Modelling and simulation of flow through a flow bench Using SolidWorks

Aim:

To design a flow bench with an inlet valve and a port then to run a flow simulation using Solidworks at different valve lift conditions.

Objective:

1. To create a Flow bench with inlet valve and a port of suitable dimension.
2. Then to Perform a parametric test for the grid dependence of the analysis.
3. Then to analyze the flow characteristics under various valve lift conditions with a suitable fine mesh grid.
4. Then to obtain the plot for lift vs mass flow rate.

Theory:

A flow bench is a device used for testing the internal aerodynamic qualities of an engine component and is related to the more familiar wind tunnel. It is used primarily for testing the intake and exhaust ports of cylinder heads of internal combustion engines.

A flow bench consists of an air pump of some sort, a metering element, pressure and temperature measuring instruments such as manometers, and various controls. The test piece is attached in series with the pump and measuring element and air is pumped through the whole system.

Grid dependency test is the analysis of a model under the same conditions with different mesh refinement. This test obtains the ideal grid refinement number for the simulation.

Software Used:

Solidworks

Part Modelling:

The Flow bench is created using SolidWorks under the below mentioned dimensions,

Dimensions of Flow Bench:

• Inner diameter = 75 mm
• Length of cylinder = 125 mm
• Intake port diameter = 10 mm
• Shell thickness = 0.2mm

Procedure :

1. Initially the Part model of flow bench is created using SolidWorks.
2. Then Flow Simulation Add on is chosen.
3. Then a new project in flow simulation is created.
4. The Working fluid is set as air and the flow as laminar & turbulent
5. Then the outlet mass flow rate is set as goal plot and pressure & velocity is set as cut plot.
6. Then the initial simulation is run with the above conditions.
7. After the Simulation is complete a new parametric study for grid dependency test is created.
8. Then four studies are created with increasing levels of mesh i.e., 3,4,5 and 6.
9. Then the mass flow rate with mesh level is compared. And the most accurate mesh for valve lift test is chosen based on the results obtained.
10. Then a new parametric study is created for valve lift. Five studies is created for the different values of valve lift from 1 mm to 5 mm.
11. Finally the resulted mass flow rate is compared with the mesh level.

Results and Plots:

1.Grid Dependence Test:

1.1.Case(1) For Mesh Level-3

1.2.Case(2) For Mesh Level-4

1.3.Case(3) For Mesh Level-5

1.4.Case(4) For Mesh Level-6

1.5.Goal Plot Results :

2.Parametric Study for Valve Lifts:

2.1.Case(1) Design Point-1 (Valve Lift- 1 mm):

Velocity Distribution :

Pressure Distribution :

2.2.Case(2) Design Point-2 (Valve Lift- 2 mm):

Velocity Distribution :

Pressure Distribution :

2.3.Case(3) Design Point-3 (Valve Lift- 3 mm):

Velocity Distribution :

Pressure Distribution :

2.4.Case(4) Design Point-4 (Valve Lift- 4 mm):

Velocity Distribution :

Pressure Distribution :

2.5.Case(5) Design Point-5 (Valve Lift- 5 mm):

Velocity Distribution :

Pressure Distribution :

The pressure in the inlet manifold is more than the static pressure at the outlet. Initially when the valve is closed pressure in the cylinder will be same as the static pressure at the outlet.

When the valve lift position increases the pressure drop value reduces. Now since the pressure drop values decreases for the increase in valve lift between the inlet and the outlet, velocity of the gases flowing across the valve.

2.6.Global Mass Flow rate Vs Valve Lift:

2.7.Surface Mass Flow Rate at different valve lifts :

When the Valve lift is minimum, pressure developing in the cylinder is at lower rate. And the pressure developing is high when the lift is maximum Initially, the pressure drop is high hence the tendency of the gases to flow from the region of higher to lower pressure is high.

Hence the conclusion is that the mass flow rate is increases for a small lift in the valve position. And gradually decreases for higher values of the valve lift.

References:

1. https://en.wikipedia.org/wiki/Air_flow_bench
2. http://www.flowperformance.com/system.html

Conclusion:

Mass flow rate decreases with the increase of valve lift but in general, the mass flow rate is directly proportional to valve lift in reality, thus mass flow rate increases when valve lift increases. Because, area increases with the increase in valve lift and that results into increase of mass flow rate.

The accuracy of the results is directly based on the mesh size. The more refined the mesh is the greater is the accuracy of the results obtained.