Modelling and simulation of flow through a flowbench

Aim :  Create a 3D model of a flow bench and run flow analysis. Also obtain a plot of lift vs mass flow rate

Also , need to do the following

• Grid dependence test
• For three grids run your simulation at a particular valve lift and explain the results
• Effect of valve lift on mass flow rate
• Once decided the best grid, run a parametric sweep to show the effect of valve lift on mass flow rate.

Introduction :

Flow simulation is a form of computational fluid dynamics which digitally replicates flows in surface water or collection systems. Performing flow simulation allows for the prediction and analysis of how a flow might be impacted by complex geometry in an operational environment.

Basic theory on the simulation :

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.

Total Pressure :

Total pressure is the measure of the total energy of the airstream and is equal to static pressure plus velocity pressure. The total pressure is the sum of the static and dynamic pressures. Total pressure is the total of static pressure p, dynamic pressure q, and gravitational head.

Static Pressure:

Static pressure is the pressure that a fluid exerts when it is not moving.

Mass Flow Rate:

The mass flow rate of a system is a measure of the mass of fluid passing a point in the (m) system per unit time.

Entire case setup :

• The geometry and the valve has been created .
• Now create the lids for both the inlet and exit of the geometry to make the model water tight to perform simulation.

• Create a new project and apply the necessary boundary conditions.
• Make total pressure at inlet and static pressure at the outlet.
• For Baseline simulation :

• INPUTS	VALUES
  FLOW	INTERNAL
  TOTAL PRESSURE	401325 pa
  STATIC PRESSURE	101325 pa
  MESH SIZE	3
  VALVE LIFT	0.003m

• Surface goals are set at the outlet of the geometry for calculating the mass flow rate.
• Provide necessary mesh and given maximum refinement .
• Cut-plots are made for both velocity and pressure contour.
• Run a Baseline simulation at 0.003 mm valve lift at mesh refinement at level 3:

Velocity cut plot :

Pressure cut plot :

Goal result and plot :

• GRID DEPENDENCY TEST :
• Now create a new parametric study for mesh refinement level for 4 , and 6.and give necessary input and output parameters as following :

Velocity cut plot :

Pressure cut plot :

Goal result and plot :

OBSERVATION :

• From the graph, we can see that as the refinement level increases mass flow rate magnitude also get more optimum.
• There are no subsequent changes in pressure plots.
• But in the Velocity plot, when the fluid enters the combustion chamber for different grid sizes the velocity pattern is considerably changing.
• With the grid size of 5, we observe a pattern that can be Desirable for Accuracy and on Simulation Time.
• Hence for proper results and plot description, we go with grid size 5. Although, we may go for a higher value but that may increase the computation time as well.

VALVE LIFT PARAMETRIC STUDY:

Here , i have taken values for 8 points from 0.001m to 0.008m.This is said the Valve lift.

In this,for different values of the valve lift , how the pressure and velocity varies with respect to the flow rate is being observed.

• create a new parametric study for dimension parameter (valve lift) and mass flow rate is taken into account for calculation.

• Click on the run button.
• Then,the desired results are then obtained for mass flow rates at different lift values.

Velocity Cut plots for Design point 1 to 4 :

 Velocity Cut plots for Design point 5 to 8 :

 Pressure Cut plots for Design point 1 to 4 :

Pressure Cut plots for Design point 5 to 8 :

Goal Results and Plot :

MASS FLOW RATE VS. VALVE LIFT :

Observation :

VELOCITY CONTOUR: As the valve lift increases , there is increase in velocity along with increase in mass flow rate.

PRESSURE CONTOUR: When the valve is closed (or min.valve lift) there will be the maximum pressure inside the cylinder and when the valve opens there is a fall in pressure, which drop from high pressure to low pressure.

This helps to not increases the pumping cost because the pressure drop increases gradually with the valve lift.

Conclusion :

• The Mass flow rate increases with the increase in the valve lift.
• Mesh refinement gives us the Best possible value but increases the simulation time.
• So,Flow bench is very much useful to determine the flow rate and flow velocity.