Chapter 14

MULTIPLE CYLINDERS

Chapter 14 MULTIPLE CYLINDERS

The following tutorial files are used in this chapter:

MULTIPLE_CYLINDERS/save_es-ice.multiCylinder

MULTIPLE_CYLINDERS/manifoldTwin.dbs

This chapter demonstrates the es-ice multiple cylinder feature, where a multiple cylinder engine model is created from a single cylinder model by copying and transposing cells. By default, Cylinder 1 is located relative to coordinate system 1. Using the Multiple cylinders panel, Cylinder 1 can be redefined with respect to a new coordinate system. Similarly, new cylinders can be added to the model and positioned with respect to user-defined coordinate systems. The angle-offset between cylinder cycles is also set, thus determining the cylinder crank angle relative to Cylinder 1.

In the following example, a single-cylinder model is used as the basis for creating a V-Twin engine model. The single cylinder is similar to that used in the Trimming tutorial of Chapter 4 but is modified into a full four-valve cylinder. The intake port is also shorter to accommodate an intake manifold. These changes were made via the STAR-CCM+ meshing facilities but are not described here, as this chapter focuses on the multiple-cylinder feature in es-ice.

The cylinders are angled at 45 degrees to each other about the z = –280 position and the crank angle is offset by 350 degrees, as illustrated in Figure 14-1.

Figure 14-1 Diagram of cylinder configuration

The steps to set up a multiple-cylinder case for this tutorial are outlined below:

1.Resume from an existing es-ice model file

2.Set up the cylinders in the Multiple cylinders panel

3.Create and check the multiple-cylinder mesh

4.Specify appropriate Star Controls

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Resuming the es-ice Model File

Resuming the es-ice Model File

The tutorial starts from an es-ice model file supplied with the STAR-CD installation. The model contains an assembled template, but Star setup has not yet been run. This stage of the modelling process is equivalent to that described in Chapter 4, “Running Star Setup” for the Trimming Method tutorial.

To resume the es-ice model file:

•Ensure that

save_es-ice.multiCylind er is in your current working directory and launch es-ice in the usual manner

•In the Select panel, click Read

Data

•In the Read Tool, click the ellipsis (...) next to the Resume box and select

save_es-ice.multiCylind er from the file browser. This action will load the model and display the template mesh in the

Template window.

Making, Cutting and Assembling the Template

If you have an es-ice model file, but not an Ice template file (save_ice), you are recommended to enter es-ice and generate it using with the current version of the code.

•In the Select panel (see the left of Figure 14-2), click Create Template

•In the Create Template panel, click Make Template to generate a new save_ice template file

•When the child process is complete, click Read Template

•In the Select panel, click Trimming

•In the Trim panel (see the right-hand side of Figure 14-2), click Cut

•When the child process is complete, click Assemble to generate an assembled mesh with the current version of es-ice

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Chapter 14	MULTIPLE CYLINDERS
	Setting Up Multiple Cylinders

Figure 14-2 Multiple cylinder Create Template and Trim panels

Setting Up Multiple Cylinders

Use the Star setup panel to generate the files needed to import the model into pro-STAR. In these steps, you will also use the Multiple cylinders panel to set up parameters for Cylinder 1 and 2.

•In the Select panel, click Star Setup

•Ensure Start (deg) is set to 320

•Set Stop (deg) to 1400 so Cylinder 1 covers a full intake stroke before combustion and Cylinder 2 covers a full exhaust stroke after combustion

•Ensure pro-STAR 4.20 is selected from the pro-STAR drop-down menu

•Click Multiple cylinders to open the

Multiple cylinders panel

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Checking the Computational Mesh

In the Multiple cylinders panel, set the parameters defining the location and orientation of Cylinder 1.

•Select Cylinder 1 in the list at the top of the panel

•Set the Z Rotation to 180 to rotate Cylinder 1 about the z-axis, so that the intake ports on both Cylinders 1 and 2 face inwards

•Set the Z Center to –280 to define the z-coordinate about which the Y Rotation applies

•Set the Y Rotation to 22.5 to define the rotation of Cylinder 1 in the X-Z plane about the Z Center

•Set Coordinate system to 21 and click Define to define the coordinate system ID for Cylinder 1

•Click Replace to replace the default settings for Cylinder 1 with the ones specified above

Next, set the parameters defining the location and orientation of Cylinder 2.

•Set Angle offset to -315 degrees to define the crank-angle offset of Cylinder 2 relative to Cylinder 1

•Set Delta Y to 50 to translate Cylinder 2 in the y-direction, as the cylinders are not in-line due to independent crank pins

•Set Z Rotation to 0

•Set Z Center to -280

•Set Y Rotation to -22.5

•Set Coordinate system to 22 and click Define to define the coordinate system ID for Cylinder 2

•Click Append to add a cylinder with the current settings to the model

•Close the Multiple cylinders panel

Finally, run Star setup to store the geometry changes and generate the files required for pro-STAR input.

•In the Star setup panel, click Star setup

Checking the Computational Mesh

The Create Result panel generates a mesh to be used by STAR at a specified crank angle. You can employ this feature to check such a mesh and ensure it is suitable for the solver. The mesh is checked at TDC, BDC and at maximum intake and exhaust valve lifts. Cylinder 2 uses the same mesh and events as Cylinder 1 so if Cylinder 1 is valid, Cylinder 2 should also be valid. You can therefore save time by

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Chapter 14	MULTIPLE CYLINDERS
	Checking the Computational Mesh

checking only the computational mesh for Cylinder 1. To create and check the mesh at TDC:

•In the Select panel, click Create Result

•In the Create Result panel, ensure Angle (deg) is set to 360

•Select the Interpolate toggle button

•Click Create Result to create the mesh at 360 degrees crank angle. This is stored in your working directory in a database-format file called

result.d360.0.dbs

•When the mesh-creation child process is complete, click Read Result to read the mesh into the Workspace window

•Enter the following command to check for negative-volume cells

Check, NegVolume

Figure 14-3 shows the mesh at 360 degrees crank angle.

Figure 14-3 Multiple cylinders at 360 degrees crank angle

•Repeat the previous steps with Angle (deg) set to 540 to create and check the computational mesh at 540 degrees crank angle, shown in Figure 14-4

Figure 14-4 Multiple cylinders at 540 degrees crank angle

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Checking the Computational Mesh

You can now create a section plot through Valves 1 and 2 on Cylinder 1 for a visual inspection of the mesh around the intake valve at maximum lift. This check requires a section plane positioned at y = –19.5, with a section-normal in the y-direction.

•Set Angle (deg) to 469, the crank angle at maximum intake valve lift for Cylinder 1

•Click Create Result, then Read Result

•Enter the following command to check for

negative-volume cells

Check, NegVolume

•Enter the following commands to define the section plane point and normal

SPoint, 0, -19.5, 0 SNormal, 0, -1, 0

•In the Plot Tool, change the Plot Type from Hidden to Section

•Select View 0 -1 0 for the Views

•Click CPlot to display the section plot, as shown in Figure 14-5

Figure 14-5 Section plot at 469 degrees crank angle

•Repeat the previous steps with Angle (deg) set to 964 to create and check the computational mesh at maximum exhaust valve lift, shown in Figure 14-6

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