Modelling and simulation of flow through a flowbench

1. AIM

To model and simulate flow through a flowbench and analyse the results.

2. OBJECTIVES

1. Create a 3D model of a flow bench.
2. Run flow analysis.
3. Plot lift vs mass flow rate.
4. Run Grid dependence test.
5. For three grids run simulation at a particular valve lift and explain your results.
6. Effect of valve lift on mass flow rate.
7. For the best grid, run a parametric sweep to show the effect of valve lift on mass flow rate

3. INTRODUCTION

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. 

4.CAD GEOMETRY

5. FLOW SIMULATION

SOLIDWORKS Flow Simulation is an intuitive Computational Fluid Dynamics (CFD) solution embedded within SOLIDWORKS 3D CAD that enables you to quickly and easily simulate liquid and gas flows through and around your designs to calculate product performance and capabilities.

The major tabs in Flow simulation

PARAMETERS

1. Internal flow simulation
2. Steady state study
3. Pressure: 101325KPa
4. Temperature: 293.2K
5. Velocity along X axis: 600m/s
6. Medium : Air
7. Wall conditions: Adiabatic with 0 micrometer roughness,

Boundary conditions

1. Inlet pressure at inlet port vent : 401325KPa
2. Outlet pressure at piston cylinder bottom : 101325KPa

STEPS

1. Model the system using solidworls sketch, boss extrude and revlolve tool.
2. Lids are created at the inlet port and bottom of cylinder to make the model water tight.
3. Activate the flow simulation plugin of solidwokrs in add-ins tab.
4. Select wizard and input respective details including medium as per parameters given above to set the project. 
5. Set the computational domain to 3D and set the domain in such a way that the silumation result is not affected.
6. Insert a local mesh on the surface of airfoil for more accurate results.
7. Set surface goals (Forces on X and Y axis) to get drag and lift forces.
8. To conduct grid dependecy test a new parametic study is created. Different grid sizes from 3 to 6 were given at a 0.003m valve lift to simulate and deciding which will be best for rest of simulation and was run to get cut plots for pressure and velocity.
9. After identifying the best global grid mesh size create an another parametric study for getting mass flow rate at that grid size for different valve lifts.

Boundary settings

Grid depenedency test settings

6. RESULTS, OBSERVATIONS AND CONCLUSIONS

 Grid dependecy test 

Taking the mass flow rate as positive because here negative sign in result is due to mass flow rate going outside the lid (sign convention).

Grid size level = 3

Grid size level = 4

Grid size level = 5

Grid size level = 6

The results using a mesh grid level of 6 is giving more optimum value and the contours are more promising. As the mesh size became fine from coarse, the value of average mass flow rate coming from the outlet for a particular valve lift decreases or it converges towards more accurate results. Also in the pressure contour and velocity contour the parameters become more differentiable. So mesh grid size 6 is considered for further study.

Mass flow rate vs Lift parametric study

 Lift = 0.001m

Lift = 0.002167m

Lift = 0.00333m

Lift = 0.0045m

Lift = 0.00567m

Lift = 0.00683m

Lift = 0.008m

Effect of valve lift on mass flow rate

1. As the valve lift increases, mass flow rate also increases simultaneously. But after a certain extent of valve lift , the mass flowrate is invariant of the valve lift.
2. From velocity cutplots, it can be concluded that as valve lift increases the velocity of fluid entering into the cylinder also increases. 
3. At the area of valve near the openings it creates vortices due to sudden contraction and expansion in area.
4. As the lift increases we can see a high pressure region near the node of valve where the rod is attached to valve poppet, which will help in pushing in the air into the cylinder.
5. Maximum velocit is seen in the region of valve where there is samll slanting which helps in moving the air more effectively to the cylinder. Also it is helping in creating eddies and vortices.
6. The swirling effect reduces as the valve lift increases can be observed in the velocity contours.