Challenge

Week 3 Challenge : CFD meshing on Turbocharger

SSwapnil Suhas Jogal31 Aug 2022

ANSA CFD

AIM/OBJECTIVE:

1) To check for the geometrical errors to make appropriate volumes.

2) Create and assign PIDs as shown

3) Perform surface mesh with the given target lengths as per PIDs

4) Perform volumetric mesh for the required volumes as shown

Given:

a) Turbocharger.ansa file to be downloaded

b) Target lengths as per PIDs

Blade stage-1 = 1 mm
Blade stage-2 = 1 mm
Impeller = 2 mm
Shaft rotor = 1 mm
Turbo casing = 5 mm
Compressor casing = 5 mm
Inlet casing cover = 5 mm

TURBOCHARGER:

In an internal combustion engine, a turbocharger (often called a turbo) is a forced induction device that is powered by the flow of exhaust gasses. It uses this energy to compress the intake gas, forcing more air into the engine in order to produce more power for a given displacement.

A turbocharger is a device fitted to a vehicle’s engine that is designed to improve the overall efficiency and increase performance. This is the reason why many auto manufacturers are choosing to turbocharge their vehicles.

How does it work?

A turbo is made up of two halves joined together by a shaft. On one side, hot exhaust gasses spin the turbine that is connected to another turbine which sucks air in and compresses it into the engine. This compression is what gives the engine the extra power and efficiency because as more air can go in the combustion chamber, more fuel can be added for more power.

How a turbocharger works—a closer look

The basic idea is that the exhaust drives the turbine (the red fan), which is directly connected to (and powers) the compressor (the blue fan), which rams air into the engine. For simplicity, we're showing only one cylinder. Here then, in summary, is how the whole thing works:

Cool air enters the engine's air intake and heads toward the compressor.
The compressor fan helps to suck air in.
The compressor squeezes and heats up the incoming air and blows it out again.
Hot, compressed air from the compressor passes through the heat exchanger, which cools it down.
Cooled, compressed air enters the cylinder's air intake. The extra oxygen helps to burn fuel in the cylinder at a faster rate.
Since the cylinder burns more fuel, it produces energy more quickly and can send more power to the wheels via the piston, shafts, and gears.
Waste gas from the cylinder exits through the exhaust outlet.
The hot exhaust gases blowing past the turbine fan make it rotate at high speed.
The spinning turbine is mounted on the same shaft as the compressor (shown here as a pale orange line). So, as the turbine spins, the compressor spins too.
The exhaust gas leaves the car, wasting less energy than it would otherwise.

BASIC STEPS TO BE FOLLOWED WHILE STARTING THE ANSA

Click on the ANSA v22.1.0 in the Start Menu to open the ANSA software.

After clicking the ANSA v22.1.0 the above window pops up. In the above poped up window, select the CFD in Layouts.

In additional ANSA command arguments change the other to -performance_mode 3

Always remember not to click/tick on Dont ask me again. Finally click the OK button.

After opening the above window, right click on the top tab with icons and select the show labels and click apply to all

Open the downloaded Turbocharger.ansa file as shown below

On opening the model you will see the following:

Single cons, Red cons or Double cons and hot points.

Our first target would be to remove the Red cons

Turn on the shading mode by using the red encicled button as shown in the below figure.

Turn on the PID mode by clicking the buttons encircled in red as shown below

The following is the view of model in PID mode

Using Ctrl + Shift you can turn on the wireframe mode. Ctrl + Shift + Mouse left / right / middle button can be used to orient the model the way we want to observe.

Turn on PID properties using red encircled button as shown above, a new window pops up named Properties.

By turning off the bulb in the Properties window, we identify that the 11 Default PSHELL Property was overlapping with the 20 Default PSHELL Property. This overlapping can be removed by deleting the 11 Default PSHELL Property.

Deleting is done by right click on the 11 Default PSHELL Property and then click on the delete as shown above.

On clicking the delete, a new window named Delete Options pop up, in that click on the OK button and that PID is deleted.

On turning on the bulb of 20 Default PSHELL Property and in the propeties window we observe that unwanted overlapping body is deleted.

Now we see on overlapping or extra surface encircled in red as shown in above figure.

We delete that surface by using delete under Faces in TOPO and then selecting the surface required to be deleted, a new window pos up Face Delete List. In the window select the Face ID and click the delete button.

Now we make the proper surface at the place where unwanted surface has been deleted.

The new surface is created using New under Faces in TOPO, on clicking the New a window named New Face Options pop up, in that we select the COONS encircled in blue and the using the Loop option encirled in blue we select the curves on which surface has to be generated.

On Middle click of the mouse a temporary surface is generated along with the new window poping up coons confirming with us with the temporary surface generated is OK or Not.

Once we click the OK the surface is generated

Now we see there is a red cons presesen in the green encircled area as shown in above figure. We will try to resolve this.

Using Intersection under Faces we try to check the intersection error, First we select the purple highted surface and the second surface selected is blue and the press the middle mouse button.

We delete the first face / area as this is not required

We keep the second face / area as this required by us.

We delete the third face / area as this is not required by us.

We keep the fourth face / area as this is required by us.

After the intersection is done, we observe that the edges of the at the red encircled portion is not proper.

We create cut using the Cut under Faces in TOPO

We delete the unwanted face as shown above. We Also deleted the unwanted hot points generated due to cut options we used.

