Discretization of 3D intake manifold using GEM-3D

IC-Engine Calibration Using GT-Power and GT-Suite

Assingment:10 (Discretization Techniques)

Objectives:

• 1. To Explore the "Tutorial- single cyl DI". In Case Setup, considering case-1 with discretization length 40 mm & case-2 with discretization length 0.1 mm for intake runner. Comparing both the results for the following paramaters i.e. Parameters-Torque, BSFC, max cylinder pressure and simulation time.

• 2. To Explore tutorial No-2 (GEM3D) - “Building intake manifold from STL model”.

1. To Explore the "Tutorial- single cyl DI".

Model:

The first step is to create a discretization length as a parameter and then we can keep varying the discretization length for different cases in the CaseSetup.

In the CaseSetup, two cases are created in which case-1 is set with default values i.e. RPM= 3600 and Length(Descretization Length)= 40 mm. For case-2, the RPM is constant i.e. 3600rpm and Length(Descretization Length)= 0.1 mm.

Results:

Here the simulations are carried out for two different cases i.e. Discretization length=40mm and 0.1mm. The RPM=3600 is maintained constant for both the cases.

As the model used here is a single cylinder and we changed only the intake runner there is no much impact on varying the discretization length.

From the below table we can observe that there is no much difference in the BrakePower value for both the cases. There is a slight variation in the Air Flow Rate i.e. for 40mm=179.5kg/h and for 0.1mm=176.5kg/h. Also the difference bwtween the two cases for BSFC is also minimal.

The maximum pressure when the discretizationlength =40mm is 117.11bar and when the discretizationlength =0.1mm is 115.18bar.

Simulation Run Time:

The run average time for discretization length=0.1mm is very hign when comapred to first case. The Factor of Real time plot shows the variation for both the cases.

Conclusion:

	Discretization Length= 40mm	Discretization Length= 0.1mm
Torque(N-m)	96.2	95.9
BSFC(g/kW-h)	238.2	238.9
Maximum Cylinder Pressure(bar)	117.11	115.18

2. To Explore tutorial No-2 (GEM3D) - “Building intake manifold from STL model”.

Inorder to open the existing geometry, we need to open GT-SpaceClaim > Import the "phelum" file i.e. the STL file of the geometry.

In space Claim we can do some modifications as required. To extract the fluid volume we need to go to GEM-3D.

Once the geometry opens in GEM-3D, as we are working on Engine, Intake, Exhaust system we need to select "GEM3D(.gem)".

The GEM-3D will create a mesh shape omponent from the imported shape and add it to the model. This is a cadd-model i.e. fluid domain. And now we need to convert this into different individual components.

Seperating Sections by Cures:-

Now the above geometry is divided into small volumes. To do this, we need to go to 'Convert ' from the top toolbar > select the geometry > click on 'Shape Operations' > select "Seperate By Curves". Then set the Tolerance value as 1.

Now select the openings where there is exchange of air and delete them.

Now we have to divide the runners and other volumes. For this we use 3-point cutting plane. Select three points on the bottom surfacewhere the runners are linked to generate the plane. Here we need to set the location such that the plane doesnot cut the runner. Select the second part of the runner and click "Clip". Now we can see runners are different from plenum.

The next step is to convert the runners into pipes. Select a particular [runner and right click on it we get "Convert Shape to Component".

In this step we specify the bend type, crossection variation and also we specify the port size definition i.e. we measure the approximate diameters for both the ports. The pressure,temperature,composition and the wall temperatures are speicfied. Hence the pipe is generated for the first section of runner.

The similar procedure is carried out for rest of the 3runners. Now the first section of all the 4 runners are converted into pipes.

Now we need to convert the second section of the runners. The pressure,temperature,composition and the wall temperatures are considered. Hence the pipe is generated for the first section of runner.

The similar procedure is carried out for rest of the 3runners. Now the second section of all the 4 runners are converted into pipes. Also the extra plane between two sections is deleted.

In conversion process for runners, the info regarding the curved entry from the manifold was lost.This curved entry would represent a better flow transition than a default orifice connection, so manually we add an orifice connection represent.

Here right click on the first region of runner, select port-1 and choose connection as "OrificeConn". Forward discharge coefficient is specified as parameter for all the 4runners. The discharge coefficient=0.95.

In order to make clear for GT about the intake and outlet , we need to specify the second region of runners also.In the same way give the port connection accordingly. For the outlets we add "Subassembly connection" to clearly show the difference in inlet and outlet.

The same procedure is followed for rest of the runners at outlet by changing the port id's for each outlet.

Now we need to divide the pipe section. As we can see there is some angle to the pipe at a particular place we divide the pipe selection as shown. By using Pipe Normal cutting plane we select the pipe region.

Similarly the second part is also divided and the same procedure is carried out to specify the parameters.

Now for the inlet, we should add a connection. Go to add connection, select port 1 and connections as "Subassembly connection" and port i'd is specified as 5 and this is considered as inlet.

The next step is to seperate the manifold from the flowsplit. To simplify the geometry we can hide all the components that we converted before.

Now the top component is divided by using "3-Points Cutting Plane".

Now we need to convert the top part from shape to component.

Next, we need to convert the center section into a flowsplit. By using the "3-Points Cutting Plane' and do it for both the sides.

Now the middle mortion cannot be divided because there is a common entry i.e. from same path its going to two runners. Now we have 3 flowsplits, so we should convert shape to component.

Now unhide all the components and check if there are any gaps. We find gaps between the pipe and plenum and it should closed using extruded connections by using connection option. i.e. Flow> connections > Flow connection. After selecting the option it will show the posiible connections. Select them to close the gap.

Now we need to discretize the model. Before we discretize the model we should do the orientation and then descretize.

Now the 3D model is converted to 1D model. We need to allign the connections in a a systematic way. Hence we get the below 1D model as output.

Conclusion:

Therefore, the intake manifold is built from the STL model.