Steady state simulation of flow over a throttle body
Introduction
A throttle valve is a device which can be used to regulate the air-fuel mixture in an engine. It can be fully opened or closed, depending on the need. In this study a steady state simulation is performed for a throttle valve using converge CFD.
Aim
- Set up and run the steady state simulation for flow over throttle body.
- Post process the results and show pressure and velocity contours.
Procedure
Fig. 1 shows the simple geometry used in this study. A bounding box is created to view the overall dimensions.
Fig. 1 Throttle body in elbow geometry.
Converge was used to set up the basic analysis parameters. The simulation was allowed to proceed for 15,000 iterations, though convergence was observed well before. Using the fixed embedding option, an inlfation layer was created around the throttle valve. The default turbulent model, K-epsilon RNG was chosen for this case. Inlet was set to a total pressure of 1.5e5 Pa, and outlet to 1e5 Pa to create a pressure drop. Throttle and the remainder of the geometry was set to wall.
Data was stored every 1000 iterations, however at the end only the last values are studied since this is a steady state analysis. Mesh size was kept at 0.002 mm (dx dy dz). Fig. 2. shows the mesh.
Fig. 2 Cell count and adopted mesh.
Results
Fig. 3 Mass flow rate, id 2 = inlet, id 3 = outlet.
Fig. 4 Velocity, id 2 = inlet, id 3 = outlet.
Fig. 5 Pressure, id 2 = inlet, id 3 = outlet.
Looking at the above mentioned plots, it can be inferred that at around 8000 iterations the solution has converged.
Fig. 6 Velocity.
Fig. 7 Pressure.
Conclusion
In this study, a steady state simulation was performed using converge. While 15000 iterations limit was provided, the simulation converged much earlier. Looking at the contours, for the provided boundary conditions, after the throttle a low pressure region is observed, due to seperation. In the future study, a transient analysis will be performed to better understand the flow dynamics.