Week 11.1: Turbo Charger Simulation Project

Turbo Charger Simulation Project

• Aim:

To simulate a transient simulation on a turbocharger made-up model and to analyse its impellers speeds on 3 different pressure ratio cases. Also calculate the end time required to obtain max impeller speed once it reaches steady state.

• Theory:

1. Turbo Charger:

A turbocharger, formally a turbosupercharger and colloquially known as turbo, is a turbine-driven, forced induction device that increases an internal combustion engine's power output by forcing extra compressed air into the combustion chamber. This improvement over a naturally aspirated engine's power output is because the compressor can force more air—and proportionately more fuel—into the combustion chamber than atmospheric pressure (and for that matter, ram air intakes) alone.

- Working:

In naturally aspirated piston engines, intake gases are drawn or "pushed" into the engine by atmospheric pressure filling the volumetric void caused by the downward stroke of the piston (which creates a low-pressure area), similar to drawing liquid using a syringe. The amount of air actually drawn in, compared with the theoretical amount if the engine could maintain atmospheric pressure, is called volumetric efficiency. The objective of a turbocharger is to improve an engine's volumetric efficiency by increasing the pressure of the intake gas (usually air) allowing more power per engine cycle.

• Procedure:

Model was pre-processed and suitable boundary flagging was performed. The scale was reduced to meters from mm.

- Geometry:

- Turbine:

- Case Setup:

1. Application: General flow

2. Solver: Transient solver

3. Simulation type: Gas

4. Simulation time parameters:

start time: 0 sec

end time: 0.006 sec

5. Regions and initialisation:

In this step, we have created a region of the fluid and initialise the species value as follows:

N2= 0.77

O2= 0.23

6. Boundary conditions:

7. Physical Models:

RNG K-epsilon, FSI

- Fluid Structure Interaction:

8. Grid control:

element size: x=y=z=1e-4m

9. Output files:

- 3D files: 6e-5sec

- Text output: 1e-5sec

- Restart files: 6e-5sec

- Max number of restart files saved: 3

• Results:

- Mesh:

- Total cell count:

- Mass flow rate:

- Torque:

- Rotational velocity:

• Conclusion:

- Speed of impeller/turbine:

- In order to achieve max impeller speed, the simulation is required to run longer until the simulation reaches steady state. Therefore, we need to extend our end time accordingly.

at PR 3 we achieved an impeller speed of 1070 rpm. Now in order to achieve 2000rpm when ran till it reaches steady state is given by,

0.006(2000/1070)= 1.12sec

Therefore, we need to run for 1.12 sec inorder to find out the max speed of impleller.