ELSA SPRAY MODELLING	Chapter 23
Saving the Model File

Saving the Model File

Having completed the es-ice part of the CFD model set-up, save your work up to this point in an es-ice model file.

•In the Select panel, click Write data

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

•Close es-ice

STAR Set-up in pro-STAR

This section covers the required settings in pro-STAR, which is where the ELSA spray model, boundary conditions and STAR analysis controls are specified. 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 ELSA and ECFM-CLEH is given 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.Activate the Lagrangian model for particle tracking

3.Define scalars required by the ELSA model

4.Set up the Lagrangian droplet physical models and controls

5.Define the injector boundary conditions

6.Set up the numerical analysis controls

7.Add an Extended Data segment to the problem file, as currently required by the ELSA model

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 increase 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 (see Figure 23-34)

•Click the Resize, Model and Events buttons in sequence

•Close the es-ice panel

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Figure 23-34 es-ice panel

Activating the Lagrangian model

To set up an ELSA run, you must first activate the Lagrangian model in pro-STAR:

•In the pro-STAR Model Guide, select Analysis Features (see Figure 23-35)

•Set the Multi-Phase Treatment option to Lagrangian

•Click Apply

Figure 23-35 ELSA Analysis Features panel

Defining the ELSA scalars

Three ELSA-specific scalars are required for this case:

•LIQM_ELSA — The liquid phase of the fuel injected through the nozzle

•LSFD_ELSA — The liquid surface area density, used to determine the mean size of the liquid droplets (i.e. the droplet diameters)

•LIQV_ELSA — The vapour phase of the fuel taking part in combustion

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The LIQM_ELSA and LSFD_ELSA scalars were defined as passive scalars (tracers) in the es-ice Star Controls panel. In this section, you must redefine LIQM_ELSA as an active scalar with properties that match the liquid fuel. The LSFD_ELSA scalar remains passive. You must also change the settings defining the mass diffusivity constant for both scalars.

A fuel vapour scalar (Scalar 1) has already been defined automatically by the ECFM-CLEH model, but you must change its name here to LIQV_ELSA so that it is compatible with ELSA’s naming conventions. Changing the fuel vapour scalar name also requires redefinition of the reaction scheme.

First, redefine the LIQM_ELSA scalar:

•In the pro-STAR Model Guide, select Thermophysical Models and Properties > Additional Scalars > Molecular Properties (Scalars) (see Figure 23-36)

•Set the Scalar # to 48

•Set Influence to Active

•Set the panel parameters as follows:

•Density (kg/m3) — 824.6

•Molecular Weight (kg/kmol) — 208.2

•Expansion Coefficient — 0

•Molecular Viscosity (kg/ms) — 0.00137563

•Specific Heat (J/kgK) — 2203.67

•Conductivity (W/mK) — 0.134905

•Heat of Formation (J/kg) — -1.69896e+06

•Temperature of Formation (K) — 298.15

•Click Apply and then click OK to close the warning message

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Figure 23-36 LIQM_ELSA properties

•Click Define Polynomials

•In the Polynomial Function Definition panel (see Figure 23-37), set the panel parameters as follows:

•Tmin — 200

•Tmax — 750

•C1 — 6.8912

•C2 — 0.0895922

•C3 — 0.000294643

•C4 — -1.05188e-06

•C5 — 1.04676e-09

•Enthalpy — -42247.5

•Entropy — -48.5848

•Click Apply Coefficients followed by Close

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Figure 23-37 LIQM_ELSA polynomial

Check the LSFD_ELSA scalar:

•Set the Scalar # to 49 (see Figure 23-38)

•Make sure that the Influence setting is Passive

•Click Apply

Figure 23-38 LSFD_ELSA properties

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Define the LIQV_ELSA scalar:

•Enter the following commands to rename Scalar 1 (fuel vapour) as LIQV_ELSA

SCMODIFY, 1, NAME LIQV_ELSA

•Set the Scalar # to 1. Note that the name displayed on the panel has changed to LIQV_ELSA (see Figure 23-39)

Figure 23-39 LIQV_ELSA properties

Redefine the reaction scheme:

•Enter the following commands to define the leading reactant (i.e. LIQV_ELSA)

CRTYPE, 1 LREACT, 1

LIQV_ELSA

•Enter the following commands to define the reaction scheme

REACTION, 1 1 14.9 0 10.3 9.2

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where:

1 — the number of LIQV_ELSA kilomoles in the reaction 14.9 — the number of Oxygen kilomoles in the reaction 0 — the number of Oxygen kilomoles in the products 10.3 — the number of CO2 kilomoles in the products 9.2 — the number of H2O kilomoles in the products

• Enter the following command for a stoichiometric check of the chemical reaction scheme

CRSCALAR, MAP, 1, DBASE

Define the binary properties of the ELSA scalars:

•In the pro-STAR Model Guide, select Additional Scalars > Binary Properties (see Figure 23-40)

•Select the Diffusion Velocity Correction check box

•In Scalar Mass Diffusivity, select Scalar Number 48 and set the Constant (m2/s) to 1e-10

•Click Apply

•Select Scalar Number 49 and set the Constant (m2/s) to 1e-10

•Click Apply

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