Chapter 17 DIESEL ENGINE: STAR SET-UP IN es-ice and pro-STAR

The following tutorial data files are used in this chapter:

CLOSED-CYCLE_POLYMESH/injection.tbl

This chapter details the physics set-up in es-ice and pro-STAR for both the full-cylinder and sector Diesel engine models presented in Chapter 15 and Chapter 16 of this volume.

STAR Set-up in es-ice

This section covers the settings required in the Star Controls panel, which is where the model physics (combustion model, initial conditions, boundary conditions, etc.) are defined. Before attempting this part of the tutorial, it is important that you familiarize yourself with the Star Controls panel by completing the example in Chapter 6 of this volume. In the following sections, most of that panel’s settings are presented in summary form, but information specific to diesel models is described in more detail.

The required Star Controls panel settings are as follows:

1.Load model — load the model into Star Controls

2.Analysis setup — select the desired combustion model and define parameters for scalar initialisation

3.Combustion — specify combustion and ignition parameters

4.Initialization — specify the engine initial conditions

5.Boundary conditions — specify the engine boundary conditions

6.Post-setup — specify the post-processing requirements

7.Time step control — specify the time step settings

8.Write data — write the files needed to import the model into pro-STAR

Load model

In the Load model view of the Star Controls panel, (see Figure 17-1):

•Click Load model to load the model in the Controls Workspace window

Figure 17-1 Closed-cycle Star Controls > Load model panel

Analysis setup

In the Analysis setup view of the Star Controls panel (see Figure 17-2):

•Check that the Combustion toggle button is selected

•Select ECFM-3Z, compression from the combustion model drop-down menu to specify compression ignition conditions

•Select n-dodecane from the fuel drop-down menu

•Set the Cetane number to 60

•Ensure that Mixture option is set to Phi and enter 0.85 for the air-fuel ratio

•Ensure that EGR definition is set to Air+Exhaust and enter 10% for the EGR percentage

•Set Residual to 5% to specify that the cylinder contains 5% residual gas at the start of the analysis

Figure 17-2 Closed-cycle Star Controls > Analysis setup panel

Assembly

In the Assembly view of the Star Controls panel (see Figure 17-3):

•Click Finish as you do not need to add any static meshes to the model

Figure 17-3 Closed-cycle Star Controls > Assembly panel

Combustion

In the Combustion view of the Star Controls panel (see Figure 17-4):

•Set the Tabulated Double-Delay Autoignition Model option to On (see “The Double-Delay autoignition model” on page 8-46 of the User Guide and “The Double-Delay autoignition model” on page 11-72 of the Methodology volume for more information on this model).

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Figure 17-4 Closed-cycle Star Controls > Combustion panel

Initialization

In the Initialization view of the Star Controls panel (see Figure 17-5):

•Select Constant Omega from the Velocity drop-down menu to specify an

initial rotational velocity about the global z-axis

•Set the rotational velocity magnitude Omega to 2000

•Set the Pressure to 9.87 and the units to bar

•Set the Temperature to 583 K

•Select I-L (turbulence intensity and length scale) from the Turbulence drop-down menu. Note that you should only use this option if the initial velocity is non-zero. This is because the initial turbulence level is calculated using velocity data, so a zero value causes the solver to fail.

Figure 17-5 Closed-cycle Star Controls > Initialization panel

Boundary conditions

In the Boundary conditions view of the Star Controls panel (see Figure 17-6):

•Set the Combustion dome regions boundary type to Fixed and the

Temperature to 450 K

•Set the Piston crown region boundary type to Fixed and the Temperature to

450 K

•Set the Cylinder wall region boundary type to Fixed and the Temperature to

400 K