Week 4: Project - Steady state simulation of flow over a throttle body
Aim :- Flow over a throttle body using steady state simulation.
Objective
1.Post process the results and show pressure and velocity contours.
2.Show the mesh (i.e surface with edges)
3.Show the plots for pressure, velocity, mass flow rate and total cell count.
4.Create an animation in which it throttle movement should be visible.
Introduction-
A throttle is the mechanism by which fluid flow is managed by constriction or obstruction. The throttle on a gasoline engine is typically a butterfly valve. In a fuel injected engine, the throttle valve is placed on the entrance of the intake manifold, or housed in the throttle body. In a carbureted engine, it is found in the carburetor. When a throttle is wide open, the intake manifold is usually at ambient atmospheric pressure. When the throttle is partially closed, a manifold vaccum develops as the intake drops below ambient pressure.
Procedure for steady state simulation
Import the given geometry in converged CFD
Imported geometry is cleaned for the simulation, check the diagnosis dock for overlaping ,crack , open edges etc.
Assign the boundary name ie inlet, outlet , throttle valve ,Elbow etc
Case setup
Application type-Time based
Materials-Predefined mixture-Air
Run parameter
Boundary condition
Inlet -inflow-pressure-1.5 bar
Outlet-Outlet-1bar
Throttle wall- Stationary wall
Elbow body- Wall
Flow occurs due to the pressure difference between inlet and outlet boundary condition. Air is used as a fluid with O2 and N2 mass fraction are 0.23 and 0.77 respectively. The temperature is maintained at 300K.
Grid size
dx=0.002m dy=0.002m dz=0.002m
Fixed embedding
Fixed embedding basically used for the local refinement near the throttle .
Embaded layer -3
Scale-2
Mode -permanent
Scaling refers to the multiplication factor of the mesh. In our case base grid for the entire domain is 0.002 in all x,y,z direction after the scaling up to third layer near throttle valve mesh refined.
Without embadding with 4mm grid size.
The base mesh of the entire body is shown ,the mesh for the throttle valve is refined.
Simulation time parameter
Simulation is run for 15000 cycles. Simulation uses density steady solver with the pisco algorithm.
Initial time step-1e-9s
Minimum time step-1e-9 s
Maximum time step-1s
Turbulance Model
RNG-K-e model is used
After setting all the parameter export the input file and ecxecute the file in cygwin64 Terminalby using
mpiexec.exe -n 4 converge-intelmpi restricted executable.
For generating the log file use
There after move the post processor 3D and convert the 3D file in post processing.
Result
Velocity contour
Pressure contour
Vector
From the above vector contour it can be seen that velocity is maximum at the region where the flow is restricted. When the valve is fully open flow through the elbow is free ,velocity is lower as thw surface of the throlled.
Average velocity, mass flow rate , total cell count and total pressure can be seen in the plot below
Mass flow rate
Total cell
From the above plot we can analyze that solution is converged at 4000 cycles.
Conclusion
The flow through open valve has been simulated for full open condition of the valve. The pressure and velocity distribution of plot and contour has been observed.