Saving the Model File

Figure 17-9 Closed-cycle Star Controls > Time step control panel

Write data

In the Write data view of the Star Controls panel:

•Accept the default settings and click Write data to generate the files required by pro-STAR

Saving the Model File

•In the Select panel, click Write data

•In the Write Tool, enter save_es-ice.diesel and click Save to save the model

• Close es-ice

At this stage, you can continue setting up the model physics in es-ice and pro-STAR by going to Chapter 17 and following the description therein.

STAR Set-up in pro-STAR

This section covers the required settings in pro-STAR for a diesel fuel injection engine, which is where the fuel spray, liquid film and STAR analysis controls are defined. Before attempting this part of the tutorial, it is important that you familiarize yourself with the pro-STAR interface by completing the example in Chapter 7 of this volume. In the following sections, most panel settings are only presented in summary form, but information specific to diesel models and fuel injection is described in more detail.

The required steps are as follows:

1.Start up pro-STAR, open panel es-ice.PNL and use it to import the data created in es-ice

2.Select the Lagrangian and Liquid Film modelling options

3.Set up fuel injection parameters

4.Set up liquid film properties

5.Set up the STAR analysis controls

6. Save the model and create the STAR geometry and problem files

Using the es-ice Panel

Use the es-ice panel to import the mesh and physics settings created in es-ice and saved via the Write data operation in Star Controls. Also resize the pro-STAR memory allocation and define moving mesh events.

•Launch pro-STAR in the usual manner

•Select Panels > .es-ice from the menu bar to open the es-ice panel, as shown in Figure 17-10

•Click Resize, Model and Events in sequence

•Close the es-ice panel

Figure 17-10 es-ice panel

Selecting Lagrangian and Liquid Film Modelling

To model fuel injection, activate the pro-STAR Lagrangian and Liquid Film options.

•In the pro-STAR Model Guide, select Analysis Features as shown in Figure 17-11

•Set the Multi-Phase Treatment option to Lagrangian

•Set the Liquid Films option to On

•Click Apply

Figure 17-11 Analysis Features panel

Setting up the Fuel Injection Model

Enter control parameters that determine how fuel droplets are handled in the STAR solver.

•In the pro-STAR Model Guide, select Lagrangian Multi-Phase > Droplet Controls (see Figure 17-12) and set the panel parameters as follows:

•Set the Interpolation Method to Use Vertex Data

•Set the Under-Relaxation of Lagrangian Sources to 0.5

•Set the Droplet Trajectory Maximum File Size (Mb) to 400

•Set the Maximum Number of Parcels to 500000

•Click Apply

Figure 17-12 Droplet Controls panel

Specify the droplet physical models that determine the droplet behaviour during the analysis.

•In the pro-STAR Model Guide, select Lagrangian Multi-Phase > Droplet Physical Models

•In the Global Physical Models tab (see Figure 17-13), set the panel parameters as follows:

•Set the Turbulent Dispersion to On

•Set the Gravity Effects to On

•Set the Collision Model to Advanced (you may choose to turn Off this model to reduce the run time)

•Click Apply

Figure 17-13 Global Physical Models panel

•In the Droplet Physical Models tab (see Figure 17-14), set the panel parameters as follows:

•Set the Momentum Transfer > Correlation to Standard

•Set the Mass Transfer Calculation to Standard

•Set the Heat Transfer Calculation to Standard

•Set the Droplet Break-Up > Break-Up Model to Reitz

•Set the Droplet-Wall Interaction > Droplet Behavior to Bai

•Set the Droplet-Wall Interaction > Wall Heat Transfer to On

•Ensure that Droplet-Wall Interaction > Thermal break-up is activated

•Set Boiling to On

•Click Apply

Figure 17-14 Droplet Physical Models panel

Specify the droplet physical properties by selecting the appropriate droplet material.

•In the pro-STAR Model Guide, select Lagrangian Multi-Phase > Droplet Properties (see Figure 17-15) and set the panel parameters as follows:

•From the drop-down menu at the top of the panel, select the Define from NIST table option to open the droplet properties database

•In the Component Properties table, select row 1

•In the NIST database, select C14H30 (N-TETRADECANE). This fuel is selected because the NIST database provides the correct liquid fuel density for the analysis conditions. The fuel evaporates to Scalar 1, which is C12H26 in this case.

•Click Select

•In the Component Properties table (see Figure 17-16):

•Set Mass Fraction to 1 and press <Enter> on the keyboard

•Set Evaporates to Scalar to 1 and press <Enter> on the keyboard

•Click Apply

1

2

3

Figure 17-15 Droplet Properties database

Figure 17-16 Droplet Properties panel

Finally, specify the fuel injection and atomisation parameters.

•In the pro-STAR Model Guide, select Lagrangian Multi-Phase > Spray Injection With Atomization (see Figure 17-17) and set the panel parameters as follows:

•Set the Atomization Model to Huh

•Set the Nozzle L/D to 6

•Set the Nozzle CD to 0.7

•Click Apply Spray Options

•Set the Injection Temperature (K) to 310

•Set the Hole Diameter (m) to 0.0004

•Set the Coordinate System to 11

•Select Table from the Mass Flow Rate drop-down menu and enter injection.tbl in the Table filename box

•Set the Number of Parcels/Injector (/sec) to 5e7

•Click Update Injector

Figure 17-17 Spray Injection With Atomization panel

•If you are continuing from the closed-cycle polyhedral meshing tutorial, repeat the previous steps for all injectors so that each uses the same settings except for Coordinate System. The Injector Number is increased using the