Modelling and simulation of flow through a flowbench

Aim: In this project, we create a 3D model of a flow bench and run flow analysis & perform the following operations:

• Grid dependence: For this test, we run the simulation for three different grids at a particular valve lift and compare results in order to decide which mesh level is more precise.

• Effect of valve lift on mass flow rate: Here we run a parametric sweep to show the effect of valve lift on mass flow rate for the selected grid level.

Definitions:

• Flow bench: It is a simple device to measure and quantify the amount of air flowing through the cylinder head runners and intake manifolds.
• Valve lift: It is the distance by which the valve is raised from its seated position when it is opened.

Dimensions:

• Cylinder diameter = 5 cm
• Length of the bore = 10 cm
• Inlet manifold diameter = 1.25 cm
• Shell thickness = 1.5 mm
• Lids were created at both ends of the flow-bench.

Procedure:

• A cylinder and valve are created with the given dimensions.
• Valve dimensions are constrained in order to move the valve vertically.
• Inlet total pressure(lid-1): 401325 pa & Outlet static pressure(lid-2): 101325 pa is given at both ends. This pressure difference helps the air to flow towards the lower pressure side.
• A study is made in order to observe the effect of grid level on simulation results and best grid level is chosen for further study.
• A parametric sweep is done for observing the effect of valve lift on the mass flow rate with the best-chosen grid level.
• Global and surface mass flow rate are taken as goals.
• Velocity and pressure cut plots are made for observation.
• Valve lift range: 2-6 mm and grid level: 5 are chosen for the parametric study.

Results:

Grid dependency: Valve lift is taken as 0.004m

Goal (Value)	Design Point 1	Design Point 2	Design Point 3
Level of initial mesh (Automatic Mesh)	3	4	5
GG Mass Flow Rate 1 [kg/s]	0.000134496	-0.000109739	-0.000253286
SG Mass Flow Rate 1 [kg/s]	-5.967376687	-5.134766864	-4.874011194

Grid level: 3

Grid level: 4

Grid level: 5

By the observation the grid level 5 has fewer discontinuities and disturbances hence it is chosen for further studies. Even a high level of the grid can also be chosen for a much better result but it takes much long computation time.

Effect of valve lift on mass flow rate:

For this test the valve lift is taken in the range from 2-6mm and grid level:5 is taken from the above observations.

Valve lift: 2mm

Valve lift: 3mm

Valve lift: 4mm

Valve lift: 5mm

Valve lift: 6mm

Conclusion: With increment in valve lift the pressure drop decreases which is an advantage because lower the pressure drop much better the design of the port.

Goal (Value)	Design Point 1	Design Point 2	Design Point 3	Design Point 4	Design Point 5
Valve Lift [m]	0.002	0.003	0.004	0.005	0.006
GG Mass Flow Rate 1 [kg/s]	1.39253E-05	-0.001064847	1.60634E-05	-0.000495434	2.35706E-05
SG Mass Flow Rate 1 [kg/s]	-3.917664019	-4.629334198	-5.445871471	-6.130338075	-6.713494898

Velocity (Max)[m/s]	21.14789224	21.70390317	23.70802607	23.67276183	24.48277106
Pressure (Max) [Pa]	394691.3545	386185.3904	386921.1753	379020.3594	375378.3951

Obseravtions:

• From the pressure values, we can observe that as the valve lift increase the pressure decreases due to the increase in valve open flow area.
• From the velocity values, we can observe that as the valve lift increase the velocity increases.
• The swirling effect reduces as the valve lift increases can be observed in the velocity cut plots.
• Mass flow rate reduces as the valve lift increases this is because of the resistance to the flow due to the attachment to the valve seat and valve head.
• As the valve lift continue to increase, a larger intake valve opening allows for greater induction mass flow rate which causes the increase of discharge coefficient.