Multi Body Dynamics Simulation on I.C Engine Valve Train using Solidworks

AIM: To create a 3D model of an I.C engine valve train and a perform a Multi-Body Dynamics Simulation using SolidWorks.

OBJECTIVE:

The main objective of this simulation is to plot the following graphs for each of the following cases :-

1)Valve Lift

2)The contact force between:

1. Cam and Push Rod
2. Pushrod and Rocker Arm
3. Rocker Arm and Valve

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

INTRODUCTION

The valve train refers to the assembly of components designed to open and close the intake and exhaust valves. 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 combusion chamber once combustion is completed.

COMPONENTS OF THE VALVE TRAIN ASSEMBLY

The valvetrain consists of all the components responsible for transferring the rotational movement of the camshaft into the opening and closing of the intake and exhaust valves. Typical components are listed below in order from the crankshaft to the valves.

1. Cam

   The timing and lift profile of the valve opening events are controlled by the camshaft or, a single cam in this case, through use of a carefully shaped lobe on a rotating shaft. The camshaft is driven by the crankshaft and— in the case of a four-stroke engine— rotates at half the speed of the crankshaft.

2. Pushrod/ Cam Follower

   A cam follower is long, slender metal rod used in overhead valve engines to transfer motion from the cam to the valve . The bottom end of a pushrod is fitted with a lifter, upon which the camshaft makes contact. The camshaft lobe moves the lifter upwards, which moves the pushrod. The top end of the lifter pushes on the rocker arm, which opens the valve.

3. Rocker arm

   Depending on the design used, the valves are actuated by a rocker arm, finger or bucket tappet,based on contact from the cam follower. Overhead valve engines use rocker arms, which are actuated by a pushrod and pivot on a shaft or individual ball studs in order to actuate the valves.

4. Valves

   Most modern engines use poppet valves type, although sleeve valves, slide valves and rotary valves have also been used at times. Poppet valves are typically opened by the camshaft lobe or rocker arm, and closed by a coiled spring called a valve spring.Valve float occurs when the valve spring is unable to control the inertia of the valvetrain at high engine speeds (RPM).

CALCULATION - CAM LIFT

Case 1:-

Cam Lift = 3.5mm

Cam lift = L-R1+R2

3.5 = L -12.5 + 10

L = 6mm

Case 2:-

Cam Lift= 6 mm

Cam Lift = L-R1+R2

6 = L - 10 + 5

L =11mm

MODELS OF VALVE TRAIN COMPONENTS

CAM WITH CAM LIFT= 6 mm

CAM WITH CAM LIFT= 3.5 mm

CAM FOLLOWER/ PUSH ROD

ROCKER ARM

VALVE

VALVE STEM

ASSEMBLY WITH A CAM OF CAM LIFT= 3.5 mm

ASSEMBLY WITH A CAM OF CAM LIFT= 6 mm

PARTS AND ASSEMBLY FILES + DATA SET:

https://drive.google.com/drive/folders/1eDitFbwaayCdcAIYcyrdIos4QP-FRMWC?usp=sharing

ANIMATION

ASSEMBLY WITH A CAM OF CAM LIFT= 6 mm

ASSEMBLY WITH A CAM OF CAM LIFT= 3.5 mm

PROCEDURE FOR SIMULATION

1. The components are properly constrained and assembled based on the respective cam lift conditions
2. SolidWorks motion is enabled and a motor running at 1500 RPM is added to the cam.
3. The respective component contacts are selected accordingly and a spring is added to the valve.
4. The spring has a free length of 100 mm and a stifness of 10 N/mm
5. The fps is set to 9000 and the simulation is run accordingly. The plots generated in both cases are shown below.

PLOTS

CAM LIFT 3.5mm

CAM LIFT 6mm

RESULTS AND CONCLUSION

The plots show that valve lift increases with increase in cam lift and that it also depends on profiles of the cam and rocker arm.Also, the magnitudes of contact forces between each of the components also increases with increase in cam lift.The spring stiffness also plays a crucial role in this moton analysis.

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.

Ans:

The contact forces between the Rocker arm and valve varies while measuring with respect to magnitude and the X-direction because, the first case only involves measuring the net force whereas measuring along the X-direction includes the magnitude and direction as well, thus showing a large number of negative values unlike the first case in which only the magnitude of the force is displayed.