Setting the Inlet and Outlet Boundary Conditions

Air enters through the intake port inlet with a static temperature of 330 K and a pressure of 2.5 bar. At the inlets of the GAVs, you introduce methane gas with a total temperature of 330 K, where the gas admission starts at 230.0 deg CA and ends at 246.0 deg CA. You import a table that describes the mass flow rate of the methane gas as a function of crank angle. To avoid diffusion of flow quantities at the GAV inlets, you exclude the flow-boundary diffusion fluxes. At the exhaust port outlet, you set a pressure of 1.5 bar and a static temperature of 700 K.

To set the boundary conditions:
  1. Set the inlet boundary conditions for the intake port:
    1. Right-click the Engine > Intake Port > Inlet node and select Edit.
    2. Within the Edit dialog, in the Pressure group box, click Import.
    3. In the Import Table dialog, navigate to the inCylinder folder of the downloaded tutorial files, select twoStrokeEngine_IntaketPort_Inlet.csv, and click Open.
      In the Graphics window, a plot opens that displays the a constant pressure of 2.5 bar for all crank angles. The correct table columns and units for the pressure are assigned automatically.
    4. In the Static Temperature group box, from the File drop-down menu, select twoStrokeEngine_IntaketPort_Inlet.
    5. Set Temperature Column to T_K.
      The plot in the Graphics window updates to add the temperature data—a constant temperature of 330 K for all crank angles.


      The correct species mass fractions for the inlet are set by default.
    6. Click Apply, then Close.
  2. Set the inlet boundary conditions for the GAVs:
    1. Right-click the Engine > GAVs > GAV 1 > Inlet node and select Edit.
    2. Within the Edit dialog, in the Boundary group box, set Type to Mass Flow Inlet.
    3. In the Total Temperature group box, select Constant from the drop-down menu, then set the constant value to 330.0 K.
    4. In the Mass Flow Rate group box, from the drop-down menu, select Table, then click Import.
    5. In the Import Table dialog, navigate to the inCylinder folder of the downloaded tutorial files, select twoStrokeEngine_GAV_Inlet.csv, and click Open.
      The correct table columns and units are assigned automatically.
      In the Graphics window, a plot opens that displays the mass flow rate as a function crank angle.


    6. In the Species Mass Fraction group box, set the following properties:
      Property Setting
      Air Mass Weighting 0.0
      Exhaust Mass Weighting 0.0 (default)
      Fuel Mass Weighting 1.0
    7. Click Apply, then Close.
    8. Repeat Steps 2 a - f for the Engine > GAVs > GAV 2 > Inlet node.
  3. Exclude the flow-boundary diffusion fluxes:
    1. In the Explorer pane, select the Simulation tab.
    2. In the simulation tree, expand the Continua > Default Gases > Models node.
    3. Select the following nodes in order and deactivate Flow Boundary Diffusion:
      • Segregated Flow
      • Segregated Fluid Enthalpy
      • ECFM-3Z
      • Conditional Enthalpy
    4. Select the In-Cylinder tab.
  4. Set the outlet boundary condition for the exhaust port:
    1. Right-click the Engine > Cylinder > Outlet node and select Edit.
    2. In the Edit dialog, in the Pressure group box, click Import.
    3. In the Import Table dialog, navigate to the inCylinder folder of the downloaded tutorial files, select twoStrokeEngine_ExhaustPort_Outlet.csv, and click Open.
      In the Graphics window, a plot opens that displays a constant pressure of 1.5 bar for all crank angles.


    4. Click Apply, then Close.
  5. Save the simulation .