Modelling and simulation of flow through a flowbench
Objective: To model a flowbench assembly and to simulate the flow through the flowbench
Description:
An air 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. 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. A flow bench is one of the primary tools of high performance engine builders, and porting cylinder heads would be strictly hit or miss without it.
Specification of the flowbench geometry:
Bore: 0.05 m
Stroke: 0.10 m
Shell Thickness: 0.002 m
Inlet port diameter: 0.03 m
Fillet Radius: 0.04 m
Valve geometry Specification:
Diameter of valve: 0.021 m
Length of valve: 0.09 m
Flowbench Geometry
Procedure:
- The geometry and valve has been created with the above specifications
- Lids are created on both the openings to make the model water tight in order to simulate a flow simulation
- Boundary conditions are provided as Total Pressure on the inlet (Pressure= 133325 pascal and temperature=293.2 K) and Static pressure on the outlet (Pressure= 101325 pascal and temperature= 293.2 K)
- Surface goals are introduced to calculate mass flow rate
- Mesh are generated
- Cut Plots are introduced in order to visualise the velocity and pressure contour
- Flow Trajectory are introduced to visualise the flow and Swirl inside the cylinder
Grid Dependency Test (Mesh Refinement):
The test was conducted for a valve lift of 0.005 m and mesh size of 3, 4, 5
Case 1:
Mesh Size 3
Mass Flow Rate for Mesh Size 3:
Case 2:
Mesh size 4
Mass Flow Rate for Mesh Size 4:
Case 3:
Mesh Size 5
Mass Flow Rate for Mesh Size 5
Results:
From the above grid dependency test we can see that with increasing mesh size the result of mass flow rate converges to an exact value.
So, the test is further carried out with a Mesh Size of 5
Valve Lift Parametric Study:
This test is carried out in order to visualise the Velocity and Pressure Contour for a varied valve lift
Valve Lift values: 0.001, 0.002166, 0.00333, 0.0045, 0.00566, 0.006833, 0.008 (All are in metres)
Case 1:
Velocity Contour
Valve Lift: 0.001 m
Pressure Contour:
Case 2:
Velocity Contour
Valve Lift: 0.002166 m
Pressure:
Case 3:
Velocity Contour
Valve Lift: 0.00333 m
Pressure Contour:
Case 4:
Velocity Contour
Valve Lift: 0.0045 m
Pressure Contour:
Case 5:
Velocity Contour
Valve Lift: 0.00566 m
Pressure Contour:
Case 6:
Velocity Contour
Valve Lift: 0.006833 m
Pressure Contour:
Case 7:
Velocity Contour
Valve Lift: 0.008 m
Pressure Contour:
Mass Flow Rate for Design Points:
Graphs for Design Points:
Explanation:
Velocity Contour: As the valve opens gradually there is an increase in velocity of the flow and mass flow rate also increases gradually.
Pressure Contour: When the valve remains closed there is an increase in pressure inside the inlet port as seen from the pressure contours. But, as the valve opens gradually the pressure drops across the inlet port and air flow from high pressure region to low pressure region.
**Note: Too much pressure drop may increase pumping cost**
Flow Trajectory:
This Test is being carried out in order to visualise the flow inside the cylinder and the swirl develop inside it. The flow trajectory simulation was performed with a valve lift of 2 mm.
Points inferred from the above experiments:
- The flowbench geometry plays a very important role in order to decide the flow velocity and mass flow rate of the fluid
- The mass flow rate increases with the increase in valve lift
- Flow Trajectory shows a clear view of swirl pattern inside the cylinder
- The values of the mass flow rate and velocity converged to an exact value with the mesh refinement enabled