Modelling and simulation of flow through a flowbench
Objective: To create a 3D model of a flow bench and run flow analysis. You will be obtaining a plot of lift vs mass flow rate
Problem Statement:
To do the following
- Grid dependence test
- For three grids run your simulation at a particular valve lift and explain your results
- Effect of valve lift on mass flow rate
- Once you have decided the best grid, run a parametric sweep to show the effect of valve lift on mass flow rate
Theory:
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.
Study Setup:
Draw a Circle of the following dimensions.
Extrude by 0.1m.
Create this profile.
Then create a plane at the endpoint and draw the circle with the dimensions.
Use the sweep option to perform the operation and get the desired feature.
Then create a profile appropriate constraints so that the lift can be varied for the valve.
Use the sweep feature on the profile.
Using the shell option select the two faces one of them as shown in the figure below and select a thickness of 0.002.
The part is created successfully.
Then in Flow Simulation Add-In use the lid option to create the lids on both the open faces.
Later Use the wizard option in the flow simulation. Follow the default steps and make changes in the windows as shown below.
After pressing the Finish button on the wizard move to the boundary conditions. Apply the boundary conditions as shown below.
Goals are added as shown below.
Then the mesh size is varied accordingly.
Using the Cut Plot and Goal Plots the results can be obtained.
The parametric Study is created with the following input parameters.
The output parameters consist of all the goals and the cut plots. Then we run the program to obtain the results.
Results:
Grid Dependency Test:
Level of Initial Mesh - 3
These are the velocity and pressure plots for Level of Initial Mesh - 3.
Level of Initial Mesh - 4
These are the velocity and pressure plots for Level of Initial Mesh - 4.
Level of Initial Mesh - 5
These are the velocity and pressure plots for Level of Initial Mesh - 5.
We can concur that with the increase in the mesh size for the same lift the results tend to be more accurate. As we keep on increasing the mesh level we increase the accuracy of the end results as they are directly proportional. But it can be observed that the time taken to get the results also raises because of more computation and may be limited by the system capacity as well. So from these three cases the last one i.e Level of Initial Mesh - 5 because of the better and closer results. The graph also gives us a glimpse of why the increase in mesh size is desirable.
Now the parametric study is run with Level of Initial Mesh - 5 with the study parameters as mentioned above.
The results obtained for different valve lifts are shown below
Design Point 1
These are the velocity and pressure plots for Design Point 1.
Design Point 2
These are the velocity and pressure plots for Design Point 2.
Design Point 3
These are the velocity and pressure plots for Design Point 3.
Design Point 4
These are the velocity and pressure plots for Design Point 4.
Design Point 5
These are the velocity and pressure plots for Design Point 5.
Design Point 6
These are the velocity and pressure plots for Design Point 6.
Design Point 7
These are the velocity and pressure plots for Design Point 7.
This is the plot for lift vs mass flow rate.
Conclusion:
From the plots above it can be concluded that with the increase in the lift the mass flow rate also decreases. But the other parameters such as the pressure and the velocity increase along with the mass flow rate. Because the valve starts to open it provides a channel for the fluid medium, in this case, the air to pass in due to which we can observe the pressure rise. As the pressure rises so the airstrikes and enters the passage with a greater velocity which can also be observed in the plots displayed above.
The simulation has been successfully run and the desired plots and results are obtained.
References: