Modelling and simulation of flow through a flowbench

Aim:To create a 3D model of a flow bench and run flow analysis.

1. Grid Dependence test i.e. to choose the best grid size at a particular lift of valve.

2.To run a parametric study at that grid size at different valve lift in order to obtain a plot of lift vs mass flow rate.

Introduction:

An air flow bench is a device used for testing the internal aerodynamics 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 engine. 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.

Grid Dependence test is something in which we will make our mesh grid size finer for more accurate results.

Procedure: First of all we have to create a flow bench model for analysis. I have choosen the "MMGS" unit system in SOLIDWORKS 2018.

Dimension of Model:

Diameter of Cylinder=100mm

Diameter of inlet port=20mm

Length of cylinder=70mm

Diameter of valve base =20mm

Flow Bench Model:

Cut Section View:

In the flow bench analysis we are actually want to see the effect of valve on mass flow rate. So to attain the valve lift(i.e. the up and down motion of the valve) we have to constrain the dimension of valve so that it can move up and down.

Constraints on Valve:

When the model is prepared we have to do Grid Dependence Test:

First I have choosen 'air' as a fluid and then take velocity of 10m/s in the x direction.

At inlet port i have apllied boundary condition Total pressure and at outlet the boundary condition is static pressure.

For Mesh Grid Size 3 and at a valve lift of 1mm:

For Mesh Grid Size 4 and at a valve lift of 1mm:

For Mesh Grid Size 5 and at a valve lift of 1mm:

So after grid dependence test I came to conclusion that the grid size of 5 will be more accurate for this calculation. As with the increase in mesh the no. of elements increases and so the result will be more accurate.

Now finally we have to do parametric study, in this study we are actually going to check the effect of valve lift on mass flow rate. that is at different valve lift what is the velocity and mass flow rate. Since we have choosen mesh grid size of 5 as a best for analysis and local mesh is provided at the valve.

Meshed Model:

I have choosen surface mass flow rate at the outlet of the cylinder i.e. at the bottom of cylinder.

I have calculated the result at five different lift values.

Result: At diff valve lift the mass flow rates are:

At Design Point1(at .0004m) the velocity plot is:

At Design Point 2(at .00155m) the velocity plot is:

At Design Point 3(at .0027m) the velocity plot is:

At Design Point 4(at .00385m) the velocity plot is:

At Design Point 5(at .005m) the velocity plot is:

Plot of mass flow rate vs valve lift:

Conclusion: The flow bench analysis is very helpful as it shows the dependence of parameters like velocity ,pressure and mass flow rate on each other. As the valve lift increase the mass flow rate of air increases but the velocity and pressure decreases. The parameters are important such that it helps in reducing the effect of knocking in the engine .As stated above the change is pressure and area helps increasing in velocity .