Modelling and simulation of flow through a flowbench

AIM: To do flow simulation of fluid flowing through a valve at different valve lift.

Objective:

To do fluid simulation across the valve at different valve conditions.

To check the flow trajectory of the fluid flowing through a valve.

Introduction:

Among the key factors that severely influence both fuel efficiency and pollutant emissions, engine coherent flow structures such as swirl and tumble motions are of primary importance.

These unsteady flow structures depend on the geometry of the engine and its operating conditions, so that some synthesis parameters, namely the permeability and the Swirl and Tumble ratio, are required.

The synthesis parameters are of paramount importance during design stage in order to predict and optimize the engine performance.

Since direct measurement of the flow structures in dynamic engine operation is currently feasible only with test engines equipped with optical access, these parameters are indirectly evaluated using stationary flow benches.

This experimental equipment measure the flow rate across the engine head without taking into account the real engine geometry.

Modelling:

To start with the modelling i have created a new part file then i have made an arbitary circle of radius then i have extruted upto a certain distance.

Then i have started new sketch created a lines which became path for the circle that is to be swept along on it.

Then i have provided the fillet at the joint of the lines.

Then I have created a plane with taking refrence of the line & the end point of that line.

Then as i have created a circle by taking the centre of that new plane then as I have mentioned earlier i have swept that circle along the path.

Thus, the Inlet mamifold is created and then we have to provided a way for the fluid to enter the chamber via inlet manifold as we have till now created only a solid body.

So to do this, all I have done that I have provided a shell of thickness 2 mm. Thus, the inlet manifold with the chamber is ready.

Now, as the inlet manifold is open there is continuous flow of the fluid to the chamber, and if it is open then we can't provide a closed chamber where the fuel will burn.

So, to continuously close and open the inlet of fuel to the chamber, we have to create a valve which will restrict the fuel to enter the chamber when the fuel is being compressed.

Therefore, I have started then creating a valve at the inlet of the chamber.

To start with, i have created a plane near the inlet of the chamber at the centre of the inlet of the manifold while creating a refrence axis at the centre of the manifold.

Then i have created an arbitary shape of valve & then fix some values at the bottom of the valve so to have a upward motion without creating any changes in the sketch.

Also to do flow simulation i have fixed the distance between top surface of cylinder & the point at the valve.

Then I have used revolved boss/base command to create a solid part of the valve.

Flow Simulation:

To do flow simulation, i have to make the model water-tight, to do so I have created lids at the open surfaces of the inlet mainifold and the bottom face of the cylinder.

Then, I started the wizard, named the project, selected the SI unit system & then I have choosen the internal flow then I have ticked on the time dependent & select the total time as 4 milliseconds.

Then, I have provided an inlet velocity at the X-axis.

Then, I have inserted the boundary conditions such as the inlet Static pressure and the total pressure at the bottom of the cylinder at the face of the lid.

Here, the total pressure at the bottom surface is much lesser than the inlet pressure as suction is possible in this case only.

Then, i have provided a local mesh at the surface of the valve.

Then i have inserted the global goals & surface goal such as Mass flow rate.

Then, I have Run the simulation.

Afterwards, when the simulation over I checked for the plots like velocity and pressure. I have also inserted the flow trajectories for this.

The flow Trajectory obtained for this simulation:

Grid Dependency test:

Then to check for the grid for the further parametric study I then checked for the grid test.

To check the grid I have inserted some different cell values of the mesh in x, y and z directions.

The results of the grid dependency test is given below.

The grid dependency test takes more than 3 hours to complete the test.

Even then the Grid cells for Design Point does not evaluate as it takes more memory of my computer to generate the mesh and also my computer was as hot as burning flames. so I decided to stop the simulation for the third design point.

Then I have tried for running parametric study at Design Point 2 but the computer closes the Solidworks application as it was using too much of memory for running continuously upto the eight parametric studies therefore, then I have decided to run with the initial Design Point-1 for the parameteric study as it does not uses too much of memory and also it works fine for this project.

Here is the grid test Pressure and velocity plots at the same valve lift but with different initial mesh values:

Pressure Plot for Design Point -1 (Grid Dependency Test)

Pressure Plot for Design Point -2 (Grid Dependency Test)

Velocity Plot for Design Point -1 (Grid Dependency Test)

Velocity Plot for Design Point -2 (Grid Dependency Test)

Parametric Study:

As the simulation gets over. Then I have run a new parametric study with the most suited grid.

But this time I have given some initial parameters such as the distance between the Top surface of the cylinder & the point on the valve as i have fixed earlier during the parametric study.

Then, I have put the distance in the range of 1 mm to 8 mm with different values.

Then, I have inserted the output parameters such as velocity plot & the pressure plot.

Then I run the parametric study & wait until all of the eight differents computation works gets completed.

Here is the results for the parametric study;

The Velocity Plot differs as shown in this way:

The Mass flow rate vs valve lift is shown as below:

Results:

The Mass flow rate can be is calculated as shown in above table.

Here, the negative sign indicates that mass is leaving the model and we will consider the modulus of those negative values.

Errors while performing Calculations and their solution.

More time will the software will take to calculate if you do not provide the specific values of mesh.

Do not provide higher values of the initial mesh values in x, y and z directions.

Also, the calculation keeps on running if you provide more total time for simulation. provide as low as possible value of total time.

The Grid refinement level should be also based upon your computer specification. Do not provide higher refinement value. Keep it as required.