Analysis on Gearbox sloshing effect using ANSYS Fluent

Introduction:

The gearbox is a complex system having mechanical elements ranging from gears, bearings, free-running clutches, etc. All these members require an ample amount of lubricant for trouble-free running.

Viscosity is a measure of the lubricant\'s resistance to flow. It forms a layer between contacting surfaces which prevents metal to metal contact. Lubricant should maintain proper viscosity to form a stable oil film at the specified speed and specified temperature of operation.

Fig. Gearbox

Fig. Two spur gears inside the casing

Case description:

The gearbox contains a particular amount of lubricant which has been splashed by rotation of gears. The simulation has been performed for two kinds of geometry. those are lower clearance and higher clearance between two spur gears. And two type of lubricants have been used for both the geometries. Those are water and oil.

Case 1: Lower clearance gearbox with water as a lubricant

Case 2: Lower clearance gearbox with oil as a lubricant

Case 3: Higher clearance gearbox with water as a lubricant

Case 4: Higher clearance gearbox with oil as a lubricant

User-specified function for gear motion:

#include \"udf.h\"

DEFINE_CG_MOTION(right_motion, dt, vel, omega, time, dtime)
{
	vel[0] = 0.0;
	vel[1] = 0.0;
	vel[2] = 0.0;

	omega[0] = 0.0;
	omega[1] = 0.0;
	omega[2] = 2.0e2; /* [rad/s]*/
}
DEFINE_CG_MOTION(left_motion, dt, vel, omega, time, dtime)
{
	vel[0] = 0.0;
	vel[1] = 0.0;
	vel[2] = 0.0;

	omega[0] = 0.0;
	omega[1] = 0.0;
	omega[2] = -2.0e2; /* [rad/s]*/
}

The above function denotes two directions of motion with an angular speed of 200 rad/s. It provides angular rotation about z-axis to the two spur gears.

Mesh details:

	Gearbox with Low clearance	Gearbox with Large clearance
Method	All Triangles	All Triangles
Element Size	1 mm	1 mm
Capture proximity	Yes	Yes
Number of Elements	28327	30235

Fig. Mesh details of Gearbox with low clearance

Fig. Mesh details of Gearbox with high clearance

The Dynamic meshing option was enabled for all cases. Because, when the model has motion in a particular direction, the mesh of fluid domain will change accordingly.

Details of Remeshing settings:

Minimum length scale = 0.000203 m

Maximum length scale = 0.001671 m

Maximum cell skewness = 0.550079 m

The fluid domain has been created by using Cell registration in Adaptation control. By using this option, the elements are in that region can be marked. Any fluids can be assigned to that fluid region while patching.

Material Properties:

Oil:

Density = 871 `(Kg)/m^3`

Dynamic viscosity = 0.04006889 `(Kg)/(m*s)`

Water:

Density = 998.2 `(Kg)/m^3`

Dynamic viscosity = 0.001003 `(Kg)/(m.s)`

Air:

Density = 1.225 `(Kg)/m^3`

Dynamic viscosity = 1.7894e-5 `(Kg)/(m.s)`

Simulation details:

Type of Simulation: Transient

Type of model: k-epsilon with Realizable and Enhanced wall treatment model

Gravity: - 9.81 `m/s^2` in Y- Axis

Solution Method: Pressure - Velocity coupling

Scheme: Semi-Implicit Method for Pressure Linked Equation (SIMPLE)

The above details are used to simulate the Lubricant splashing inside the gearbox casing while the motion for all mentioned cases.

Results from case 1:

1)

The above plot shows the residuals from solving the governing equation at each iteration. The simulation has been performed for 0.1570 sec. The time duration for completing one complete rotation of gears is 0.0314 sec. Hence, the simulation has been performed for 5 complete rotation.

2) Animation video:

Results from case 2:

1)

The above plot shows the residuals from solving the governing equation at each iteration. The simulation has been performed for 0.1570 sec. The time duration for completing one complete rotation of gears is 0.0314 sec. Hence, the simulation has been performed for 5 complete rotation.

2) Animation video:

Results from case 3:

1)

The above plot shows the residuals from solving the governing equation at each iteration. The simulation has been performed for 0.1570 sec. The time duration for completing one complete rotation of gears is 0.0314 sec. Hence, the simulation has been performed for 5 complete rotation.

2) Animation video:

Results from case 4:

1)

The above plot shows the residuals from solving the governing equation at each iteration. The simulation has been performed for 0.1570 sec. The time duration for completing one complete rotation of gears is 0.0314 sec. Hence, the simulation has been performed for 5 complete rotation.

2)Animation video:

Conclusion:

1) The oil and water can be used as a lubricant because of both the fluids were sloshed all over the space in the gearbox.

2) The oil has higher Dynamic viscosity than water. The oil carried by gear tooth has been retained due to high resistance to flow.

3) The higher clearance gearbox takes more time to reach the lubricant on the top of the gearbox.