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Tutorial: Thermomechanical Analysis of a Engine Piston

eingine piston simscale thermomechanical simulation

This article provides a step-by-step tutorial for a thermomechanical simulation of a engine piston. We take are analyzing the piston under a maximum pressure and temperatures.

We are following this workflow:

  1. Prepare the CAD model and select the analysis type
  2. Assign materials and boundary conditions
  3. Create the mesh
  4. Run the simulation and analyze the solutions

1) Prepare the CAD model and select the analysis type

Once you clicked the button above, you should see the following model of an engine piston.

cad model engine piston tutorial starting point
Cad model of an engine, this is how your project should look like after importing it to your workbench

1a) Create topological entities

Prior to start the simulation we recommend to create topological entities. You can also do that at any point of the simulation setup, but it makes sense to do it in the beginning.

We already created the entities covering the top, the rings and the ring grooves according to the following picture.

topological entities for the engine piston overview
Topological entities for the engine piston

Now you only need to create the set for the interior and the skirt of the piston, which is basically everything other than what is already assigned to sets. The following picture shows what to do:

how to create a new topological set
Create a set for the interior and skirt of the piston
  1. Hide all entities
  2. Activate the box selection
  3. Select all remaining parts
  4. Hit the + next to Topological Entity Set and give it a name

1b) Create the simulation

start the simulation for the engine piston
Create the simulation

Hitting the create simulation button leads to the following options:

select thermomechanical in simulation library
Choose Thermomechanical as analysis type

Choose Thermomechanical as analysis type and create the simulation.

2) Assigning the material and boundary conditions

2a) Gravity

defining gravity in simscale acording to the coordinate system
Define gravity in the model according to the coordinate system

2b) Define a material

assign material and specify your own properties
Assign aluminium as material for the engine piston

2c) Assign the boundary conditions

Now we need to assign both the thermal and mechanical boundary conditions. Let’s start with the thermal ones.

Therefore add a boundary condition and select convective heat transfer:

choose convective heat transfer boundary condition
Choose convective heat flux as a boundary condition
assign a boundary condition simscale
Assign the first boundary condition

Define the convective heat flux boundary condition for all topological entities according to the following table:

geometric partreference temperature [°C]heat transfer coefficient [W/(K*m^2)]
ring 1450150
ring 1 groove4501000
ring 2450150
ring 2 groove380400
ring 3380150
ring 3 groove380400
interior and skirt380650

Now we define the mechanical boundary conditions, which will be three pressure boundary conditions (top and the first two rings) and two remote displacements.

select new boundary conditions simscale
Select 3* pressure and 2*Remote displacement

Once you created the three pressure boundary conditions assign them according to the following table:

EntityPressure [Pa]
Ring 114e7
Ring 24e6

Now create the two remote displacements and give them the following properties:

define remote displacement simscale deformable
Define two remote displacement

Now all boundary conditions are assigned and we can proceed creating the mesh.

We don’t have to worry about the numerics and the simulation control settings, as their default values are optimized according to the chosen analysis type, hence valid for the majority of simulations. If you are a simulation expert however, you can have a look at them and change the settings as you like.

3) Mesh

To get the mesh we use the standard algorithm, which is a good choice in general as it is quite automated and delivers good results for the most geometries.

The only change we need to do here is changing the sizing to manual and define 1.8e-3 m as a cell size and enable 2nd order elements. Make sure your setting look like the picture below:

mesh settings for an engine piston simulation
Apply a standard mesh, use manual sizing with a maximum edge length of 1.8e-3 m and second order elements

The resulting mesh will have about 235k nodes and look like this:

mesh of engine piston
Mesh of the engine piston

4) Start the simulation

starting a new simulation simscale
Start the simulation

Now we can start the simulation and after about 10 minutes we can have a look at the results.

how to access the simscale post processor
How to access the SimScale post-processor

5) Post-Processing

displacement and von mises stress of an engine piston
Scaled displacement and von mises stress
heat flux and temperature distribution of an engine piston
Heat flux on the clipped model and temperature distribution

Analyze your results with the SimScale post processor. Have a look at our post-processing guide to learn how to use the post-processor.

Congratulations! You finished the tutorial!

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