MODELLING AND SIMULATION OF FLOW THROUGH A FLOWBENCH

AIM: TO MODEL A FLOWBENCH AND RUN FLOW SIMULATION IN SOLIDWORKS

INTRODUCTION: An airflow 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. 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 porting cylinder heads would be strictly hit or miss without it.

A flow bench consists of an air pump of some sort, a metering element, pressure and temperature measuring instruments such as manometers, and various controls. The test piece is attached in series with the pump and measuring element and air is pumped through the whole system. Therefore, all the air passing through the metering element also passes through the test piece. Because the volume flow rate through the metering element is known and the flow through the test piece is the same, it is also known. The mass flow rate can be calculated using the known pressure and temperature data to calculate air densities and multiplying by the volume flow rate.

PROCEDURE:

1. Initially, a Flow bench model is prepared in SolidWorks with appropriate dimensions followed by closing the openings to make it watertight.
2. The Flow Simulation Wizard is run to define an internal flow with an inlet velocity of 300 m/s.
3. A Grid Dependency Test is run to determine the Mesh Level that gives the most accurate results. The Mesh Levels at which the simulation is carried out are 3,4,5. Also, Local Mesh refining is specified, to decrease the mesh size or increased the number of fluid cells at the valve boundary.
4. The boundary conditions are assigned wherein the inlet possesses total pressure of 3 bar and the outlet possesses static pressure of 1 bar.
5. After the execution of the simulation, the velocity and pressure cutplots are projected, helping in selecting the mesh level suitable for carrying out the Parametric Study.
6. At Mesh Level 5, a Parametric Study is run and the Valve Lift dimension is specified as the dimension parameter. The range of lift is assigned.
7. The output parameters are also selected and the study is run for the design points obtained, I.e. the Valve lift values.
8. The Cutplots and Graphs are obtained for evaluation.

RESULTS:

• MESH LEVEL = 3:

VELOCITY CUTPLOT

PRESSURE CUTPLOT

• MESH LEVEL = 4:

VELOCITY CUTPLOT

PRESSURE CUTPLOT

• MESH LEVEL = 5:

VELOCITY CUTPLOT

PRESSURE CUTPLOT

*The Mesh Level shows the most accurate results and is used to conduct the parametric Study.

PARAMETRIC STUDY: At Mesh Level of '5'

VALVE LIFT -

• Design Point 1 = 0.001m
• Design Point 2 = 0.0024m
• Design Point 3 = 0.0038m
• Design Point 4 = 0.0052m
• Design Point 5 = 0.0066m
• Design Point 6 = 0.008m

The mass flow rate is maximum for the largest valve lift because of the greater amount of gas shut from the intake manifold to the combustion chamber. When the opening is small, the mass flow rate becomes constant in a shorter instant whereas, for significantly larger valve lifts, the convergence is achieved in a greater time period.

CONCLUSION: The simulation helps to identify the best geometry of the intake manifold to have a minimum pressure drop to avoid any pumping losses. Also, flow trajectories can help to visualize the swirl that the flow must possess in order to increase the efficiency of the engine where the setup is to be employed.