MBD Simulation on IC Engine Valve Train

MBD Simulation on IC Engine Valve Train

Aim:

• Model the parts and assemble them in SolidWorks.
• Run the simulation using the below parameters

Obtain the

• Valve Lift.
• The contact force between

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

Explain 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.

Write Cam Lift Formula.

Objective: -

The main objective is to model an IC engine valve train which consists of essential parts such as a cam, push rod, rocker arm, valve mount, and valve, then assemble them in SolidWorks.

Introduction of Valve-Train

A valve-train or valve train is a mechanical system that controls operation of the valves in an internal combustion engine, whereby a sequence of components transmits motion throughout the assembly. A conventional reciprocating internal combustion engine uses valves to control the flow of the air/fuel admix into and out of the combustion chamber.

A typical valve train consists of valves, rocker arms, pushrods, lifters, and camshaft(s). Valve train opening/closing and duration, as well as the geometry of the valve train, controls the amount of air and fuel entering the combustion chamber at any given point in time. Timing for open/close/duration is controlled by the camshaft that is synchronized to the crankshaft by a chain, belt, or gear. The camshaft is located within the engine block, and operates directly on the valves, or indirectly via pushrods and rocker arms. Because they often require pushrods they are often called pushrod engines.

Design all the different parts of the valve train arrangement separately. The parts are as follows.

1. Cam
2. Push-rod
3. Rocker Arm
4. Valve Engine
5. Valve Mount

Creating a 3D Model

CAM: -

A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path.

PUSH ROD: -

This is the part to which the lift is provided, which is transmitted to the rocker arm.

ROCKER ARM: -

This is part which is connected to push rod in one end and valve on the other end.

VALVE ENGINE: -

This allows the air-fuel mixture to enter the cylinder or exhaust the gases out from the cylinder by opening and closing of the inlet/exhaust port.

VALVE MOUNT: -

This acts as the stoppage for the valve and limits the movement of the valve.

FINAL ASSEMBLY: -

Assembly is made using the assembly mate option by properly aligning them as shown. Physical dynamics is used here for making contact between valve, rocker arm, push rod and cam which locks them in position and motion analysis is performed.

Motion Analysis:

To run the motion analysis first go to motion study and establish contact between Cam and push rod, push rod and rocker arm, rocker arm and valve. Next, give the rotation to the cam with 1500 RPM. Set up a linear spring between a valve and the valve mount with the spring stiffness of 10 N/mm and free length 45 mm. Change the frames to 7200 frames per sec and use precise contact. Select the entire assembly and assign the material as follows, go to Material-Edit material and select Cast Carbon Steel and click apply. There will be an indication of the material assigned with a change in colour of the entire assembly. Now click the calculation button. Run the analysis for the required time.

Cam Lift Formula:

Case 1: Cam lift = 3.5mm

R1= 12.5mm

R2= 10mm

Therefore, L=3.5+R1-R2

L=3.5+12.5-10 =6mm

Case 2: Cam lift = 6mm

R1= 12.5mm

R2= 10mm

Therefore, L=6+R1-R2

L=6+12.5-10 =8.5mm

Results for the Simulation

CAM LIFT 3.5MM

Contact force between Cam and Push Rod(Magnitude)

Contact force between Push rod and Rocker(Magnitude)

Contact force between Rocker Arm and Valve(Magnitude)

Contact force between Rocker Arm and Valve(X direction)

Linear displacement between Cam and Push Rod(Magnitude)

CAM LIFT 6MM

Contact force between Cam and Push Rod(Magnitude)

Contact force between Push rod and Rocker(Magnitude)

Contact force between Rocker Arm and Valve(Magnitude)

Contact force between Rocker Arm and Valve(X direction)

GRAPH PLOT OBSERVATION

CASE 1

• This shows the contact force between the Cam and the Push rod the maximum force is around 756 N, this is when the push rod comes down after the cam lift. The contact force during the cam lift is around 100 N(between 0 & 192 N).The other forces are due to friction while the push rod slides over the cam.
• This is almost same as that of the graph between cam and push rod but only the magnitude of the contact force varies.
• The Magnitude represents net contact force between the parts, while the contact force along X direction is the frictional force between the bodies that arises due to the rocker arm sliding over the surface of valve head. The change in direction of the force is because the rocker arm first slides towards origin giving a positive friction force (opposing the motion) and then slides away from the origin giving rise to friction in negative x direction. Therefore, the plots are opposite to each other.

CASE 2

• The explanation is same for the cam lift of 6mm, only it differs in magnitude of contact forces. The movement in this case is quite smoother compared to the cam lift of 3.5mm as observed. As the cam lift increases more air-fuel mixture can enter into the cylinder of IC engine.

ANIMATION

https://youtu.be/W-yBPyAuK0c

https://youtu.be/-0eHBXeZ5To

CONCLUSION

Hence we are successfully find the result.