Modelling and simulation of flow through a flowbench

OBJECTIVE :

• To simulate the flow inside a flowbench geometry.
• To compare the mass flow rates for different valve lifts.

INTRODUCTION :

An air flow bench is a device used for testing the internal aerodynamic qualities of an engine component. It is used primarily for testing the intake and exhaust ports of cylinder heads of internal combustion engines. It is also used to test the flow capabilities of any component such as air filters, carburetors, manifolds or any other part that is required to flow gas.

SETUP EXPLANATION :

1. First, the flowbench geometry is modelled using appropriate dimensions as shown below :

2. The valve sketch is fully defined such that the valve lift can be varied by changing the dimensions.

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3. Lids are added to the inlet and outlet ports to make the geometry watertight.

4. Then, a new setup wizard is created and internal flow study with air as the working fluid is selected.

5. Mesh Setting is set to level 5.

6. Boundary Condition is given as :

• Inlet Total Pressure = 101325 Pa
• Outlet Static Pressure = 51325 Pa

7. Surface Goal of mass flow rate is set at the outlet lid.

8. Velocity cut plot is inserted at the front plane.

9. Flow trajectory from inlet to outlet is inserted with 100 flow streams in between.

10. After that a parametric study is perfermed to get the contours of velocity cut plot at different mesh settings which we call Grid Dependency Test.

11. Now, another parametric study is performed to get velocity countours, outlet mass flow rate and flow trajectories for different values of valve lift.

RESULTS :

Study 1 : Grid Dependency Test :

The model is evaluated at 1 mm valve lift for mesh settings of 5, 6 and 7. The following plots were obtained :

As observed, with mesh setting of 7, the plot looks more accurate. Also, the value of mass flow rate changes a bit with every mesh setting indicating that mesh setting 7 is the most accurate one.

Study 2 : Valve Lift Parametric Study :

At 1mm Valve Lift :

At 2mm Valve Lift :

At 3mm Valve Lift :

At 4mm Valve Lift :

At 5 mm Valve Lift :

Variation Of Mass Flow Rate with Lift :

CONCLUSIONS :

1. From the velocity plot, it can be concluded that the velocity at the downstream of the valve increases as the valve lift increases.
2. From the mass flow rate vs valve lift plot, it can be concluded that the mass flow rate increases as the valve lift increases but the rate of increase. This indicates that after a point the valve lift wont have any effect on the mass flow rate.

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