Parametric study of a Flow bench Valve lift Vs Mass Flow Rate

Introduction; A Parametric Study on flowbench - Modelling & CFD simulation

- An air flow bench is a device used for testing the internal aerodynamic qualities of an engine component A flowbench is a device used to design the intake port / exhaust ports of an IC engine.

- A 3D model of a flow bench is created using solidworks & parametric study is performed with varying values of valve lifts to obtain the plot of valve lift vs mass flow rate & the pressure drop in the system.

Intial Parameters;

Cylinder model dimensions;

• Bore diameter is 50mm.
• Length of cylinder 100mm.
• Intake manifold diameter is 25mm

Boundary conditions;

• Inlet total pressure - 401325 Pa at temperature 293.2 K
• Outlet static pressure - 101325 Pa at temperature 293.2 K
• Type of wasll considered - Real wall.

Steps;

1. Create the model using above dimensions with valve
2. Apply boundary conditions
3. Create cut plots to view the velocity profile for varying value of valve lifts
4. Create surface goals - Total Pressure & Mass flow rate
5. Run parametric study for varying values of mesh levels & obtain the best mesh value
6. Run parametric study for varying values of valve lift with constant value of best mesh level obtained in previous step
7. Analyse the plots & graphs generated

Grid Dependency Test - Grid dependence test is a method in the which the model is subjected to successive small cell sizes / mesh sizes for performing the calculations. When the element size decreases the percentage error in the results reduces or it means that the solution converges to a better solution. For the cylinder model with constant lift of 4mm the mesh level is varied for 3 values.

For mesh level- 2 For mesh level- 3 For mesh level- 4

Plots for varing mesh level - 2, 3 & 4

Inference; From the above we can oberve that with increase in mesh level the pressure drop across the system reduces thereby the flow rate increases with fluctuation. By considering the above graphs the first 2 graphs tends to converge to a better solution as the refining of cells increases. Hence we choose mesh level 4 for the parametric study to show the effect of valve lift on the mass flow rate.

Variation of velocity with valve lift varing from 1mm to 8mm with increments of 1mm

Inference from above plots;

• Initially when the valve is closed, the pressure inside the cylinder will be same as the static pressure at outlet
• When valve lifts gradually, the pressure starts developing inside cylinder

Plots for varing valve lifts for constant mesh level of 4

Inference from above graphs;

• As the valve lift increases the mass flow rate increases & the total pressue inside the system increases
• As the valve lift increases the pressure drop across the system decreases