Week 4: Project - Steady state simulation of flow over a throttle body

OBJECTIVE: To observe the flow of air over a throttle body elbow using COnverge studio and Cygwin for running the simulation files from Converge.

PROCEDURE:

1. Load the .stl file in Converge studio. When we laod the file we need to scale it asour license allows only a certain Number of cell count for the model.

For this we first need to go to transform and click on Scale Model. When we open that window we get a Scale option and we can choose the amount we need to scale the model. We chose 0.01 for scaling the current model.

2. Now we need to check for any anomalies in the geometry. initially after we removed the outer part of the pipe, we considered the pipe to have neglegiable thickness. After that we got many open edges in the Geometry.

For that we used the patch option and patched the surfaces which got us 0 errors.

3. Now we setup the case for this simulation.

For that we need to define a predefined mixture air. For all the other values are to be left as it is.

Run parameters for this simulation. We will be running a steady state Simulation at first and then for simulating the flow through the throttle we will switch to a transient flow. This flow is a pressure based simulation where we defined a steady state monitor.

Now for the boundary conditions we have marked various boundaries for each component.

Elbow - Wall

Inlet - Inflow

Outlet - Outflow

Throttle - Wall.

These boundary values are for steady state. For transient state the condition remains the same except for Throttle which get converted to a movable wall.

We need to model the wall in such a way that we change the throttle timings according to the angles.

This is to be done so that we can observe the transient flow over the throttle body as the throttle moves in different times at different angles.

The above is the sheet created by me according to the specifications given.

After this we start the simulation through cygwinn.

RESULTS

Firstly we started with a steady state simulation for this throttle body movement.

Mesh for the Elbow with fixed embedding

For this simulation we preffered a coarse embedding at the edges of the throttle profile because we wanted to get a good profile at the edges of the throttle. We would have gotten a bad result due to the small distance between the walls of the elbow and the throttle itself. By adding an embedded region we are able to obtain a more refined animation for the throttle in both steady as well as the transient case.

Pressure contour at 25 degree angle.

In the above image we can observe that the pressure from the inlet is about 1.3 bar and as it hits the throttle at 25degrees it gets distributed to some parts and thus the flow is evenly distributed on towards the outlet. In the animation we will be able to observe a constant prerssure ditribution even as the throttle moves by the profile we have submitted.

For the velocity contour we used the same analogy as we used in the pressure part.

We can observe clearly in the image that the velocity wheen it hits the throttle has increased from 150 to about 300 and this is due to the fact that the air flow has been obstructed by the throttle positioning. We will be able to notice the flow distribution in the video.

Mass flow rate at the Inlet

We can see from the plot that the mass flow rate slows decreases but as it hits the throttle it increases and then tries to come to a steady state as it proceeds to the outlet.

Mass flow rate at the Outlet

We can observe that the mass flow rate has kept on increasing as the air pressure goes to the outlet and then after the 8th ms it tries to come to a steady state solution.

Pressure Plot for transient Analysis.

CONCLUTIONS

As we have chosen a much fines mesh our cell count only went upto about 3500 cells for the entire simulation.

We can also observe that the total pressure of the system has increased but the static pressure decreases. This is due to the fact that the throttle does not seal the elbow completely and thus we can observe leackages.

The link to the Files is :

https://drive.google.com/drive/folders/1C0bx079W5_ID5n2Aj2r6B-V9klPrGPC5?usp=sharing