Week-11 : Discretization of 3D intake manifold using GEM-3D

Aim:

Discretization of 3D intake manifold using GEM-3D

Objective:

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

• Parameters-Torque, BSFC, max cylinder pressure
• simulation time

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

Part 1

• Simulation  Model

• 1D conversion model

• Case setup as a function of discretization length

• Results:

  • Real-time rate

• Time factor

• Engine performance

Part 2

Importing the plenum .stl file to GEM 3D

• Open file to open plenum.stl model.
• Select next and make sure the surface radio button is selected.

Removal of caps using a selection of curves

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

Separation of runner from the manifold

• From the convert tab, select the 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 the runner.
• Assign port number.
• Keep an appropriate dimension of the pipe and keep it fixed 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 a forward discharge coefficient of 0.95.

Adding subassembly connection to flow direction:

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

Divide manifold intake pipe and convert to flow:

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

Separating 90 deg flow split from the manifold

Converting manifold into smaller section and converting to flow components

Adding flow connection

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

Discretized the model

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 in 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.