OS-T: 1385 Heat Transfer Analysis on Piston Rings using Thermal Contact

Piston rings fit on the outer surface of a piston in an engine and they transfer heat from the piston to the cylinder wall.

This tutorial demonstrates the heat transfer analysis on a set of piston rings (Figure 1).

The inner ring takes the heat flux (10.0W/m2) from the piston. The outer surface of the ring that contacts the cylinder wall is maintained at a temperature of 0° C. The heat transfer is modeled by using thermal contact definition between the two rings.

The thermal boundary condition, heat flux loading, and a linear steady-state heat conduction subcase have already been defined in the initial base model. The focus of this tutorial is on defining the thermal contacts between the rings.

Figure 1. Piston Ring Arrangement
The following exercises are included in this tutorial:
  • Define contact surfaces between the rings
  • Define thermal contact at the interface
  • Solve the heat conduction analysis with OptiStruct solver
  • Post-process the results in HyperView

Launch HyperMesh and Set the OptiStruct User Profile

  1. Launch HyperMesh.
    The User Profile dialog opens.
  2. Select OptiStruct and click OK.
    This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Import the Model

  1. Click File > Import > Solver Deck.
    An Import tab is added to your tab menu.
  2. For the File type, select OptiStruct.
  3. Select the Files icon files_panel.
    A Select OptiStruct file browser opens.
  4. Select the Rings.fem file you saved to your working directory. Refer to Access the Model Files.
  5. Click Open.
  6. Click Import, then click Close to close the Import tab.

Set Up the Model

Create Set Segments Between the Rings

In this step, the contact surfaces will be created, and the thermal contact will be defined.

  1. In the Model Browser, right-click and select Create > Set Segment.
  2. For Name, enter RING1 inner surface.
  3. Click the Elements Selection and click add solid faces option to select faces in the inner surface of RING1, as shown in Figure 3.

    Figure 2. Selection of solid faces from the toolbar

    Figure 3. Contact surface on the inner surface of Ring 1
  4. Similarly, repeat the same process to define contact faces on the outer surface of RING2.
  5. For Name, enter RING2 outer surface.

    Figure 4. Contact surface on the outer surface of Ring 2

Create Thermal Contacts Between the Rings

In this step, the thermal contacts will be defined between the rings.

  1. In the Model Browser, right-click and select Create > Groups.
  2. For Name, enter Thermal contact.
  3. In the Property Option, click Property Type and select FREEZE from the drop-down menu.
  4. For SSID, select RING2 outer surface.
  5. For MSID, select RING1 inner surface.
  6. For CLEARANCE field, enter 0.0.
    This will help close the contact; thereby, ensuring the heat transfer across the interface.
    As described at the beginning of this tutorial, the heat transfer boundary condition (Temp RING2 outer), heat flux input (Heat flux) are already in the model. An OptiStruct steady-state heat conduction loadstep, referring to the boundary condition and flux, has been defined, as well. The heat transfer results are requested in loadsteps panel. Refer to tutorial OS-T: 1080 for the details on how to define heat transfer boundary condition, heat flux, and the output request.
    Note: Without the thermal contact, the heat transfer would not occur at the interface of the rings. In this case, the outer ring would remain at zero temperature and the inner ring would take all the heat.

    Figure 5. Contact definition between the ring

Submit the Job

  1. From the Analysis page, click the OptiStruct panel.

    Figure 6. Accessing the OptiStruct Panel
  2. Click save as.
  3. In the Save As dialog, specify location to write the OptiStruct model file and enter Rings_complete for filename.
    For OptiStruct input decks, .fem is the recommended extension.
  4. Click Save.
    The input file field displays the filename and location specified in the Save As dialog.
  5. Set the export options toggle to all.
  6. Set the run options toggle to analysis.
  7. Set the memory options toggle to memory default.
  8. Click OptiStruct to launch the OptiStruct job.
If the job is successful, new results files should be in the directory where the Rings_complete.fem was written. The Rings_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Post-process the Results

Temperature and flux contour results for the steady-state heat conduction analysis are computed by OptiStruct. HyperView will be used to post-process the results.
  1. From the OptiStruct panel, click HyperView.
    HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView.
  2. Click Close to close the message window, if one appears.
  3. On the Results toolbar, click resultsContour-16 to open the Contour panel.
  4. Select Subcase 1 - heat transfer as the current load case in the Load Case and Simulation Selection window.
  5. Select the first pull-down menu below Result type and select Grid Temperatures(s).
  6. Click Apply.
    A temperature contour plot is now available.
  7. Select the first pull-down menu below Result type and select Element Fluxes(V).
  8. Click Apply.
    Both temperature and flux results are shown below.

    Figure 7. Grid Temperature Plot

    Figure 8. Element Flux Plot