MBD Simulation on IC Engine Valve Train

Abstract:

In this project “Multibody Dynamics of IC Engine Valve Train”, the modelling of different parts of valve train are modelled in SolidWorks software and assembled them. After the assembly the Motion Analysis has been done to obtain the Valve lift and the contact force was found out between (i) the cam and push rod (ii) Pushrod and Rocker arm and (iii) Rocker arm and valve.

Introduction:

                A valve train is a part of an internal combustion engine that controls the operation of the intake and the exhaust valves. There is an intake valve that allows the air-fuel mixture into the combustion. The Exhaust valve allows the exhaust gases out of the combustion chamber after the process is completed.

Aim: The main aim of this project is to run the motion study on valve train and analyze the results using different parameters which are in the following table:

Material properties of Cast carbon Steel:

CAD models of the components of the Valve Train:

Cam:

 The function the camshaft is to control the timing and lift of the valve opening.

Valve:

The valve used in most modern engines are called a poppet valve. Some valves like sleeve valves, slide valves and rotary valves are also used.

Rocker Arm:

Rocker-arms are used in overhead valve engines, which are actuated by a pushrod and a pivot on a shaft.

Push-Rod:

The pushrods are long and slender metal rods that are used to transfer the motion from the camshaft to the valves.

Valve-Mount:

Assembly:

General Setup for Motion Analysis (For both the Cases)

• Speed = 1500 rpm
• Material = Cast Carbon Steel (Applied to each part of the valve train)
• Frames per second = 9000 fps
• A linear spring is provided between the valve stem and valve.
• Spring stiffness = 15 N/mm
• Spring is pretensioned with L = 45mm
• 

Solid Contact 1:

Solid Contact 2:

Solid Contact3:

Spring Stiffness

CALCULATION AND RESULTS FOR THE GIVEN PROBLEM:

To find the values of cam lift, the above given formula is used:

Case:1 Cam lift = 3.5mm

Applying the formula

3.5 = (L1-17.5) + 10

L1= 11 mm

RESULTS:

Plot 1: Valve lift (Case 1)

Observation from excel spreadsheet:

The maximum position of valve obtained was 52.04 and the minimum position of valve was obtained was 50.28. So the VALVE LIFT = 1.76 mm

Plot 2 : Contact force between Cam and Push rod (Magnitude)

Observation:

Max value = 3212.09

Min value = 0

Average value = 240.58

Initially from the plot we can see that there is sudden increase in the value of contact force  due to jerk and there is up and down between the values of contact force but the average value was obtained as 240.58

Plot 3 : Contact force between Push rod and Rocker arm (Magnitude)

Plot 4: Contact force between Rocker arm and valve (magnitude)

Observation:

Max value = 571.68

Min value = 0

Average value = 96.54

Plot 5: Contact force between Rocker arm and valve (X-direction)

Max value = 138.65

Min value = -45.52

Case:2 Cam lift = 6mm

Applying the given formula:

6 = (L2 – 17.5) +10

L2 = 13.5mm

Results and Plots of CASE2:

Plot 1:

Valve lift of CASE2:

Max value = 54.15 mm

Min value = 50.27 mm

Valve lift = 3.88 mm

Plot 2

Plot 3

Plot 4

Plot 5

EXPLANATION OF RESULTS AND CONCLUSION:

The valve lift obtained for Case 1 = 1.76 mm

The valve lift obtained for Case 2 = 3.88 mm

From all the plots of both the cases it was found that the initial values obtained was very high and there was sudden decrease in the values of contact force. After that the values of contact forces varies slightly up and down.

Why the contact force between the rocker arm and valve varies while measuring w.r.t. the X direction and measuring w.r.t. magnitude?

In the both the Cases (i.e. CASE 1:plot 4 and  plot 5 and CASE 2: Plot 4 and Plot 5)

In both the cases of MAGNITUDE the line of contact force is changing continuous while in the X-Direction it was seen that that lint of contact force is positive and negative and it varies throughout the experiment.

In cases of MAGNITUDE the frictional forces and loss of energy due to it occurs in all the directions so it was obtained higher as compared to the values in the cases of X-direction, the frictional force and energy loses occurs only in single direction.

Animation Links:

CASE 1: https://youtu.be/0wqkYjzt1WU

CASE 2:https://youtu.be/EDL99IMRa70

References:

https://studentlesson.com/valvetrain-definition-working-principle-parts-functions/

https://blogmech.com/engine-variable-valve-actuating-mechanisms/