Flow Simulation Project 4 : Modelling and simulation of flow through a flowbench

AIM :

Modelling and simulate flowbench.

Objective :

• To create a 3D geometry of the flow bench and analysis the flow simulation. To run the grid dependency test at three levels.
• To plot of lift vs mass flow rate.

Theory :

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. 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.

3D Model

Procedure :

• Initially create the 3D model of the flow bench and create a 3D model of Lift valve.
• Make sure while creating Lift valve of the 2D sketch, constraint it properly except the vertical motion.
• Then go to the flow simulation create lid on both the side (inlet and exit) and make the boundary conditions at the inlet (total pressure=172369 Pa) and at the exit(static pressure=101325 Pa) and select the wall as real wall.
• Now go to the parametric study and run the simulation at the different grid level at(3, 4 and 5), so on this test we are getting more accuracy in in grid level 5. So we’ll go to the new parametric study and click on goal and select the mass flow rate and then click on cut plot and then select front plane to cut.
• Open the parametric study and click on add simulation parameter and add the different Lift distance. And add the output as mass flow rate and cut plot and then run the simulation.

Grid Dependency Test :

Grid convergence is the term used to describe the improvement of results by using successively smaller cell sizes for the calculations. A calculation should approach the correct answer as the mesh becomes finer, hence the term grid convergence.

The normal CFD technique is to start with a coarse mesh and gradually refine it until the changes observed in the results are smaller than a pre-defined acceptable error. There are two problems with this approach. Firstly, it can be quite dificult with other CFD software to obtain even a single coarse mesh result for some problems (particularly when time is pressing). Secondly refining a mesh by a factor of 2 can lead to an 8 fold increase in problem size so even more time is needed. This is clearly unacceptable for a piece of software intended to be used as an engineering design tool operating to tight production deadlines. These and other issues have added greatly to the perception of CFD as an extremely dificult, time consuming and hence costly methodology.

Grid level 3

Grid level 4

Grid level 5

We conclude that when increase in grid level then increase the accuracy of the calculations and avoid the errors.So the best Grid level is 5

RESULTS

Valve Lift Parametric study

Valve Lift=0.001

Valve Lift=0.002

Valve Lift=0.003

Valve Lift=0.004

Valve Lift=0.005

Valve Lift=0.006

Valve Lift=0.007

Valve Lift=0.008

TABLE

PLOT:

Mass flow rate vs Valve Lift

Conclusion :

After calculating and studying the plots, it can be conclude that the Valve Lift is increasing ,the velocity at the inlet is also increasing and pressure is decreasing. the flowbench at the different Valve lift can be observed that the mass flow rate is varying.