Week 4: Project - Transient simulation of flow over a throttle body
Aim :- Transient simulate the flow through a throttle body through 25 degree angle of rotation of the throttle plate with time.
Introduction
A throttle valve is integral part of the IC engine and is basically used to control the engine speeds. It consist of a throttle plate that is connected to actuators which is further connected to accelerator peddle. When accelerator peddle is pressed the throttle valve opens, allowing air to enter in to the combution chamber and when the accelerator peddle is let go it closes and chokes the inflow of air.
Procedure
Import the geometry in converge studio by dragging method.
The characteristics length of the elbow can taken as 0.2m
Avg inlet velocity of steady state is about 190 m/s
Flud flow time =1.05*10^-3 sec.
End time =0.01 for 10 times fluid flow through the pipe.
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- Rotating
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.
The base mesh of the entire body is shown ,the mesh for the throttle valve is refined.
Simulation parameter
Simulation is run for 0.01 s. Simulation uses transient 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
mpiexec.exe -n 2 converge-intelmpi restricted </dev/null> logfile &
There after move the post processor 3D and convert the 3D file in post processing.
Result
Throttle valve geometry
Above image shows the valve at zero position
Movement of throttle valve
Pressure Contour
Velocity Contour
Stream line contour
Plot
Observation from the plot
When the valve is moving total cell count moving unpredectiable there after total cell count remains constant. We can say that every change in the angle of the valve total cell count changed.
2. From the above graph we can say that velocity fluctuating between 0 to 0.002 s because throttle valve is moving in this time period.
3. Mass flow rate decreases when the throttle valve moves from 0 to 25 degree angle.
4. Pressure is higher at the entrance of the pipe after striking the fluid to the throttle valve pressure decreases .
Conclusion
The flow through open valve has been simulated for partially open condition of the valve. The pressure and velocity distribution of plot and contour has been observed.