Modelling and simulation of flow through a flowbench
Aim: To create a 3D model of a flow bench and run the flow analysis.
Description:
COMPUTATIONAL FLUID DYNAMICS: The field of study devoted to solution of the equations of fluid flow through use of a computer (or, more recently, several computers working in parallel). Modern engineers apply both experimental and CFD analyses, and the two complement each other.
Flow bench:
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, carburettors, 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.
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. Therefore, all the air passing through the metering element also passes through the test piece. Because the volume flow rate through the metering element is known and the flow through the test piece is the same, it is also known. The mass flow rate can be calculated using the known pressure and temperature data to calculate air densities, and multiplying by the volume flow rate.
Figure 1: Typical Flow Bench schematic
Grid Dependency test
Grid convergence is the term used to describe the improvement of results by using successively smaller cell sizes for the calculations. A calculation should approach the correct answer as the mesh becomes finer, hence the term grid convergence.
The normal CFD technique is to start with a coarse mesh and gradually refine it until the changes observed in the results are smaller than a pre-defined acceptable error.
Objective:
- To conduct the Grid Dependency test.
- To obtain a plot of lift vs mass flow rate.
- To run a parametric sweep to show the effect of valve lift on mass flow rate
Figure 2: Flow of the project.
Steps Followed:
- A flow bench geometry is created using the video provided by skill Lync.
- Flow simulation is opened.
- Then some initial conditions are provided such Fluid type, thermodynamic parameters, analysis type.
- Flow domain is setup.
- Boundary conditions are provided.
- Discretisation is done(meshing).
- For results the plots are created at required positions are created the cut plots.
- Then flow simulation is run.
- Desired outputs are saved.
- Same process is followed for all 3 kinds of meshes.
- On the basis results, mesh size 7 is selected for further study.
- A parametric study is done for different valve lifts.
- Plots are exported and saved.
Results:
Mesh dependency test:
Case 1: Mesh size 3
Figure 3: Flow trajectory.
Figure 4: Velocity Plot
Figure 5: Mass flow rate curve.
Case 2: Mesh size 5
Figure 6: Flow trajectory.
Figure 7: Velocity Plot
Figure 8: Mass flow rate curve.
Case 3: Mesh size 7
Figure 9: Flow trajectory.
Figure 10: Velocity Plot
Figure 11: Mass flow rate curve.
Figure 12: Comparison of mass flow rates.
- Mesh 3 (size 7) is the most suitable because results are converging and plots are clear.
Parametric Study of mesh 3:
Valve lift= 8mm
Valve lift= 6.6mm
Valve lift= 5.2mm
Valve lift=3.8mm
Valve lift=2.4mm
Valve lift=1mm
Conclusions
- As the valve lift increases the mass flow rate also increases.
- As the mesh fineness increases, the results are much better.
Link for CAD files:https://drive.google.com/file/d/1j3gW1HFgueajnMXQPQhQNYvw429HiyPR/view?usp=sharing