Proportional Valve simulation

Objective

To simulate proportional valve, run 6 cases: 3mm, 4mm and 5mm lift sizes with and without Adaptive Mesh Refinement (AMR), make a plot ilustrating pressure force along Z and lift dependance.

Theory

Proportional valve is a valve which relies on the statics to supply reduced pressure to an output line. In all devices which's operation range experiences various levels of pressure, safety system is necessary in order to avoid overpressure.

Proportional valve is used in many industrial cases. For instance, it's used in automobile's brake system to reduce brake fluid pressure to the rare brakes.

We also meet proportional valve in turbocharger system. when the air coming from a compressor wheel reaches maximum operating pressure, so called "blow-off valve" opens to get rid of overpressure in an IC engine.

Proportional valve has a spring which is designed as it will compress when the pressure reaches the specific value. To correctly estimate a spring force we simulate cases in order to get the fluid pressure force acting on a valve when the pressure reaches the maximum operating value.

Case set up

We are running a simulation of a proportional valve, where the inlet pressure is 30bar and the outlet pressure is 1 bar. there are 2 different things between the all cases. The first, we have 3 lift sizes: 3,4 and 5mm. The second, we run all those 3 cases with and without Adaptive Mesh Refinement (AMR).

• Geometry

As a fluid we are using air (real gas) Redlich-kwong.

• Run parameters

• Steady state monitoring

• Time parameters

• Boundary conditions

• Initialization

• Turbulence model

• Mesh (Base grid)

• Mesh (AMR)

The reason we use AMR is to capture flow stucture more properly. we have a high pressure difference between the inlet and the outlet, considering that turbulence will occur, meaning that velocity and temperature second derivatives, which indicates the curvature of a function, will vary. that's why we are using temperature AMR in our case.

POST PROCESSING

• comparing 3mm lift case with and without AMR

Mass flow

Total pressure at the outlet

Velocity at the outlet

It's clear that the same cases with and without AMR shows different output values. we should rely on the case where AMR is included because as we talked, when turbulence occurs in the flow we need refined mesh to correctly capture flow sturture.

• 3,4 and 5mm lift sizes with AMR

Mass flow

Total pressure at the outlet

As we see we get the highest total pressure at the outlet in 5mm lift case. This is because of the velocity at the outlet which is the higest in 5mm case (please see the next figure). Total pressure equal to static plus dynamics pressure, according to the boundary conditions static pressure at the outlet is constant in the all cases so which may vary is dynamic pressure. The simulation shows that in 5mm lift case we get the highest velocity, therefore highest dynamic pressure.

Velocity at the outlet

Due to huge pressure difference between the inlet and the outlet we get high velocities at the outlet. we get the highest velocity when the lift is 5mm, it's because of compressibility, while increasing the gap the fluid is less compressed, therefore velocity increases.

• Note: The spike at the end of the 5mm case simulation (orange colour) is a bag of the compilator.

• Velocity and Pressure contours (Animations)

3mm lift case

4mm lift case

5mm lift case

• Pressure force along Z vs lift (with and without AMR)

With AMR

Without AMR

With AMR we are getting higher values of the pressure force acting on a spindle valve along the Z axis.

• Pressure force along the Z axis (with and without AMR)

As shown in the plot above, when the lift is increased pressure force along the Z axis decreases. when the lift increases high pressure fluid has more area to travel through, therefore fluid is less compressed and travels the gap more freely, velocity increases and ststic pressure acting on the spindle valve decreases.

Conclusion

we successfully simulated proportional valve case, once more realised the power and importance of AMR. post proccesed the different cases and explained the results.