Challenge

Discretization of 3D intake manifold using GEM-3D

Aim:

Objective:

1. Tutorial- single cyl DI add case 2 with discretization length 0.1 mm for intake runner and compare with default case 1

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

Steps to convert 3D intake manifold using GEM 3D to 1D GT model:

Importing the plenum .stl file to GEM 3D

Removal of caps using selection of curves

The inlets and ends of 4 intake runner are closed, so these caps are necessary to open for available to flow.
Select separate by curve option, to separate geometry by parts based on the surface of object.
Set tolerance limit to 1
End section of runner and plenum are separated from main shape, we can delete them from model.

Separation of runner from manifold

From convert tab select 3 point cutting plane.
A cutting plane is created by clicking on three point on the model to define a plane.
Once the plane is created, translate the plane so that it separates the runner and manifold.

Converting runner to flow component

Now we convert the shape to components by right clicking on it.
Select the geometry type we would like to convert. Select pipe in case of runner.
Assign port number.
Keep an appropriate dimension of pipe and keep it fix till the end of the pipe.
Repeat it for other runner ports.

Adding orifice connection:

To add a custom orifice, right click choose orifice connection and provide ID no.
Give forward discharge coefficient of 0.95

Adding subassembly connection to flow direction:

Select the port 2 to runner end and set ID no 1. Set the flow direction to outlet.
This helps GEM 3D to determine direction from any specified values.
Repeat the procedure for other runners.

Divide manifold intake pipe and converting to flow:

The entrance appears as a pipe section with round and D shape, then a 90 deg bend. The straight section can be converted to pipe.
Select cutting plane from convert tab, choose pipe normal cutting.
To separate the D section from flow split section, we drag the cutting plane till it reaches the end it joins manifold.
The plane can be translated as far there is no abrupt change in dimension.
Now we provide the connection to the end pipe, by right clicking on it, select add connection, select port ID 1 set flow direction as inlet.

Separating 90 deg flow split from manifold

The aim is to cut the top flow split section without cutting through manifold.
Select 3D cutting plane from convert tab. Choose three point on the top of manifold.
The cutting plane is rotated and adjusted in a way so that it does not cut the manifold plenum.
The cut model should look like below

Converting manifold into smaller section and converting to flow components

Choose 3 points cutting plane and select one end. The plane appears and it is translated and fixed between first and second runner.
Similar cut is made between third and fourth runner by restore plane option.
Convert each section into flow components. Select flow split as geometry and define the ports.

Adding flow connection

To align the pipe properly we add flow connection
To join the runner click on flow connection face at the end of first runner, then click at the intake of second runner.

Discretized the model

To discretized select export GT model from home tab or toolbar. This opens discretization window.
Choose discretized length 40mm, GEM 3D will discretize and map it to GT ISE.
Proper orientation must be maintained to discretize properly.

Simulation model:

6-cylinder DI engine model

1D conversion model:

Case setup as a function of discretization length

To observe the change in discretization

GT POST:

Real time rate

Time factor

Engine performance

Conclusions:

The average run time for case 1 is 1.3 sec and for case 2 is 1145 sec.
The factor of real time for case 2 has increased to 14450 which is very high.
Negligible changes of values can be observed such as BP, BT, BSFC max pressure and max temperature.
Since no significant changes are found so the intake discretization length should be 0.44 times bore and for exhaust it is 0.55 times the bore.

Ship work like this
in your own course.