Modelling and simulation of flow through a flowbench
Aim: Create a model of a 3D flowbench and run flow analysis. Also obtain plot of lift vs mass flow rate
Objective:
- Grid dependence test
- For three grids run your simulation at a particular valve lift and explain your results
- Effect of valve lift on mass flow rate
- Once you have decided the best grid, run a parametric sweep to show the effect of valve lift on mass flow rate
Introduction:
Computational fluid dynamics is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid flows
Total pressure is the sum of static pressure and velocity pressure. Static pressure exists in a non-moving fluid. Velocity pressure is the pressure needed to accelerate air from zero velocity to a certain velocity that is proportional to the air stream kinetic energy
The mass flow rate is the mass of a liquid substance passing per unit time. In other words, Mass flow rate is defined as the rate of movement of liquid mass through a unit area. The mass flow is directly dependent on the density, velocity of the liquid and area of cross-section. It is the movement of mass per unit time.
Procedure:
Geometry of the flow bench and valve lift
Baseline Simulation Results:
Velocity Plot
Pressure Plot
SG Mass Flow Rate
Grid Dependency Test
We run a parametric test where for constant valve lift of 0.003m and set three different grid sizes ranging from 4 to 6. We obtain velocity and pressure plots for these three design points.
- Grid Size 4
Velocity Plot
Pressure plot
- Grid Size 5
Velocity Plot
Pressure plot
- Grid Size 6
Velocity Plot
Pressure plot
SG Mass Flow Rate
Results and observations:
- From the graph above, we can see that as refinement level increases the mass flow rate value becomes more optimum.
- There are no subsequent changes in the pressure plots
- In the velocity plots, however, when fluid enters the combustion chamber for different grid sizes, the velocity pattern is considerably changing.
- We could’ve gone for a higher value but that would increase the computation time considerably.
Valve Lift Test
WIth a grid size of 5, we run another parametric study where we change the valve lift from 0.001m to 0.008m with 8 intervals. All other parameters are kept the same but we add a flow trajectory. We add a local mesh around the valve to get better results. We are looking to obtain velocity plots, pressure plots, mass flow rates for different values of valve lift and flow trajectories for each design point.
- Valve lift at 0.001m
Velocity Plot
Pressure Plot
Flow Trajectory
- Valve lift at 0.002m
Velocity Plot
Pressure Plot
Flow Trajectory
- Valve lift at 0.003m
Velocity Plot
Pressure Plot
Flow Trajectory
- Valve lift at 0.004m
Velocity Plot
Pressure Plot
Flow Trajectory
- Valve lift at 0.005m
Velocity Plot
Pressure Plot
Flow Trajectory
- Valve lift at 0.006m
Velocity Plot
Pressure Plot
Flow Trajectory
- Valve lift at 0.007m
Velocity Plot
Pressure Plot
Flow Trajectory
- Valve lift at 0.008m
Velocity Plot
Pressure Plot
Flow Trajectory
Graph
Results and Observations
- From the pressure plots, we observe that as the valve lift increases, the pressure decreases.
- From the velocity plots, we observe that as the valve lift increases, the velocity increases.
- The swirling effect reduces as the valve lift increases and can be observed in the velocity trajectory plots as well.
- 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 lift valve continues to increase, a larger intake valve opening allows for greater production of mass flow rate which causes an increase in discharge coefficient.