We create a new surfaceas shown above and we remove the curvy edge error.

Now we attempt to remove the red cones encircled in blue color as shown in the above image.

Since in the above image we were not able to exact shape of surface, we split the surface into three surfaces by creating the curves.

We select Transform under Curves in TOPO and select the curve, press the middle mouse button / scroll and then select the hot points starting from the arrow till the other hot point where the curve has to be formed as shown in below image encircled in black.

Similarly we follow the above procedure to generate the curve on the other side as shown in below image.

Once the surface is generated we delete the curves that were created to generate the surfaces.

Now we attempt the remove the red cons present in the impeller casing.

We create a hot point as shown above.

Now we are transfroming the surface.

Select the entity as shown above and do the middle click of the mouse.

A new window pops up named Copy Entities. Use the selected option as shown in above image.

Now using fill hole option we create a surface at the curve highlgihted portion.

Then we did a Topo for the impeller casing.

We perform a geometry checks and found fivr intersection errors. We attempt to remove these intersection errors.

Similarly we delete the unwanted surfaces near the rotor shaft blades near the rotor.

Now we project the cons on the shaft surface to delete the overlapping surface.

Now we delete the unwanted surface.

We delete this face.

We delete this face

We delete this face.

We do a geometry check and found one intersection error which has to resolved.

We delete this face.

Now we are creating the surface as shown in the above figure.

Now we again do the geometry and found no intersection errors at the rotors and rotor shaft.

Now we run the geometry checks for the entire geometry and found four intersection errors.

We attempt now to resolve these intersection errors.

We delete the ovelapping surface and delete the portion of shaft in the compressor casing.

We delete this face.

Now we are projecting the curve or coons present on the compressor casing onto shaft so that we remove the faces in the casing thickness.

We delete this face

We delete this face.

Now we have projected the curves near the impeller casing onto the shaft and delete the portion of the rotor shaft.

We delete this face.

We delete this face

We delete this face.

We did the the geometry checks and found the intersection error at the junction of impeller and shaft.

We do the Topo and there will be an autofix.

Here we came to a point where all the geometry clean up and intersection error are removed.

Now to have an water tight mesh we will fill all the gaps exposed.

We will close this gap also.

Now we have closed all the gaps.

Now we will assign the PIDs

After clicking apply make a selection by left click on the mouse and pressmiddle mouse button / scroll

We can delete the unwanted PIDs as shown in the above figure.

Now the PIDs are assigned with the required names and unwanted PIDs are deleted.

We now start with the surface meshing with target length as 5mm for Compressor Casing, Inlet Casing Cover and Turbo Casing.

Using Properties window we turn off the bulb except for Compressor Casing, Inlet Casing Cover and Turbo Casing.

Using Length under Perimeters in MESH under poped selection window, Select Perimeters using left mouse button make a selection window

This is how it appears after selection is done.

By pressing the middle mouse button, a window named Length Parameters pops up, in that enter the Length as 5 and press OK.

In selection window, Select Macros using left mouse button make a selection window and then by pressing the middle mouse button a window named Length Parameters pops up.

Enter Length as 5 and click OK.

We select Visible under Spot Mesh in Mesh Generation encircled in Red.

Finally the surface meshing of Compressor Casing, Inlet Casing Cover and Turbo Casing with target length as 5 mm has been done as shown in the above figure.

Now we perform the surface meshing impeller with target length as 2mm. To do that turn on the bulb of Impeller only as shown in the above figure.

Using Length under Perimeters in MESH under poped selection window, Select Perimeters using left mouse button make a selection window

By pressing the middle mouse button, a window named Length Parameters pops up, in that enter the Length as 2 and press OK.

In selection window, Select Macros using left mouse button make a selection window and then by pressing the middle mouse button a window named Length Parameters pops up. Enter the length as 2 and click OK.

We select Visible under Spot Mesh in Mesh Generation.

Finally the surface meshing of Impeller with target length as 2 mm has been done as shown in the above figure.

Now we perform the surface meshing Blade Stage 1, Blade Stage 2 and Shaft Rotor with target length as 1mm. To do that turn on the bulb of Blade Stage 1, Blade Stage 2 and Shaft Rotor as shown in the above figure.

Using Length under Perimeters in MESH under poped selection window, Select Perimeters using left mouse button make a selection window.

By pressing the middle mouse button, a window named Length Parameters pops up, in that enter the Length as 1 and press OK.

In selection window, Select Macros using left mouse button make a selection window as shown above.

Then by pressing the middle mouse button a window named Length Parameters pops up. Enter the length as 1 and click OK.

We select Visible under Spot Mesh in Mesh Generation.

Finally the surface meshing of Blade Stage 1, Blade Stage 2 and Shaft Rotor with target length as 1 mm has been done as shown in the above figure.

When we turn on the impeller along with Blade Stage 1, Blade Stage 2 and Shaft Rotor we see Unmeshed : 18 as shown in above figure.

This is near the area boundary where there is meeting of nodes of surface with target length 2mm and target length 1mm.

We select Select under Spot Mesh in Mesh Generation and then select PID region of impeller and do the middle click.

The meshing is done and clashes of meshing near the two node length meeting at the common crossover takes place are nullified.

Similar unmeshed is shown when the Turbo Casing is turned on. Again we follow the same procedure over here as we have done with impeller and rotor shaft.