Project : Steady state simulation of flow over a throttle body
AIM:
To simulate and study flow around the throttle valve in an elbow in steady condition.
OBJECTIVE:
1)To setup case for steady state flow over throttle body which is maintained stationary.
2)To simulate the flow and post process in paraview.
3)Plot and analysis for different mesh size.
INTRODUCTION:
Throttle is a flow control mechanism used for various applications related to flow.Such as IC engine applications, HVAC application.The working of throttle is simply by reducing or increasing the flow area to either reduce or increase the amount of flow in relation to pressure.One example of throttle valve is Butterfly valve.
The flow we are simulating in this case is simple construction of following throttle body.
GEOMETRY:
The geometry dimensions are as follows
Lx=0.106314 m
Ly=0.119998 m
Lz=0.0171742 m
Case Setup:
Boundary Flagging:
Application Type:
Selecting Time Based Simulation With air as predefined mixture.
1)Gas Simulation:Keeping default values
2)Global Transport Properties:Keeping default values
3)Run parameters:
Using Steady State pressure based solver
4)Steady state monitor
Monitoring average velocity at inlet after 500 cycles and for sample size of 500 cycles with allowed tolerance of 0.001
5)Simulation Time Parameter:
The maximum cycles are kept at 15000 cycle assuming this much will be sufficient flow convergence.
The minimum time step is kept at 1e-9 and maximum at 1 sec.
6)Solver parameters:Pressure Based solver
Boundary Conditions:
1)Inlet :
Inflow boundary condition with 150000 Pa of pressure at 300 k with air as intake.
2)Outlet:
Outflow Boundary condition with atm pressure of 100000 Pa if any backflow is there it is of air.
3) Wall:
For turbulent flow LAW OF WALL is to be applied.
4)Throttle
Stationary with law of wall
Region and Initialisation
Initial condition :
Create a region inside the geometry consisting air at atm conditions.
Turbulence Modeling:
Keeping it as RNG k-ε model.
Base Grid:
For Case 1: 0.004 for dx dy dz
For Case 2: 0.002 for dx dy dz
Fixed Embedding
Boundary Embedding of Permanent Type For Throttle with 2 layer and scaling factor 3.
Output files:
Writing Output files for every 1000 cycles.
Results:
1.Velocity Contours:
CASE1:4e-3
CASE2:2e-3
2.Pressure Contours:
CASE1:4e-3
CASE2:2e-3
5)Mass flow rate
CASE1:4e-3
CASE2:2e-3
6)Average velocity plot
CASE1:4e-3
CASE2:2e-3
7)total pressure plot:
CASE1:4e-3
CASE2:2e-3
8)total cell count:
CASE1:4e-3
CASE2:2e-3
ANIMATIONS:
Velocity Contours:
Pressure contours:
Conclusions:
1)Animations shows aburpt changes first but then solution converges there is small variations in velocity around throttle where there is gap between wall and throttle.
2)Not much velocity variation in axial direction as throttle is stationary and fully open.
3)The pressure builds around the side of throttle on inlet section as pressure is high.
4)As sufficient amount of cells are available at emedding around throttle the mesh size of 2e-3 gives better results. Mesh size of 4e-3 lacks in cell to capture effect around throttle.