Project Transient simulation of flow over a throttle body

TRANSIENT SIMULATION OF FLOW OVER A THROTTLE BODY

AIM:

To simulate flow over a throttle body with different angles and understand the flow behaviour and transient simulation.

INTRODUCTION:

This simulation is done for visualising flow over the body, and how the velocity of the flow affects near the throttle body region, and to know what happens when a flow is obstructed by a body, such as throttle body.

Mesh: dx = 0.002m dy = 0.002m,  dz = 0.002m

Fixed embedding : Embedding layers : 2, scale 3

CASE SETUP:

The inlet boundary condition is given as pressure with a value of 150000 Pa.

The outlet boundary condition is given as pressure with a value of 100000 Pa.

The boundary condition for throttle body and the hose is given as wall. For this simulation, the throttle body is simulated in a transient condition by keeping at various angles.

Initial state – 0 degrees

2 ms – 25 degrees

MESH SURFACE:

PRESSURE CONTOUR:

VELOCITY CONTOUR:

The velocity plot shows the region where the flow gets obstructed. At 25 degress, the flow is obstructed and flown above and below the throttle body, creating high and low pressure regions. Since there is no shaft placed for the throttle body, there is a gap in the area, and since the area is small the velocity increases, leading to pressure drop.

The difference in velocity for different angles over the throttle body and the hose is observed in the animation.

PLOTS:

PRESSURE PLOT (INLET):

The pressure indicates the initial condition which is given, since this is measured at the inlet.

PRESSURE PLOT (OUTLET):

The total pressure indicates the static pressure and the dynamic pressure measured at the outlet. The changes can be observed when the throttle movement starts at 2ms , which when the throttle body obstructs the flow, after which, the pressure comes to a steady value.

VELOCITY PLOT (INLET) :

The velocity plot indicates the average velocity measured at the inlet and the changes can be observed when the throttle movement starts at 2ms , which when the throttle body obstructs the flow, after which, the velocity comes to a steady value.

VELOCITY PLOT (OUTLET) :

The velocity plot indicates the average velocity measured at the outlet, and this velocity is created due to the pressure difference of 50000 Pa between the inlet and outlet and the changes can be observed when the throttle movement starts at 2ms , which when the throttle body obstructs the flow, after which the velocity comes to a steady value.

MASS FLOW RATE (INLET) :

This indicates the mass flow rate from inlet which has converged to approximately -0.045 kg/s. The changes can be observed when the throttle movement starts at 2ms, which when the throttle body obstructs the flow, after which, the mass flow rate comes to a steady value.

MASS FLOW RATE (OUTLET) :

This  indicates the mass flow rate measured at the outlet which has converged to approximately  0.045 kg/s. The changes can be observed when the throttle movement starts at 2ms, which when the throttle body obstructs the flow, after which, the mass flow rate comes to a steady value.

TOTAL CELL COUNT:

The total cell count for this simulation is around 39950. The change in cell count can be observed when the throttle moves, as the fixed embedding option tries to add cells every time , when the throttle body moves along its axis.

SIMULATION TIME CALCULATION:

The characteristic length of the pipe along x-axis, i.e the bounding box length is 0.1 m. Since we need the length of the pipe, and it will be larger than the length of the box, when measured, approximating the value to 0.2 m.

The average velocity at the inlet obtained from the steady state simulation is 104 m/s.

So, the time which the flow takes to go through the pipe one time is calculated  by,

Flow through time = 0.2 / 104

Flow through time = 1.92 x 10^-3  s.

So, considering 5 times the time obtained to attain a steady state, it is 9.62 x 10^-3 s. Rounding off the value to 0.01 seconds and the throttle body is simulated.

CONCLUSION:

This simulation is done to understand the flow behaviour in transient condition through a hose (pipe) when it is obstructed by a body such as throttle body. This simulation also shows the flow over reduced area , which increases the velocity over the area and hence reduced pressure and the flow is observed when the throttle moves from zero degree along its axis to 25 degree at 2ms .

ANIMATION LINK: https://drive.google.com/file/d/1VyuGbkbpyLrNlg7vzjfwVmXNJjZoGf8W/view?usp=sharing