Exploring the Discretization process in GT-Power

Aim

To study the effect of Discretization length of the intake runner on engine performance parameters and simulation time and to explore a tutorial on the Discretization process.

Explanation

A 1 cylinder Diesel engine model is used to study the Discretization length

The above discretization length values used is for the intake runner. For case 1, the discretization length is 40 mm and for case 2, the discretization length is 0.1 mm.

Engine performance parameters

Engine Torque comparison:

CASE-1

CASE-2

Engine BSFC comparison:

CASE-1

CASE-2

Engine Peak Pressure comparison:

CASE-1

CASE-2

Simulation time Comparison:

When you increase the discretization length, more number of sub volumes are present in your flow domain. Hence you capture the changes in the flow properties very well, which calculates the performance parameters accurately.

When you have more flow volumes, you calculate the pressure losses accurately which results in the decrease in volumetric efficiency.

Exploring a Discretization tutorial

The Discretization is a process of dividing the CAD geometry in to different flow regions and converting them in to a 1D GT Model components.

CAD GEOMETRY:

The above CAD model is the intake manifold of an engine.

STEP-1-DIVIDING THE GEOMETRY IN TO DIFFERENT FLOW VOLUMES:

The above cutting plane options are used to divide the given CAD model in to different flow domains. The below image shows a 3 point cutting plane.

The cutting plane can be rotated and translated to place it at the required position and direction.

The above image shows a CAD geometry divided in to different flow regions.

STEP-2-CONVERTING THE FLOW DOMAIN IN TO GT-COMPONENTS:

STEP-1

We have to select which type of component is the flow Volume and the Port no.1 is Inlet and 2 is outlet.

STEP-2

It takes the geometry details of the flow volume.

STEP-3

This step takes the values of various physical parameters related to the flow component.

STEP-3-ADDING CONNECTIONS TO THE FLOW COMPONENTS:

Flow connections like orifice and assembly extension can be added for the flow components as shown below.

A shadow can be seen in the above image which is an orifice between two pipes to include flow losses due to change in the cross section of flow volume.

Similarly a gap between any two flow components can be filled as shown in the below image,

After completing all these steps the discretized CAD model has to be exported in to a GT-MODEL as shown below