MBD Simulation on IC Engine Valve Train

AIM

To Design and run the simulation of IC Engine Valve train.

THEORY

The valve train of an IC engine control the flow of gases into and out of the combustion chamber. This includes the components like valves and related components which directs air-fuel mixture to enter the combustion chamber, close the combustion chamber during compression and combustion, and release exhaust gases when combustion is complete. The type of valve train used for a reciprocating engine depends on the engine design parameters. Valves experience various chemical, mechanical and thermal stresses during operation. Components should maintain their basic shape and dimensions for the expected life of the engine.We Engineers determine the valve material, shape, specifications, and to match the requirements of engine.

Design of valve train utilizes components in the compression system to maintain proper valve and valve spring position in the cylinder block. A valve spring retainer maintains spring contact with the valve stem and helps to align the valve spring. Providing the essential requirements of maintaining valve spring contact and spring alignment is essential. Valves in small engine rotate about the valve stem axis at varying rates. Valve rotation has an overall positive effect on valve life. Rotation provides temperature distribution in the valve head and a mild scraping action that cleans the valve interface of any crushed combustion deposits.

OBJECTIVE

• Modelling the parts and assemble them in SolidWorks.
• Simulation as per the below parameters

Sl.No	CAM Lift (mm)	Speed (RPM)	Material
1	3.5	1500	Cast Carbon Steel
2	6	1500	Cast Carbon Steel

Obtaining the plots mentiones below with respect to time

• 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.

CAM Lift Formula.

in the bove figure

(D1)- 35 mm
(D2)- 20 mm
(L)- 30 mm

CAM Lift = (L-R1)+R2

Simiullarly as per our requirements,

So @ 3.5mm lift we get L=11mm

@6mm lift we get L=13.5mm

3D MODELS

1.VALVE

2.PUSH ROD

3.ROCKER ARM

4.VALVE MOUNT

5. CAM @3.5mm lift

5. CAM @6mm lift

ASSEMBLY

@3.5mm cam lift @6mm cam lift

MOTION ANALYSIS

Creating two assemblies of valve train for two different cam designs.

Contacts are provided in order to run motion analysis of the mechanism.material properties of Cast Material used :Carbon steel.

CASE 1 @ 3.5mm cam lift Rpm = 1500

plots

CONTACT FORCES BETWEEN COMPONENTS

1.CAM VS PUSHROD

2.PUSHROD VS ROCKER

3.VALVE VS ROCKER(Magnitude)

3.1 VALVE VS ROCKER (x comp value)

VALVE LIFT

we observe a valve lift of 52.7mm in this case approximtely

CASE 2 @ 6mm cam lift Rpm = 1500

Plots

1. CAM VS PUSHROD

2. ROCKER VS PUSHROD

3. VALVE VS ROCKER(Magnitude)

3.1 VALVE VS ROCKER (x comp value)

VALVE LIFT

we observe a valve lift of 53.4mm in this case approximtely

CONCLUSIONS

• We obtain the linear displacement of 52.7mm and 53.4mm approximtely for 3.5mm &6mm cam lifts respectively.
• Large valve of displacement for the second case is observed. So, we can adjust how much the valve opens by changing the design parameters.
• The peeks in load time plot occurs when the cam pushes pushrod upwards and through rocker arm, the valve moves downward i.e. when pushrod slides on the varying profile of the cam. The load remains constant when pushrod slides over the circular profile of the cam and valve is at its initial position.
• For cam lift=3.5, the max load recorded is of 2900 Newton between the cam and the pushrod.
• For cam lift=6, the max load of recorded 3600 Newton occurs between the Rocker arm and the pushrod.
• From the above results, the magnitude of the contact force is more in the second case when compared to first case. Since there is increase in cam lift, the cam pushes the push rod with more force, moreover, spring is more compressed, hence, the contact force is large.
• The reason 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 is. In x-component force, negative force is achieved because the rocker arm slides both forwards and backward during one complete rotation of the CAM and hence the friction force acts in both directions.
• The magnitude of the contact force between the rocker arm and the valve pushes the valve downwards, but its X component gives us only the friction force of the rocker arm sliding over the face of the valve head.
• Valve timing plays a vital role in running the engine. The parameters must be controlled for better engine output. From the above plots, we can determine the loads which are actually developing on different parts during operation and take control over it by changing the parameters.