Modelling and simulation of flow through a flowbench
MODELING AND SIMULATION OF FLOW-THROUGH A FLOWBENCH
AIM:
- For this project, you will create a 3D model of a flow bench and run flow analysis. You will be obtaining a plot of lift vs mass flow rate.
- You need to do the following:
- Grid dependence test.
- For three grids run your simulation at a particular valve lift and explain your results.
- Effect of valve lift on the mass flow rate.
- Once you have decided on the best grid, run a parametric sweep to show the effect of valve lift on the mass flow rate.
INTRODUCTION:
An airflow bench is a device used for testing the internal aerodynamic qualities of an engine component.
fig(1) - 3D model of flowbench.
It is used primarily for testing the intake and exhaust ports of the cylinder heads of the 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 port in cylinder heads would be strictly hit or miss without it.
SPECIFICATIONS:
Parameters
Bore diameter - 50mm
Length of the cylinder - 100 mm
Intake manifold diameter - 25mm
Boundary conditions
Inlet total pressure - 172369 [Pa] at temperature 293.2 [K]
Outlet static pressure - 172369 [Pa] at temperature 293.2 [K]
Wall condition - Real wall [no slip boundary condition]
GRID DEPENDENCY TEST:
A mesh convergence test or grid dependency test should mean computing the solution on successively finer grids. The difference between the two refinements is usually taken as a measure of the accuracy of the coarser of the two.
Now we run a 3D model simulation with 3 grid refining cell values(grid level sizing) in order of 2, 3, and 4 respectively at a particular valve lift of 4mm.
Refining grid level at 2 :
Refining grid level at 3 :
Refining grid level at 4 :
PARAMETRIC STUDY FOR GRID DEPENDENCY TEST
| Goal (Value) | Design Point 1 | Design Point 2 | Design Point 3 |
| Level of initial mesh (Automatic Mesh) [ ] | 2 | 3 | 4 |
| D3@Sketch5@Try_simulation.Part [m] | 0.004 | 0.004 | 0.004 |
| SG Mass Flow Rate 1 [kg/s] | -0.064370686 | -0.064115021 | -0.060764993 |
| SG Max Total Pressure 1 at inlet [Pa] | 172369.2452 | 172369.3454 | 172369.4123 |
| SG Max Total Pressure 1 at outlet [Pa] | 101727.0607 | 102197.6736 | 103091.8793 |
| Pressure drop [Pa] | 70642.1845 | 70171.67187 | 69277.53306 |
The plot between a valve lift of 4mm vs mass flow rate at the different refinement of grid level
| Goal (Value) | Design Point 1 | Design Point 2 | Design Point 3 |
| SG Mass Flow Rate 1 [kg/s] | -0.064370686 | -0.064115021 | -0.060764993 |
According to the grid dependency test, a higher refinement level makes the mesh finer thus results in better accuracy.
Thus we choose the grid-level sizing of 4 by comparing all other refining cells.
MASS FLOW RATE VS LIFT PARAMETRIC STUDY
| Goal (Value) | Design Point 1 | Design Point 2 | Design Point 3 | Design Point 4 | Design Point 5 | Design Point 6 | Design Point 7 | Design Point 8 |
| D3@Sketch5@Try_simulation.Part [m] | 0.001 | 0.002 | 0.003 | 0.004 | 0.005 | 0.006 | 0.007 | 0.008 |
| Level of initial mesh (Automatic Mesh) [ ] | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
| SG Mass Flow Rate 1 [kg/s] | -0.037598137 | -0.06414915 | -0.085199572 | -0.110442084 | -0.124926958 | -0.137146124 | -0.146514541 | -0.153925997 |
| SG Max Total Pressure 1 at inlet [Pa] | 172369.0579 | 172369.4097 | 172370.1379 | 172369 | 172369 | 172369 | 172369 | 172369 |
| SG Max Total Pressure 1 at outlet [Pa] | 101735.1531 | 102308.285 | 104605.9084 | 106612.3805 | 108643.8906 | 109753.4653 | 110807.3059 | 111295.0196 |
| Pressure drop [Pa] | 70633.9047 | 70061.12472 | 67764.22944 | 65756.61946 | 63725.10938 | 62615.53469 | 61561.69408 | 61073.98045 |
VALVE LIFT AT 0.001m
VALVE LIFT AT 0.002m
VALVE LIFT AT 0.003m
VALVE LIFT AT 0.004m
VALVE LIFT AT 0.005m
VALVE LIFT AT 0.006m
VALVE LIFT AT 0.007m
VALVE LIFT AT 0.008m
EFFECT OF VALVE LIFT ON MASS FLOW RATE
Here negative sign in the result is due to mass flow rate going outside the lid (sign convention).
From the parametric study, we came to know that as the valve lift increases the flow rate of mass decreases in the result is due to mass flow rate going outside the lid.
OTHER RESULTS:
PRESSURE DROP
Formula: Pressure drop = Total pressure inlet - Total pressure outlet
A pressure drop occurs when frictional forces, caused by the resistance to flow, act on a fluid as it flows through the tube. Pressure drop increases proportionally to the frictional shear forces. High flow velocities and/or high fluid viscosities result in a larger pressure drop. Low velocity will result in lower or no pressure drop.
Here in our case as the lift valve increases mass flow rate decreases will lead to result in low velocity thus the pressure drop will be lower at each lift of the valve.