Week 4: Project - Transient simulation of flow over a throttle body
Aim: To Perform transient flow simulation over the throttle plate using converge CFD.
1. Introduction:
The above picture depicts the elbow pipe with throttle plate(blue ), inlet(green) and outlet(red).In SI engine throttle plate plays a vital role in controlling the airflow and fuel mass inside the cylinder. The fuel and air mass is controlled through the movement of the throttle plate at certain angle `theta` which varies through the engine cycle operation. In this project, the movement of the throttle plate is set in such way that it valve/plate rotates by 25 degrees from 0- 2 ms and constant dwell at 25 degrees from 2- 4 ms. Eventually, by 8 ms plate should return to its home position.
Figure- Throttle body-[1]
2. Case Setup
2.1 Mesh
| Base mesh | |
| Base Grid, mm | 2 |
| Min Grid Size, mm | Scale 3,0.25 |
| Max number of cell |
The same generation strategy which has been implemented in steady-state simulation is considered here. For more information please refer to the Steady-state simulation project report.
The figure on the left side depicts the mesh generation when the throttle plate is moving. A zoomed mesh generation near the throttle plate is shown on the right side. It's clearly visible that the base is kept at 2 mm and an embedded scale of 3 is used due to which a finer mesh generation is observed at the throttle plate.
Below is the video link of the mesh generation.
https://youtu.be/I6jBcXPYTkg
2.2 Boundary Conditions
| Sl no | Type | Fluid | Pressure and Temperature |
| Inlet | Inflow | Air(O2-0.23 and N2-0.77) | 1.5 bar |
| Outlet | Outflow | Air (O2-0.23 and N2-0.77) | 1 bar |
| Throttle Plate | Wall-Movable | - | |
| Elbow | Wall-Fixed | - |
Throttle plate movement profile:
Below is the video link for the throttle plate movement.
https://youtu.be/YtdJB6767oU
The picture shows the throttle plate movement with respect to time.
3.Results
3.1 Plots
Average Mass flow rate:
Average Velocity:
In the above velocity plot, it can be observed that as the flow hits the throttle plate velocity profile gets turbulent while the throttle plate is in dynamic mode, as the throttle plate returns to the original position the velocity stabilises.
Total Pressure:
Static Pressure:
3.1 Contours
Pressure
The pressure at downstream of the throttle plate is high due to choking of the air mass flow. Flow separation is observed at the downstream due to the high pressure and velocity drop.
Velocity
Velocity is very high near to the elbow valve due to the narrow path for the flow.
Below is the video link for velocity contour
References:
1.An electronic throttle control strategy including compensation of friction and limp-home effects:
Deur, Josko and Pavkovic, Danijel and Peric, Nedjeljko and Jansz, Martin and Hrovat, Davor, Year-2004-IEEE