precisely timed to allow the engine to run efficiently in all conditions. In a four stroke engine, the intake valve(s) open up at the start of the suction stroke and the exhaust valves open up during the exhaust stroke when the piston returns from BDC to TDC.
Assembly:
Cam Lift Formula:
Based on this formula the following shows the calculation of the lift:
For 3.5 mm Cam Lift:
Cam Lift, 3.5 = (L-12.5)+5
L = 11mm
For 6 mm Cam Lift:
Cam Lift, 6 = (L-12.5)+5
L = 13.5mm
Procedure:
1.The 3D models are created based on thegiven drawing
2. After the models are created they are assembled and the required constraints are provided.
3. Cam is made as rotor and a speed of 1500rpm is provided.
4.contacts are provided between all the components
5.Finally the Simulation is run and the outputs are plotted.
Link for the Components and Assembly:
https://drive.google.com/drive/folders/1iLqLpqQqH1ZxYeRnG9K-rBkTj9C9KBBc?usp=sharing
Link for animation:
Output Plots Obtained:
For 3.5mm Cam Lift:
Contact force of Cam and Push Rod:
Contact force of Push Rod and Rocker Arm:
Contact force of Rocker Arm and Valve:
Contact force of Rocker Arm and Valve in X direction:
Valve Displacement:
For 6mm Cam Lift:
Contact force of Cam and Push Rod:
Contact force of Push Rod and Rocker Arm:
Contact force of Rocker Arm and Valve:
Contact force of Rocker Arm and Valve in X direction:
Valve Displacement:
Contact forces and Displacement of 6mm is greater than3.5mm lift.
Displacement for3.5mm Lift is 2.2mm
Displacement for 6mm lift is 5mm
Contact force between the rocker arm and valve varies in x- directon because the negative force is achieved as a result rocker rm sliding in both forward and backward during the cam rotation.Hence the x direction value gives us the frictional force of rocker arm over Valve