Modelling and simulation of flow through a flowbench
AIM: Modelling and Simulation of flow through a Flowbench.
Objectives of the project:
- To create a 3D cad model and run a baseline simulation.
- To perform a grid dependency test at a particular valve lift.
- To perform valve lift test at a particular grid size.
- To study velocity and pressure plot and explain the results.
- To compare the results for effect of valve lift on mass flow rate.
Introduction:
Computational fluid dynamics is a branch of fluid mechanics that uses numerical analysis and algorithms to solve fluid flows situations. High-performing computers are used to conduct the calculations required to simulate the interaction of liquids and gases with surfaces defined by boundary conditions.
CFD is based on the Navier Stokes equation. Arising from applying Newton’s second law to fluid motion, together with the assumption that the stress in the fluid is the sum of a diffusing viscous term and a pressure term, these equations describe how the velocity, pressure, temperature, and density of a moving fluid are correlated.Computational fluid dynamics or CFD analysis is one of the key analysis methods used in engineering applications.
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.
Static Pressure:
Static pressure is the pressure you have if the fluid isn't moving or if you are moving with the fluid.Static Pressure is the resistance to airflow (friction) caused by the air moving through a pipe, duct, hose, filter, hood slots, air control dampers, etc.
Mass flow rate:
Mass flow rate is the mass of a substance which passes per unit of time.
Geometry of the Model:
Flowbench:
Dimension of the valve lift:
Parameters for the Baseline Simulation:
Output:
Baseline Simulation Plots:
Velocity Plot:
Pressure Plot:
Graph(Mass flow rate):
Grid Dependency Test:
Parameters for Grid Dependency Test
In order to vary the level of mesh refinement, we run a parametric study for a constant valve lift of 0.002m.In this study, we provided input of different mesh grid sizes ranging from 4 to 6.Also, we compute the Velocity and pressure plots for these values as an output parameter in this study.
Output Results for above Study:
Grid Size 4:
Velocity Plot at valve lift of 0.002m
Pressure Plot at valve lift of 0.002m
Grid Size 5:
Velocity Plot at valve lift of 0.002m
Pressure Plot at valve lift of 0.002m
Grid Size 6:
Velocity Plot at valve lift of 0.002m
Pressure Plot at valve lift of 0.002m
Graph(Mass flow rate):
Results and Observations:
- It is observed from the above graph that as the level of mesh refinement increase, mass flow rate magnitude also increases.
- Also, when the fluid enters the combustion chamber for different mesh grid sizes the velocity pattern changes considerably in the velocity plot.
- There are no subsequent changes observed in the pressure plot.
Valve Lift Test:
Parameters for Valve Lift Test:
In this test, we run another parametric study where we changes the valve lift from 0.001m to 0.008m with 8 intervals in between them with a constant mesh grid size of 5. In this study, we compute the output values for velocity plot, pressure plot, mass flow rate for different valve lift, flow trajectories, etc.
Output Results for above Study:
Valve Lift Test at 0.001m
Velocity Plot at Mesh size of 5
Pressure Plot at Mesh size of 5
Velocity trajectory at valve lift of 0.001m
Valve Lift Test at 0.002m
Velocity Plot at Mesh size of 5
Pressure Plot at Mesh size of 5
Velocity trajectory at valve lift of 0.002m
Valve Lift Test at 0.003m
Velocity Plot at Mesh size of 5
Pressure Plot at Mesh size of 5
Velocity trajectory at valve lift of 0.003m
Valve Lift Test at 0.004m
Velocity Plot at Mesh size of 5
Pressure Plot at Mesh size of 5
Velocity trajectory at valve lift of 0.004m
Valve Lift Test at 0.005m
Velocity Plot at Mesh size of 5
Pressure Plot at Mesh size of 5
Velocity trajectory at valve lift of 0.005m
Valve Lift Test at 0.006m
Velocity Plot at Mesh size of 5
Pressure Plot at Mesh size of 5
Velocity trajectory at valve lift of 0.006m
Valve Lift Test at 0.007m
Velocity Plot at Mesh size of 5
Pressure Plot at Mesh size of 5
Velocity trajectory at valve lift of 0.007m
Valve Lift Test at 0.008m
Velocity Plot at Mesh size of 5
Pressure Plot at Mesh size of 5
Velocity trajectory at valve lift of 0.008m
Graph(Mass flow rate):
Results and Observations:
- It is observed from the above plot that as the valve lift increases, the velocity increases and the pressure decreases.
- In case of pressure plot, as valve lift increases pressure decreases due to the increase in distance between valve lift opening and the cylinder.
- Pressure is maximum at a minimum valve lift of 0.001m.
- From the velocity trajectory,it is observed that due to high pressure swirling effect takes place.
- From the graph,it is observed that as valve lift increases the mass flow increases if we considered only the magnitude or absolute value of mass flow rate.
- If the valve lift continue to increase, then larger intake of mass take place at valve opening which causes deacrease in the pressure.
- When the valve lift increases by an amount, we observe a considerable changes in the velocity plot a fluid enters the region.