BENCH FLOW ANALYSIS USING SOLIDWORKS

AIM

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

Plot a curve for Valve Lift Vs Mass flow rate

BASE LINE SIMULATION

There are various parameter and values are used to run the Flow simulation for Base line

PARAMETER	VALUES
Inlet (Total pressure)	151987.5 Pa
Outlet (Static pressure)	101325 Pa
Mess size	5
Valve lift	3 mm
Working fluid	Air

BODY OF CONTENT

Introduction

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.

STEPS FOR DESIGNING

Before starting make sure the unit is in meter

1. Firstly we need to make circle of proper dimension as shown in figure.

2. After that we need to extrude the circle by the help of extrude feature. Here I am extruding with 10 cm.

3. After that go to front plane and select new sketch for making inlet port.

We make sketch just like as shown in figure. After that make a circle at the end of sketch in order to make pipe like structure for inlet of air.

4. After that go to sweep feature in order to make pipe like geometry. Select circle and line in order to make the pipe.

5. Now go to the shell option and select inlet and outlet face of the design and provide suitable thickness to make it hollow like structure.

6. In order to make valve of the flow bench we need to make axis and plane to do sketching.

Now make the design of the valve just like as shown in figure.

And at last go to sweep feature to make the valve.

7. In order to see the geometry we can use cut section option to see the internal part also as shown in the figure.

8. At last we need to make the geometry close for doing flow simulation for that we need to make lid at the inlet as well as outlet section.

STEPS FOR FLOW SIMULATION

Before doing Flow simulation make sure that the geometry is close at inlet and outlet port.

1. Go to the WIZARD option to start a flow simulation. After that one dialog box will appear. Write project name which you want to give the name to it. After that click on next.

2. When you hit the next button it asks to set the unit system. For my project i used as SI unit. After that click on next button.

3. After click on next it will ask to define the flow type whether it is external or Internal. My aim is to study inside the Flow bench so I used internal.

There are several additional features also present like gravity, time dependent etc select the option if required in study. After that hit next button.

4. After that select the fluid which you want to take in your study and click on add button in order to add the fluid. Here I have used air as a fluid.

5. After that choose roughness of the wall if it has otherwise click on next.

6. After that provide essential details like velocity and click finish button.

7. After that your design will be enclosed in the chamber which is our domain of interest as shown in figure below.

8. In order to provide boundary condition for the design we need to right click on boundary condition and select insert boundary condition as shown in figure. Here I am giving two types of boundary condition one is at inlet and another is at outlet.

For inlet I am using total pressure of value 1.5 times of atmospheric pressure that is 151987.5 Pa.

For outlet I am using static pressure and the value is atmospheric pressure as show in the figure.

9. To study the flow analysis we need to select the quantity which we need to study.

In order to study the quantity, we need to right click on goal and select insert surface goals after that select the quantity which you want to study. Here I am using mass flow rate.

10. Now in order to insert mess we need to right click on global mess and select edit definition option. After that provide the mess size according to your laptop specification.

11. After that click on run button in order to start the simulation process.

After that one dialog box will appear where we have selected new calculation option and click on ok button.

12. After completing the flow simulation. Now go to result option and right click on cut plot and select insert option. Select velocity for showing cut plot of velocity.

13. The distribution of velocity is shown in the cut plot as shown in figure.

GRID DEPENDENCY TEST

Consider the valve is at 3mm and the grid size is 3, 4 ,5.

Based on that the velocity cut plot obtain are

1. For grid size 3

2. For grid size 4

3. For grid size 5

Based on that result obtain are shown in the figure below

Grid size	Mass Flow Rate (Kg/s)
3	-0.051121392
4	-0.050363976
5	-0.048150854

The mess size getting finer when we increase the grid size and it will give the accurate result.

As shown in figure that the mass flow rate is less for grid size 5 because the accuracy is very much high. So, I used the grid size of 5.

Valve lift parametric study

For doing valve lift parametric study I have provided the dimension between valve and the cylinder which is consider as variable in the valve lift parametric study.

Here I have started the opening of valve from 1mm to 8mm gap.

For different values of valve lift we get the different mass flow rate.

The sketch name D6 is consider as a valve opening dimension. The dimension given in the figure is 3mm but after varying it in parametric study it starts from 1mm and end at 8mm.

The variation of lift is represented with red colour as shown in figure.

RESULTS

Case 1. When the lift is 1mm

Cut plot of velocity

Cut plot for pressure

Case 2. When the lift is 2.2mm

Cut plot of velocity

Cut plot for pressure

Case 3. When the lift is 3.3mm

Cut plot of velocity

Cut plot for pressure

Case 4. When the lift is 4.5mm

Cut plot of velocity

Cut plot for pressure

Case 5. When the lift is 5.6mm

Cut plot of velocity

Cut plot for pressure

Case 6. When the lift is 6.8mm

Cut plot of velocity

Cut plot for pressure

Case 7. When the lift is 8mm

Cut plot of velocity

Cut plot for pressure

B. Flow Trajectory

The flow trajectory of velocity of the air inside the flow bench is shown in the figure below

Animation of the Flow Trajectory

C. Plot for Mass Flow Rate and Valve Lift

The data obtain after completing parametric study for the valve lift is as shown below

Valve Lift (mm)	Mass Flow Rate (Kg/s)	Average Total Pressure (Pa)	Average Velocity (m/s)
1	-0.018949591	104307.7214	12.03667402
2.2	-0.036655254	104517.9653	20.66178582
3.3	-0.05288253	104405.4837	28.6148426
4.5	-0.066866682	104457.4455	36.16486243
5.6	-0.077474373	104336.7283	37.11540093
6.8	-0.084645094	104328.8699	40.41220394
8	-0.091777312	104315.356	43.33763729

As the mass is leaving from the system so, the mass flow rate is negative.

The plot for positive mass flow rate is shown in figure below

D. Effect of Pressure on Valve Lift

E. Effect of Velocity on Valve Lift

CONCLUSION

1. For higher value of grid size the mass flow rate decreases because the mess size gets reduce for higher value and it increases the accuracy.
2. As the Valve lift increase the mass flow rate also increases as shown in the plot.
3. The negative mass flow rate represent the mass is leaving from the system.
4. The velocity increases as the Valve Lift increases.
5. The pressure is almost constant when we increase the Lift of the valve.

REFERENCES

1. Video lecture of skill lync
2. Wikipedia